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Less Air Pollution in Southern California Linked to Less Asthma in Children

MedicalResearch.com Interview with:

Erika Garcia, PhD, MPHPostdoctoral ScholarDivision of Environmental HealthDepartment of Preventive MedicineKeck School of MedicineUniversity of Southern CaliforniaLos Angeles, CA 90089-9237

Dr. Garcia

Erika Garcia, PhD, MPH
Postdoctoral Scholar
Division of Environmental Health
Department of Preventive Medicine
Keck School of Medicine
University of Southern California
Los Angeles, CA 90089-9237

MedicalResearch.com: What is the background for this study?

Response: It is known that air pollution can exacerbate pre-existing asthma, but what is not yet established is whether air pollution exposure contributes to the development of new cases of asthma. There is increasing scientific evidence supporting a role of air pollution in asthma development.

In this study we examined whether reductions in air pollution levels in Southern California were associated with subsequent reductions in rates of new-onset asthma in children. We separately evaluated four pollutants: nitrogen dioxide, ozone, coarse particulate matter (PM10), and fine particulate matter (PM2.5).

MedicalResearch.com: What are the main findings?

Response: We found that lower air pollution levels were related to lower rates of new-onset asthma in children. Between 1993 and 2006 there was an average reduction in nitrogen dioxide of 22% (4.3 ppb) and this corresponded with a 20% decline in the rate of new asthma cases. Similarly, for fine particulate matter the average reduction was 36% (8.1 ug/m3) and this was related to a 19% lower asthma rate. Findings were not limited to any specific subgroup of children; that is, there was no evidence that the findings were driven by a subgroup of children or that they would be different between different groups of children, such as boys compared with girls. We tested the robustness of the results by conducting sensitivity analyses to see if the results held up under different analysis assumptions. Results for nitrogen dioxide were robust, while those for fine particulate matter were less robust.

MedicalResearch.com: What should readers take away from your report?

Response: The study’s findings are encouraging because they show a clear benefit of lower air pollution levels. And it supports the idea that the number of new asthma cases in children can be reduced through improvements in air quality. That being said, there must be continued efforts to reduce air pollution in the Los Angeles region as well as other high pollution areas. The greater Los Angeles region ranks as one of the most polluted regions in our country for fine particulate matter and ozone. And in the past few years we’ve already seen an uptick in nitrogen dioxide levels in the South Coast Air Basin. With more people and more cars, and ports getting busier, air pollution may continue to increase.

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: Given improvements in air quality throughout the U.S. and around the world in the past several decades, it would be beneficial to examine whether the same trends of lower air pollution and lower rates of asthma are observed elsewhere. Furthermore, examining age windows of exposure could provide us with a better sense of when children are most vulnerable to the effects of air pollution exposure in the development of new-onset asthma.

MedicalResearch.com: Is there anything else you would like to add?

Response: In the United States 1 in 12 children has asthma. Asthma may affect the child’s long-term health, ability to attend school, and parents’ work attendance, and it imposes an economic burden due to medical costs of treatment and school or workplace absenteeism. Exposure to air pollution is widespread; everyone is exposed. This study looked at over 20 years of data in Southern California children and found that reductions in air pollution were linked with lower rates of new-onset asthma in children. This was a nice quantification of the public health benefit of air quality improvements of the last couple decades in Southern California. Reductions in childhood asthma could have economic, long-term health, quality of life, and overall societal benefits.

No disclosures. 


Garcia E, Berhane KT, Islam T, et al. Association of Changes in Air Quality With Incident Asthma in Children in California, 1993-2014. JAMA. 2019;321(19):1906–1915. doi:10.1001/jama.2019.5357


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Jun 1, 2019 @ 12:43 am




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