Air pollution isn't just bad for the heart and lungs; it appears to be bad for the brain as well.
Cerebral brain volume decreased and silent strokes, known as covert brain infarcts, increased as air pollution levels rose. Clearly, the pollution was doing nothing good for people's brains.
“Long-term exposure to air pollution showed harmful effects on the brain in this study, even at low levels, particularly with older people and even those who are relatively healthy,” Elissa H. Wilker, the lead author of a study that monitored the changes in people's brains as they aged, said in a statement.
Air pollution in general has been linked to a variety of health problems, including anxiety.
An increase in pollution of just 2 micrograms per cubic meter of fine particles in the air where a person lived was associated with a 46% increase in covert brain infarcts and a 0.3% decrease in cerebral volume.
This study focused on a specific type of air pollutant, fine particles, also called PM2.5. These particles are 100 times thinner than a human hair and travel deeper into the lungs than larger particles do. They mainly arise from combustion — the burning of wood and coal, car exhaust, and industrial processes — and they can remain in the air for weeks and travel hundreds of miles, crossing state lines.
Almost 950 healthy residents of Boston and other parts of New England and New York participated. All were enrollees in the Framingham Offspring Study, research that has been going on for decades. All were 60 years of age or older at the start of the study.
MRI scans of the brain taken between 1995 and 2005 revealed that an increase of 2 micrograms per cubic meter of fine particles in the air where a person lived was associated with a 46% increase in covert brain infarcts and a 0.3% decrease in cerebral volume, a decrease in brain volume similar to what would be seen in one year of brain aging, according to Wilker, researcher in the Cardiovascular Epidemiology Research Unit at Beth Israel Deaconess Medical Center and the Harvard T.H. Chan School of Public Health in Boston.
In most metropolitan regions, the localities with the cleanest and the dirtiest air show at least a 2 microgram per cubic meter difference in their concentration of fine particles.
Covert brain infarcts, typically located in deep regions of the brain, have been associated with neurological abnormalities, poorer cognitive function and dementia.
According to the World Health Organization, fine particulate matter affects more people than any other pollutant does. Not only do these particles penetrate deeply into the alveoli of the lungs, they can also contribute to the narrowing of arteries that supply blood to the brain. More information on fine particulate matter is available from the EPA and AirInfoNow.
The study appears in Stroke.