Dr. Albert Rizzo: Welcome back to Lungcast, the monthly respiratory health podcast series from the American Lung Association and medical news site HCP Live. I'm your host, Dr. Albert Rizzo, Chief Medical Officer of the American Lung Association.
If you're watching this on YouTube, be sure to subscribe to our channel at Lungcast to get updates on new episodes and interview segments. If you're listening on your podcast player, you can do the same there. You can also access more Lungcast episodes and segments at HCP.com and Lung.org.
Ambient air pollution has been a recurring national story this past year, with West Coast and Canadian wildfires leading to harmful air exposure risks for many Americans. But as our country's focus on climate-related respiratory health grows, it's critical not to forget the impact of indoor air pollution.
Most people are aware that outdoor air pollution can impact their health, but indoor air pollution can also have significant and harmful effects. EPA studies indicate that indoor levels of pollutants may be two to five times, and sometimes as high as 100 times, higher than outdoor air levels. This is especially concerning because most people spend about 90% of their time indoors.
Today's topic looks at indoor air pollutants that are less visible than wildfire smoke, such as mold and toxic chemicals like asbestos. We'll focus on a segment of our population who may be more impacted based on age and development: children in school environments.
To guide us, we are joined by Professor Mark Hernandez, the SJ Archuleta Professor of Civil and Environmental Engineering and Director of the Aerobiology and Disinfection Lab at the University of Colorado.
Dr. Albert Rizzo: Dr. Hernandez, thank you for taking the time today.
Dr. Mark Hernandez: Good morning, thanks for having me.
Dr. Albert Rizzo: Nearly 57.5 million students and school employees enter the doors of our nation’s schools every day. According to the US EPA, half of these adults and children spend their school days breathing air polluted with toxic chemicals, mold, viruses, bacteria, asbestos, pesticides, smog, particulates from vehicle pollution, and more.
Before we discuss the health impacts of poor indoor air quality, Dr. Hernandez, could you tell us what you feel are the leading indoor air quality issues schools need to address?
Dr. Mark Hernandez: If we're talking priority, I’d start with ventilation, which I measure through CO2 levels—essentially the amount of stale breath that builds up during routine occupation. CO2 trends often correlate with other airborne particles, although smog is mostly outdoor-related. Many indoor pollutants are generated by occupant activity. So CO2 measurements are a good proxy for fresh air levels and are reflected in current professional guidelines from societies like ASHRAE and the CDC.
Dr. Albert Rizzo: Some school buildings are new, some old, and resources vary across districts. What advice would you give administrators for where to start addressing indoor air quality?
Dr. Mark Hernandez: Building age doesn’t always indicate air quality. Some older buildings have excellent ventilation, while some newer energy-efficient buildings are tightly sealed. The key is to measure the air quality—you can’t manage what you don’t measure. The simplest measurement is carbon dioxide, which gives a good baseline for ventilation and air exchange.
Dr. Albert Rizzo: That makes sense—similar to how doctors don’t judge patients by appearances alone.
Dr. Mark Hernandez: Exactly. Metrics are crucial.
Dr. Albert Rizzo: Let’s shift to how indoor air quality impacts children’s health. Nearly 1 in 13 school-age children has asthma, a leading cause of school absenteeism. Indoor allergens, dust, pests, mold, and diesel exhaust from school buses can exacerbate asthma and allergies. Can you also comment on non-respiratory effects, like cognitive function?
Dr. Mark Hernandez: There are several points here. While I’m an engineer, not a medical doctor, epidemiological surveys show higher asthma rates in areas with high industrial activity, construction dust, and diesel pollution. Allergy and asthma triggers worsen outcomes, especially for children—they are not just small adults.
From a building science perspective, the goal is to bring in as much fresh air as possible while filtering outdoor pollutants. This helps reduce indoor-generated particles, including bacteria, fungi, and dust. Essentially, bring in fresh, particle-free air and displace the stale indoor air.
Emerging research shows that high CO2 levels alone can reduce cognitive function. Students get tired faster and may perform worse academically. The solution is better ventilation with measurable and consistent air exchange.
Dr. Albert Rizzo: How often are these air quality measurements reviewed by school districts? Is it regulated?
Dr. Mark Hernandez: I wish it were regulated, but many districts are catching on. Monitoring is not expensive—about $60 per classroom per year. Large districts, like Montgomery County, have deployed 10,000 monitors, and others in Colorado and California are doing the same. The data show that many classrooms already perform well, but monitoring allows districts to prioritize rooms needing mitigation, a cost-effective and evidence-based approach.
Dr. Albert Rizzo: Did the COVID-19 pandemic change how schools approach ventilation?
Dr. Mark Hernandez: It raised awareness. We should have been doing this anyway. Think of buildings like cars—you wouldn’t drive without a dashboard. The pandemic highlighted that fresh air reduces infection risk and improves outcomes for students with allergies or asthma.
Dr. Albert Rizzo: Especially for children, who cannot choose whether to be in a building.
Dr. Mark Hernandez: Right. Children deserve dashboards that show real-time air quality. Facilities managers are responsible for ensuring the air quality is as good as possible. Some districts, like Boston and Denver, are leading the way.
Dr. Albert Rizzo: Health equity is a concern too—resources vary across districts.
Dr. Mark Hernandez: Absolutely. Air is the equalizer—you can’t choose what you breathe. Monitoring allows districts to target interventions, like in-room air filters, where they are most needed. Colorado deployed 30,000 classroom filters based on monitoring data. These solutions are affordable and practical.
Dr. Albert Rizzo: Are there signs parents or healthcare providers should watch for that indicate poor air quality may be affecting a child?
Dr. Mark Hernandez: I’m not a medical doctor, but fatigue and tiredness can be indicators. Monitoring air quality directly is more effective than looking for symptom clusters. We are currently studying absenteeism in conjunction with the University of Colorado Medical School to see if improved air quality reduces respiratory-related absences.
Dr. Albert Rizzo: Advocacy by parents and healthcare providers seems important.
Dr. Mark Hernandez: Yes, and Boston’s live dashboard is a great example. Air quality issues are long-term exposure concerns. Short-term measurements are less helpful; what matters is seasonal, consistent monitoring and comparison to guidelines.
Dr. Albert Rizzo: Are these guidelines publicly available and understandable?
Dr. Mark Hernandez: Yes. Professional societies like ASHRAE and the CDC, along with universities and NGOs, provide guidance on air exchange rates, CO2 levels, and particulate matter, adapted for indoor environments.
Dr. Albert Rizzo: Thank you, Dr. Hernandez, for your insights. Indoor air quality is often overlooked but incredibly important.
Dr. Mark Hernandez: Thanks for having me. I enjoyed the interview.
Dr. Albert Rizzo: Until next time, remember: if you can't breathe, nothing else matters.
