#72 - John Wenger: Hydroxyl Radicals: Nature's Invisible Engine Room, Ambient Air and more

Have you ever wondered what's really happening in the air around us? In this captivating conversation with Professor John Wenger of University College Cork, we dive into the hidden chemistry that shapes our atmosphere and affects our health in ways most of us never consider.

At the heart of our discussion is the fascinating world of hydroxyl radicals – nature's invisible cleaning crew that exists at just one part per trillion in our air yet drives fundamental atmospheric reactions. These tiny, highly reactive molecules transform pollutants, create ozone, and even influence cloud formation that affects our climate. Professor Wenger shares insights from the groundbreaking EU-funded Radical Project, which developed innovative sensors to detect these previously unmeasurable atmospheric components.

The conversation shifts to real-world air pollution challenges across Ireland, where Professor Wenger's research identified how solid fuel burning creates dangerous particulate pollution spikes during winter evenings. We explore how valleys like Enniscorthy can experience pollution levels rivaling those in heavily polluted global cities, though these spikes typically last just a few hours each evening. The good news? Low-cost sensor networks are revolutionizing our ability to identify these pollution patterns and empower communities with information.

Perhaps most compelling is our discussion about the pandemic's lessons regarding indoor air quality and the ethical questions it raises. Professor Wenger reflects on how vulnerable populations continue to face accessibility challenges in public spaces due to air quality concerns, drawing parallels to other accessibility rights issues. The episode highlights how understanding air chemistry isn't just academic – it directly impacts public health policy, building design, and even questions of social justice.

Whether you're interested in environmental science, public health, or simply curious about what's in the air you breathe, this conversation offers accessible insights into complex chemistry that affects us all. Subscribe to Air Quality Matters for more discussions that bridge scientific understanding with practical solutions for healthier environments.

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Radical Project 

John Wenger UCC

Chapters

• 0:00 Welcome and Introduction
• 1:48 Understanding Hydroxyl Radicals
• 10:19 The Radical Project and Measurement Challenges
• 21:36 Atmospheric Chambers and Chemical Reactions
• 32:49 Solid Fuel Burning and Local Air Pollution
• 44:02 Low-Cost Sensors and Data Collection
• 53:12 Pandemic Lessons and Indoor Air Rights
• 1:00:19 Closing Thoughts and Outro

Transcript

Simon: 0:00

Welcome back to Air Quality Matters. We already have the tools and knowledge we need to make a difference to the quality of the air we breathe in our built environment. The conversations we have and how we share what we know is the key to our success. I'm Simon Jones and coming up a conversation with John Wenger, professor of Physical Chemistry at University College Cork. Strap in folks we're talking about hydroxyl radicals. Yeah, I know, I didn't have a clue either, but it turns out these little things are one of the engine rooms of our environment, have a massive impact on our air chemistry. That makes a lot of the pollution that we talk about on this show and very tricky to measure in the parts per trillion and not around for very long. But John and an international team have been doing some amazing work over the last few years. Looking at just this have state-of-the-art atmospheric labs down here in Cork where we're recording today. And who doesn't love a bit of air chemistry? I've known John since he chaired the Ventilation Advisory Group which I served on during the pandemic here in Ireland and was really looking forward to catching up with him post-Covid to chat about this, the Radical Project and air pollution in general. Lucky enough to be recorded here in the Great Hall in UCC, university College Cork. I really hope you enjoy this one. Please don't forget to check out the sponsors in the show notes and at airqualitymattersnet.

Simon: 1:44

This is a conversation with John Wenger. There were kind of three things, three areas we were going to have a look at today. One was about free radicals and atmospheric chemistry in general, I think, and your labs and what you're doing here, stuff on ambient air pollution. Oh, what happened with that contract, by the way, the Queen's Jobby, do we know? Are you part of that? Has it been awarded?

John: 2:07

It's been reviewed, okay, but we were the only consortium that was going for it, because you have to have a big inclusive consortium. And so we worked hard to get what we thought was a good consortium together. That included the relevant academic institutions, the relevant bodies, north and south county councils, all right, so it's quite a big consortium. But yeah, we're the only one going in um, so I expect we'll get funding for yeah, it's just, it's like it's in the review phase, is it no?

John: 2:37

yeah, yeah yeah, so this is a program called peace plus and and the the issue there is related to the second part, um, which is it's really driven by the solid fuel burning issue. Yeah, okay that the legislation is different north and south and essentially, uh, coal cheaper coal from wilden island can be brought into the republic yeah but it doesn't have the same standard, right, um?

John: 3:06

so they're looking to, in the end, looking for ways to change the legislation north, but they don't have a an information basis to do it, because there's no research at all on the sources and how big's the issue with agricultural driven pms, because that's one of the things that I only copped.

Simon: 3:27

You know, it's amazing how much you realize you don't know every time you go to various things and somebody goes. Well, of course, we're looking at agricultural particulate matter and I'm going agricultural. What now and so and for recollection, that was methane and other gases from agriculture creating air chemistry and particulates.

John: 3:50

I mean the chemistry from methane is extremely slow. It's a greenhouse gas, so it doesn't really react very well with the hydroxyl radical. It's too slow to act on a local basis. It moves around the world all right. It moves on the planet before it eventually gets, uh, degraded. That's why it's got such a long lifetime, so it's very slow to react. And what we have, though, from agricultural emissions is ammonia.

Simon: 4:13

Right, that's the key yeah, that's it, yeah, that's the key thing, all right.

John: 4:16

So the ammonia in the gas phase comes on in water and but also it combines with acidic gases like sulfuric acid, nitric acid. So any binds with acidic gases like sulfuric acid, nitric acid. So any NOx species if you had a NOx or SO2, eventually gets oxidized into the acids and then you get an acid-base reaction. Some simple chemistry for an assault, acid plus base, gives you assault. You might remember that from leave-insert chemistry or O-level chemistry, whatever you did. And this is a source of particulates. So this is stuff emitted as a gas but then forms particles in the air, so it's secondary PM2.5. And so when you see ammonium in particulate matter, you've got a good trace back to the agricultural source, all right. So this is omnipresent. Everywhere we go, we see methane, so we see ammonium in the particulates.

John: 5:06

Okay, interesting we're linking this now slight complication is that there is ammonia emissions in the urban environment as well. So from the some of the diesel type vehicles, especially with the ad blue chemistry that is the urea compound, and there may be some ammonia coming from those sources as well in the urban environment. But but in the main it's agriculture and this secondary particulate matter just means that this elevated background and we do see some highs in springtime when there's a lot more manure and so on being spread right and slurry of things yeah, because those emissions volatilize and they end up converting into particles.

Simon: 5:47

So it's not. You don't see it in the data that you're looking at. We'll come on to this, but we're digressing immediately, which is always great, john, you're not seeing. It's not kind of event driven. In the same way, we might see PM events of cold nights and coal fires and things like that. When you're looking at ammonia driven particulate matter, are you able to spot what's driving it?

John: 6:12

there is some seasonality to it okay, but in the end it is all year round. Oh yeah, because you do have the animals are living all year round, right, so those emissions do occur all year round, but they're heightened during the slurry or manure spreading season. So when you put that stuff on the fields and you know you're living in ireland, right, so you can get those smells quite often right next door to it?

Simon: 6:33

yeah, for sure, and do. Does it? Do we know? Does it carry the same risk as some of the other, particular the heavy metals or the carbon-based particulates? Is there a kind of a direct link to these PMs?

John: 6:49

Ammonium sulfate or ammonium nitrate per se wouldn't be anywhere near as toxic to things like pHs from combustion or emissions from direct combustion sources from direct combustion sources. So in that sense, no, but it just does add to the burden of PM2.5. So it basically gives us an elevated background. If you were to be on the west coast of Ireland, where the wind's coming in from the Atlantic, you have very low particulate matter. As you move across eastwards you're picking up all those emissions and you're going to get higher particulates just as a compound, compound, compound, yeah, yeah interesting, and so you can see ammonium more or less everywhere, so there's been extensive studies now across europe.

John: 7:40

And ammonia, the gas. Because of this ammonia, now the gas has been included in the new EU Air Quality Interactive. Okay, so it's one of these newer species, like black carbon.

Simon: 7:55

And is it included for its particulate generating potential rather than its direct toxicity?

John: 8:03

Yes, by and large by and large. So it really is about its secondary particle form and ability. Interesting, it's the only. It's the main base in the atmosphere that reacts to the acids yeah all right. So all the combustion processes produce nox, nitrogen oxides, which then can be converted into things like nitric acid. Um, sulfur dioxide gives you sulfur, sulfuric acid. They can get incorporated into water droplets or they can combine with the gases directly, and then you get salts, and these just add to the particle growth, particle mass that's present in the atmosphere PM2.5.

Simon: 8:42

Well, let's come back onto PM5, all right, because that is question two. Um, in first instance, I want to understand what the hell a radical is right in as simple terms as possible. Um, you were generous enough to show me around your labs about a year and a half ago, maybe even two years ago now, and it was. It's a phenomenal piece of kit and research, obviously, and you've been part of a big international project looking at free radicals. Yeah, could you give me the lowdown on what we're talking about here, because it's certainly the first time I heard of it? And then I think, unless you're into ambient air quality or chemistry, this may, may not be familiar to a lot of people.

John: 9:23

Yeah, so I think I mean, people would have heard about free radicals in the body, maybe, okay, uh, in a similar way, there are free radicals in the atmosphere, in the air. Um, free radicals just basically very reactive, short-lived chemical species. Uh, from a chemistry point of view, they have an unpaired electron, and that electron wants to find another electron, right, and so it means that it's very reactive. It wants to make chemical bonds all right, so it's very reactive. In the body, free radicals can do a nice job of mopping up some pollutants into the body.

