Autism may be caused by toxins breathed in by millions every day

Autism may be caused by toxins breathed in by millions every day

• READ MORE: More than 44million Americans are living in areas with air pollution

Air pollution breathed in by women during pregnancy may be linked to a greater risk of developing autism, according to new research.

A review of the latest literature found babies with a genetic predisposition to autism exposed to four common air pollutants were more likely to develop the condition.

It's thought that when breathed in during early childhood or in the womb these pollutants can get into the bloodstream. There, they can bypass the protective layers of the brain, causing inflammation, changing the way nerves function and develop.

Autism rates have been rising across the world over the past few decades. A recent analysis showed that in the US, rates have nearly tripled in children and young adults- and about three in every 100 kids has autism spectrum disorder (ASD).

Dr Haitham Amal, the head of the department of Laboratory of Neuromics, Cell Signaling, and Translational Medicine at Hebrew University of Jerusalem, said they were trying to understand what might be contributing to this rise in disease.

His lab has mainly focused on nitric oxide (NO), a a gas released when fuel gets burned in cars.

Dr Amal said: 'My lab has shown that NO plays a major role in ASD.'

This comes as the American Lung Association reports that 39 percent of the US lives in an area with high amount of air pollution, including some of those chemicals studied in the new paper.

Use the map below to see how the air in your town matches up.

Some of the cities with the worst air pollution included Phoenix, Arizona, San Jose, California and Eugene, Oregon. Organizations like the EPA are tracking these pollutive chemicals, and reporting them so you can have an idea of your risk.

In the new study, published in the journalBrain Medicine, Dr Amal's team reviewed studies that looked at children with autism, studies that used human cells and studies that used mice.

They studied four different components to air pollution: particulate matter, nitrogen oxides, sulfur dioxide and ozone.

Particulate matter, which is microscopic pieces of dust, liquid or smoke produced from construction sites, power plants and cars.

It's between seven and 30 times smaller than the diameter of a human hair.

Sulfur dioxide is a colorless gas or liquid, and it's produced when fossil fuels are burned or when metal like aluminum gets smelted, according to Wisconsin Department of Health Services.

Ozone is a colorless, odorless gas produced from chemical plants, oil based paint and print shops, according to the EPA.

They found that people with a genetic predisposition to autism who were exposed to air pollution in early life were more likely to develop the condition than people exposed to less air pollution.

The authors didn't provide a figure, but older research from Harvard found that exposure to air pollution like particulate matter may raise the risk of ASD by as much as 64 percent.

Doctors aren't sure what causes the condition, but about 15 percent of autism cases are linked to a specific gene mutation. Other people may be more likely to develop autism if someone in their immediate family has the condition.

They aren't certain why they might be linked, but have a few theories.

First, when someone breathes in one of these pollutants, it can cause inflammation in the nerves which harm them over time and lead to dysfunction.

People are most vulnerable to these affects when they're developing in the womb and in early childhood, because their brains are still forming, Dr Amal said.

Studies have shown that these tiny pollutive particles can even directly enter the fetal brain, he said.

Long term changes to the way the brain functions can cause some of the behavioral symptoms associated with autism, he said.

According to the NIH, ASD is a developmental disorder that affects how people interact with others, communicate, learn and behave.

It could also be causing a higher incidence of autism because intaking air pollution can interrupt the production of some chemicals that rule the brain, including dopamine and norepinephrine.

These chemicals are crucial in the decision-making process and in brain development in general.

Whatever the cause, Dr Amal said he's proud of his research team, which is one of the first to link these air pollutants to the autism spectrum.

When asked what his greatest achievement was, Dr Amal said: 'discovering that nitric oxide plays a key role in autism.'