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Going Beyond ‘Yellow’ Snow: Contaminants in White Flakes Come from Many Directions

A young girl enjoys building a snowman, but is it still safe?   ©Lars Plougmann/Wikimedia (CC BY-SA 2.0)
A young girl enjoys building a snowman, but is it still safe? ©Lars Plougmann/Wikimedia (CC BY-SA 2.0)

As winter snowfalls make their way to the Earth, it’s time for children to cavort in piles of white, making snow angels, snow men, having snowball fights—and chomping on fistfuls of the fluffy white flakes. Eating snow is a time-honored part of winter fun, even though it’s usually accompanied by stern warnings to steer clear of “yellow” (peed-in) snow.

Now, a closer look at snowflakes and other winter precipitation may encourage adults and children to consume snow with caution—or not at all.


Snow: Not as Pure as It Appears

In interviews with NPR, Jeff S. Gaffney, a professor of chemistry at the University of Arkansas, Little Rock, says if snow had an ingredient list, it would be topped by H2O and followed by “various and sundry things depending on where it [comes from],” including compounds and metals such as sulfates, nitrates, formaldehyde, and mercury.

Meanwhile, John Pomeroy, a researcher who studies water resources and climate change at the University of Saskatchewan, suggests that it may be best to wait a few hours after the snow begins to fall before anyone starts munching. “Snow acts like a kind of atmospheric ‘scrubbing brush,’” he explains. “The longer the snow falls, the lower the pollution levels in the air, and thus in the snow.”


“Snow acts like a kind of atmospheric ‘scrubbing brush,’” Pomeroy explains.

Although snow becomes like a giant “net” for pollutants, it is Gaffney’s opinion that contaminants in snow are “all at levels well below toxic.”

Not everyone shares that opinion.

Parisa Ariya of McGill University, Canada, states in the Huffington Post that, “As a mother who is an atmospheric physical chemist, I definitely do not suggest my young kids… eat snow in urban areas in general.”

Ariya headed up the team of researchers whose 2016 study indicated that snow absorbs chemicals from gasoline exhaust, which would include toluene, xylenes and the known carcinogen, benzene.

White Salt in White Snow

But the issue of contaminants in snowfall extends beyond yards to water bodies and snowfall on roads.

Spreading rock salt on icy or snow-covered roads and highways appears to be an easy fix, but it is not without environmental consequences. Rock salts make driving safer but contribute to rusting cars, roadway cracking, and other problems.

Although it is said, “as pure as the driven snow,” unfortunately, snow is a catchall for vehicular exhaust particulates, persistent organic pollutants (POPs), trace metals, and chlorides from road salts—this is the downside to snow’s absorbent tendencies.


Snow is a catchall for vehicular exhaust particulates, persistent organic pollutants (POPs), trace metals, and chlorides from road salts.

Rock salt is essentially the same as table salt—sodium and chloride—but as rock salt melts, snow forms runoff that can make its way into nearby creeks, marshes, and lakes. This toxic chemical cocktail has the potential to reach aquifers, pipes, and waterways where it can be detrimental to humans, flora, and fauna. This also applies to conventional ice melts, which typically include a combination of sodium or chloride with other ions or ionic compounds. Examples include calcium chloride, magnesium chloride, potassium chloride, sodium acetate, and blends of the above.


Deicers applied on roads can become runoff that ends up in water bodies.   ©Oregon Department of Transportation/Wikimedia (CC BY 2.0)
Deicers applied on roads can become runoff that ends up in water bodies. ©Oregon Department of Transportation/Wikimedia (CC BY 2.0)

The chloride in rock salts can negatively impact water quality to the point of contributing to algae blooms. Chloride salts are soluble, but they do not really break down and will accumulate at the bottom of water bodies where they affect anything living there. In a story featured by My Champlain Valley, a news organization in Burlington, Vermont, Mitch Vestal, president of Advanced Organics, says that as these particles collect, “we end up with algae blooms[,] and ... that problem gets worse as chloride salt accumulations grow.”

