Pinterest and Instagram are full of recipes that use snow—think snow cones, slushy cocktails, and DIY ice cream. And while frozen margaritas sure sound like an ideal way to make the best of a blizzard, is it even safe to consume those freshly fallen flakes?

The scientific answer: Maybe.

Snowflakes are born high up in the atmosphere when water vapor condenses and forms ice crystals around microscopic dust or pollen. By the time the flakes hit the ground, they’ve absorbed lots of other droplets and accumulated many more crystals—and what they contain is pretty disgusting. “Most atmospheric water and precipitation contains traces of gaseous and particulate contaminants,” explains Parisa A. Ariya, PhD, a professor of chemistry and atmospheric and oceanic sciences at McGill University. Ariya coauthored a recent study that found snow absorbs toxic organic compounds in vehicle exhaust.

As gross as all that seems, it’s important to consider how much contamination we’re actually talking about—and how much is too much.

“It is well known amongst snow chemists that fresh Arctic snow goes very well with 15-year-old single malt whisky,” joked John Pomeroy, PhD, a water-resource and climate-change researcher at the University of Saskatchewan, in an interview with NPR last year.

In other words, if you don’t live in an urban area with pollution and a lot of vehicle traffic, then eating snow is probably fine, says Ariya. “I give snow to my children in remote Canadian sites even just outside the city,” she explains. “You should recognize that there is dilution of pollution from the emission source.”

Even if you live in a less-populated area, you still need to be careful about the snow you scoop up. We all know to steer clear of (cough) yellow snow; you should also avoid pink or “watermelon” snow as well. It owes its rosy hue to algae that live in melting snow, and those algae can have a laxative effect. Additionally, skip windblown (or “driven”) snow, which mixes with dirt and other ground-level contaminants. Plowed snow is another “don’t”—it often contains sand and chemicals picked up from the road.

Long story short: In some cases, you’re better off using a shaved-ice machine to make dessert or your next cocktail. Don’t worry: Your Instagram followers will love those treats, too.

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