John: 10:01

Too many free radicals can also be a problem, though, right, because that can lead to some stress situations In the atmosphere. It turns out that free radicals drive the chemistry of the troposphere, the lower part of the atmosphere, and in particular one called the hydroxyl radical. So this is water, but you remove one of the hydrogens, basically, and you've got the hydroxyl radical, and so this is a very short-lived species that is like a gas phase species. It's very reactive and it's present in extremely small concentrations. The concentrations during the day are something like about one in a part per trillion. Phases are a part per trillion level. So one radical in a trillion molecules of air, that's 10 to the 12.

Simon: 10:44

Yeah so it's tiny.

John: 10:45

It's way less than the concentration of ozone. It's about a millionth less than the concentration of ozone in air.

Simon: 10:51

I'll have to do my second game with that, because when I'm explaining to people the tiny amount of stuff we're talking about with air quality, I do the. Can anybody here tell me what? A million seconds is Right, you know? And it's like 12 weeks or something, right, and and then a billion seconds is 32 years, like the leap is enormous. Yeah, um, so a trillion. I dread to think what, what we're talking about in just tiny, tiny amounts of this tiny, tiny amount.

Simon: 11:22

But so if it's so tiny, is it important then? Is it driving something? Because?

John: 11:28

it's so reactive.

John: 11:29

It's so reactive that even at small concentrations it just reacts with almost everything.

John: 11:36

So the hydroxyl radical will react with NO2 from combustion, sulphur dioxide react with carbon monoxide, it will react with methane, albeit a bit slowly.

John: 11:46

It will react with all of the organic compounds that are emitted from man-made sources like combustion vehicles, wood burning, industrial uses, home care products, as well as natural sources like vegetation plants and so on. So all of these species will react with a hydroxyl radical and they'll undergo oxidation. It turns out that the hydroxyl radical reacts but then is regenerated during the day. So there are various cycles and so it just goes round oxidizing things, because the air is, the atmosphere is like an oxidizer, okay, and the nitrogen doesn't do very much. But the 21% of oxygen is really key because once you start the reaction with a radical, you then get oxidation of species okay. So, for example, when we emit VOCs, volatile organic compounds from various sources could be a vehicle exhaust, for example during the day, when the hydroxyl radical is present. I forgot to say that it's only really present during the day because it's produced from sunlight, the action of sunlight on various chemicals, including ozone.

Simon: 12:51

So it's similar to ozone, then it's a kind of a sun-driven thing, yep.

John: 12:57

And in fact the hydroxyl radical. While it's made from ozone, it also produces ozone as well, right? So there's various chemical cycles here. The hydroxyl radical comes out with an organic compound. We convert NO to NO2. No2 becomes broken down by sunlight to give you O. O plus O2 gives you O3. And we get radicals being produced. But it's cycling around again.

Simon: 13:21

Yeah.

John: 13:21

So when I do my lectures to undergraduates, there is various cycles where you have ozone production from OH and you get oxidation of volatile organic compounds, so the OCs get converted to ozone, and also the organic compounds can get converted to oxidation products, and some of which have low volatility and make particles, and so these are secondary organic aerosols, and it turns out that these particles from organic reactions contribute to some of the largest uncertainty in climate. I understand another climate situation at the moment. Okay, because these particles are seeds for clouds, they're cloud condensation nuclei, as they're called, and in addition, they also can be breathed in. They're so small, they're cloud condensation nuclei, as they're called, and in addition, they also can be breathed in. They're so small, they're like PM2.5, and so they have health effects. So understanding this chemistry is crucial for understanding atmospheric composition, understanding ozone formation and secondary pollutant formation, including particles which affect air quality, health and climate and I'm guessing one of the challenges is because they're so volatile, it makes them incredibly transient.

Simon: 14:30

So measuring them and understanding them, while you can understand the chemical reactions, actually testing theories and measuring this stuff, I guess, is pretty complex to do.

John: 14:45

Yeah, I mean the origins of this chemistry go back to the los angeles smog. You know, during the 1950s people were realizing that the damage that this smog was doing okay, and they figured out that ozone was a key component. How, where's this ozone coming from? Ozone is only, is only made. Ozone is not emitted really. It's always made in the atmosphere through reactions of sunlight. And they finally worked it out. It's this oxidation of organic compounds initiated by the hydroxy radical. So it's sunlight plus VOCs, organic compounds plus nitrogen oxides, gives you ozone and that's the LA smog situation. And that now has happened all around us, not in such extreme cases as the Los Angeles smog, all the time. But this was the real reason why. You know, the state of California led a lot of the legislation on air pollution right.

Simon: 15:39

So it's a real engine room of chemistry. These three radicals, it's the starting powder for a lot of the stuff that's going on.

John: 15:44

Room of chemistry these three radicals, it's the starting powder for a lot of the stuff that's going on, yeah they really initiate the chemistry of our atmosphere and, as I said, even though they're present at such low concentrations, they drive the chemistry and they control in a large way atmospheric composition.

Simon: 16:02

Even though it's so dispersed, even though it's so dispersed, even though it's such small amounts, it's potent enough at scale to have an impact. Yep, so so, even though you're looking in the parts per trillion, it it. When you have a free radical, it it's changed and gone. What's sunlight's creating that radical in the first instance? That's what you're saying. So it's changed and gone. What's sunlight's creating that radical in the first instance? That's what you're saying. So it's sunlight breaking down right stuff creating these radicals, one of them being hydroxyl radicals. Yep, and it's that, that's just. Even though it's small, it's everywhere all of the time. Yep, creating.

John: 16:39

And then it chain reactions, chain reactions. It gets, it gets produced again yeah uh, it kind of kind of disappears at night time. Then another radical called the nitrate radical, no3, takes over at night and we know less about that. But it turns out that the chemistry at night time can be important, especially for biogenic VOCs. So VOCs come from forests and plants and so on. Yeah, turns out to be really quite important for NO3, the nitrate radical.

Simon: 17:07

Yeah, all the kind of the pinenes, all of that stuff being generated.

John: 17:13

Exactly and on a global sense. 90% of the VOCs emitted do come from natural sources.

Simon: 17:21

Yeah.

John: 17:21

And they have the largest impact on climate. As I said, they become oxidized to give you these organic aerosols, tiny particulates. The haze over a forest is quite well known. There's blue haze. Yeah, this is that secondary organic aerosols and they scatter light, but they also are the seeds for clouds and some of that complex chemistry and physics how these particles interact with water droplets and form clouds is really behind some of our largest uncertainty in climate models.

Simon: 17:54

So is there a big gap in knowledge here with free radicals? Is that the big challenge is its measurability, understanding its impact, how it changes like. What's the? What are the questions that are trying to be answered around free radicals at the moment? I mean, we understand they're there, we understand they're reactive, we understand there's. They're the engine room of a lot of complex chemistry. Um, but does it matter? And is it asking questions we don't have the answers to at the moment? Is that kind of where we're at with it?

John: 18:33

The detail is in the chemistry, because there's such a large range of volatile organic compounds and they all react very differently towards the hydroxyl radical. Methane, for example, is extremely slow. You compare methane to alpha-pinene. You said that earlier on. Alpha-pinene is nearly 100,000 times faster to react than methane is. So we find out how fast different species react. We work out some of their oxidation products, we work out which of these products can go on to form the aerosol. So we identify the chemical reaction pathways that lead to aerosols.

John: 19:13

In the same way, we can look at man-made emissions and look at what happens to wood burning. Do wood burning emissions produce more toxic material as they become chemically processed in air? More toxic material as they become chemically processed in air? Yeah, do some of those emissions from vehicles become more toxic or less toxic, less toxic? And so we follow some of that chemistry.

John: 19:32

We can do that in the field, but it's extremely complex because there's literally hundreds of thousands of individual organic compounds in air at tiny trace level concentrations, each of them reacting at different rates, contributing different amounts to the secondary pollution. We can do that and we can also decide to go into the lab and focus on individual components, for example, study alpha-pionine, for example. Study benzene coming from automobiles and focus on one of those chemical pathways. Take alpha-pionine, for example. Study benzene coming from automobiles and focus on one of those chemical pathways. And take alpha-pionine, for example. I would say there's literally 500 studies at least on alpha-pionine and we still probably haven't fully nailed it. Okay, because the chemistry is so complex, it's very reactive and once you produce, once you have one initial reaction, you get several pathways and then you get several other pathways.

Simon: 20:26

And it's just like this explosion of branches.

John: 20:29

Yeah, you get like an explosion, and so this is where it's incredibly difficult, and taking that information that we generate from the lab and parameterizing it for climate models, for example, is a really big challenge as well, because it's relevant right, for example, is a really big challenge as well Because it's relevant, right. But we've got to work out how to represent that information in a model, in a real-world model, and so I'm talking about lab science, I'm talking about the field observations, but then also feeding information into a model as well, and the whole area of atmospheric science now is a combination of laboratory science, field measurement and modelling, and linking those three is key.

Simon: 21:12

And with radicals and hydroxyl radicals? Is it purely about understanding why we're seeing what we're seeing, or do we consider them a pollutant in their own right, something that we could control or limit the amount of or do something? Is it, is there some avenues of science that way, or is it? Is it just there? It always will be, like the sunlight, it's just the engine room of it's the secondary stuff we care about and it's just about understanding that process. Or is there an element of this of trying to understand why we're seeing lots of it at certain times or in certain conditions and understanding if we can break that chain and limit them in some way that we might stop some of those secondary pollutants?

