Experts say brains could decrease in size and people who have been most exposed to certain types of air pollution could suffer from strokes or dementia.

The lead author of the study, Elissa H. Wilker, Sc.D., mentioned that the most affected people are middle-aged or older.

The research targeted 943 people who were at least 60 years old. They lived in areas where pollution is not significant and their health was first regarded as healthy.

An MRI (magnetic resonance imaging) was used to analyze the brain functions and structures of all the participants. The images were used to determine what effect pollution has on the brain.

According to the researchers, the brain volume was smaller by 0.32 percent in relation to an increase of less than 2.5 micrograms of fine-particle pollution per cubic meter.

This pollution often comes in a wide variety of sources like car exhaust.

Dr. Sudha Seshadri, Professor of Neurology at the Boston University School of Medicine, stated that people who live in highly populated areas are likely to have a brain volume smaller than other people of the same age.

This discovery points out the devastating effects air contamination has.

The MRI scans also revealed that pollution could result in an increased 46 percent chance of a person having a silent stroke if exposed to air pollution.

Fine-particle pollution may be more damaging for the brain than other types of contamination. It can lead to brain atrophy associated with aging.

Atmospheric pollution can be caused by wood burning, automobiles, power plants. PM2.5 material is often caused by these sources of air pollution. Tiny pieces of debris often penetrate deep into the lungs, causing strokes and cardiac arrest, according to researchers. Investigators say it remains uncertain how air pollution affects the brain directly, but they theorize the material could increase inflammation, which has been directly linked to stroke in cardiac arrest risk.

The study found a direct correlation between air pollution levels in strokes caused by a blood clot. Silent strokes often occur without the affected person’s knowledge, and are often are more dangerous due to a lack of medical attention.

It remains unclear whether any studies are planned to follow up on the preliminary observations. Scientists have long sought to determine the effects of air pollution on society, making it likely additional studies will take place.

The results of the study were published in Stroke, the American Heart Association journal and are consistent with other studies in the field.