Coarse particulate matter may increase asthma risk
Dec. 12, 2017–Children exposed to coarse particulate matter may be more likely to develop asthma and to be treated in an ER or be hospitalized for the condition, according to new research published online in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
In "Long-term Coarse PM Exposure Is Associated with Asthma Among Children in Medicaid", researchers report that coarse particulate matter, the kind of air pollution created by physical processes such as tire and break wear, agricultural tilling, salt spray and dust created in manufacturing, appears to put children at greater risk for asthma, independent of exposure to fine particulate pollution.
Coarse particulate matter (PM10-2.5) measures from 2.5 to 10 micrometers; fine particulate pollution (PM2.5) measure 2.5 micrometers or smaller. By comparison, a human hair is between 50-70 micrometers thick.
The authors noted that there is substantial evidence that PM2.5 impacts respiratory and cardiovascular health, and this is why the Environmental Protection Agency monitors and regulates fine particulate pollution.
"We did this study to understand whether, in addition to PM2.5, coarse particulate matter contributes to asthma development and morbidity," said Corinne A. Kent, MD, PhD, lead study author and associate professor of pediatric allergy and immunology at Johns Hopkins University School of Medicine. "The most recent assessment by the EPA concluded that there wasn't enough data to say one way or another whether PM10-2.5 causes negative health effects."
The researchers analyzed the records of 7,810,025 children (age 5 to 20) living across the country who were enrolled in Medicaid over a two-year period, 2009-2010. The researchers adjusted their findings for race and ethnicity, sex, age, poverty, education and how urban the neighborhood the children lived in was. The researchers also accounted for PM2.5.
The study found for each microgram/m3 increase in PM10-2.5:
- asthma diagnosis increased by 0.6 percent,
- ER visits for asthma increased by 1.7 percent, and
- hospitalizations for asthma increased by 2.3 percent.
These findings were even stronger for children 11 and younger. The authors speculate that the stronger association is a result of asthma typically developing at younger ages and that young children are more likely to spend time outdoors and be harmed by air pollution.
The authors said that study limitations include the fact that there are few locations that monitor PM10-2.5. Most monitors measure only PM2.5, which the current study found was even more likely to be associated with an asthma diagnosis, ER visits and hospitalizations. The researchers used statistical methods to predict concentrations of PM10-2.5 across the U.S. This allowed them to study such a large number of children, including those who do not live near a monitor.
"The first-ever analysis of the long-term effects of coarse particulate matter on asthma," the authors wrote, "provides evidence supporting the harmful effects of coarse particulate matter on respiratory health."
Dr. Keet noted that the EPA is currently conducting a comprehensive review of the science related to the health effects of particulate matter as mandated by the Clean Air Act. "Reductions in PM2.5 have led to improvements in childhood respiratory health, but there is still a great burden of asthma in children," she said. "Our findings, along with others, suggest that PM10-2.5 likely contributes to asthma, too, and that regulation and monitoring of coarse particulate matter should be considered."
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About the American Journal of Respiratory and Critical Care Medicine (AJRCCM):
The AJRCCM is a peer-reviewed journal published by the American Thoracic Society. The Journal takes pride in publishing the most innovative science and the highest quality reviews, practice guidelines and statements in pulmonary, critical care and sleep medicine. With an impact factor of 12.996, it is the highest ranked journal in pulmonology. Editor: Jadwiga Wedzicha, MD, professor of respiratory medicine at the National Heart and Lung Institute (Royal Brompton Campus), Imperial College London, UK.
About the American Thoracic Society:
Founded in 1905, the American Thoracic Society is the world's leading medical association dedicated to advancing pulmonary, critical care and sleep medicine. The Society's 15,000 members prevent and fight respiratory disease around the globe through research, education, patient care and advocacy. The ATS publishes three journals, the American Journal of Respiratory and Critical Care Medicine, the American Journal of Respiratory Cell and Molecular Biology and the Annals of the American Thoracic Society.
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