Chemistry influences particulate matter’s health effects

Exposure to fine airborne particles (PM_2.5) increases the risk of health problems like heart attacks. Limits on this pollution in many countries account for only the particles’ size, not their composition. Now research by Scott Weichenthal, an environmental epidemiologist at McGill University, suggests that chemistry matters. People who are exposed to PM_2.5 with higher levels of sulfur and transition metals are more likely than people exposed to PM_2.5 without that chemistry to go to the hospital for an acute cardiovascular event.

Weichenthal’s team used hospital admission data, daily ambient PM_2.5 measurements, and monthly chemical analysis of particles captured at 34 locations in Canada. People living near sites where PM_2.5 was elevated in both sulfur and transition metals were at higher risk of a cardiovascular event (Environ. Health Perspect. 2021, DOI: 10.1289/EHP9449). High levels of S and copper, for example, increased the risk by about 10%, Weichenthal says. He hypothesizes that S makes a particle more acidic, making metals more bioavailable. When suspended in a simulated lung-lining fluid, collected particles that were high in S and metals depleted levels of a collection of biochemicals that protect the body from oxidative stress. This suggests that the particles’ health effect might be associated with their oxidative potential.

High levels of S and metal are “a flag for fossil fuel combustion,” says George Thurston, an environmental health scientist at New York University. He says this research indicates that treating all PM_2.5 the same, regardless of the source or composition, underestimates the public health value of regulating fossil fuels.