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California Environmental Health Tracking Program

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Last Edited: 9/29/2010

Asthma and the Environment

There is increasing evidence and awareness about the relationship between asthma and the environment.  Since there are many non-environmental factors that contribute to asthma, there have been efforts to estimate what proportion of the asthma burden is related to the environment.

  • In a study conducted by the World Health Organization, it is estimated that 44% of the asthma burden worldwide is due to the environment 1
  • In the U.S., an expert panel estimated that 30% of asthma exacerbations among children were related to the environment-- this was associated with an annual cost of $2.0 billion 2

While there is some evidence that environmental factors can cause asthma, we know much more about indoor and outdoor environmental factors that can exacerbate asthma symptoms or trigger asthma attacks. 

Indoor air quality

Indoor air quality in the home and workplace is a concern for people with asthma.

In the home, some indoor air pollutants, also known as asthma triggers, are associated with both the development and exacerbation of asthma, including3:

  • House dust mites
  • Environmental tobacco smoke
  • Cockroaches
  • Dander from cats

Other indoor air pollutants are known to trigger asthma attacks, such as:

  • Mold
  • Chemicals
  • Strong odors

At the state-level, efforts to improve indoor air environments are focused on schools, childcare centers, homes, institutional settings, and workplaces. These efforts involve reducing exposures to environmental triggers. To learn more about what the State is doing to address indoor environments and asthma, see Goal 4 in the Strategic Plan for Asthma in California 2008-2012 (PDF).


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Asthma and the workplace

Work-related asthma is asthma that can be caused or triggered by conditions or substances in the workplace.

  • In California, estimates indicate that 137,000 to 315,000 adults have asthma related to their work environment 4
  • Currently, there are approximately 350 substances known to cause new onset asthma in the work place

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Environmental tobacco smoke

Exposure to environmental tobacco smoke (ETS), also called second hand smoke, can cause symptoms and asthma attacks in both children and adults.

  • Exposure to ETS may also cause the development of asthma in children and adults 5,6
  • In 2005, the California Air Resources Board estimated that exposure to ETS contributes to 202,300 excess childhood asthma episodes or asthma attacks per year 7

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Outdoor air quality

Exposure to outdoor air pollutants are known to be associated with:

  • Asthma severity
  • Hospitalizations
  • Emergency department (ED) visits
  • Asthma deaths

Outdoor air pollutants may even by related to the risk of developing asthma.

An increase in asthma-related ED visits and hospitalization among both children and adults has been seen with exposure to 8-12.

Other pollutants related to increased asthma ED visits include8-12:

  • Carbon monoxide (CO)
  • Nitrogen dioxide (NO2)
  • Pollution from coal and petrochemical sources

The California Air Resources Board (ARB) estimates13:

  • Exposures to high levels of PM2.5 and ozone are associated with 81,000 to 320,000 cases of asthma and other respiratory symptoms annually
  • The economic cost of these cases is estimated to be between $1.6 and $6.2 million dollars annually 

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Climate Change

Climate change adversely impacts ambient temperature, levels of air pollution, and the amount of pollen in the air.  These are associated with asthma exacerbation14.

It is important to continue to track the impact of climate change in California, as this phenomenon will continue to have an impact on asthma and other health outcomes.


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1. Pruss-Ustun A, Corvalan C. Preventing disease through health environments. Towards an estimate of the environmental burden of disease. World Health Organization. 2006.
2. Landrigan PJ, Schechter CB, et al. Environmental Pollutants and Disease in American Children: Estimates of Morbidity, Mortality, and Costs for Lead Poisoning, Asthma, Cancer, and Developmental Disabilities. Environ Health Perspect. 2002:110:721-728.
3. Institute of Medicine Committee on the Assessment of Asthma and Indoor Air. 2000. Clearing the Air: Asthma and Indoor Air Exposures. Washington, DC: Institute of Medicine.
4. Flattery J, Sutton P, Harrison R, Stockman JK, Von Behren J, Kreutzer R. “Work-Related Asthma”. California Asthma Facts. August 2004: 2(2). Environmental Health Investigations Branch, California Department of Health Services.
5. Etzel RA, How Environmental Exposures Influence the Development of Exacerbation of Asthma. Pediatrics. July 2003:112(1): 233-240.
6. Thorn J, Brisman J, Toren K. Adult-onset asthma is associated with self-reported mold or environmental tobacco smoke exposures in the home. Allergy. Apr 2001;56 (4):287-292.
7. California Air Resources Board, 2005.
8. Peel JL, Tolbert PE, Klein M, et al. Ambient air pollution and respiratory emergency department visits. Epidemiology. 2005;16(2):164-174.
9. Norris G, VoungPong SN, Koenig JQ, et al. An association between fine particles and asthma emergency department visits for children in Seattle. Environ Health Perspect. 1999;107:489-93.
10. Sun HL, Chou MC, Lue KH. The relationship of air pollution to ED visits for asthma differs between children and adults. Am J Emerg Med. 2006;24:709-13.
11. Slaughter JC, Kim E, Sheppard L, et al. Association between particulate matter and emergency room visits, hospital admissions and mortality in Spokane, Washington. J Expo Anal Environ Epidemiol. 2005;15:153-9.
12. Villenueuve PJ, Chen L, Rowe BH, et al. Outdoor air pollution and emergency department visits for asthma among children and adults: A case-crossover study in northern Alberta, Canada. Environ Health. 2007;6:40.
13. Available on the California Air Resources Board website:

14. Babin SM, Burkhom HS, Holtry RS, et. al. Pediatric patient asthma-related emergency department visits and admissions in Washington D.C. form 2001-2004, and associations with air quality, socioecononmic status and age group. Environ Health. 2007: 6-9.