Scientists have long been aware of the link between poor air quality and respiratory and cardiovascular illnesses. But, recent evidence indicates that dirty air can also be dangerous to your brain. Numerous studies have shown a correlation between polluted air and brain disease. Because 90% of the world is breathing air that fails to meet The World Health Organization’s standards, this issue can have dire consequences for a large population of the world.

What pollutants are the most hazardous?

Air pollution is made up of a complicated combination of suspended gases, solids, and liquid particles. There are numerous toxic ingredients in this mix, including ozone, sulfur dioxide, and carbon monoxide, all of which can cause serious health issues.  But, the component that appears most damaging to the brain is PM.

PM 2.5, also known as fine particulate matter, generally comes from smoke, dust, and exhaust. PM 2.5 is 30 times smaller than the width of the average human hair, so small that it can remain airborne for long periods of time, and infiltrate buildings and our bodies. Ultrafine particles are even smaller, less than .1 micrometer across. Their tiny size makes them almost impossible to monitor.

The problem with these tiny particles is that they are able to get around the body’s defenses against unwanted intruders.

“The health effects of air pollution are all about particle size,” says Cory-Slechta, neurotoxicologist Deborah Cory-Slechta at the University of Rochester in New York.

PM 2.5 particles are so small that they may even be able to go straight from the nose to the brain, bypassing the blood-brain barrier. And they don’t travel alone. On the surface of these particles are a whole range of contaminants including chemical compounds and metals.

What does PM do to your brain?

Once inside the body, PM can travel to the brain in a number of different ways where they interfere with immune cells and cause inflammation and a host of other issues. Studies around the world have linked dirty air with a rise in various brain diseases.

In Mexico City, nanoparticles closely associated with abnormal proteins that are hallmarks of Alzheimer’s and Parkinson’s were found in the brainstems of 186 young people who died suddenly.  In Ontario, Canada, studies showed that people who lived closer to major roads had a higher risk of developing dementia. In Barcelona, students at schools with more traffic pollution displayed slower cognitive development.  And, in the United States, women who lived in areas with pollutants that exceeded the EPA’s recommendation were twice as likely to develop dementia. All of these studies indicate a strong correlation between dirty air and cognitive issues.

What is being done to address this issue?

Since neither US regulations nor the Environmental Protection Agency has cited the impact of air pollution on the brain, not much has been done to address the problem. However, there are scientists working to change that.

Nicolai Kuminoff, an environmental economist at Arizona State University (ASU) in Tempe led a natural experiment to discover if there was a relationship between air pollution and dementia in humans. In the mid-2000s, the EPA began to enforce a maximum PM2.5 threshold around the country. Areas that did not meet the standards were forced to clean their air, while areas that had pollution just below the threshold were not required to do anything.

Kuminoff and his colleagues found that the federal regulations may have led to nearly 182,000 fewer people with dementia in 2013. They determined that additional regulations would avoid even more cases of dementia.

Although this research is in the early stages, it points to encouraging evidence that further regulations on pollutants will have a positive impact on brain health.

How can we protect ourselves?

The best way to limit your exposure to PM 2.5 is to avoid areas with poor air quality. Living in cities, manufacturing areas, and any place near major highways can increase your risk of brain disease or cognitive issues. But, it isn’t only outdoor air that is problematic.  Studies show that indoor air is often up to five times more polluted than outdoor air. Fortunately, there are a number of ways to reduce your exposure to both indoor and outdoor pollutants.

To minimize your exposure to outdoor pollutants:

  • Check your air quality before going out.
  • Go outside in the mornings, when ozone levels are lower.
  • Walk away from traffic.
  • Stay near trees or shorelines.

To minimize your exposure to indoor pollutants:

  • Ensure that gas stoves are well ventilated.
  • Reduce the use of harsh cleaners and scented products.
  • Keep windows and doors open as much as possible.

While all of these measures can help reduce pollutants, perhaps the most important step to improving indoor air quality is to purchase an air purifier.  Look for a  high-quality air purifier that can both remove harmful gases, and eliminate particulate matter down to .1 microns.