Why clean air

Why indoor air matters

One solution, three interventions.

Improving the air in schools is one of the few things that simultaneously improves education outcomes, reduces the society-wide burden of infectious and noncommunicable disease, and builds a society resilient to pandemics.

01 · Health

Dirty air is a leading cause of death and disease

Air pollution contributed to 7.9 million deaths in 2023, of which 6.8 million — 86% — were noncommunicable disease: chronic respiratory disease, heart disease, lung cancer, diabetes, and dementia.
More than 700,000 children under five died from causes linked to air pollution in 2021, making it the second-leading risk factor for death in that age group after malnutrition.
A child’s lungs are still developing, so the air they breathe in their earliest years shapes how those lungs work for life. Early respiratory infections make asthma far more likely.
232 million healthy years of life were lost to air pollution in 2023. Dementia alone accounted for more than 625,000 deaths.

02 · Learning

Unhealthy air is a tax on every hour of instruction

The smallest particles don’t stop at the lungs. They pass into the bloodstream and reach the brain, where they interfere with how children think, hold information, pay attention, and process what is in front of them.
Asthma affects about one in sixteen U.S. children and is a leading cause of chronic absenteeism, accounting for an estimated 13.8 million missed school days a year. Poor air quality, especially indoors, can trigger asthma flare-ups.
When pollution spikes on the day of a test, scores drop — from Tel Aviv to China. Filtering the air on test day alone improves performance.
In a randomized trial, air purifiers cut student absences 12.5%. Swedish daycares that installed them saw illness-related absences fall by more than a third.

03 · Pandemic resilience

We solved water and food. We never solved air.

In the late 1800s, U.S. cities invested billions in today’s dollars in water filtration and typhoid rates plummeted. Our food supply is so safe that outbreaks are national headlines. Airborne disease still travels freely through schools, daycares, offices, trains, and hospitals.
Biosecurity researchers rank airborne pathogens as the likeliest source of a truly catastrophic pandemic, because respiratory spread is the one transmission route fast enough to outrun quarantine, contact tracing, and border controls.
Lower respiratory infections caused 2.5 million deaths in 2023 — the fourth-leading cause of death across all ages, and the second-leading cause in children under five.
Children may be the index case in household transmission as much as 70% of the time.

This is tractable. Rising wildfire smoke, growing awareness of the cognitive gains from healthy buildings, and the acceptance of airborne transmission have moved indoor air from a niche engineering concern to a mainstream public-health, education, urban-governance, and economic issue. We can build a society resilient to pandemics by addressing needs people have today.

Read the underlying research

The diagnosis

The obstacles are structural, not technical.

We regulate the air outside schools far more seriously than the air inside them. Outdoor air has federal standards, monitoring stations, public alerts, and an Air Quality Index. A classroom full of children generally has none of those protections. During wildfire smoke the contradiction becomes obvious: officials tell children to go indoors, even though outdoor air becomes indoor air unless the building actually removes the pollution.

01

We do not measure it, so we cannot manage it

You can check outdoor air quality on your phone from a distributed monitor network. There is no equivalent for the room you are sitting in. This is changing faster than most problems on this list, because sensor prices have fallen sharply over five years and districts like Boston Public Schools have started publishing classroom-level data. But the default is still that a school has no idea how clean its air actually is.

02

No one has defined safe indoor air

This continues to surprise us every time we hear it. The United States, like most of the world, has no health-based standard for indoor air quality. We have lived through a respiratory pandemic. We are living through years of worsening outdoor air pollution reaching indoors. We have defined what safe levels of outdoor air and water quality are. And yet we still have not defined what a safe indoor space looks like, in schools or anywhere else.

03

The products sold to schools do not match what classrooms need

Together with the Center for Green Schools at the U.S. Green Building Council, we have run focus groups and interviews with district leaders, facilities managers, teachers, and state officials who deployed purifiers and sensors during the pandemic. Understandably, decision-makers were in a hurry and under significant pressure during an emergency, without clear school-appropriate specifications. Devices were often too loud, too weak for the room, awkward to place long term, or expensive to maintain — so staff turned them down or unplugged them.

04

No one is in charge of indoor air

No one has indoor air quality as a priority on their job description, whether for managing it in a building or for strategically overseeing policy. Most schools don’t have a person in charge of maintaining safe indoor air, city and state governments don’t have a point person, and the U.S. federal government has an overlapping alphabet soup of agencies with some involvement but no final ownership.

Thankfully, every one of these challenges has a fix.

The way forward

Schools are the most strategic place to start.

Cleaner air for our children means fewer sick days, higher test scores, healthier kids, and a society more resilient to airborne pandemics — for just a few dollars per student each year. Three things make schools the right first move.

Reason one

Physical scale

Education buildings represent 14% of all U.S. commercial floorspace, the largest share of any building category after warehouses and offices. America’s roughly 130,000 K–12 schools serve nearly 50 million public school students, plus millions more in private schools. Roughly a quarter of the population passes through a school building every day.

Reason two

Epidemiological importance

Children may be the index case in household transmission as much as 70% of the time. Clean the air where children gather and the benefit does not stop at the school gate — it follows them home, into workplaces, and across the community.

Reason three

Concentrated decisions

The 200 largest districts alone enroll over 14 million students, roughly 28% of all public school students. A small number of decisions reaches an extraordinary number of children, which makes this a problem philanthropy can actually move.

The evidence

Randomized trials, natural experiments, and cohort studies — including the inconvenient findings.

Research library

What we’re doing about it

A portfolio built to move from proof to policy to scale.

Our programs

Work with us

School leaders, funders, policymakers, researchers — the next step is a conversation.

Get in touch

The air indoors is invisible most days. It quietly determines our health and education outcomes.