Air Pollution and Your Brain

By Michelle Becker

Graphic depiction of the brainNext week is Air Quality Awareness week, which is a time to reflect on how far we have come in our understanding of the health effects of air pollution. We know air quality can affect the lungs and heart and cause serious health problems, as documented in a large body of scientific literature. However, we don’t know very much about the potential effects on the brain.

That is why EPA supports research through its Science to Achieve Results (STAR) grant program to further examine potential health effects of air pollution. The Clean Air Research Center (CLARC) at Harvard University receives funds from EPA to explore the health effects of air pollution mixtures across organ systems and during various stages of human life.

Recently, the center published a study in the journal Stroke that looked at what may happen to the brain of older adults after long-term exposure to fine particle pollution (PM2.5), which is emitted from tail pipe emissions as well as other sources. The study included 943 individuals over the age of 60 with no history of dementia or stroke. They also lived within 1,000 meters (0.62 miles) of a major roadway where levels of air pollutants are generally higher.

Researchers looked at pictures of the brain using a technique called Magnetic Resonance Imaging (MRI) to identify the differences in certain brain structures. Then they considered the pictures in connection with the distance participants lived from a major road.

After considering all the data and a number of other factors that might affect the brain, the researchers found that exposure to outdoor PM2.5 was associated with a decrease in total cerebral brain volume and an increase in covert brain infarcts (known as “silent” strokes because there are no outward symptoms). The impact of being close to roadways was less clear.

So what are the potential implications? A decrease in cerebral brain volume is an indicator of degeneration of the brain, which can lead to dementia and other cognitive impairments. Also, an increase in covert brain infarcts increases a person’s risk for a major stroke.

To give you a better idea about PM2.5 (particulate matter of 2.5 microns in diameter) the average human hair has a diameter of 100 microns. So these air pollutant mixtures are roughly one quarter the diameter of a single hair on your head. That is to say, very small. Yet these small particles pack a big punch when it comes to our health. The study demonstrates an increase of just 2 micrograms per cubic meter can cause brain deterioration.

This study is one of the first to look at the relationship between air pollution and the brain so the evidence is suggestive. The study contributes to a growing body of scientific research that is exploring the cognitive connections to air pollution. So this week while we think about air quality, let’s remember that small things can make a big impact and that science can help us to learn more about air quality and our health.

About the Author: Michelle Becker, M.S, is currently working with the Air, Climate, and Energy research program in EPA’s Office of Research and Development through a Skills Marketplace opportunity. The project has allowed her to increase her scientific communication skills and to learn more about EPA funded research to protect human health.

Editor's Note: The views expressed here are intended to explain EPA policy. They do not change anyone's rights or obligations. You may share this post. However, please do not change the title or the content, or remove EPA’s identity as the author. If you do make substantive changes, please do not attribute the edited title or content to EPA or the author.

EPA's official web site is Some links on this page may redirect users from the EPA website to specific content on a non-EPA, third-party site. In doing so, EPA is directing you only to the specific content referenced at the time of publication, not to any other content that may appear on the same webpage or elsewhere on the third-party site, or be added at a later date.

EPA is providing this link for informational purposes only. EPA cannot attest to the accuracy of non-EPA information provided by any third-party sites or any other linked site. EPA does not endorse any non-government websites, companies, internet applications or any policies or information expressed therein.