Asthma and Air Pollution

This page last reviewed April 14, 2016

collage of air pollution and person with nazel spray

Asthma is a chronic lung disease that continues to be a health concern in California, the United States and many other countries around the world. Asthma is a condition in which an individual’s airways narrow, swell and produce extra mucus. This can make breathing difficult and trigger coughing, wheezing and shortness of breath. Children and certain racial groups, especially African Americans and Native Americans, have experienced relatively greater increases in asthma prevalence. Low income individuals also experience higher rates of asthma.

A national survey performed in 2010 found that the fraction of Americans ever diagnosed with asthma has been increasing in recent years, and that it reached 8.4% in 2010. This represents an increase of more than 15% between 2001 and 2010, or roughly 25.7 million Americans with asthma. The survey found that in California 13.1% of adults and 12.5% of children, collectively about 5 million people, reported that they had ever been diagnosed with asthma. In addition, nearly 692,000 California children reported experiencing current asthma symptoms.

There are many asthma triggers in addition to air pollution. These include pollens, dust mites, animal dander, and fragrances, among others.  Typically an individual asthmatic responds to a unique subset of asthma triggers.  Air pollution is a well-documented asthma trigger for some asthmatics; however, the role air pollution plays in initiating asthma is still under investigation and likely involves a complex set of interactions between indoor and outdoor environmental exposures and individual genetic susceptibility.

The Research Division of the Air Resources Board (ARB) has been a leader in developing and supporting research that seeks to improve understanding of the relationship between air pollution and asthma. ARB has funded a number of research studies investigating the influence of air pollution exposure on asthma. The table below lists a selection of these studies along with brief summaries of the study findings.

The largest study on children and asthma funded by ARB is the Children's Health Study, which was performed at the University of Southern California.  Among many findings, the study found that children who participated in several outdoor sports and lived in communities with high ozone levels were more likely to develop asthma than similarly active children living in areas with less ozone pollution. Also, children living near busy roads had an increased risk of asthma, and asthmatic children exposed to higher levels of air pollution were more likely to develop symptoms of bronchitis. Living in areas of high air pollution has been shown to cause measurable lung damage in children aged 10–18.Click on these links to go to the Children’s Health Study final report (Epidemiologic investigation to identify chronic effects of ambient air pollutants in Southern California.), project summary, and the USC Children’s Health Study webpage

Recent ARB-funded Studies on Air Pollution Exposure and Asthma

Click on the study title for more information on the study.

Risk of pediatric asthma morbidity from multipollutant exposures.This study found that emergency department visits and hospital admissions for asthma increased in children who experienced higher levels of PM2.5 and ozone exposure in summer, and higher levels of carbon monoxide, NO2, and NOx exposure in winter. Hispanic and African American children, and those without private insurance tended to live in areas with higher levels of traffic-related air pollution.
Is disparity in asthma among Californians due to higher pollutant exposures, greater susceptibility, or both? The study found that some lower income and minority groups are more impacted by air pollution due to higher exposures than other groups. The study also found that certain lower income and minority groups are more vulnerable to the effects of air pollution exposures than other groups at the same levels of exposures.
Effect of GSTM1 genotype on ozone-induced allergic airway inflammation.This study investigated the lung function and allergic responses to controlled ozone exposure in a group of allergic asthmatic adults. The results indicate that exposure to ozone can intensify responses to inhaled allergen. Contrary to expectations, the ability of the individual subject’s body to produce key antioxidants did not influence lung function or immune responses to ozone or allergen.
Traffic-related air pollution and asthma in economically disadvantaged and high traffic density neighborhoods in Los Angeles County, California.Higher levels of exposure to traffic air pollution increased the likelihood that a child had doctor-diagnosed asthma, used asthma medication, and had current wheeze, wheeze during the past year, orreduced measures of lung function. Children living in lower socioeconomic status neighborhoods had greater risk than those in more affluent neighborhoods. Differences between the responses of girls and boys suggest that gender may influence susceptibility to air pollution.
Traffic pollution and children's health: refining estimates of exposure for the East Bay children's respiratory health study.This was a study of children living at varying distances from high-traffic roads in Alameda County, California, a highly urbanized region characterized by good regional air quality due to coastal breezes. The highest risks of asthma were among those living within 75 m of a freeway/highway and those exposed to high levels of nearby traffic density. The findings support the conclusion that even in an area with good regional air quality, proximity to traffic is associated with adverse respiratory health effects in children.
Fresno Asthmatic Children's Environment Study (F.A.C.E.S.)The results from this study suggest an association between exposure to NO2 and both short and long-term reductions in lung function. Exposure to traffic derived air pollution was also associated with reduced lung function. Lung function tended to be better in children that lived further from busy roads, indicating that exposure to traffic-related air pollution could negatively impact lung function.

Click here for a list of all ARB-funded studies on air pollution and asthma.

General information and fact sheets on asthma


NHLBI (National Heart, Blood and Lung Institute) - Information on Asthma and Other Lung Diseases

American Lung Association - Asthma Information Page

Asthma information for kids from the American Academy of Allergy and Immunology

Asthma in Children: News from the National Institutes of Health

Asthma in the United States: Asthma data from the Centers for Disease Control and Prevention   

U.S. EPA - Asthma Resources


For more information please contact the ARB's Public Information Office at (916) 322-2990.