John: 22:04

it's always going to be there, right? I mean, it's natural chemistry, um, this natural chemistry can get enhanced in more polluted environments.

John: 22:12

So when we have very polluted, smoggy cities, for example, there are extra gases in the air and that can also be a source of hydroxyl radicals, and so you get faster oxidation chemistry you get more chemical processing and that means it occurs in a shorter timescale and therefore you get more local processing and that means it occurs in a shorter time scale and therefore you get more local pollution. Okay, so if the chemical reaction is very quick, that will lead to local pollution. If it's very slow, then the stuff doesn't really react very much like methane and it spreads around the world. Stuff of intermediate reactivity has more like a regional impact, you know, a countrywide or even going across a continent, say, and so we break down our impact of different emissions into the impact being local, regional or global, and it's that speed of the chemical reaction which really governs that.

Simon: 23:10

So tell me a little bit about the research that you've been bit about the research that you've been doing and the lab that was set up, and you were part of a big cohort to do this. What was the idea behind that particular body of research?

John: 23:21

so for quite some time now. Um, we have been working on uh laboratory studies using atmospheric simulation chambers, okay, so the idea here is to recreate the atmosphere as close as you can in the lab. So we have a large facility which is a room you can actually walk into it where we put our vapors and our gases and our particles. We study systems of interest we might want to look at I don't know, say benzene chemistry. We can add that into our particles. We study systems of interest we might want to look at I don't know, say benzene chemistry. We can add that into our reactor. So the reactor is this vessel which is transparent, it's a Teflon film and we have ultraviolet lamps to mimic sunlight so they can generate the radicals. And then we study the chemistry using a wide range of instruments to look at the processes that are going on. We can monitor the different gases, the organic compounds and also secondary particle formation.

John: 24:18

So there's a whole smog formation process in the lab and originally they were called smog chambers. Now we use them for different things, but initially in California, when they were first invented, they were called smog chambers and the idea, of course, is that when you go to the lab you can control that environment and that's the big thing about it because you can change the concentration of the stuff right. You can add however amount of nitrogen oxides you want, you can add ammonia gas, you can add existing particles, you can change the light wavelength, you can change the temperature, you can maybe change relative humidity. You've got all of those possibilities in a controlled environment, like an atmospheric simulation chamber that you don't have outside.

Simon: 25:03

Yeah.

John: 25:04

Now, what you do get. What you don't get is the complexity of the atmosphere, but what you do get is the chance to study a system in isolation. So typically we'd be looking at individual compounds. Yeah, what you don't get is the complexity of the atmosphere, but what you do get is the chance to study a system in isolation.

John: 25:13

Yeah, so typically we'd be looking at individual compounds. But people have been playing around a bit more now with real-world emissions and we've done that ourselves. So, for example, we have done some studies on the chemistry of emissions from little trees so Sitka spruce is the most widely planted tree in Ireland and the UK actually, because it grows very well, very quickly. But those emissions, the smell of the forest, they go into the air, right. So we took the vapors that are emitted from some of those trees and put them into a chamber and oxidised whole world emissions from trees. People have done it with car emissions, wood burn emissions, yeah, and so you can do individual studies, individual chemical studies, so you can do the more complex real world.

Simon: 26:05

So you can see that single pollutant branching out into all sorts of different chemistry, as you were describing it. Or you can introduce more complex soup of chemicals and see. So you can. You can do things at different levels and understand different outcomes. That's going to be very hard to measure. I mean that stuff's happening live, in real time could be any number of chemicals that are being produced at any one time. How do you even go about measuring that in real time? That's not an easy task with very expensive equipment, right.

John: 26:37

so, yeah, um, but I mean the last, the last 10 to 15 years, I've seen an explosion in online mass spectrometry, okay, so this allows you just to sample the air, whether it's gas or particulate, and get a chemical breakdown of the composition, okay, and so we've been trying to identify what's in particles, what's in the gas phase, and trying to piece together this complicated chemical picture.

Simon: 27:08

It's complicated chemical jigsaw really. It's BCA particulate matter as well, can it? Yeah, we can do that as well, right?

John: 27:14

So and there's been a lot of advances the last 10 or 15 years. Now it is complex, whether you're in the lab as well as the field. You know. If you take alpha pine and, as I said earlier on, you can have 50 different species, some in the gas phase, some in the pyrocl phase, some in both. And getting a handle on that complexity and breaking it down to get something useful right yeah, you need the instruments to do that. With these instruments comes a lot of data collection and with the data collection comes a lot of data analysis. So all of my research team now and many research teams, numbers of experts around the world, are now writing their own code, writing their own programs to, to, to analyze data quickly and efficiently and um I was going to say, like with the chemistry and the the amount of data is it?

Simon: 28:03

are we talking?

John: 28:03

obscene amounts of data and computing needed to untangle this stuff a full mass spectrum every second, right, yeah, and and we've been doing some monitoring just recently now with colleagues from Galway We've been a six-month measurement campaign, right? So you've got huge millions and millions of data points and so you need good tools to analyze that right, customized tools for your analysis as well.

John: 28:33

In the main, yeah, yeah, yeah, I mean the community does work together and share tools, right, but yeah, they need to be good right, Because you've got so much data to get through.

Simon: 28:42

I know a number of data scientists and inevitably they all end up being programmers and coders, because the stuff just doesn't exist to do what they want to do with the data, so they have to be able to do it themselves. So I've always been really impressed that these people that can look through this data also writing stuff in order to be able to look at it in the way they want to look at it yeah what about the hardware itself?

Simon: 29:06

is that? Is the hardware pretty delicate and hard to maintain and complex and like how is it? Is it high? Is it a high maintenance thing trying to get good, because you know they say junk in, junk out. I mean it's got to be all about the sensitivity and the calibrators.

John: 29:26

The real high performance instruments are these mass spectrometers. So they okay, okay, lots of research groups would have those and are using those, and now routinely. I'm not saying it's straightforward and it's still not straightforward, but we use them all the time and we are getting better at developing and using the tools to get the most information out from the analysis right. We also have, on the other end, we have kind of routine analyzers. We have some sensors for all the pressure, temperature, humidity, co2, whatever else. But we also have standard gas monitors for nitrogen oxides, ozone, so2, and all that sort of stuff.

Simon: 30:05

Yeah.

John: 30:06

And the other thing that we do in UCC my colleagues Andy Reif and Dean Menabos do. They develop new measurement techniques to measure different atmospheric species. So looking at different ways to measure NO2, different ways to measure ammonia and so on is a big focus. And also now we're also looking at radicals to measure radicals using these more traditional spectroscopic techniques, but also using low-cost sensors, right. So we're trying to do a whole range of different things, and one of those is also improving the measurement techniques that we have available I was going to ask that because that was one of the outputs from this particular study, wasn't?

Simon: 30:45

it was the looking at developing simpler. Developing simpler, more low-cost ways of measuring what's going on with radicals, which is not easy, I'd imagine. No, it's not easy. You certainly can't wheel around half a million pieces of equipment on trolleys around Cork City Centre trying to.

John: 31:07

So here's the deal. The hydroxyl radical I mentioned before is crucially important. It drives the chemistry of the atmosphere, but we don't measure it yet, which is amazing, right? I mean we can measure all the other stable gas molecules and everything else. Now it is difficult, admittedly, and the equipment to do it is really complex, expensive, hard to use and not transportable. It's laser-induced fluorescence or it's complicated mass spectrometers. Very few research groups in the world do this okay, so it's not routine at all, and so the idea of our Radical project, which is an EU project, was to build a sensor, a very small sensor, just like an air quality sensor, but detecting radicals, and so this is a very ambitious project because, as you know, hydroxyl radicals are present at extremely low concentrations, they're very short-lived and very reactive, and so there's a lot of challenges there in being able to measure something like that, like on a normal gas-phase molecule like ozone.

John: 32:07

A lot of cross-positivity is there in sensors for that kind of thing, yeah exactly, and so this radical project actually was a great project, because it combined physicists, material scientists, atmospheric chemists, and we had some technology companies as well all coming together bringing their own individual expertise to design and test a sensor for radicals, and the idea was quite different Rather than using light or a mass spectrum to measure the radicals, we were just using electrical detection. It's a very simple, straightforward a silicon-based device that can be manufactured quite cheaply, quite cheaply, but that would also have the sensitivity and, hopefully, the selectivity, to measure radicals. We've just come to the end of the project now, and we had some success. I think it was a big challenge, right? I think if you were to sit any atmospheric scientist here today, they would say it would be an almost impossible challenge, but we did get a measure of success.

John: 33:08

We certainly used the sensor to detect hydroxyl radicals, so we got pretty much real-world sensitivity. We were at the parts per trillion level sensitivity for hydroxyl. We didn't get the selectivity that we wanted, though, so there are interference effects from other gases like ozone and nitrogen dioxide and so on, and so we've got so far, and I think that now, naturally, we're going to look to the next phase of this development, uh, that to develop the sensor further to see if we can get that selectivity yeah, it's a solid first step anyway.

Simon: 33:46

I mean in the sense that you you learned a lot about yeah, free radicals and hydroxyl radicals and you got a sense it into the ballpark.

John: 33:57

Shall we say yeah, so now it's about well we measured something, right measured something and I was delighted when we managed to, uh uh, show that it's measuring flat line on a screen going no I mean, because I mean you, if you've got no signal, that's it.

