According to a new study released by the Harvard School of Public Health, exposure to diesel emissions 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 traffic 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.

Although fine particulates are found in all vehicle pollution, they are particularly high in diesel emissions. Diesel emissions also contain higher amounts of nitrogen oxide and sulfur dioxide than gasoline fumes, and were recently labeled a group 1 carcinogen by the World Health Organization.

One question that remains unanswered is whether “clean diesel” is a safer alternative to gasoline.

SEE ALSO: Will America Avoid Europe’s ‘Clean’ Diesel Problems?

In order for diesel to be considered “clean” it must have “ultra low” sulfur levels (15 parts per million as opposed to the 500 ppm in regular diesel), and be treated with exhaust-scrubbing components. Exhaust “after treatment” includes the catalytic converter and increasingly urea injection, or “diesel exhaust fluid.”

These extra factors result in less harmful emissions, but the call is for more research to be done to support the claim that diesel emissions can be kept acceptably safe.

As some Europeans bear down on the real-world versus lab efficacy of diesels they’ve embraced and increasingly proliferated over the past decade or more, with voices calling for its banning, such as in city centers like London, stories are putting a spotlight on diesel.

SEE ALSO: Diesel Faces Judicial Scrutiny in the UK

True also is gasoline emissions may be toxic, even fatal, if breathed in sufficient quantities.

In Europe particularly, tailpipe emissions are being accused of being higher under government test cycles. Further, with the vastly higher number of diesels, including older, out of compliance, and modified diesels on the road, real world air quality has made diesel emissions a real concern.

In the U.S., the EPA makes diesel match the exact same requirements as gasoline engines. This at least is true of new vehicles, not necessarily for older or modified or out-of-compliance vehicles also on Americans roads.

Another question then becomes is diesel exhaust undesirable at any level? Advocates against diesel are working to prove the answer is yes, while diesel proponents are working to prove the answer is no.

Daily Mail

Huffington Post