Is it okay to eat snow?

Winter is coming – and with it hopefully the snow. If you want to let the delicate flakes melt on your tongue, you should pay attention to a few things.

How unhealthy is a portion of snow? If you consider a few things, nothing stands in the way of a little culinary but the colder meal.

Every year you can hardly resist the joy of the first snow. If it quietly trickles from the clouds and collects at best in a thick layer on the ground, the landscape disappears as if under white cotton candy. While adults rarely give in to the impulse to eat snow, children gaze skyward with their tongues sticking out and lick the thick flakes off their gloves. But is eating snow healthy?

What is snow made of?

Somewhere in the back of my mind there is still the information that eating snow is unhealthy, if not even dangerous, because it contains too many pollutants and impurities. But is this true?

For a snowflake to form, three prerequisites must be met: a temperature below zero degrees, sufficiently high humidity plus condensation nuclei. If the air contains enough water vapor, the vapor condenses on one of these nuclei – usually a chemical particle in the air. Below zero degrees, these water droplets freeze into ice crystals and link up with other ice crystals to form an ice crystal lattice. By the time the snowflake falls from the cloud, it is made up of about 10 million ice crystals, most of which form a hexagonal prism. Temperature and humidity are responsible for the shape: for example, if it is warmer than -5 degrees, larger snowflakes will form than if the temperature is cooler and the air is therefore drier. Stars are formed only at a temperature of -12 degrees.

A snowflake is made up of 100 percent water. But as it travels through the atmosphere and lies on the side of the road, it can pick up small particles, so that when we want to eat it, it is enriched with some unwanted "additives".

Snow binds pollutants

On its way through the atmosphere, the snowflake encounters tiny pollutants and microplastic particles, some of which have been transported long distances through the atmosphere. "With snow, pollutants bind to the condensation nucleus, condense on the snow or are washed out of the air by the snow through collision. If the snow lies for a long time, then additional dust can be deposited on the snow surface" explains a spokeswoman for the Bavarian State Office for the Environment (LfU), which has been determining inputs of poorly degradable organic pollutants at various research stations in the Alpine region for 15 years as part of the PureAlps project. The results of years of monitoring pollutants in the Alps show numerous substances that are difficult to break down in the air, precipitation, soils and plants. "We are investigating particularly problematic pollutants such as mercury, flame retardants, dioxins or organochlorine pesticides (z.B. DDT). We detect a wide range of these contaminants. In general, the cold and high precipitation in the mountains lead to a strong leaching of the pollutants recorded in PureAlps. Thus it comes that in the Alps, despite usually very low pollutant concentrations in the air, the entries can be similarly high by the precipitation as in urban areas", so the spokeswoman.

Snow from alpine peaks

This means that even remote alpine areas are no longer free of environmental risks from chemicals. One reason not to enjoy a handful of snow from the top of the Alps? "Substance-related limit values of the drinking water ordinance are not nearly reached in freshly fallen snow. The average concentration of mercury in the snow at the Zugspitze is more than 100 times lower than the limit value of the drinking water ordinance. For the insecticide DDT, measured concentrations are over 1000 times lower. Soils also filter out pollutants very efficiently, so that in the area of the Zugspitze, the spring water in the Partnach valley contains even lower concentrations of these substances than in freshly fallen snow," reassures the spokesperson for the Bavarian State Office.

Gallery: Homemade glaciers

Microplastics in snow

A 2019 study by the Alfred Wegener Institute and the Swiss WSL Institute for Snow and Avalanche Research SLF examines the concentration of microplastics in snow from different global locations and what role atmospheric transport plays. It shows that snow even in the most remote regions of the Alps or Arctic contains microplastic particles. Different plastics were detected in varying concentrations depending on the region: The highest concentration of 154.000 particles per liter the AWI researchers found in samples from a Bavarian country road. Arctic snow still contained up to 14.000 particles per liter. Different plastics could be detected depending on the location. While nitrile rubber (frequently used in seals and hoses), acrylates and plastic-containing paints (frequently used on the surfaces of buildings, ships, cars and offshore installations) were found in the Arctic, the samples from the countryside mainly contained various types of rubber, which are used in car tires, among other things.

Snow from the garden

It is obvious and easy to teach children not to eat gray snow from the roadside. But what about the supposedly white snow in your own garden or on your car?? Sea ice physicist Dr. Stefanie Arndt of the Alfred Wegener Institute at the Helmholtz Centre for Polar and Marine Research gives the all-clear: "Eating snow is definitely ok! Microparticles can be found even in drinking water or everyday food, it is the same with snow. Of course, when you take snow from the meadow, you have to make sure that the snow layer is thick enough so that you don’t pick up anything from the ground."

The same note comes from the spokesperson of the Bavarian State Office for Health and Food Safety (LGL): "Since pure snow consists only of water, an uptake of small amounts is usually unproblematic. In practice, however, the problem is that contaminants that may be present beneath the snow surface, such as z. B. excreta from animals, are not detected and could be ingested if necessary."

How much snow is healthy?

Grey and yellow snow are therefore taboo. Then there remains the question of how much snow one is allowed to eat. Is a handful allowed, or half a snowman still in the tolerable range? Dr. Arndt reports that "on polar expeditions, snow is used as a source of liquid and for cooking. The available snow is melted to cook food in it or to use it as a base for tea and coffee."Boiling is not a must, because "snow in its pure form does not need to be boiled. At the most, snow from deeper layers, which has a certain age, can be boiled to kill germs. Normally, however, snow can be taken exactly as it is."

Theoretically, man could quench his thirst with snow. In practice, however, there are problems: Snow as frozen water has a much lower density than water in liquid form. You would have to melt about ten liters of snow in your mouth to drink one liter of water. Melting makes the mouth freeze after a short time and costs the body valuable energy. This can become a problem in an emergency situation. So it has happened that climbers have died of thirst in the snow.

In addition, humans cannot live on snow alone, a balanced diet is important as always. Snow is free of mineral salts and thus has a similar effect on the body as distilled water, whose disturbed salt balance then reacts with nausea, headaches or palpitations. "Snow is not enriched with minerals on its way through the atmosphere. This is the difference to, for example, river water. If the snow falls out of the atmosphere as a pure form of snow, it naturally lacks this enrichment. That is, I should not live exclusively on snow for weeks, because then minerals that are important for the body are missing," says the sea ice physicist.

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