John: 34:12

You know, you just got to work to, especially the guys in the in in the lab, my students, my researchers that, um, just just as long as you get a signal, then you've got something to play with. You got, you got the start right and you can play with it. Um, and we did, and we got response from oh, which is really good. We got responses from other gases and actually there are potential side benefits from that. Right, because we think we can possibly take this as a platform and, with certain different types of coatings or manufacturing procedures, we might be able to tell a device to be an ozone sensor, to be an NO2 sensor, to be an ammonia or hydroxyuretic sensor.

Simon: 34:51

Yeah, you might have broken ground in trying to measure the impossible, but you've made what's already possible even better, perhaps because we've got ozone sensors and NOx sensors and so on, but this might be a better way of measuring them and more precise.

John: 35:07

You know you're taking on a big challenge with the hydroxyl radicals, and the real strength is the use of electrical detection as opposed to spectroscopy or mass spectrometry, which involves expensive equipment. If you've just got electrical current, that's it. You can have a small device, right. You don't have to have all the fancy optics for spectroscopy or the spectrometer for mass spectrometry, you've just got a little sensor, just like a portable or stick-on-the-wall air quality sensor.

Simon: 35:38

So the project's finished. Now it's wound up.

John: 35:40

The project has just come to its end and we are at the stage there. We are looking at the next phase. We have some ideas already and so we are having continued discussions with consortia to work out exactly what are the next steps. But we have some ideas in train and we're also actually just received news that with that type of platform we've now got an opportunity to dial up for a pneumonia sensor. So I think that as a group now this collaboration between the material scientists who make these devices and the atmospheric scientists looking for the application, you know we've actually it's been quite fruitful.

Simon: 36:19

Yeah, there's some good potential outputs from this stuff. That's always encouraging. Yeah, how long a period of time was the project? Is it kind of like a four year project?

John: 36:27

This was a four year project? Yeah, and it was.

Simon: 36:32

Was it funded by? It was a.

John: 36:33

European funded project Research groups from Bulgaria, germany, uk, greece, ireland and different expertise brought from different areas. Yeah, really helped make the difference there, for sure.

Simon: 36:56

Was there anything that surprised you in this?

John: 36:57

study. That was something that you. You learned what you didn't think that it worked.

Simon: 37:00

No, yeah, uh, no, it was really easy. What you're seeing with the chemistry, or even what you were seeing with the, the labs and the tests, well, the sensitivity I was surprised at.

John: 37:07

yeah, okay, because, um, when we we used this artificial source to generate the hydroxyl radicals in the lab at quite high concentrations so they were elevated, I thought, yeah, we're seeing parts per billion, not parts per trillion. The light source away, the radical source away a bit further, we were able to measure more realistic concentrations, more real-world concentrations. We were in the right range. So that was a little bit surprising that we had the sensitivity. Sure, we could detect parts per billion of ozone, but can we detect parts per trillion?

Simon: 37:48

a thousand times less of this very short-lived radical species, and we did and what about the co-benefits of all of that knowledge and equipment and resources that have been buried into, particularly here in ucc with the labs and what have you? Is there ongoing uses now for both for that chamber and the knowledge that you built in internally here to measuring this kind of stuff?

John: 38:11

so the ongoing collaboration, as I mentioned, that we're working on the next project now for ammonia sensor. We're looking to carry on with the radical work I think a european level with the european consortia. The chamber also is used by a variety of other projects, so we have a project called atmo trace where we're developing new spectroscopy techniques for different species as well. We're looking at emissions from agriculture OK, we're looking at emissions from slurry and we're also looking at a whole range of other VOC chemistry. As I mentioned, these secondary organic aerosols are a very important topic. So we have a variety of projects ongoing which use the chamber facility as well and how do?

Simon: 38:56

how do these lab projects like radical then connect with your kind of field research and with general atmospheric chemistry and air pollution? You, you're taking what you're learning from that and applying it to the other stuff that you're doing, which we'll come on to next, around ambient air pollution and things. Yeah, um.

John: 39:19

nearly always. Any new technique is always developed in the lab um, and then you scale up and you scale up, you go for you just see if you can see something, and then you look for potential interferences and then you test it under a range of different conditions. That controlled atmosphere is key to being able to do that. And then ultimately you go to the complex of the real world. And so we haven't quite done that with the radical sensor, but we have done it with the other spectroscopy techniques that the guys in our group have done.

John: 39:50

So, for example, colleagues have taken some optical setup, used it to detect nitrogen dioxide NO2, in the lab on the optical bench like a laser bench, and then you use it in the chamber where you can control the conditions. And then you go out to the field and I was chatting to a colleague earlier on today. He's going to go out tomorrow with this in a car, all right, and so they're trying to test this as a mobile sensor already. And so you do this gradual, stepwise progression. But you start from an empty laser bench, you start from an empty bench in the lab and you build up in terms of the complexity.

Simon: 40:34

Yeah, understand the fundamentals, yeah, understand the principles and just steadily apply it and scale it, apply it and scale it and so on.

John: 40:41

Yeah, and you know experiments in the chamber on this chemistry, voc, chemistry, um are really important because if we're going to do some measurements in the lab, we might measure in the field. We might measure some stuff and go where does that come from? Okay, if we're going to do some measurements in a lab, we might measure in the field, we might measure some stuff and go.

John: 40:54

Where does that come from? Okay, well, we're in an urban environment, there's lots of traffic nearby. Maybe it could come from benzene. Let's go and look at the reaction of benzene. Benzene does produce this compound. Okay, so we know that benzene chemistry is occurring outside, and vice versa. We do some chemistry on I don't know isoprene in the lab and we say, oh, this is interesting, it produces these species. Do we see those in the field? Yes, isoprene chemistry is going on in the field, and then the chemical processes that we study in the lab can be used to interpret the data in the field. And that's where you get more complex air quality modelling, looking at the impacts of emissions, different emission scenarios on secondary pollutant formation.

Simon: 41:42

So this is where you start getting to what you're doing with the ambient air monitoring out there, where you're taking less complex data sets but much, much bigger, and the chemistry that you're understanding in the lab are helping you develop the models and the formulas to understand what you're seeing at scale, so you can get a sense of why are we picking up and seeing this in this situation, and then, when you see it appearing in the data, you've got a fundamental understanding of why it's there.

John: 42:12

Then, yeah, so we do this combined approach. And also to bridge as well. They shouldn't work on their own. There should be connections, and we try and do that whenever possible.

Simon: 42:23

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Simon: 43:44

Links are in the show notes at airqualitymattersnet and you can find them at 21degreescom. That's 21degreescom. That's 21degreescom. Now back to the podcast. Now, it's a fascinating area, um, an area I don't think I've ever heard talked about before free radicals and hydroxyl radicals, but it sounds like it's a fundamental engine room of a lot of what's going on. Yeah, um be interesting to see what the next step looks like. Do you know where you are? Are you out for funding? Have you formed an idea of what the next project looks like?

John: 44:17

yeah, we're working on it. We're just trying to identify the best call because, um, some of the funding, um programs, are more directed towards faster technology development there. There are still issues with some of the fundamental science, the exact mechanism, the sensing mechanism that we're trying to pin down. I think we want to do some more fundamental work before we are able to, I think, get this selectivity, because I think we will be able to get this selectivity, but we need to understand that fundamental sense and mechanism. What's going on when the hydroxyl radical hits the surface, interacts with the stuff on the surface?

John: 44:58

yeah causes that electrical current to be generated. Um, what's going on?

Simon: 45:03

and so we're trying to understand some of that, with theoretical approaches as well as experimental work and, as you were saying, at a global level this stuff, it has the potential to impact the environment, atmospherics and global warming and all these kind of things. So understanding free radicals and their impacts on clouds and pollution and particle generation and you know, feeds into better models to understand and predict yeah, I.

John: 45:30

I think if you can measure the radicals in the ambient environment, you've got an idea of what we call the oxidizing ability of the atmosphere. If the OH radical concentration is low, then it's not going to be a very reactive atmosphere. If it's high, it's going to be a reactive atmosphere. Yeah, okay, and so you've got that handled. We just don't have that information. You can, using chemistry models, do some predictions, and Kraftner's predictions are quite good, but we could certainly benefit from a lot more measurements and you need an accessible, low-cost technique to do that.

John: 46:07

Because not everybody has the ability to deploy this expensive kit to measure radicals.

Simon: 46:12

From a pure chemistry perspective, have you been able to kind of theoretically run the numbers? Are there runaway scenarios like we get a lot with global warming of hitting certain benchmarks or points where we're creating so much of this stuff that there is unintended consequences of global warming or changes in the atmosphere? Is there some unintended chemistry potential downstream? Do you think at a, at a climate change level, I mean?

John: 46:45

we do see, as I said, this chemistry is natural chemistry and it's enhanced and we just add more stuff to the air. So when we have these additional VOCs and nitrogen oxides from combustion processes and so on, then you do get this enhancement.

John: 47:02

So, the hydroxyverical will react with what's in the air to make ozone. But once you add a lot more VOCs and NOCs then you get a lot more ozone formation, a lot more aerosol formation, and so we see that in specific environments. But the daily nature of the OH production and so on means that this is a cycle more or less. As we go forward. Are things likely to change? Maybe emissions, certainly from plants, are going to change with the warming climate. We're already seeing, I think there's a big concern are going to change with the warming climate. We're already seeing, I think, as a big concern. Quite a hot topic at the moment is wildfires, so the impact of wildfires on air quality. What about those emissions? There's a lot of black carbonaceous material going into the air, those particulates, but also there's a lot of volatile semi-volatiles that go with them too. Right, the stuff you're smelling is the volatile semi-volatiles. Okay, the stuff you're breathing in is all of it. Uh, and that's a free lunch for radicals the one thing that is changing is.

