It was a cold day in Seoul, South Korea, when the unexpected came tumbling down. The year was 2006, and snow was falling across the capital. This snow, sprinkling sheets of itself across the country, was different — it was yellow.
The snow contained dust and sand from the deserts of northern China, creating a yellow snow storm. Officials issued a warning of the health hazards the snow would bring, because it was filled with pollutants, particularly heavy minerals.
The rare polluted weather event served as a reminder that yellow snow isn’t always what we think it is.
What is yellow snow?
It’s common for parents to warn their children not to eat yellow snow because it may be contaminated with urine, according to Nationwide Children’s Hospital. The icy substance, however, can also be caused by pollutants.
Snow that comes in contact with the ground can turn yellow by the pigments in falling leaves, pollen, sand or dust. Algae and bacteria can turn snow red, green, orange, brown or grey-black. Plowed snow is at an even greater risk of contamination, because it can become mixed with dirt and road salt chemicals.
What are the dangers of eating yellow snow?
Eating snow in general is not advisable. According to the National Snow and Ice Data Center, digesting it is so energy-demanding on the body that eating snow can actually dehydrate a person. Yellow snow contaminated with pollutants can cause worse damage.
Western University Department of Chemistry researcher U. Eduok, who studies persistent organic pollutants, said the pollution often found in yellow snow can cause long term health problems.
“Upon exposure during winter, these chemical pollutants find their way into the snow, then into surface water and up the food chain,” Eduok told The Conversation. “They can adversely affect aquatic life when subsequently introduced into the aquatic ecosystems.”
“POPs and exhaust particulate matters can affect human health,” he continued. “They can cause allergies, hypersensitivity, birth defects and neurological disorders. Most POPs are carcinogens. Some of them may alter the nervous systems, leading to chronic health conditions. POPs can also affect reproductive health and disrupt the immune system. Some particulate matters cause lung inflammation and increase the risk of blood clotting.”
If you have snow, avoid taking a bite. Because of animal waste or something worse, the yellow snow can turn your winter wonderland into something far less fantastical.
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