Fresh, white, pristine snow can seem like a tempting treat on a day out skiing or walking through a snowy landscape. When you’re thirsty and standing in the snow, it’s natural to think that putting a handful of this pristine white substance in your mouth will relieve the dryness. It’s almost a universal ritual: children (and not-so-children) see snow for the first time and, before making a doll or a ball out of it, they already try to taste it as if it were an exclusive winter treat.
While it is not advisable to eat large quantities of snow, a small mouthful of fresh, clean snow in a natural environment, away from sources of contamination, should not present a significant health risk. To minimise the risks, make sure the snow is completely white and avoid areas close to roads, urban areas or areas where animal activity is evident.
It is best to eat the snow from the top surface, away from the ground, and make sure it is not an unusual colour. Although not a practice to be repeated frequently, eating snow in an isolated, clean place can be a harmless and fun experience if you’re careful.
However, as harmless as it may seem, eating snow carries a number of risks to your health and well-being. Here are five reasons why you should avoid eating snow, even at the most tempting times.
Snow is not as pure as it looks
Although it may look like an immaculate blanket of white, snow is far from pure. As snowflakes fall into the atmosphere, they pick up particles of pollution, dust and chemicals from the air, including traces of industrial emissions, vehicle fumes and heavy metals. In fact, scientific studies have shown that snow in urban areas and near industrial zones can contain worrying levels of toxic pollutants, such as sulphur dioxide and ammonia. Here are some of the pollutants that can be found in snow mainly in or near urban areas:
- Heavy metals such as lead, mercury and cadmium from industrial and car emissions. Eating snow at the side of the road is certainly not a good idea.
- Black carbon particles, a product of the incomplete combustion of fossil fuels.
- Toxic chemical compounds, notably sulphur dioxide, nitrogen oxides and ammonia, released by factories, power stations and agricultural activities.
- Microplastics, found even in polar regions, from the wear and tear of plastic products and synthetic fabrics.
Even in remote regions, snow can incorporate pollutants carried by air currents over long distances. Studies have detected pesticides used in intensive agriculture or mineral dust from the Sahara in the snow of the Alps and the Arctic. Ingestion of these compounds can have long-term negative effects on health, particularly on the respiratory and digestive systems.
Risk of hypothermia
Consuming large quantities of snow can have a significant impact on core body temperature and the body’s thermal balance. As you know, there are different types of snow and the information below varies, but in general, snow is made up of 90% air and 10% water. It can also be found at temperatures close to or below 0°C. When snow is ingested, the body must consume energy to heat it and transform it into liquid, a process that results in additional loss of body heat and makes it difficult to maintain an optimal core temperature.
Thermoregulation in the event of heat stress is particularly delicate in conditions of extreme cold, where the body is already working hard to avoid hypothermia. Scientific studies have shown that cooling of the digestive tract, even in small areas such as the mouth and oesophagus, can provoke a vasoconstriction reflex reaction, further reducing the body’s ability to retain heat.
The most vulnerable groups are children, because of their higher surface-to-volume ratio, which makes them more prone to rapid heat loss, and thinner people, who have less adipose tissue for thermal insulation. In these cases, the risk of snow-induced hypothermia is even higher.
Presence of bacteria and micro-organisms
Although associated with cold, pristine climates, snow is not free of bacteria, viruses and other micro-organisms. Freezing water does not eliminate these pathogens, but acts as a preservation mechanism that allows them to remain dormant until they find conditions favourable to their proliferation.
What’s more, snow that accumulates on surfaces such as branches, roofs or the ground can easily become contaminated. These surfaces are often exposed to a wide variety of contaminants, including animal waste, excrement and chemical residues. For example, faeces and urine from birds, wild animals and pets can leave bacteria such asEscherichia coli and Salmonella on snow, as well as parasites responsible for diseases such as leptospirosis and giardiasis.
A study published in theInternational Journal of Environmental Research and Public Health highlighted that even in apparently pristine environments, snow can contain environmental bacteria such as Pseudomonas and Acinetobacter, some of which are resistant to antibiotics. This type of contamination is more common in areas close to human settlements, in busy areas of ski resorts or in areas frequented by animals.
Consumption of snow that has been in contact with these sources of contamination can present a significant health risk, particularly in terms of gastrointestinal infections and parasitic diseases.
Impact on hydration
While it seems logical to think that snow can quench thirst, its composition does not allow it to perform this function effectively. Composed essentially of air and frozen, the body has to expend extra energy to warm it up and transform it into liquid before it can be processed. This can have theopposite effect to that intended, causing dehydration rather than preventing it. Studies in mountain medicine have shown that direct consumption of snow can cause irritation of the gastrointestinal tract due to its low temperature, aggravating the feeling of dehydration. What’s more, dehydration is not just a loss of water, but also ofessential electrolytes. As snow contains no minerals, eating it does not replenish these vital substances.
It’s better to drink than eat snow: in survival situations, it’s advisable to melt snow before eating it to avoid these negative effects. To melt snow effectively, place it in a metal container and heat it over a constant heat source, such as a fire or portable stove. Start with a small amount of snow, or add a little water if you have some, to speed up the process and prevent it from burning. In an emergency, you can melt the snow by placing it in an airtight bag inside your coat, taking advantage of your body heat. If you can, filter or boil the resulting water to remove contaminants and make sure it’s safe to drink. If you think you may be exposed to a critical situation, remember to take water purifiers such as chlorine tablets (Aquatabs), iodine tablets (Potable Aqua) or chlorine dioxide tablets (Micropur Forte) with you.
Risk of toxic substances in coloured snow
In certain environments, it is possible to observe snow with unusual colours: yellowish, reddish, orange or even greenish. These hues, which may seem curious or natural, are often a sign of contamination or the presence of organisms that could present a health risk. Here are the different colours that snow can take on and their causes:
- Yellow snow: This often indicates contamination by animal urine or faeces, which can introduce bacteria such as Escherichia coli or Salmonella. In some cases, it may also contain mineral-rich dust carried by the wind from desert regions.
- Red snow or “watermelon”: caused by algae of the genus Chlamydomonas nivalis, which thrive in cold conditions. Remember blood rain? It’s the same thing, but in the snow. These algae produce carotenoids that give them their reddish colour, but they also release chemical substances that can be toxic or cause gastrointestinal irritation if ingested.
- Orange or brown snow: this can be caused by fine particles carried by the wind or by industrial pollutants. These particles often contain heavy metals and other elements that are toxic to health.
- Greenish snow: sometimes the product of specific bacteria or algae, whose chemical composition can be harmful to the body.
Although these colours can be visually striking, it is safer to admire them from a distance. Eating coloured snow can expose the body to toxins, bacteria or other contaminants that can cause serious infection or poisoning.