John: 47:58

The one thing that is changing is we're getting more wildfires, and so we're getting probably more event-based things like, typically, um, you would get winter air pollution, summer air pollution events, but now we're also getting wildfire, air pollution events, and these can be huge, right, they're the size of a continent, right, you know. So these are. We're in Ireland, uk. We're in a part of the world where it's not a very big problem, but we do have some problems. The wildfires just recently in Ireland, uk. We're in a part of the world where it's not a very big problem, but we do have some problems. The wildfires just recently in Ireland, right, and they will be in the summer. And when you go to Southern Europe, it's a very big problem now. And, of course, united States, canada, australia and lots of other countries. So I do think the wildfire issue is leading to a change in our composition and it's event-based. But if these events are going on at different times all around the world, then you are changing composition.

John: 49:02

And we're lucky we don't have where we are, we don't have events where we have to stay locked inside until on the air purifiers, right the air filters. Stay locked inside until on the air purifiers right the the air filters.

Simon: 49:16

Um but but there are in the usa, right, there are other countries, I don't know. And it's a fabulous segue, john into my next segment, which is uh, there's periods of time, whereas I've been in nenniskorthy where you probably need to shut the windows and turn the filter on yes, because the particulate, yeah, smoke and wood burning and peat burning and coal burning and what have you so we still get pockets of very poor air quality in Ireland. In certain atmospheric conditions, certain areas of the country can have very poor outcomes, can't they?

John: 49:45

yeah, yeah yeah, and we've done research into this now for the last 10 to 15 years. We initially started in Cork City and we were quite surprised to find that there was a lot of coal burning, peat burning, wood burning. So in the winter months the particulate pollution is quite elevated. It's probably double, on average, the amount of pollution in the summer. So this is obviously a very seasonal effect. And it was evening.

John: 50:11

And then the chemical signature of the particulates showed that we had coal and peat and wood burning. And this is Cork City 15 years ago, where, by the way, there was already a ban on bituminous or smoky coal. And so we thought, wow, that's quite serious air pollution which wasn't really thought about as being a big problem, and certainly at that time people weren't looking very much at the composition. It's when you look at the composition of the particulates can you say, oh yes, that chemical signature corresponds to wood burning, that chemical signature corresponds to peat or coal or traffic or so on. Okay, so different chemicals. So, for example, sea spray would give you a sodium chloride signature. Wood burning we identified by potassium. Okay, because it's always present in living material and recently living material. You'd look at carbon, organic carbon.

John: 51:17

You look at some other fragments from breakdown of things like cellulose, lignin, all right, and you can work out. These come from wood burning. And then you do your fingerprinting Yep, we've got coal, we've got wood, we've got paint. And so we said, if it's bad in Cork City, what's it like in places where there's no ban in place? And there are literally tens, if not a hundred, towns in Ireland that at that time didn't have a smoky coal ban, but because they were not on the gas grid, solid fuel burning was a regular nightly event just to heat the house.

John: 51:45

And we went to three small towns Enniscorthy is one of them and we measured the same elevated pollution levels at night. Really quite bad in some areas. Enniscorthy was the most polluted at the time and we had this kind of winter smog. So it's like the London smog of days gone by were present in small towns, and this problem we saw in many small towns across Ireland. And again, it was all three solid fuels. It wasn't just coal but it was peat and wood as well, and we saw all three solid fuels present in the emissions that we were measuring.

Simon: 52:21

Yeah, and it's real. I mean, I live near Enniscorthy and when you drive in on those winter evenings there's a lot of sports pitches up on the hill in enniscorthy the, the ga pitch, the rugby pitch, the soccer pitches are all in a similar area. Yeah, and they've all got big floodlights lit and it looks like there's fog. Yeah, it's very pronounced. You come in and you can taste it in the air. It's very, very prolific and at multiple folds over the WHO limits, for particular matter at those times.

John: 52:56

So I think it's a very real thing. And Esquithy also is the setting, the topography, and it's set in the valleys. So, combined with the temperature inversion because of the winter months, night time, you also have the topography, which just kind of acts like a trap really for the pollution right. And then Eskowth is one of those towns that had a particular problem. But our research was acted upon, we fed all this information into the Department of the Environment and it was used.

John: 53:27

I mean, for many years they were talking about a ban on smoky coal extended nationwide, and we said great, but peat and wood also contributes, so we also need action. It's a solid fuel building problem. It's not just a coal problem. And eventually there was new solar fuel regulations brought in into Ireland in 2022, which was a nationwide ban on smoky coal in 2022, which was a nationwide ban on smoky coal. But there's also no more large-scale extraction and selling of peat.

John: 54:00

And there's some measures on wood as well. The humidity Wet wood is more pollutant than dry wood and so on. So look those measures. Actually, the timing was unfortunate because they were introduced at the time of the start of the Ukraine war and the cost of living crisis and everything else, so it was a bit difficult. But the latest news is that we've just finished a measurement campaign in Anas Korthi and a project called TownAir with colleagues from the University of Galway and there's an improvement right. So our first measurements in Anasiscorthy were 10 years ago and what we see is a good reduction in PM2.5. We see less carbonaceous material, so over the time their quality in Enniscorthy has improved quite a bit. So obviously, hopefully, the regulations have played a role there and the local authority as well. Workfield County Council has been quite active in promoting the use of cleaner ways to heat your home.

Simon: 55:03

Yeah.

John: 55:03

So I think that, combined with the scientific information, has hopefully had an impact.

Simon: 55:08

Yeah, and particularly in these smoky old towns that you get, I mean, they're quite evocative in some ways and that you know in in a strange more way, even though I know how awful it is, there is something quite evocative about that smell. When you come into an old town, smoky town, there's a smell of peat and coal in the air that is of a time gone era. You know, it's a bit like when the uh, we've got a couple of steam engines around where I live and when they go chuffing down the road that the amount of pollution that comes off these things is horrendous, yeah, yeah, but there's a but, there's a smell to it that the smells of history. There's something about it that's quite strangely evocative and at the same time of being there is, and I think to an Irish person, especially of the smell of a good peat fire.

John: 55:57

Yeah, because it's evocative, right. Yeah, and furthermore it's part of tradition.

Simon: 56:01

Yeah.

John: 56:01

I mean, that was one of the issues here, I think, was that it's such a part of history, you know, digging up peat and using it for your fuel. It's tradition, right, and part of culture in a way, especially the rural way of life and so that was a that was an issue that had to be dealt with.

Simon: 56:19

I think um in ireland yeah, and, to be fair, it's one of the few air quality events that you can actually see and taste, so it's not like this is an invisible problem. Right, like you know, you're not speaking to the residents of enniscorthy and they go. What air quality problem I don't know there's. You know anybody that lives anywhere near enniscorthy? The nose in winter?

John: 56:41

it's poor air, the key thing about it is that you get these huge spikes in, in particular, pollution that last in two or three hours. Look hundreds of microgram per meter cubed. Yeah, yeah, hundreds right.

Simon: 56:53

Yeah.

John: 56:54

You know almost like Delhi levels of air pollution, but they are only for those few hours and when you take the annual average statistics for the whole year, it really isn't that high, Right? But you get these very highly polluted periods, cold winter evenings where, if you're elderly and you've got respiratory issues, or if you have a I don't know, maybe your child has asthma.

John: 57:29

You're thinking I'm not going to sign up to soccer practice tonight, right, yeah, and so I think it was important to make that connection that it's not just compliance level and your average data, it's those little periods of time where people might be going out for a walk or doing something, and if you've got that information that you can share with them, they can make decisions that could affect their health, right? So I think that's really important to do to get information out there.

Simon: 57:56

How much of a problem do you see with the ambient air monitoring you've been doing with traffic pollution in Ireland? Are there areas of the country where you're seeing significant levels of pollution, NOx's and just soft oxide and particulate matters and so on?

John: 58:13

The research that we do is focused on a field measurement campaign that's intensive, with all of instrumentation, for a season, maybe a year if we can. For example, we went to Dublin Port and monitored for a year, looking at ship emissions and other emissions. Routine monitoring is carried out by the EPA and in other countries the environment agencies would do the same thing. They set up monitoring networks, typically run by the local authorities, measuring typical pollutants like PM, nitrogen oxides and ozone especially, and what we see is that PM levels are by far the highest in the winter and by far during those cold winter nights. So it's very much, even without taking our fancy equipment to these places, you can say right 8 o'clock on a cold December night, that's going to be solid fuel burning.

Simon: 59:07

This isn't people going out into their cars at 8 o'clock at night sitting there warming up in the cars.

John: 59:12

I mean in comparison the little bump due to rush hour traffic is really quite a little bump, so direct particulate pollution from traffic is much, much less. There could be some secondary pollution from the processing of the emissions, that's secondary organic aerosols I was talking about, but in many cities this nitrogen dioxide problem. I think that is very much traffic related.

Simon: 59:42

One of the things I was surprised to learn from an air quality conference I was at last year was how much of a problem commercial kitchen pollution is in big urban centres.

Simon: 59:54

So, in London, just behind road traffic, pollution is commercial kitchens for particulate matter and other pollutants, which was a complete surprise. I wouldn't have even thought of it, to be frank. But yet you go into the, the restaurant quarters in london, and everybody knows that lovely smells. It's the barbecue smells the cooking, the all of that is pollution and it's it's like a third or something of the pm pollution certain areas.

John: 1:00:25

Yeah, I remember we've been on a measurement campaign in paris and we were near chinatown yeah and it was again a big thing and it's been identified. People have done research on this.

