Something in the Air: Autism Risk May Be Tied to Pollution

Autism risk may be tied to fine particulate matter exposure in pregnant women

(RxWiki News) Researchers may be one step closer to understanding what causes autism. The possible cause? Air pollution.

A new Harvard study found that pregnant women — particularly those in their third trimesters — who were exposed to a type of air pollution faced a raised risk of having a child with autism.

Researchers are unsure of the exact cause of autism. It is believed that genetics play a large role, while others propose that environmental factors — like air pollution — contribute to the disorder.

"Our data add additional important support to the hypothesis that maternal exposure to air pollution contributes to the risk of autism spectrum disorders," said study author Marc G. Weisskopf, ScD, PhD, associate professor of environmental and occupational epidemiology at the Harvard School of Public Health in Boston, in a press release.

Autism is a neurodevelopmental disorder in which a child shows reduced social skills, poor verbal and nonverbal communication and repetitive behavior (such as stacking up objects over and over again).

This study found that pregnant women exposed to high amounts of fine particulate matter faced a nearly fifty percent greater risk of having an child with autism than those exposed to low amounts.

Fine particulate matter can include a number airborne contaminants that measure 2.5 microns wide or smaller. One micron is equal to 0.001 millimeters, or about 0.000039 inches.

According to the US Environmental Protection Agency (EPA), fine particulate matter is made up of tiny particles and liquid droplets, such as acids, chemicals, metals, and small pieces of dust or soil. It is often found in smoke and haze from sources like forest fires, power plants and other industry emissions and car exhaust. Air pollution particles smaller than 10 microns can easily pass through the nose and throat, entering the lungs and causing serious health issues that affect the heart and lungs, the EPA notes.

Dr. Weisskopf and team worked with data from a past study of the health of 116,430 US female nurses. These researchers identified 245 children born with autism from 1990 to 2002 in the study group. They then collected data on where the nurses lived during the span of their pregnancies. They also gathered data on the air pollution levels of particulate matter in those areas at that time.

Women exposed to high levels of particulate matter during pregnancy were more likely to have a child with autism than women exposed to low levels.

These findings suggest a tie between pollution and autism, but they do not confirm that pollution causes the disorder.

The raised chance of having a child with autism only appeared in women exposed to pollution during pregnancy. Exposure to fine particulate matter nine months before or after pregnancy did not appear to affect the chance of having a child with autism.

While all trimesters appeared to be affected by pollution exposure, Dr. Weisskopf and colleagues studied which trimester was most affected. They found that women exposed in their third trimesters were most at risk. They were 1.42 times more likely to have a child with autism than those in their first trimesters. Women exposed to particulate matter in their second trimesters were 1.06 times more at risk of having a child with autism than those in their first trimesters.

Dr. Weisskopf and team noted that they did not have access to data about indoor and home pollution exposure or the sources of the pollution.

This study was published Dec. 18 in Environmental Health Perspectives.

The Environment and Health Fund (Israel), the National Institutes of Health, and the Autism Speaks Foundation funded this research. The authors disclosed no conflicts of interest.

Review Date: 
December 17, 2014