ALERT: Snow Releases Toxic, Carcinogenic Pollutants When Melting

A new study from McGill University, in collaboration with école de technologie supérieure in Montreal, revealed that snow can accumulate toxic and carcinogenic pollutants that can be released back to the air as the snow melts.

The study, published in the journal Environmental Pollution, showed that snow has the ability to absorb certain polycyclic aromatic hydrocarbons, which are organic pollutants known to be toxic and can cause cancer.

"When one goes outdoors in winter, and there is fresh snow, one can sense the air has a different smell -- it usually smells 'crisper'. Once the snow has been on the ground for some time, the effect goes away. When the weather warms up, the air acquires yet another smell," said Yevgen Nazarenko, a postdoctoral researcher at McGill University and lead author of the study, in a press release. "This is what led us to wonder about how exactly snow interacts with air pollutant."

For the study, the researchers put fresh snow in a temperature-controlled glass sphere built in the lab. Using gasoline-powered engine from a modern light duty vehicle as an exhaust, the researchers then analyzed the interaction between car emissions and snow in a low ambient temperature.

The researchers found that snow can take up large mass of organic pollutants and aerosol particles from the gasoline engine exhaust in just 30 minutes. Additionally, the type of fuel injection in the engine could influence how the exhaust particles react to the cold temperature and snow.

Surprisingly, snow can also take up airborne particulate matter and alter the concentration of different nanoparticles. The researchers observed that the interaction with snow and the cold temperature increased the relative presence of smaller nanoparticles in the polluted air above the snow.

Air pollutants may undergo chemical transformation when accumulated in a snowpack, creating additional pollutants with different toxicity and carcinogenicity. Some of these toxic and carcinogenic chemicals can volatilize back into the air or accumulate in melted water as the snow melts.

With their findings, the researchers noted that melting snow could lead to a higher short-term concentration of certain pollutants in the air, soil and surface of bodies of water.