Simon: 1:00:34

It's called cooking organic aerosol yeah all right, because it contains different types of organic compounds and not nice companies. There. You've got like probably aromatic hydrocarbons, or there are fatty acids and things like that.

John: 1:00:46

So these um, materials that are byproducts of food cooking, that just condense into that kind of mist of particulates that you can see and obviously the aromas that go with them as well. Right, and so it's. Yeah, the phrase is cooking organic aerosol and it can be significant in some areas. Yeah, so a lot of the things that we do. I mean, I know your indoor air quality is your hot topic. I mean cooking does affect indoor air quality, but it can affect outdoor air quality too.

Simon: 1:01:16

Yeah, sure, have you been pulled into indoor air quality much with what you do A little bit Particularly with the particulate matters and the heating fuels, solid fuels and things like that. Have you found yourself looking at indoor emissions of that as well as outdoor?

John: 1:01:34

Yes, um, to some extent. I mean um. So we got involved more with indoor air research at the height of the pandemic right, it was for different reasons, but I mean the same sort of measurements that you can make outdoors, you can make indoors, and there is a huge level of interest in indoor air pollution, especially people that have wood stoves or fires in their home. Now we haven't done this research, but there are researchers in the UK that have showed that you get elevated PM levels, elevated particulate matter levels, you get elevated benzene, you get carbon monoxide, you get all the obvious combustion pollutants indoors to a much greater extent than somebody who doesn't have a fire or doesn't have a stove. So that is true. We are hoping to do some research soon.

John: 1:02:31

We put an application to do some monitoring in towns, outdoors but also indoors, and the idea is to have some monitoring outdoors at fixed sensor locations but also indoors, and also some mobile sensors. So we've got the whole lot. Yeah, okay, so we do think that will provide a huge amount of valuable data. Know that one of the best things you can do to improve um, but to get uh people to raise awareness and get people thinking about their air quality and what they're doing is to get them involved with the projects as well, right? So yeah, absolutely, that could be a nice way to to go to a town and do a combination of that outdoor, indoor and and mobile monitoring, bringing communities, and then everybody gets a buy-in and understands what they're doing. Are they in the homes, and so on Might be affecting the air that everyone breathes.

Simon: 1:03:35

Where's the gaps in ambient air pollution monitoring and research at the moment? Do you think I mean I'm sure there's many, but in the sense that research at the moment? Do you think, I mean I'm sure there's many, but in the sense that? Is it the majority of it, a policing issue at this stage of just networks of sensors understanding patterns and events and drivers, or is there some kind of fundamental research still being done or trying to trying to learn about air quality outside? What's getting people excited in that?

John: 1:04:11

kind of broader ambient air monitoring space. These days there is a lot of things actually, and in terms of the composition of the particulates, I think, that people are starting to look at some new metrics. Okay, so the toxicity of the particulates. So people are not just saying how much PM, it's like, what's in the PM and what is it doing to you?

Simon: 1:04:31

Yeah, I get in trouble for this all the time, john, because I keep teasing people that particular matters just like TVOCs. It's almost a meaningless value, and they'd argue no, it isn't. I mean, there's some straight lines between the the raw number of pms and public health, um, and we often know where they come from, whereas tvocs could literally be anything, um, but in a strange kind of way it is the same thing. You know, we're talking about pm as if it's a a thing, but it's. It is different sources, different toxicities, different like it's. It's a complex beast of its own right but it's the same way.

John: 1:05:08

When you look at food right, yeah, pm, you could say it's just the same as calories. Okay, yeah. But then you divide the pm into different components, all right, like I don't know, carbonaceous material, ammonia and sulfate nitrate, organics, chloride, whatever. And then you divide the food into salts, sugars, carbohydrates, fats, whatever.

Simon: 1:05:30

Yeah, it's a great analogy actually.

John: 1:05:32

So then you can say, right, I want that information, I don't just want calories. I want to know how much fat is in there. I don't just want PM. I want to know how much toxic polycythic aromatic hydrocarbons are in there. I want to know how much nickel is in there. I want to know how much bad stuff is in there and how much good stuff is in there. Yeah, how much of it is sea salt?

John: 1:05:53

So just that one parameter isn't sufficient in many cases it's fine as a metric for comparison with other places and looking at trends and everything else, but for its impact you've got to break it down.

Simon: 1:06:12

And where's the technology for that? I mean, at the moment we're now getting pretty comfortable with optical particle sensors at scale. We're fairly happy with the numbers, the consistency of the numbers that we're getting now at scale with these things, um, but that's a completely different ball game to speciating particulate matters like on the ground. What's the practical ways that this is being done now and is there some development potential? Are we finding cheaper ways of speciating particles, so to close off on the speciation that is important for toxicity.

John: 1:06:49

this oxidative potential is now in the EU Air Quality Directive, the new EU Air Quality Directive, so this is an important metric that will we will be coming across a lot more over the next 10 years, for sure.

Simon: 1:07:03

Okay, so say that again to me, john, that in the EU Directive, the, we will be coming across a lot more of the next 10 years for sure. Okay, okay. So say that again to me, john, that the in the EU directive the oxidative the term oxidative potential Oxidative it is the ability of the particulates to cause oxidative stress in the body.

John: 1:07:23

Right, okay, okay, their potential to cause oxidative stress.

Simon: 1:07:24

Stress, it's a measure of their toxicity interesting to humans and that's measurable in a different way to speciating it. Is it that?

John: 1:07:32

yeah, there's a combination of toxicology measurements and so on. So it does. It does start to become multidisciplinary, right?

John: 1:07:39

yeah but you do need high grade, research level instrumentation to get that chemical breakdown. Yes, and then there's some assays, some ways to do this, measure this oxidative potential. But now in the new EOI Quality Directive there's also black carbon, soot, if you like. There's also ammonia and also particle number and size distribution. So there's a broader recognition now of just not what we become familiar with. You know, pm, doxoso, it's all the other stuff as well, and so we're now starting to see some.

Simon: 1:08:13

Not all measurement sites are going to have these things, but certainly some information in each area excuse me, would be important okay, yes, you might have one main site doing the more complex measurements and a series of satellite sites doing more basic ones, but building a picture, a super site.

John: 1:08:32

So this is the phrase that's used A super site. So there are a number of those in the UK. We're hoping to get one established in Ireland, but there are quite a few places in Europe, especially in America now, that would have these air quality super sites where you imagine everything. Yeah, and they can't have those everywhere because they're highly instrumentated, very expensive to maintain, complex data sets, everything else. But they're starting to give us new information.

John: 1:08:59

Yeah, sure, and help us with the context of what we're seeing with the lower grade sites, basically experimented with these for the last few years now and seen how good they are and how they can best be used. All right, and in summary, we see that the PM low-cost sensors now are really pretty good for outdoor ambient air quality. We find that if we co-locate them with a reference instrument, a 50,000 euro instrument that is approved, certified, uh, we get in the main, excellent correlation for pm 2.5. Yeah, pm 10 slightly different story, but fear for pm 2.5 and then we can get correction factors. You can make them more robust with temperature, humidity corrections, but in the main you get a good indicative value for a low-cost PM sensor.

John: 1:10:04

And the value then is that you can deploy these sensors all around the town. And so we've been looking at that, where we deploy a bunch of sensors together for about a month. Look at how they'll vary. Almost all of them agree extremely well. We might kick the odd one out for not being very good and then we locate them around the town and now around a town or a city, be it an idea of the variation in particulate matter yeah, and so, and that might be topography, direction of streets, the type of environment all sorts of things.

John: 1:10:39

So we've seen, for example, if you deploy them in residential areas in winter months, you get these peaks in the winter, solid fuel burning right and so on. So you can identify these hotspots and you can interrogate them and you can compare them to each other so the data is comparable, Rather than having one margin site in a town. If you have 15 sensors giving you information that are comparable, you've got that depth of information to answer specific questions which are the pollution hotspots in town?

Simon: 1:11:16

And then how can we use that data? And the big data can unpack the sources just by timings and patterns and so on, the sources just by timings and patterns and so on, like sometimes, like you say, it doesn't take a genius to figure out. At eight o'clock on a december cold, yeah evening, when you see a spike in pms, you know you could, you could bet your house on what is driving that particular level, unless somebody's lit a dumpster fire under that particular particle counter, like there's a good chance you're going to see smoky fuels driving a lot of that right. Or at nine o'clock on a Monday morning in the centre of town, and so on and so forth.

John: 1:11:51

And we're also using some statistical approaches to do that as well. So we are looking at a fluctuation in a signal, a very high frequency signal, for example, in a smoky emission. That might have a lot of variation, whereas you've got a slow-moving regional air mass, the pollution level doesn't really change right. So we can see, we can separate out local from regional pollution.

Simon: 1:12:17

Yeah.

John: 1:12:17

And that's one of the things that we can do already we think with these low-cost sensors, can do already, we think, with these low-cost sensors, and you can also get an assessment of the representativeness of the designated monitoring station. If the environment agency says, oh, we're measuring here, obviously they would do their best to choose the site according to requirements, but how does it compare to where I live, how does it compare over here and here and here? If you do the measurements, then you got that information. Yeah, so you got an idea of the representativeness of these locations. So I think there's lots of value for these sensor networks if the data is used in a good way to generate supplementary information. Yeah, it's not compliant, but it adds to the picture.

Simon: 1:13:05

You think that's where the potential is locked in at the moment. Is that potential to create value with low-cost sensors at a larger scale, to make the invisible visible? Engage it does raise awareness.

