Kidsdata.org offers the following measures of air quality:

• Number of Days with Ozone Levels Above Regulatory Standards
• Annual Average Particulate Matter Concentration

Air pollution is a serious environmental threat to children’s health (1). Recent research has shown that environmental contaminants can put children at risk of developing serious illnesses (2). Exposure to air pollution, especially at high concentrations and durations, is related to increased risk of respiratory problems, heart disease, cancer, and adverse reproductive or pregnancy outcomes, among other health problems (1, 2, 3). Children are more vulnerable to pollutants because, compared to adults, they breathe more air relative to their size, and thus experience greater proportionate exposure to chemicals (2). In addition, children are at greater risk of harm from contaminants because their bodies and organs are not fully developed (2).

Air pollution can occur outdoors or indoors. Examples of outdoor pollutants include fine particles in the air (from motor vehicles, industrial sources, etc.), ground-level ozone (a primary component of smog), noxious gases, and tobacco smoke (3). Examples of indoor air pollution include carbon monoxide, household chemicals, building materials, allergens (e.g., cockroaches, animals, dust, etc.), mold, and tobacco smoke (3). Among common outdoor air pollutants, fine particulate matter and ground-level ozone are considered the most widespread threats to human health, according to the U.S. Environmental Protection Agency (4).

Ground-level ozone—a primary component of smog which is formed from pollutants emitted by cars, power plants, and other sources—poses considerable health risks. In 2016, California counties averaged 22 days with ozone concentrations above the U.S. regulatory standard, down from 44 days in 1980. Of the 49 California counties with data in 2016, 13 did not record any days when ozone levels exceeded regulatory standards. However, six counties, all in Southern California and the Central Valley, recorded 60 or more such days.

Despite year-to-year fluctuations, California’s annual average concentration of fine particulate matter (PM 2.5) in the air has declined overall, from 17.6 micrograms per cubic meter (µg/m³) in 1999 to 9 µg/m³ in 2016, echoing national trends. PM 2.5 levels also vary widely among counties for which data are available; in 2016, the annual average concentration of PM 2.5 ranged from 2.9 µg/m³ in Lake County—well below the federally recommended limit of 12 µg/m³—to 15.9 µg/m³ in Kern County.

Pound for pound, children are more vulnerable to toxic chemicals in the environment when compared to adults (1, 2). Exposure to air pollutants may lead to long-term health problems, including respiratory diseases, cancer, and heart disease (1, 2, 3, 4). Indoor air quality at home and in child care and school settings is also critically important, as it has been shown to affect children’s health and academic performance (2).

Policy options to improve air quality, and children’s environmental health overall, include:

• Continuing to enforce and strengthen laws and regulations that limit the generation of vehicle emissions and other contaminants, along with agricultural and industrial practices that cause air pollution and pesticide exposure (2, 5)
• Improving and promoting effective implementation of policies and guidelines that control indoor air quality in schools and child care settings, addressing issues such as mold, chemical exposure, pest control, building ventilation, and hazardous building materials (6, 7)
• Focusing broadly on multiple deficiencies and hazards in housing environments and early childhood settings—e.g., advancing strategic partnerships among organizations focused on health, housing, education, and environmental protection—rather than focusing on single factors, such as lead exposure (6, 8)
• Supporting public education about the health risks of poor indoor environments and how to make improvements; also, supporting workforce development, training, and assistance for professionals in multiple sectors (e.g., housing, child care, etc.) to address indoor health hazards (6, 8)
• Continuing to support research on the connections between the environment and children’s health, as well as effective strategies to improve environmental health (2, 6, 8)