At low concentrations, chloride is benign, but when it becomes more concentrated, it can become toxic to plankton and fish. Salt water is more dense than fresh water and changes the way in which water mixes. Salt water’s “heaviness” can result in the formation of saline pockets (meromixis) near the bottom of lakes. These have the potential to create biological dead zones resulting from a “depletion of oxygen … and reduction in the cycling of nutrients.” Chloride can become a permanent pollutant with no easy fix, as removing salt from fresh water is an expensive treatment.

Possible Alternatives to Rock Salts

Many cities in the United States and Canada are using food byproducts, such as beet juice combined with salt, as deicers. According to The Conversation, “sugars in beet wastewater apparently make it more effective at lower temperatures than salt water or brine alone, lowering the melting point of the ice to below -20 [°]C from –10 [°]C.” As a result, less chloride can be used on roads.

Not only does beet juice lower the freezing point of water, it is also sticky and adheres better to the roadways than rock salt. Cheese brine, pickle juice, and even beer have also been used as a deicer. Similar to how dissolved salts lower water’s freezing point, such solutes also do so by obstructing the water molecules from forming their solid structure.

A downside of such solutes are their odors, which can be unpleasant. Another negative effect has to do with the surrounding environment: As the organic properties in alternative remedies wash into waterways, they deplete the oxygen in the water, reducing what is available for aquatic life.


As the organic properties in alternative remedies [to rock salts] wash into waterways, they deplete the oxygen in the water, reducing what is available for aquatic life.

Other natural alternatives to rock salts are being researched.

Some insects, spiders, and fish create antifreeze proteins in their bodies. For example, eighteen out of seventy-five species of Alaskan insects indicated the presence of antifreeze proteins, according to one study. In addition, it has been shown that notothenioid fish in Antarctica synthesize antifreeze proteins in their bodies to survive in the Southern Ocean.

According to Monika Bleszynski of the University of Denver, “My colleagues and I are learning how to make our own antifreeze compounds through imitation. Our first challenge is to learn how the natural versions work, so we can recreate them. While there’s still much we don’t understand, we are using advanced computer modeling to see how antifreeze proteins interact with water molecules.”

Bleszynski is working to synthesize a compound with the hydroxyl group—the same group found in antifreeze proteins and conventional antifreeze (ethylene glycol) for vehicles—to replicate its mechanism of binding with water molecules directly to make it more difficult for water to form its solid structure.

And There Are Microplastics…

Microplastics are found in water bodies, marine animals, and even the atmosphere, but what about snow?

A recent study by scientific researchers at the Alfred Wegener Institute, Helmotz Centre for Polar and Marine Research (AWI) in Bremerhaven, Germany, indicates that microplastic particles are being found in areas as remote as the Arctic and the Alps.

The study, published in the journal Science Advances, shows that these microplastic particles are caught up in the atmosphere and returned to Earth via snowfall. A team led by Dr. Melanie Bergmann and Dr. Gunnar Gerdts reported that, “the analyses … conducted on snow samples from Helgoland, Bavaria, Bremen, the Swiss Alps and the Arctic confirm that the snow at all sites contained high concentrations of microplastics.”


Microplastics are even found in the Alps.   © Gzzz/Wikimedia (CC BY-SA 4.0)
Microplastics are even found in the Alps. © Gzzz/Wikimedia (CC BY-SA 4.0)

​​​So Is Snow Safe to Eat?

While there may be genuine caveats regarding snow consumption, there are many scientists who believe there is no need to sound the alarm bells on eating a few white flakes or even an entire snowball.

Staci Simonich, professor of environmental and toxic ecology at Oregon State University, agrees that most people are likely collecting snow in urban or suburban areas where pesticide concentrations are likely higher.

But she adds: “That being said, I would not hesitate for my children to have the joy of eating a handful of fresh fallen snow from my backyard. ... the pesticide concentrations are low and the amount of snow eaten in a handful is small, so the one-time dose is very low and not a risk to health.”

 

*Kate Pugnoli is an Arizona-based freelance journalist and former educator who works with nonprofit organizations.



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