John: 1:13:19

Public raise awareness Because if somebody finds out they got a sensor in the neighborhood, they might pay more attention to it. And then they say here's the data. Look, your area is actually two or three times worse than you know the main street. What do you think is more polluted? Do you think the main road is more polluted or do you think your housing state is more polluted?

Simon: 1:13:38

yeah, and you just don't know where that data is going to be used as well. I mean, I work a lot with um social housing in the uk and there's a proliferation of indoor environmental sensors going into social housing, right, um, and most of the big organizations that do that technology are leveraging outdoor weather stations to supplement what they're seeing indoors. So we're tying in data sets left, right and center that are creating these not only big picture, regional, town level scale insights, but they're being used to leverage insights of the case study homeowner my bedroom level as well. You know, am I seeing high particulate level in my bedroom because of something I'm doing in my bedroom, or is it the fact that there's high particulate matter outside at the moment and I'm bringing it in, you know, right, um? So it's fascinating to see all of this stuff intertwined and where it's going to go, um, I think so and um.

John: 1:14:40

There's also some exciting developments in the use of low-cost PM sensors, possibly with some of the gas measurements as well, for what we call source apportionments. You know that really complex chemical breakdown. I'm talking about how we can use the chemical breakdown to say we have 20% from traffic, 20% from coal burning, 10% from wood, 15% from peat. We can use low-cost sensors, sensors if we're looking at the time dependence and we're looking at maybe some other measurements, um, some of the information as well as, like habitual behavior indoors or so on, we can actually use these low-cost measurements to look at the contribution of different sources yes, it's the observed measurements, and that's where your fundamentals on the air chemistry then come into play, because it's that information that feeds those models that go.

Simon: 1:15:29

These patterns are because of the likely sources are going to be creating this chemistry and therefore these are the likely outcomes that we're going to be seeing. So, actually, rather than particulate matter causing a spike in asthma admissions, it might be the chemistry of X that's exacerbating asthma actually. So it's this, it's this source we need to try and get rid of.

John: 1:15:55

We had a great workshop here as part of the RICOL project and it was bringing together people that were looking at the sensor world you know, the electronic noses, voc sensors, ambient air quality sensors, the people that were doing the complex chemistry in the lab in the field to measure, radicals, the people developing new spectroscopy techniques and also our radical project all come together and what do we need to measure? And? And so the vocs is certainly one area that we need to work out, because um actually see total voc, even if it is or not total voc right, you just get a signal right. And if we can get some voc measurements nailed down, um some specific molecules and a very good total VOC, that would be great. And certainly linking some of those things not just PM and not just total VOC, but some individual components would be very, very valuable right.

Simon: 1:17:02

Yeah, and there's some really great work being done internationally on creating harm indexes for these pollutants. So, whilst we understand how much of this is around and we understand its toxicological and epidemiological impact at a society level, a lot of the work like Ben Jones and Max Sherman have been doing around Anne annex 86 at the moment is this kind of total harm. There's this formula for figuring out what's actually causing us harm, what do we need to worry about and what we don't. And you know, their best guess at the moment from the available research is particulate matter is accounting for about 75 of all the harm at a population level, followed by NOx and formaldehyde and ozone and radof in homes like ours. So actually the limonene or the pionine, while it might be present at an epidemiological level or a toxicological level level might be a little bit lower down the list. Actually, if we concentrate on the PMs, the formaldehydes, the nitrogen, darksides, we'll deal with about 90% of the harm according to the research. But the challenge is obviously that this is not speciated, so we don't know of that 75% of the harm we're getting from PM. Where's that harm coming from? So all that's really fascinating. Fares it from outside? I'm guessing right? Yeah, I think best guess is about 50% of particulate matter inside is from outside, roughly Right as a rule of thumb and we know rules of thumb is always a good idea.

Simon: 1:18:41

Yeah, yeah, and I'd be really interested to see how that goes. The other thing I wanted to chat to you before we go is I mean we first got to know each other as we were banged together in the pandemic as part of the response in Ireland by government to bringing multidisciplines from different areas and you and I and a bunch of others sat on the equivalent of cath nox's version in the uk in the ventilation advisory group and you chaired that. So you had the the pleasure, I'm sure, of herding cats or trying to respond to questions. And yeah, I'm just interested from because I had Cath on as well and there were a couple of kind of reflective questions kind of four or five years on, what your experience of that was as an atmospheric chemist and someone that understands air and science being pulled into a, a national emergency, and the kind of questions and responses that you were getting, what your, when you look back on that period now, what your kind of reflective thoughts on it were.

John: 1:19:56

Well, yeah, I think like a lot of people try not to go back there too often, right? Um, I think a lot of people try not to go back there too often, right my reflections. I have memories of just being so disappointed. I suppose, that there wasn't greater recognition of this airborne transmission route, right? Um, given all we know about aerosol physics and everything else um, and the evidence that was rapidly coming to the fore? Um and the, the rebuttal of that um from government advisors not just in Ireland but around the world. Really, I mean that whole community kind of stuck together and wouldn't let the air quality or aerosol scientists in. So I think that, on reflection, what needs to happen is we need to have a broader approach to understanding things like virus transmission and how it can be dealt with, how it can be mitigated and everything else. Because in the end we know very well that, okay, the medics might be best placed to understand the virus when it's in the body, but when it's out in the air, that's the domain of physics and the way to treat, that is the engineers, expertise in managing air and everything else. And so the whole response was um, very much medically centered, certainly in ireland, I think, in eastern uk um, and generally around the world and and so I mean we were quite vocal about gaining better recognition of the importance of airborne transmission.

John: 1:21:50

We got somewhere in the end but probably it's not had the lasting impact, I don't think. I think there was some acceptance at the time but as far as I'm aware, the whole droplet aerosol definition is still not resolved. I mean I don't know how far it's come on, certainly amongst practitioners in healthcare and everything else I don't think they have any improved understanding. Yeah, so I think there are still knowledge gaps. I'm not saying people have gone back to exactly the way they were. I mean people will always remember the masks and everything else. But I'm a bit disappointed that things haven't. There hasn't been an impact.

Simon: 1:22:43

It's certainly in health care, right in hospitals and so on yeah, I asked kath that question and her kind of overwhelming feeling was we were asked quite complex questions in that period but actually her overwhelming sense was a recognition of just how little we knew about the performance of the buildings that we own and occupy. A lot of the challenges that we had were having to explain the basics of ventilation, explain the basics of air quality monitoring monitoring, explain the basics of hierarchies of control. You know the it seemed that there was just this fundamental disconnect somehow was kind of her overwhelming kind of reflection on it. That you know, I think people will argue eternally about the r value risk in a in a wells riley model, on whether, how, how likely you are to be infected. As ben jones puts it, we now, we now know with 100 certainty that your chance of infection is somewhere between zero and 100 percent. Um so like I think that that argument will roll on.

Simon: 1:24:01

Um but what we definitely know from my perspective, having come out of that pandemic, is we have absolutely no idea of how our buildings perform. We've had a code of practice for indoor air quality in the workplace that was launched three years ago. I haven't heard a whisper from the health and safety authority. Um I launched my consultancy at about the same time as the code of practice went live and I've got a page about indoor air quality in the workplace and I'm very well placed to help people do that. I have had zero inquiries. Well about it not a person even knows about it.

Simon: 1:24:44

Yeah, um, for me, I think, similar feeling to you. I just feel like we've come out of it and, for the vast majority of the built environment, we'd rather just forget it ever happened and probably not invest any money next time around certainly in high-level meetings that I was in, there was big concerns about the cost.

John: 1:25:04

all right, yeah, About the cost of implementing change to, I don't know, renovating buildings, overhaul of ventilation systems, additional monitoring, upgrading of facilities, the whole lot, which would go into billions right, without doubt.

Simon: 1:25:24

I just remember the conversations we had over classrooms and schools. I mean the fear of right having to recognize that somehow we might need to do something substantive with classrooms um and the oe with horror, and I mean just to stick with that.

John: 1:25:38

I mean at least it was better. The interaction with the Department of Education, for example, and also my own experience with the Department of Agriculture. They were much more willing to take on our advice and act.

Simon: 1:25:56

Yeah.

John: 1:25:57

I mean, in Ireland we were one of the first countries, I think, to have CO2 monitors placed in schools. Yeah, exactly yeah, and that robust ventilation guidance. But that was done with the department of education. I mean, they took our documents and guidance and they tailored that to their specific needs. Now, implementation wasn't perfect and was a bit difficult, because there's literally thousands and thousands of individual classrooms and all lots of things depend upon the action of the teacher and everything else.

John: 1:26:25

But you know, I mean I do think that you know it did raise awareness, it did make people think about the air, because, I mean, people don't think about the air they breathe at all. Right, it just happens we breathe 11,000 litres of air a day. We only drink two litres of water, right, and you wouldn't think, think you can see dirty water. You can't necessarily see dirty air, these whole things that we keep on coming back to make air quality visible. So in the end, you are right, when you build buildings with certain specifications, you need to monitor that, you need to monitor their performance. So I do think that's crucial and that is one lesson we should learn and fix right we should fix that problem.

John: 1:27:11

I mean I agree with you completely especially in higher risk environments like health care classrooms, because of their small size and large numbers of kids crammed into them right Other places like public transport I mean I'm sitting on buses or planes there should be more monitoring, there should be more information.

