One Take #5 Clean Air, Full Classes

Research establishes a direct link between classroom air quality and student attendance rates through a comprehensive study of 144 classrooms across 31 Midwestern elementary schools. The findings provide compelling evidence that improved ventilation and lower PM2.5 levels significantly reduce illness-related absences, even at pollution levels previously considered acceptable.

• For every 1 L/s/person increase in ventilation rate, classrooms experienced 5.6 fewer absence days annually
• Average school ventilation rate (5.5 L/s/person) fell below ASHRAE's recommended standard of 7 L/s/person
• Each 1 μg/m³ increase in indoor PM2.5 corresponded to over 7 additional absence days per classroom per year
• Negative health effects occurred at PM2.5 levels below previous "acceptable" thresholds (mean: 3.6 μg/m³)
• Investing in school HVAC improvements represents a direct intervention to improve student attendance and achievement
• Benefits extend beyond education to public health, academic equity, and economic advantages for families
• Improved ventilation and filtration systems build resilience against future airborne health challenges

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Associations between illness-related absences and ventilation and indoor 
PM2.5 in elementary schools of the Midwestern United States

Chapters

• 0:14 Welcome to Air Quality Matters
• 0:37 Study Links School Air to Attendance
• 1:42 Research Methodology and Scale
• 2:48 Key Findings on Ventilation
• 5:15 PM2.5 Impact on Absence Rates
• 6:30 Economic and Educational Implications
• 8:16 Conclusion and Future Applications

Transcript

Simon: 0:14

welcome back to air quality matters, and one take one take my take on a paper or report on air quality, ventilation and the built environment. One One take in that it's well one take and tries to summarise for you a scientific perspective on something interesting in well, usually 10 minutes or less, because who has the time to read all these amazing documents? Right, this week we're diving into a paper that really gets to the heart of something we all intuitively know but often struggle to quantify the direct link between the air in our schools and how often our kids are actually in their seats learning. It's a powerful piece of research that gives us some really solid numbers to work with, moving the conversation beyond the generalities about healthy buildings. Quote unquote the paper is from the journal Environment International and it's called Associations Between Illness-Related Absences and Ventilation and Indoor PM 2.5, in elementary schools of the Midwestern United States. It's by Shihan Deng and a team of researchers including Josephine Lau and Pavulwa Gokhi, names that many of us in the field will certainly recognise, and what they've done here is, frankly, exactly the kind of large scale real world study we need more of. So let's set the scene, because the context is everything we know.

Simon: 1:50

Children are not just little adults. They're more vulnerable to environmental conditions, their bodies are still developing, they breathe more air relative to their body size and they spend a huge chunk of their lives something like 200 days a year inside school buildings. When we talk about school performance, we often focus on the curriculum, teaching methods or funding, but what if one of the most fundamental factors is the very air the students and teachers are breathing all day? Absenteeism is the perfect metric to study this, because it's a hard outcome. It's not subjective. A child is either in school or they're not, and when they're absent due to illness, it has knock-on effects to their academic achievement, for their parents who might have to miss work, and for the entire classroom dynamic. So the core question this paper asks is simple but profound Can we draw a direct measurable line from classroom ventilation rates and particulate matter levels to the number of illness related absences? To answer this, the research team did a pretty comprehensive job.

Simon: 3:05

This wasn't a small scale lab study. They monitored 144 classrooms across 31 different elementary schools in the US Midwest. That's data covering over 3000 pupils. For two years they went into these classrooms third and fifth grade and measured the indoor environment in the fall, winter and spring they tracked carbon dioxide levels, which they used as a proxy to calculate the outdoor air ventilation rate. They also measured indoor particulate matter, specifically pm 2.5, as well as temperature and humidity. Critically. They worked with the school districts to get anonymised daily absence data for every pupil, specifically coded for illness and medical reasons. This is the crucial link. They then used some robust statistical analysis, a multi-level model for those interested to see if the environmental data could predict the absence data while controlling for things like class size and grade. And this is where it gets really interesting. They found a direct, statistically significant link to, in fact.

Simon: 4:13

First let's talk about ventilation. The study found that for every litre per second per person increase in the ventilation rate, the classroom saw, on average, about 5.6 fewer days of absence over the entire school year. Let that sink in for a minute. That's a real, tangible effect. We're not talking about a vague sense of freshness or cognitive performance. We're talking about a measurable reduction in sick days, just by supplying more outdoor air. The average ventilation rate they found, by the way, was 5.5 litres a second per person, which is below the current ASHRAE recommendation of about 7 litres a second. So these schools weren't horrendously underventilated, but they were certainly below the modern standard and the data shows it's having a real impact on health.

Simon: 5:09

But the study didn't stop at ventilation, and for me this is arguably the most critical part of the paper. They looked at indoor PM 2.5 and the relationship they found was just as strong For every additional one microgram per meter cubed of indoor PM 2.5, there was an increase of over seven days of absence per year per classroom. And here's the kicker, and this is the point we cannot afford to miss. The average PM2.5 concentrations they measured were already quite low. The mean was 3.6 micrograms per cubic metre. That's below the old WHO annual guidance of 10 and very close to the new, much stricter guideline of 5. What this tells us is that these negative health effects, which are significant enough to make children miss school, are happening at particular levels that many would have previously considered good or at least acceptable. It strongly suggests that when it comes to PM2.5, especially for vulnerable populations like children, there's likely no safe threshold. Every little bit matters. So what's the big picture here? What are the implications? Well, they're huge. Potentially. This study provides a powerful, evidence-based argument for something we in the industry have been saying for years Investing in school infrastructure, specifically ventilation and filtration, isn't a cost.

Simon: 6:46

It's an investment with a clear return. The return is in public health. Investment with a clear return, the return is in public health, in academic equity, and it has real socio-economic benefits. Fewer sick days for kids means better learning outcomes and less disruption. It also means fewer days that parents have to take off work to take care of sick children, which is a massive economic factor for families as well. This paper essentially hands a toolkit to school administrators, policy makers and parent-teacher associations when a school district is deciding on budgets.

Simon: 7:23

This research says that upgrading the HEVAX system to provide adequate ventilation and better filtration like moving from MERV 8 to 13, for example isn't just a maintenance issue. It's a direct intervention to improve student attendance and, by extension, student achievement. And, of course, in a world grappling with the lessons of COVID-19, this is more relevant than ever. The mechanisms that reduce illness related absences diluting indoor pollutants and filtering out particles are the exact same mechanisms that reduce the transmission of airborne respiratory pathogens. So the benefits are twofold you improve the day to day health and attendance of students and you build a more resilient school that is better prepared for future health challenges.

Simon: 8:11

So the bottom line of this paper is pretty clear and powerful. It's not just a theory anymore. Better ventilation and lower indoor PM2.5 levels don't just create a nicer environment. They directly translate into fewer sick days for elementary school students. The effects are measurable, significant and could occur even at low levels of pollution.

Simon: 8:36

Of course, the authors are careful to note the limitations the measurements were a snapshot in time, not continuous, and they relied on standard proxies for ventilation and particle mass. But given the scale of the study and the robustness of the analysis, the findings are incredibly compelling. Nonetheless, for me, it reinforces a fundamental truth the physical environment of a school is not separate from the educational mission. It's an integral part of it. This study provides the kind of hard data that helps us make the case, moving it from a nice-to-have to an absolute essential, because, ultimately, the air our children breathe is just as fundamental to their education as the books they read or as the teachers who inspire them. Thanks for listening. Do tune in next week for another one take. And a million thanks to our sponsors, safe Traces, who, without them, this podcast wouldn't be possible. See you next week.