More and more environmental groups are making noise about the devastating impact winter salting has on the environment which is raising awareness and forcing lawmakers to look at alternative solutions.  In Canada alone, the country applies five million tonnes (over 110 billion pounds) of salt during an average winter.  This salt contaminates ground and freshwater, degrades habitat, alters aquatic ecosystems and causes corrodes critical infrastructure such as water pipes.

The massive increase to the salt content of soil located next to roads affects roadside vegetation; often killing the vegetation and impeding its ability to grow back.  Unfortunately, many invasive plants are well-adapted to high levels of salt, leading to a greater potential for invasive species to take over and spread along roadside communities. Researchers in Massachusetts found that road salt use directly aided the spread of invasive phragmites along the Kampoosa Bog in Stockbridge.

Many wild animals such as moose, deer, cattle, woodchucks, squirrels and mountain goats require essential elements such as sodium in the springtime for bone, muscle and other growth.  Salt deposits exacerbate roadside collisions as the wild salt-seekers are drawn from miles away to lick the mass salt deposits left near highways and roads during the spring.

People living in snowy climates are well away of the devastating effects salt has on their vehicles, perhaps not on what can occur within their own bodies.  Excess salt can contaminate ground and freshwater; water that we drink and use to prepare food.  Not all the salt can be filtered out of the water and can pose health risks to those who require sodium-reduced diets or those with hypertension.

High levels of chloride in water can corrode plumbing and leach harmful metals into drinking water, posing health risks, particularly for people using well water. Corroded water pipes lead to breaks which can cause disruption in service and even flooding.  Not to mention that the elevated chloride levels can also corrode appliances using water such as dishwashers and washing machines.

Sustainable alternatives are being implemented in both Canada and the United States.  Many Canadian municipalities are using a more environmentally friendly de-icing agents such as a mixture of beet juice and salt.  Beet juice works in the same was as road salt, but the beet juice stays on the road longer, so it is not only effective, but requires fewer applications.  In Wisconsin, cheese brine; an industrial byproduct from the dairy industry that is normally dumped as waste, is being combined with salt to create a unique deicer.

More and more people are experimenting with sustainable salt solutions and hopefully in the near future less salt will be used.

Researchers examined 371 lakes and found that 44% are at risk of salinization, meaning there is a build of salt in the water table. This excess of salt negatively affects water quality, wildlife and soil.

Salt use has increased dramatically in the past 50 years and the EPA estimates that 22 million tons of salt is applied to roads annually. That salt is washed into lakes, rivers and streams.

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The city is concerned with the damaging effects of road salt.  It would ultimately get washed into storm drains which flow to a sewer treatment plant.  Will the salt corrode old metro-area pipes? It affects the roads, the steel in the bridges and the concrete and it affects your car.  And, the salt that stays on the roads will eventually get washed into the environment.

Minnesota is beginning to see some of the environmental effects of road salt use. In the Twin Cities metro area, the level of salt (chloride) in 39 surface waters now exceeds water quality standards.  An additional 38 surface waters are almost above the standard and many others remain untested.  Data shows that salt concentrations are continuing to increase in both surface waters and groundwater across the state.

The fact is that it only takes one teaspoon of road salt to permanently pollute 5 gallons of water. Once in the water, there is no way to remove the chloride. At high concentrations, chloride can harm fish, aquatic plant life, groundwater and drinking water supplies.

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Salt not only damages metal and concrete, it contaminates drinking water, kills vegetation, and accumulates in streams, lakes, reservoirs, and groundwater, harming aquatic plants and animals.  As much as 70% of salt spread on roadways stays within the watershed.

Now that we know where the salt goes, where does it come from?

The U.S. is the second-largest road salt producer worldwide after China, but we also import a good deal of the salt it uses to coat its streets. At 12 million tons per year, America is the biggest salt importer in the world. Most salt imports come from Canada and Chile.

Rock salt is formed in the ocean.  The chlorine coming from the volcanoes at the bottom of the ocean mixes with the sodium washing off the continents with rainwater to create salt.  There is a lot of salt in the oceans, but it is only about 3½% of the worlds salt supply.   Areas with thick salt deposits was probably one where an ocean was, but has since evaporated.

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Salt is a natural mineral that lowers the freezing/melting point of water.  Salt is made of two components, sodium and chloride.  When dry salt is spread onto a paved surface, it will dissolve and form a solution called brine.  It is the brine that melts the snow and ice by reducing the temperature at which water will freeze.  At 32^o water will turn to ice and above that point ice will melt.  A 10 % salt solution will freeze at 20^o and a 20 % solution freezes at 2^o, so the colder it gets, the more salt is needed. While it may sound relatively simple, it is actually quite complicated and scientific.

Salt not only damages metal and concrete, it contaminates drinking water, kills vegetation, and accumulates in streams, lakes, reservoirs, and groundwater, harming aquatic plants and animals.  It is only the beginning of February, Wisconsin hasn’t seen very much snowfall, yet our roadways are white from the dried brine.  As much as 70% of salt spread on roadways stays within the watershed.

Salt also causes soil alongside roads and sidewalks to become more acidic and reduces its ability to retain water which increases its susceptibility to erosion.  It also affects the soils ability to transfer nutrients to plants resulting in the extra nutrients being leached into the ground water.  The salt also damages trees and vegetation; it dehydrates the cells creating a drought like effect when absorbed.

In high concentrations sodium chloride can be harmful to aquatic organisms.  While most waterways have not reached a status that is considered lethal, the high concentrations the excess salinity due to the salt concentrations impedes the survival of spotted salamanders and wood frogs.  Changes in the salinity of a pond or lake can also affect the way the water mixes as the seasons change, leading to the formation of salty pockets near the bottom and biological dead zones.

Sodium is essential to life and good health at recommended levels. Since the body doesn’t produce sodium or chloride it is necessary to obtain the mineral in both food and beverage.  Road salt does have a negative impact on human health. High concentrations of sodium in groundwater increase the amount of the mineral into the body, leading to hypertension, increasing the chance of heart attacks, and strokes.  Too much salt can also irritate the stomach lining and may trigger stomach cancer.  Some states monitor their drinking water for sodium, but there are no federal regulatory standards for sodium concentrations in drinking water in the United States.

So why do we keep using road salt if it is harmful to humans, aquatic organisms and the environment?  Well, it is not only effective, but it is cheap compared to other forms of de-icing that are available.  Alternative chemicals are expensive and often require municipalities to invest in new spreading equipment.  Calcium chloride, for example, is quite effective for extremely cold temperatures, but costs five times more than road salt and is much more corrosive. Road salt it a necessary evil in some parts of the world. Its use prevents accidents and loss of productivity due to impassable roads.  The only win-win is to use road salt in the most efficient manner to decrease the amount of salt needed to keep people safe.

Road Salt White Paper

Cary Institute Special Report

Alternatives to Road Salt