A New Study Links Air Pollution to Autism

December 26, 2014

According to a new study released by the Harvard School of Public Health, exposure to fine particulate air pollution during the last three months of pregnancy can double the risk of having an autistic child.
This latest study is one among several that have demonstrated the correlation between air pollution and autism in recent years. In 2013, UCLA released a similar study establishing a link between traffic pollution exposure during pregnancy and increased incidence of autism. The study found that ozone and fine particulates were the pollutants most closely associated with autism.
In this most recent study, researchers established a test group of 245 autistic children and a control group of 1,522 children without autism, and then collected data about the levels of fine particulate matter air pollution present in their mothers’ cities of residence during pregnancy.
Study findings suggest that children of women exposed to higher levels of fine particulate matter during pregnancy have a heightened risk of autism. Children of women exposed in the last trimester of pregnancy were especially vulnerable, with an increased risk of 50 percent. The study also indicated that fine particulate matter exposure before and after pregnancy did not increase the risk of autism.
Sources of fine particulate air pollution in the U.S. include motor vehicles, power plants, wood burning, and certain industrial processes. According to the EPA, fire, dust, agriculture, and fuel combustion are the top four sources of fine particulate air pollution in the United States, while vehicle pollution is the fifth leading source.
Although this latest study doesn’t implicate any particular source of fine particulate pollution, earlier studies have focused more precisely on the correlation between vehicle emissions and autism.  The previously mentioned UCLA study released in 2013 found that prenatal traffic related air pollution exposure was associated with a higher risk of autism, and a 2012 study released by the University of Southern California found a similar correlation between traffic pollution exposure and autism.
The Harvard School of Public Health’s most recent study also cites two previous studies that looked for a more specific correlation between diesel emissions and autism. One of those studies released by the Harvard School of Public Health in 2013, examined the impact of perinatal exposure to air pollutants that had been associated with autism in prior studies including diesel, lead, manganese, and cadmium. The results of this study indicated that exposure to these pollutants was associated with a higher incidence of autism.
It is common knowledge that both gasoline and diesel emissions contribute to particulate air pollution to some degree, but the question remains whether the contribution is enough to warrant concern and action. When asked to comment on the results of The Harvard School of Public Health’s latest study linking fine particulate air pollution to autism, Executive Director of the Diesel Technology Forum Allen Schaeffer said that diesel’s contribution to fine particulate air pollution is negligible at best, with diesel engines only accounting for about six percent of the total inventory of fine particles according to EPA data.
“If you look at the EPA pie charts and data you’ll find that 94 percent of fine particle emissions come from things other than diesel engines – that means power plant emissions, wood burning, agricultural activities, industrial emissions, and gasoline vehicle emissions,” said Schaeffer. “I think that says a lot about what role diesel engines play in this overall question about fine particles.”
Since fine particulate air pollution is a complex issue with many sources, there are no easy answers in the quest to create cleaner air. But as scientific evidence continues to link fine particulate air pollution to serious health issues like autism, it seems that reducing air pollution from all sources– including vehicles– should be at the top of the public health agenda.   In 2012, the U.S. Environmental Protection Agency strengthened the annual health National Ambient Air Quality Standard for fine particles, and the UK judiciary has cracked down on vehicle-related air pollution in recent months, so it appears governmental bodies are heeding the warnings the scientific community is churning out.