With a large portion of the United States having been blanketed in snow over the past several weeks, some have taken to posting recipes for snow ice cream and other treats that use fresh powder as a base, adding milk, sugar, and toppings.

Obviously, no one is recommending anyone scoop up a bowlful of snow idling on the side of the road, full of salt, muck, and other unpleasantness. But is any snow actually safe to consume?

While you may assume snow that’s freshly fallen and collected in an undisturbed area—even a cup set out for that purpose—is free of any contaminants, don’t be so sure. According to meteorologist Mary Scarzello Fairbanks, who spoke with Prevention, snow isn't all that pristine. It's formed when water droplets freeze around some dust or debris in the air, forming an ice crystal that continues to collect water vapor and form a snowflake. When it falls, it will also collect things hanging in the air, from dirt to bacterial particles to soot. Depending on the region, snow could also contain sulfates, nitrates, formaldehyde, mercury, or pesticides. If it’s windy, snow could even mix with dirt kicked up from the soil before settling. A 2015 study published in the journal Environmental Science: Processes & Impacts even demonstrated how snow could mix with gasoline exhaust.

Theoretically, your snow ice cream could have some disgusting material as a “topping.”

At the same time, there doesn't seem to be a surge of reports of illnesses relating to chowing down on a snowball, and the contaminants it may cling to in the air are also present as we breathe. Presuming you don’t consume a large quantity of it, it’s unlikely whatever contaminants might be in the snow will be present in large enough amounts to cause problems.

Be mindful that no one is advocating for snow ingestion, just that a small bite will probably be fine.

Eating snow in an emergency is another matter. The Centers for Disease Control (CDC) warns against snow snacking for anyone stranded, like hikers, because it can lower one’s body temperature. In cases of water supply issues, the CDC says it’s safe to take collected snow and boil it to kill off any germs.

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