Air Quality: Days with Ozone Levels Above Regulatory Standard

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Alameda County
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Learn More About Air Quality

Measures of Air Quality on
Note: The information presented in this topic is not exhaustive of all relevant data and has limitations. For example, air quality is not monitored in all counties, which makes computing state-level figures problematic. In addition, indoor air quality, an important factor in children's environmental health, is not measured on

These data are offered in order to draw attention to the environmental influences on children's health and to encourage exploration of the issues. Indicators will be revised as new data emerge.
Air Quality
Lead Poisoning
Water Quality
Why This Topic Is Important
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).
For more information about air quality, see’s Research & Links section.

Sources for this narrative:

1.  Centers for Disease Control and Prevention. (2017). Health impacts of fine particles in air. Retrieved from:

2.  California Environmental Health Tracking Program. (2015). Costs of environmental health conditions in California children. Public Health Institute. Retrieved from:

3.  National Institute of Environmental Health Sciences. (2017). Air pollution. Retrieved from:

4.  U.S. Environmental Protection Agency. (2017). Criteria air pollutants. Retrieved from:
How Children Are Faring
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.
Note: Children’s environmental health is an emerging area of research, and the data currently available give a limited picture of how children in California are faring. In many cases, county-level data are not specific enough to inform conclusions about children’s health risks, but they can spark further inquiry.
Policy Implications
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)
For more information on air quality and children’s environmental health, see’s Research & Links section, or visit the U.S. Environmental Protection Agency, the California Environmental Health Tracking Program, or the Children’s Environmental Health Network. Also see policy implications for Asthma on

Sources for this narrative:

1.  California Environmental Health Tracking Program. (2015). Costs of environmental health conditions in California children. Public Health Institute. Retrieved from:

2.  U.S. Environmental Protection Agency. (2013). America’s children and the environment (3rd ed.). Retrieved from:

3.  Centers for Disease Control and Prevention. (2017). Health impacts of fine particles in air. Retrieved from:

4.  National Institute of Environmental Health Sciences. (2017). Air pollution. Retrieved from:

5.  California Environmental Protection Agency, Air Resources Board. (2017). Laws and regulations. Retrieved from:

6.  Environmental Law Institute, & Children’s Environmental Health Network. (2015). Reducing environmental exposures in child care facilities: A review of state policy. Retrieved from:

7.  U.S. Environmental Protection Agency. (2016). State school environmental health guidelines. Retrieved from:

8.  Centers for Disease Control and Prevention. (2015). Healthy homes. Retrieved from:
Websites with Related Information
Key Reports and Research
County/Regional Reports
More Data Sources For Air Quality