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Your Environment. Your Health.

U.S.-Wide Study Links Autism with Prenatal Exposure to Fine Particulate Air Pollution

Francine Laden, Sc.D.
Harvard School of Public Health, Brigham And Women's Hospital
NIEHS Grants: P30ES000002, R01ES017017

In one of the first U.S.-wide studies of air pollution and autism, NIEHS grantees report that women exposed to high levels of fine particulate matter during pregnancy — particularly in the third trimester — may have up to twice the risk of having a child with autism than mothers exposed to low levels of particulate matter.

The study examined the children of people living in all 50 states who were part of the Nurses' Health Study II, a cohort of more than 116,000 U.S. female nurses. From this group, the researchers identified 245 children with autism and a control group of 1,522 children without autism. They collected data on where participants lived during pregnancy and then predicted their exposure to airborne particulate matter, using previously validated spatiotemporal models based on data from the U.S. Environmental Protection Agency Air Quality System and various other sources.

The analysis showed that exposure during pregnancy to particulate matter with diameters less than or equal to 2.5 microns was significantly associated with an increased risk for autism. Exposure before or after pregnancy did not show such association. The association was stronger for exposure experienced during the third trimester, compared to the first and second trimesters. The scientists found little association between larger-sized particle air pollution and autism.

The researchers say that their findings suggest that air pollution is a modifiable risk factor for autism, and that reducing exposure during pregnancy could help lower the incidence of this neurodevelopmental disorder.

Citation: Raz R, Roberts AL, Lyall K, Hart JE, Just AC, Laden F, Weisskopf MG. 2014. Autism spectrum disorder and particulate matter air pollution before, during, and after pregnancy: A nested case-control analysis within the Nurses' Health Study II Cohort. Environ Health Perspect; doi:10.1289/ehp.1408133 [Online 18 December 2014].