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NERVOUS SYSTEM HEALTH

Air pollution exposure may increase risk of autism, schizophrenia

Buildings are seen through thick haze at the central business district in Guangzhou, Guangdong province in China.REUTERS/Alex Lee

Air pollution exposure has long been suspected to increase the risk of both heart and lung diseases, but another important organ may also be at risk of injury from this contaminated air: the brain.

Researchers at the American Association for the Advancement of Sciences (AAAS) annual meeting in Chicago recently detailed the impact that constant exposure to air pollution may have on the developing brain.  According to the panel, a series of mouse models have suggested that constant inhalation of air pollution may lead to enlargement of the brain’s ventricles – a hallmark of neurodevelopmental disorders such as schizophrenia and autism.

The researchers believe that the world’s increase of air pollution levels may be somewhat linked to the rising rates of central nervous system diseases over the years.

According to the organizer of the panel, Dr. Deborah Cory-Slechta, air pollution is a cocktail of various metals and gases, often consisting of many different sized particles.  The larger particles typically do not pose a risk to the body, as they are often coughed up and disposed, but the very small particles are the ones that health experts say pose the biggest health threat.

“The component people worry about the most are the smallest particles – the ultrafine particles,” Cory-Slechta, professor in the department of environmental medicine at the University of Rochester School of Medicine, told FoxNews.com.  “And the reason is because those go all the way down into the bottom of the lung.  Once they get to the bottom of the lung, they can be absorbed into the blood stream.”

Cory-Slechta said she initially started looking at air pollution in relation to the brain by accident – after some of her colleagues sent her the brains of mice that had been exposed to moderate amounts of air pollution.

“They wanted to see what the effect was on the developing lung in mice.  And they didn’t have any use for the brains, so they contacted us and said, ‘Do you want to look at the brains?’ Cory-Slechta said. “…So we took the brains, and it had been a couple months since exposure, and we couldn’t find a brain region that didn’t have inflammation going on.  Not one.”

Hoping to further analyze the relationship between air pollution and brain injury, Cory-Slectha and her team began a series of rodent studies using unfiltered air from Rochester, N.Y.  During their third study, the researchers exposed the animals to air pollution from post-natal days 4 through 13 – a critical time for brain development in mice.  They then analyzed the mice’s brains the day after the exposures had ended.

Once the brains had been sectioned for better viewing, the researchers found that all had varying degrees of damage – but most notably, the lateral ventricles were significantly dilated.  Filled with cerebrospinal fluid, the brain’s ventricles help to protect the brain, keep it clean and boost its energy.  However, when these ventricles are enlarged, it often indicates a very poor prognosis for central nervous system development.

“When the brain ventricles are too big, it pushes on the rest of the tissue,” Cory-Slectha said.  “Also, you have these tracks of what’s called ‘white matter.’  And they cross over the brain; they connect the two hemispheres. And in these mice, those are either missing, or never developed, or died.  We don’t know which, but a lot of that is missing, and that too is very characteristic of autism and schizophrenia.”

Ventriculomegaly – the enlargement of the ventricles – is also associated with a range of other brain diseases, such as bipolar disorder and Alzheimer’s disease, as well as a number of birth defects in children.  Cory-Slectha noted that this brain damage was largely seen in the male rodents – an interesting finding given that both autism and schizophrenia are mainly male-oriented conditions.

“And part of that that is so interesting is both autism and schizophrenia, not only are they primarily in males, but the rates of those have been going up,” Cory-Slectha said.  “And yet nobody can really ever explain why.  [They say] it’s the diagnoses, etc.  Well you know, air pollution has also gotten worse in some places, and you are exposed to it your entire life.  So now we have the [epidemiological research] and we have the animal studies [to support that].”

In order to further confirm the air pollution-brain injury relationship, Cory-Slectha and her team are working to get more funding to look into the potential behavioral changes that may be caused by prolonged air pollution exposure.  In the long run, she hopes that her studies will have an impact on the regulations already set in place to limit pollution in the atmosphere.

“Some of our air pollution comes from other places.  It can come across the ocean, basically,” Cory-Slectha said.  “But [our work] could change those regulations and lower them hopefully so that people aren’t exposed.  Obviously, some places are worse than others.”