Simon: 1:27:34

Yeah, and here's an interesting conversation I've had recently on the podcast with a lady called Victoria Plum. She's based in Australia, she runs something called the safer air project, right, and she comes at this from an accessibility rights perspective. She, along with her family, have suffered with long covid uh, her husband's um got a condition that makes him uh vulnerable anyway, a kidney condition, I think it is um and she's found herself advocating for people that are vulnerable to indoor environments. And there are many people anybody that's under cancer treatment that is affecting their autoimmune ability, the people with particular conditions long covid and so on, copd the whole bunch of people that are effectively excluded from spaces because of the risk of the air quality in those spaces. And actually it's an accessibility rights issue. In the same way it is for wheelchair access or hearing impaired or visibility impaired people.

Simon: 1:28:42

And I found that a fascinating angle because we actually have a lot of the levers and the legislation in place to protect people from right of access, right Because of disabilities.

Simon: 1:28:52

So often a lot of the fundamental law is already there and actually it's a it's an issue of fairness and I and I think society responds quite well in general to fairness If they feel that people are excluded in an unfair way from spaces. They'll move heaven and earth to fix that and we see that. You know, if a child has a disability, a school generally move heaven and earth to make sure that classroom's accessible for them right, or has some hearing aids to help them participate properly in the school aids to help them participate properly in the school. But there are kids who are having to wear a mask in a classroom even today because they don't want to go home and kill daddy. Yeah, you know or, as she puts it, her son that when there's a school trip she has to drive him separately, can't go on the school bus because it's an accessibility challenge to them as a family, and I find that a fascinating perspective to look at the spaces that we operate and own, that actually there's a fundamental we should be making public spaces.

John: 1:29:53

I agree, several journalists in Ireland that were really promoting this aspect, that we well, I was going to say thrown these people under the bus. But there are really promoting this aspect, that we well, I was going to say thrown these people under the bus. But there are people Literally, yeah, there are people who could die from just getting a COVID infection. They've got an autoimmune problem. They can't get the vaccine. If they get a COVID infection, they literally could die or have long COVID, which, from all I've heard, sounds pretty desperately bad and we should be. I mean, in some cases it's just very simple measures. A school takes responsibility to say look in the classrooms, we're going to do what we can for you. Yeah, we're going to improve ventilation and we're going to have some air filters in the classrooms, and these are not expensive things to do and full of co-benefits.

John: 1:30:49

You know it's like yeah that's it, I mean, you know. Oh, by the way, the other kids in the class who suffer from hay fever will benefit from these in the summer, as well, probably get some better test scores.

Simon: 1:30:59

There'll be less, less sickness from the people with benefits.

Simon: 1:31:02

You'll get less room absenteeism from teachers and school. You know, like there's all these a bit like wheelchair ramps uh, provide access to the bank for the person in the wheelchair, but also make it a lot easier for the mum with the push chair. Yeah, like it's an obvious co-benefit, and like so that there's all these co-benefits that come with it as well. So I find it a fascinating way of looking at that challenge. It actually enables us to pick buildings off one by one and introduce legislation that says by the way, if you have a building that's open to the public, you either need a safe floor or a safe room or a safe space that the people that are likely to be vulnerable can access without fear. You're not going to eliminate the risk you never will but you'll be able to reduce it for them. Yep, and give people a chance. Because she points it out, like in the uk. They were living in the uk at the time boris johnson declared freedom day and she said that's stuck in their throat enough that they ended up moving.

John: 1:32:00

It's not their freedom it was.

Simon: 1:32:01

it actually got worse for them because kids were allowed to go back to school infected, yeah, so actually it made the the world more risky for a lot of people if you're vulnerable. And the other interesting thing about being vulnerable is that very few of us can sit here and think there's a very good chance that one in four of us are going to be in a wheelchair right or lose our sight meaningfully, but we already know that one in three of us one in four of us are probably going to get cancer or some long-term illness that, due to the medication that we're on, is going to make us vulnerable to air quality. So actually that vulnerability could be any of us, much more so than a lot of other accessibility-right conditions, so it should matter to everybody as well. This is a very real thing that affects real people.

John: 1:32:55

Plus at any one time. We will know somebody ourselves, family member, friend that is vulnerable or has vulnerable family members. So I do think that would be buying if it was pushed forward, promoted, but I mean it's, it's difficult, um, I don't know how they bring it forward, but I think keep on fighting. I mean we saw the success eventually in in the uk with ella's case.

Simon: 1:33:22

Yep, you know the famous case, and Robert's yeah, and I see Deborah.

John: 1:33:27

Exactly, and so I do think, in the end, once you get a level of recognition, then you will get some impact, but it is disappointing.

John: 1:33:37

I thought one of the little wins that we had from our efforts during the height of the pandemic was this new code of practice for indoor air quality, and it's not a bad document, nice, pretty good, right, um. But the problem is all about the implementation, whether there's the will to implement it from the government, from the hsa, the health and safety authority. Um, there's not enough promotion, raising awareness about it, and there's a whole education piece that needs to be done. So I think, as you said earlier on, we've learned the extent to which we don't know things, and whilst we may know, the general population doesn't. And I do think that we have an education piece to do still, because I fear that already years have gone by where there's still no update to pandemic planning. Right, to what extent is any airborne transmission built into pandemic planning? To what extent are we future-proofing our buildings, our society, the health of our people against an airborne disease? Right?

Simon: 1:34:53

Yep, no, absolutely, and no sense that we've lent on any awareness that was built at the time and built on that, built on top of that Hang on a minute we've had an opportunity where people were suddenly aware that the air could present a risk and we've not been able to build on that effectively, which I think is a lost opportunity somehow.

Simon: 1:35:19

But, like you say, there were some successes of that group and I think, if nothing else, it enabled a multidisciplinary team of engineers and absolute scientists and public health people to come together. One of the interesting things I was going to say, actually the work that they've been doing with the harm risk the total harm index for indoor air quality has been able to put a DALI on it, a disability adjusted life metric on it, has been able to put a DALI on it, a Disability Adjusted Life Year metric on it, which is very useful at a policy level to understand the level of investment needed compared to the risk at a population level, and what they've been able to show is that the Disability Adjusted Life Years for exposure to indoor air quality is equivalent to smoking and twice as harmful as road traffic pollution and alcoholism. So it's at a level based on the harm that it causes at a society level that it should have investment. It should at least have comparable public health campaigns, like we see with road traffic accidents and road safety, about improving indoor air quality.

John: 1:36:23

But to what extent do you see that governments or government departments see this as just too big a problem to deal with?

Simon: 1:36:29

I mean, is that an?

John: 1:36:30

issue.

Simon: 1:36:32

Well, it's never too big a problem to deal with if it has a big enough DALI impact. I suppose you know smoking was a really big problem to take on right. But we recognised that it causes about 2,500 years lost to early death and disability per 100,000 of the population. That's understood to be plainly unacceptable. So you direct funds. You don't want to fix it overnight, but you start to implement rules and regulations and awareness campaigns and multidisciplinary teams to look at the problem start fixing it.

Simon: 1:37:09

Um, similarly with road traffic deaths, you know there's always that question of how much? How much more? Where do you need? Is there? Where's the baseline of just you're gonna get per hundred thousand of the population deaths? But it's understood that at about 12 000 years lost per hundred 000 of the population deaths. But it's understood that at about 12 000 years lost per 100 000 of the population. That that's somehow unacceptable. So we put a good amount of funding into fixing it because it's real people's lives that are being affected. Um, Indoor air quality sits at about 2,200, 2,300 currently. Um, so it should be intolerable. Um, it should be with even funding.

John: 1:37:51

It's also the same with outdoor air pollution. I mean this figures for an Iranian Island 1,400 premature deaths every year. Yeah, that's all Six times the amount of road deaths per year, right, um so yeah, we're talking the same kind of numbers. There's a road safety authority. Why isn't there an air pollution reducing authority?

Simon: 1:38:09

Well, there probably are. You know whatever, yeah and so on, yeah for sure.

John: 1:38:16

And so it isn't taken seriously enough, I suppose, by government departments and agencies, and I do think that we need to get better buy-in from politicians. I mean, things can come up from ground level, but you can only get so far. We tried that a lot during COVIDop, just thinking about what we did and we were, you know, prominent, we were on, we're in the radio and the newspapers or wherever else, and we were speaking to um, high level government officials, um, and in the end we had some impact, but not necessarily the impact that we wanted, right? No, and the lasting impact is minimal.

Simon: 1:39:06

Yeah, right, and you can see how delicate a thread this all hangs from. We see what's happening in science in the States at the moment defunding of institutions, defunding of research and you know this stuff can evaporate like the smoke in the air. So you know, when we get these chances to build momentum, we really have to seize them. Um, because it can so quickly, like we say, five years on, sometimes you wonder if it ever happened at all when you look around you, don't you on the, yeah, on the street and in there and so on. Yeah, really interesting. John, listen, it's been brilliant chatting to you, as it always is. Thanks so much for the time and thanks for arranging such a fabulous podcast studio. Yeah, where are we today? Just for listeners that are looking at this on video, what's the name of this?

John: 1:39:56

so this is the orla maxima, which means great hall. It's the original big hall in university college cork um, built in 1845, and so this is the big hall for functions in university, um ceremonies, award-giving ceremonies, presentations and um. It's a great place to be no, absolutely.

Simon: 1:40:17

Thanks. A million, john, appreciate it. You're welcome. Thanks for listening. Before you go, can I ask a favor? If you enjoyed the podcast and know somebody else who might be interested, do spread the word and let's keep building this community. This podcast was brought to you in partnership with Errico AECO, ultra Protect, imbiote and 21 Degrees All great companies who share the vision of the podcast and aren't here by accident. Your support of them helps them support this show. Do check them out in the links and in the show notes and at airqualitymattersnet, and don't forget to check out the youtube channel by the same name, with plenty more content due to come on that channel. Thanks very much. See you next week.