New research reveals how indoor air quality impacts child development

We often think of children’s health in terms of nutrition, vaccinations, and physical activity. But what about the air they breathe—especially indoors? A growing body of scientific evidence reveals that the quality of indoor air is a powerful, often overlooked determinant of early childhood development and long-term health.

More time indoors, more exposure

Today, most people spend over 90% of their time indoors—and this is even more true for pregnant individuals and young children. From homes and daycares to schools and vehicles, indoor spaces can harbor pollutants up to 5 times higher than outdoor levels, according to the U.S. Environmental Protection Agency (EPA).

These pollutants come from a surprising range of everyday sources: gas stoves, cleaning products, furniture, carpets, and even air that leaks in from outside. Add in poor ventilation, and you've got a recipe for chronic exposure to harmful airborne chemicals and particles.

Why children are more vulnerable

Children are not just "little adults." They breathe faster, inhale more air relative to their body size, and their organs and immune systems are still developing. This means they absorb more pollutants and are more sensitive to their effects.

The consequences?

Research links poor air quality to:

• Preterm birth and low birth weight due to prenatal exposure to gases like nitrogen dioxide

• Weakened immune systems from chronic inflammation caused by particles and allergens

• Lung development issues, limiting breathing capacity later in life

• Neurodevelopmental delays, with pollutants entering the brain and affecting memory, stress regulation, and emotional control

• Hormonal disruptions, potentially affecting puberty onset and thyroid function
  

“Too much inflammation for too long, especially when the organs and brain are still developing, can weaken the immune system and contribute to lifelong inflammatory conditions such as heart disease, diabetes, and autoimmune disorders.” — Harvard Center on the Developing Child, 2023

Air quality = brain quality

The science is clear: protecting children from air pollution isn't just about avoiding asthma. It's about supporting their brains, bodies, and futures.

A 2022 UNICEF report emphasized that 93% of the world’s children under 15 breathe air so polluted it poses serious health risks, and exposure begins in the womb. In high-income countries, indoor air pollution may be less visible—but it’s no less dangerous.

Adding to the evidence, a 2025 study by University College London followed over 9,000 children from the Millennium Cohort Study and found that exposure to air pollution—particularly fine particulate matter (PM2.5), nitrogen dioxide (NO₂), and other pollutants—between ages 2 and 4 significantly increased the likelihood of poor health by age 17. This includes heightened risks of chronic respiratory issues and diminished physical well-being. Even moderate exposure levels during this early life window had lasting effects on adolescent health outcomes.

“Early exposure to air pollution can have enduring consequences well into adolescence,” the study noted, highlighting the long developmental shadow of polluted environments.— University College London, as reported in The Guardian

This underscores that the damage from polluted air—especially indoors—may not show up right away, but it accumulates over time, shaping both health and opportunity.

a polluted city

Pollution + poverty = double risk to child development

Low-income communities and communities of color are at higher risk—not because of biology, but because of decades of discriminatory housing and zoning policies. Many families live in older, poorly maintained buildings and near sources of industrial or vehicular pollution. This isn’t just unfair—it’s a public health crisis.

What we can—and should—do

The good news? Solutions exist, and they work.

✅ Monitor indoor air quality

Using low-cost sensors in homes, classrooms, and daycare centers can help identify pollutants early.

✅ Switch to safer products

Opt for low-VOC paints and cleaning agents, and avoid items with flame retardants and phthalates.

✅ Use HEPA filters

Portable air purifiers with HEPA filters are a cost-effective way to improve air quality, especially when HVAC upgrades aren’t feasible.

✅ Build and retrofit healthier spaces

Proper ventilation, toxin-free materials, and integrated pest management all contribute to cleaner air indoors.

✅ Push for better policy and regulation

Local and national governments must prioritize indoor air quality—not just outdoor. This includes regulating emissions from gas stoves and vehicles, setting standards for childcare buildings, and investing in equitable housing improvements.

✅ Encourage regular outdoor time

While improving indoor air quality is essential, ensuring children spend time outdoors—when air conditions allow—can also support healthier development. The Onoco app is a helpful tool for parents and caregivers looking to build this habit. With Onoco’s Custom logs feature, you can easily track outdoor play or other activities that matter to your family. You choose the type of log, the icon, and the goal—giving you full control over what you want to monitor. Whether you’re logging daily walks, playtime in the park, or fresh-air naps, Onoco helps you stay intentional about your child’s environment and routines.

Air quality = brain quality

The science is clear: protecting children from air pollution isn't just about avoiding asthma. It's about supporting their brains, bodies, and futures.

A 2022 UNICEF report emphasized that 93% of the world’s children under 15 breathe air so polluted it poses serious health risks, and exposure begins in the womb. In high-income countries, indoor air pollution may be less visible—but it’s no less dangerous.

Take action now

Whether you're a parent, teacher, policymaker, or landlord, you have a role to play. Advocate for cleaner air in schools. Choose healthier materials for your home.

Because every breath a child takes shapes who they’ll become.

References

Harvard Center on the Developing Child. Air Quality Affects Early Childhood Development and Health: InBrief. 2023.

Environmental Protection Agency. The Inside Story: A Guide to Indoor Air Quality.

UNICEF. Danger in the Air: How air pollution can affect brain development in young children, 2017.

Harvard Healthy Buildings Program. 9 Foundations of a Healthy Building.