Snow often appears pristine and harmless, especially when fresh. However, the structure of snow crystals makes them highly efficient collectors of various substances as they descend through the atmosphere and settle on the ground. For this reason, consuming snow is not recommended, regardless of how clean or white it may look.
Invisible Dangers from Airborne Pollutants
Snowflakes form around tiny particles suspended in the air, acting like natural scrubbers for the atmosphere. As snow falls, its intricate, crystalline structure provides a large surface area that readily adsorbs and locks in chemical pollutants and particulate matter. A seemingly pure handful of snow can contain a concentrated mix of airborne contaminants.
In urban and industrial environments, the risks are significantly higher due to local emissions like vehicle exhaust and factory output. Snow in these areas can contain toxic compounds, including black carbon, trace metals, and volatile organic compounds like benzene and toluene. These substances are captured and concentrated within the snowpack.
Even in remote mountain regions, snow is not entirely safe from atmospheric pollution. Pollutants such as persistent organic pollutants (POPs) and pesticides can travel vast distances on air currents before being deposited onto the snow surface. The first snowfall of the season may be particularly contaminated, as it washes out accumulated atmospheric debris.
Hazards from Ground Contamination and Animal Waste
Once snow lands, it immediately begins to accumulate contaminants from the surface, introducing a new set of biological and chemical hazards. Snow that has settled acts as a blanket, soaking up whatever material it touches. Even a shallow layer of snow can be contaminated by substances often invisible to the eye.
A major concern is contamination from animal waste, a common source of illness-causing microbes. Fecal matter from wildlife, pets, and rodents can introduce bacteria like E. coli and parasites such as Giardia into the snow. These pathogens can survive in cold temperatures and cause severe gastrointestinal distress if ingested.
In developed areas, snow near roads and sidewalks is hazardous due to de-icing agents. Road salts and chemical mixtures, including magnesium chloride, are used to melt ice but are not safe for human consumption. The snow also picks up physical debris like dirt, dust, tire residue, and microplastics from the road surface.
The Physical Toll of Ingesting Frozen Water
Beyond the risk of contaminants, consuming frozen water can have physiological consequences, especially if done in large quantities. The human body must expend a significant amount of energy to melt the snow and then warm it up to core body temperature. This process is a form of thermogenesis, where the body generates heat to counteract the cold.
This energy expenditure is substantially higher than the energy required to warm liquid water, as the body must first convert the solid ice to a liquid state. For individuals in survival situations or those who are already energy-depleted, this unnecessary caloric cost can rapidly accelerate fatigue and compromise the body’s ability to stay warm.
Rapidly ingesting large amounts of extremely cold material can also cause temporary discomfort in the digestive system. The sudden exposure to near-freezing temperatures may trigger a localized vasoconstriction in the stomach lining. This can result in an upset stomach or temporary gastrointestinal distress.