One of the worst things that a child could be doing now is eating snow, as a group of scientists in Canada found that there may be no clean or pure snow after all, particularly if one lives in an urban location.

Urban snow has been found to absorb the same toxic and carcinogenic components coming from car exhaust – with the interaction between pollutants and cold temperatures even potentially causing new compounds to be released, warned study lead researcher Dr. Parisa Ariya of McGill University.

The findings, published Dec. 21, 2015 in the journal Environmental Science: Processes and Impacts, were released ahead of a WHO study on air pollution next month.

“I do not wish to be alarmist,” said Ariya in an interview, but said that snowflakes have different surfaces that can absorb gaseous or particulate pollutants.

"As a mother who is an atmospheric physical chemist, I definitely do not suggest my young kids to eat snow in urban areas in general,” she warned.

The team analyzed the interaction of these ice particles with exhaust-derived pollutants through putting snow and exhaust fumes in a chamber. From examining the chemical reactions that occurred, they found that snow efficiently removed pollutant particles from the air.

One alarming discovery: after a mere hour, the snow’s obtained chemicals from exhaust – including benzene, ethylbenzene, toluene, and xylenes – increased significantly. And some of these compounds have notable health risks.

According to the researchers, this took place because when particles exit the cooler system of an exhaust into a colder setting such as snow, the temperature gradient means that aerosols are removed by the colder surface.

University of Helsinki environmental chemist Anna Lea Rantalainen, in a comment on the study, said the findings raised more questions: given that snow efficiently removes aerosol particles coming from the air, what happens after it has melted?

If the sink is temporary, pollutant emissions could increase rapidly in industrialized areas when snow melt. Ariya added that this is important in industrial nations like China, which emit highly diverse compounds subject to be transported around the world.

Surface chemist Thorsten Bartels-Rausch of the Paul Scherrer Institute in Switzerland urged further exploration of the matter.

“Long term projects would show how exhaust gases and aerosols are taken up, to see how this changes with temperature or with the age and type of snow.”

One in eight total deaths worldwide occurs due to air pollution, stated a 2014 WHO study that claimed a strong association between exposure to pollution and diseases like cancer and heart disease.

Photo: John Talbot | Flickr

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