Is it Safe to Eat Snow?
Contributed by The Organic Trade Association

Snow seems so white and clean, it covers the stubby gray fields, hides the dirty sidewalks, and glistens in the sun. It's so soft and cool, melting on our tongues, but should we be eating snow?

How Snow Forms
Snow is formed by water vapor in the clouds moving around by winds through increasingly cooling temperatures. The water molecules stick to a microscopic piece of dust, called a nucleator. Other water molecules can join onto this, forming a crystal.

As the crystal builds, the base shape is a flat six-sided crystal, forming a three dimensional hexagon. The flat parts of the six sides are called prism faces. The other two sides are called basal faces. In total there are eight faces: top basal, bottom basal, and prism faces one through six, forming the characteristic eight faces. The crystal can continue to blow about for hours before falling to the ground. The crystal will "grow" differently at different temperatures and humidity as it is blown about, allowing for a great variety of crystal end shapes. Snowflakes are beautiful to look at.

Upon landing, the weight of the upper snowflakes will press down on those underneath, thus packing the snow. The density of freshly fallen snow can vary widely depending on the type of snow crystals that have fallen and the air temperature at ground level. The density can range from as high as a 5:1 ratio of water to air to as low as 20:1 due to wind, ground-air temperature and ground heating.

White as Snow
In the pristine vista of Saskatchewan, Canada, soil in this arctic region becomes polluted each June and July, due to melting snow. A high concentration of gamma-hexachlorocyclohexane (y-HCH) an agricultural pesticide is transported in high altitudes in the form of microscopic dust particles from the Southern United States and Mexico (1) creating toxic nucleators.

Using computer models of the atmosphere, Frank Wania of the University of Toronto has studied the mechanisms that bring heavy metals and persistent organic pollutants (POPs) to the Arctic. "There is a systematic transfer of these chemicals from warmer to colder areas. The region's environment attracts and holds volatile compounds that travel on the winds and condense out at temperatures between freezing point and -50 C. These include some PCBs--oily synthetic compounds once used widely as insulators in electrical equipment--HCHs, toxaphene, and other pesticides such as chlordane. DDT and some similar compounds tend to condense out at warmer temperatures in mid-latitudes, and are not concentrated in the Arctic in the same way as PCBs and HCHs. Other POPs, such as naphthalene, are too volatile to condense anywhere, even at the poles."

Contaminants released in the tropics can reach the Arctic surprisingly fast. "Highly volatile chemicals can get from India, say, to the Arctic in five days," says Wania. Others may take their time, falling to the ground and re-evaporating many times before completing their northward journey. Less volatile compounds often arrive bound to aerosol particles, and even within snowflakes.

 "If so", says Dennis Gregor of the Center for Groundwater Research at the University of Waterloo in Ontario, "They can produce a 'flush' of toxins in rivers when the snows melt in early summer, just when biological activity is most intense."

In April of 2002, researchers in California announced that male frogs exposed to even very low doses of a common weed killer developed multiple sex organs. "I was very much surprised at the impact of atrazine on developing frogs", said Tyrone B. Hayes of the University of California at Berkeley. "Atrazine is the most commonly used weed killer in North America, and can be found in rainwater, snow runoff and ground water."(3)

What you can do
Ski, sled and make snow creatures to your heart's desire. Admire its wonder and beauty, and don't panic if your dog or young child eats some snow. You can join an environmental organization (see links page) both global and local. Every day you can effect the environment with your dollars by purchasing food and fiber products that are grown organically, thus reducing the presence of pesticide residues.

References:
1. The effect of usage of gamma-hexachlorocyclohexane(y-HCH) in Canada on the contamination of soil and air. http://www.cmc.ec.gc.ca/~arqidor/lindane_qs.html

2. From New Scientist
Transport of chemicals around the Earth. magazine, vol 154 issue
2084, 31/5/1997, page 25 http://darwin.bio.uci.edu/~sustain/bio65/lec14/Northern%20Exposure%2031%20May%2097.htm
3. From Sounder
http://askwaltstollmd.com/archives/mcs/101157.html