Air pollution could be a risk factor for the development of multiple sclerosis, a new study has found. Researchers at the IRCCS Mondino Foundation in Pavia, Italy, detected a reduced risk for MS in individuals residing in rural areas that have lower levels of air pollutants known as particulate matter. They showed the MS risk, adjusted for urbanization and deprivation, was 29 percent higher among those residing in more urbanized areas.

The analysis was conducted in the winter, given that this is the season with the highest pollutant concentrations, in the northwestern Italian region of Lombardy, home to more than 547,000 people.

The study sample included more than 900 MS patients within the region, and MS rates were found to have risen 10-fold in the past 50 years, from 16 cases per 100,000 inhabitants in 1974 to almost 170 cases per 100,000 people today. While the increase can partly be explained by increased survival for MS patients, this sharp increase could also be explained by greater exposure to risk factors.

Particulate matter is used to describe a mixture of solid particles and droplets in the air and is divided into two categories. PM10 includes particles with a diameter of 10 micrometres of smaller and PM2.5, which have a diameter of 2.5 micrometres or smaller.

Both PM10 and PM2.5 are major pollutants and are known to be linked to various health conditions, including heart and lung disease, cancer and respiratory issues. According to the World Health Organization, 4.2 million deaths occur every year because of exposure to ambient air pollution. Three different areas were compared within the study region based on their levels of urbanization, of which two areas were found to be above the European Commission threshold of air pollution. 

The findings were presented at the European Academy of Neurology Virtual Congress.