Air pollution women breathe during pregnancy may be linked to a greater risk of developing autism, according to new research.
A review of the latest literature found that babies with a genetic predisposition to autism who were exposed to four common air pollutants were more likely to develop the condition.
It is thought that these pollutants, when inhaled during early childhood or in utero, can enter the bloodstream. There they can bypass the brain’s protective layers, causing inflammation and changing the way nerves function and develop.
The number of cases of autism has increased around the world in recent decades. A recent analysis found that in the US, rates have almost tripled among children and young adults – and that around three in every hundred children have an autism spectrum disorder (ASD).
Dr. Haitham Amal, head of the Laboratory of Neuromics, Cell Signaling and Translational Medicine at the Hebrew University of Jerusalem, said they were trying to understand what could be contributing to this increase in diseases.
His laboratory has mainly focused on nitric oxide (NO), a gas released when fuel is burned in cars.
Dr. Amal said: ‘My laboratory has shown that NO plays an important role in ASD.’
This comes as the American Lung Association reports that 39 percent of the US lives in an area with high levels of air pollution, including some of the chemicals studied in the new paper.
Use the map below to see how the air in your city compares.
Your browser does not support iframes.
Dr. Amal (center) and his team of researchers in their laboratory in Jerusalem. The team focuses on nitric oxide and its role in the brain
Your browser does not support iframes.
Some of the cities with the worst air pollution were Phoenix, Arizona, San Jose, California and Eugene, Oregon. Organizations like the EPA track and report these polluting chemicals so you can get an idea of your risk.
In the new study published in the magazine Brain medicineDr. Amal’s team reviewed studies looking at children with autism, studies using human cells, and studies using mice.
They studied four different components of air pollution: particulate matter, nitrogen oxides, sulfur dioxide and ozone.
Particulate matter, which are microscopic pieces of dust, liquid or smoke produced on construction sites, power plants and cars.
It is between seven and thirty times smaller than the diameter of a human hair.
Sulfur dioxide is a colorless gas or liquid and is produced when fossil fuels are burned or when metal such as aluminum is melted, according to Wisconsin Ministry of Health Services.
Ozone is a colorless, odorless gas produced by chemical plants, oil-based paints, and printing plants EPA.
They found that people with a genetic predisposition to autism who were exposed to air pollution early in life were more likely to develop the condition than people exposed to less air pollution.
The authors did not provide figures, but older research from Harvard found that exposure to air pollution such as particulate matter can increase 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 are more likely to develop autism if someone in their immediate family has the condition.
They’re not sure why they’re connected, but have a few theories.
First, when someone inhales any of these pollutants, it can cause inflammation in the nerves that damage them over time and lead to dysfunction.
People are most vulnerable to these conditions when they are developing in the womb and in early childhood because their brains are still forming, Dr. Amal said.
Studies have shown that these tiny pollutant particles can even directly enter the fetus’ brain, he said.
The American Lung Association ranked the top cities suffering from the worst air quality in the US – affecting approximately 131 million Americans
Long-term changes in 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 the way people interact, communicate, learn and behave with others.
It could also cause a higher incidence of autism because ingesting air pollution can interrupt the production of certain chemicals that control 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 is proud of his research team for being among 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.”