Air pollution has long been established to be bad for the health. Now a study adds one more reason to avoid it, warning expectant mothers against the danger that exposure may lead to their children developing autism later on.
It's not yet clear how air pollution manages to promote autism in children but it may have to do with a baby's brain development. Researchers found that cases of autism were likelier in children of women exposed to fine-particulate air pollution during their third trimester of pregnancy. This coincides with the time a baby's brain is developing, so one of the possible reasons is that air pollution interferes with the process, leading to autism in a child later on.
Carried out by researchers from the Harvard School of Public Health, the study involved women taking part in the Nurses' Health Study II, a pool of 116,430 female nurses in the United States recruited back in 1989, and their children born from 1990 to 2002. Children born to the participating women were randomly sampled, yielding 245 with autism and 1,522 without. Researchers also used air-quality data offered by the U.S. Environmental Protection Agency for estimations on monthly levels of pollution in the neighborhoods the participating women lived in before, during and after their pregnancy.
Exposure to air pollution is bad but researchers found that a certain type of pollution is to be blamed when it comes to increasing risks of developing autism spectrum disorders in children while they're still in utero. Fine-particulate pollution is caused by burning fossil fuels so car exhaust is a culprit, as well as industrial sources. Indoors, it's possible for fine-particle pollution to be produced by using fireplaces or burning candles.
While the link is there, researchers reiterated that there are several factors that can lead to autism spectrum disorders. These disorders are complex and may arise from a combination of genetic and environmental factors. It's definitely better for pregnant women to avoid fine-particle pollution (or all air pollution, for that matter) but doing so is not a guarantee that autism will not develop in a child.
Nevertheless, pregnant women are advised against walking along busy roads or staying near highways. If air quality is particularly poor, staying indoors is also recommended.
The study was published in Environmental Health Perspectives. Authors include: Marc Weisskopf, Francine Laden, Allan Just, Jaime Hart, Kristen Lyall, Andrea Roberts and Raanan Raz.
