Scientists from McGill University and École de Technologie Supérieure in Montreal say interactions between vehicle exhaust and snow can create a "toxic cocktail" of pollutants when the snow melts.

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Residents in many northern statescollectively breatha sigh of relief asspring temperatures melt away the snow that has been a staple for the past several months. However, researchers at McGill University in Montreal say there may be somenasty stuff lurking in that snow, and it canpose health risks.

According to a , scientists with the university and École de Technologie Supérieure in Montreal learned "urban snow accumulates a toxic cocktail from car emissions," which, in turn, are released into the environment as snow melts.

"We found that snow absorbs certain polycyclic aromatic hydrocarbons which are organic pollutants known to be toxic and carcinogenic," said Yevgen Nazarenko, a postdoctoral researcher and co-author of the study .

"Understanding how these pollutants interact with the environment, including snow, is crucial if we are to reduce the hundreds of thousands of premature deaths caused by mild air pollution in North America. Worldwide, air pollution claims as many as 8 million lives," said Parisa A. Ariya, senior author and professor at McGill’s Department of Atmospheric and Oceanic Sciences and Department of Chemistry.

The researcherslearned vehicle exhaustchanges properties depending on the temperature, the snow and the type of fuel injection in the engine.

According to the study, snow absorbs tiny nanoparticles from the exhaust. These nanoparticles can be linked to a variety of health issues, including respiratory conditions like asthma and heart problems ,the New York Times reported. The concentration of these particles above the snow increases in colder temperatures and the interaction with the snow.

These dangerous particles absorbed by the snow may then undergo chemical changes during the melting process that changes them into different and even more toxic pollutants, which are either expelled into the air or released in meltwater.

"These releases could lead to a higher short-term concentration of certain pollutants in the air, soil and surface water bodies where the meltwater runs to," said Nazarenko.

The pollutants aren't all that difficult to detect, even to the lay person, the scientists noted.

"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. This is what led us to wonder about how exactly snow interacts with air pollutants," says Nazarenko.