Most people in the U.S. spend the vast majority of their time indoors, and studies by the U.S. Environmental Protection Agency (EPA) indicate that indoor levels of air pollutants may be substantially higher than outdoor levels. Air pollutants from outdoor sources such as vehicles, industrial facilities, and wildfires can enter a building through open windows and other openings in the building envelope. Indoor sources of air pollutants include combustion devices, building materials and furnishings, household and personal care products, tobacco products, and mold/dampness. In addition, infectious aerosols can spread and accumulate indoors. US EPA, Why Indoor Air Quality is Important to Schools; US EPA, Introduction to Indoor Air Quality.
A range of serious health effects are associated with common indoor pollutants like particulate matter, radon, lead, mold, secondhand smoke, nitrogen dioxide, and volatile organic chemicals. These health effects include respiratory problems, cardiovascular disease, headaches, fatigue, skin problems, neurological impairment, developmental disorders, and cancer. NIEHS, Indoor Air Quality; US EPA, Introduction to Indoor Air Quality; Calif. Air Resources Bd., Comprehensive Indoor Air Quality Report.
Children are particularly vulnerable to the health effects of indoor air pollutants since their bodies are still developing and they have relatively higher rates of breathing and metabolism. The estimated 25 million people in the U.S. who have asthma are also at higher risk from exposure to certain indoor pollutants, and the health burden of that disease falls disproportionately on people of color and low-income children and adults. People of color are also disproportionately represented in communities with the highest levels of ambient fine particulate matter and ozone. US EPA, America’s Children and the Environment; CDC, Most Recent National Asthma Data; AAFA, Asthma Disparities; American Lung Association, State of the Air.
Climate change may exacerbate the already significant health and economic impacts of indoor air pollution, as communities experience more frequent and intense heat waves, wildfires, storms, and precipitation. Those who are most vulnerable to climate change and its adverse effects on indoor environmental quality include people “who have less economic ability to adapt to or mitigate the effects of changes in their indoor environment and those whose age or health status renders them more susceptible to environmental stresses or insults.” The National Academies, Climate Change, the Indoor Environment, and Health.
Policies to control ambient air pollution are important for reducing indoor exposures. But policies are also urgently needed to address indoor air quality directly. One important strategy is to control key indoor sources of pollutants. Another is to reduce exposure to pollutants by ensuring adequate outdoor air ventilation and air filtration to dilute and remove indoor contaminants like particulate matter and infectious aerosols. US EPA, Improving Indoor Air Quality; Berkeley Lab, Building Ventilation.
While agencies at all levels of government have important roles to play in reducing indoor air risks, it is especially important for states to establish built environment standards and practices. Multiple state agencies, from public health and education to labor and building codes, have authorities that could be used to develop IAQ policies and programs. Many states have adopted IAQ-related measures – including a number of policies and programs spurred by climate change and the COVID-19 emergency – but there remains a clear need for stronger state policies and programs.
ELI's Indoor Environments Program has developed a wide range of materials that highlight existing policy examples and discuss considerations for establishing key elements of an effective IAQ policy: required standards and practices, adequate oversight and enforcement, and financial and technical assistance for implementing evidence-based practices to prevent and fix IAQ problems.
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