NRDC's This Green Life
A Journal of Sorts
January 2009 / Links updated 2012
Salt's not the best answer

Ah, January. Up where I live, winter's white mantle is back. I don't mean snow, but the residue left on paved surfaces -- and boots -- by road salt.

Winter leap Applied to melt ice, road salt cracks pavement, undermines bridges, corrodes cars, seeps into groundwater, damages plants, endangers wildlife and alters habitat for aquatic species when washed into lakes and streams. It also hurts pets' paws. My dog, for one, goes into a terrible limp if I accidentally walk him through a patch.

Something this harmful must be a synthetic concoction cooked up in a lab, right? But no, it is usually just sodium chloride (NaCl), the same stuff that seasons your food, raises your blood pressure and makes you so much more buoyant in the ocean than you are in the pool. It only becomes troublesome when it is present at high levels where trace amounts should exist, such as freshwater ponds and the undersides of cars.

First used to clear streets in the 1930s, road salt gained traction in the 1960s. Nowadays some 10 million tons or more are used to de-ice roads each year in the United States. It is the major use of salt in this country.

Interestingly, salting roads may not result in fewer accidents. Conceivably, there would be even fewer crashes if roads were left icy and people stayed home. The research hasn't been done. No matter. When roads are clear of ice, deliveries get delivered and workers get to work -- and that's the main motive for salting roads in the first place ("the economy, stupid!").

Of course, mobility can be important for other reasons, too, as I was reminded last week when I needed to get back and forth to my mother in the hospital during a snowstorm. Ambulances, among other emergency vehicles, depend on cleared roads to get through.

Transportation professionals are not unaware of the problems caused by salt. The federal Department of Transportation even commissioned a study, completed in 1991 by the Transportation Research Board, a division of the National Academies, that compared the costs (all kinds, including environmental) of salt and a more benign alternative, calcium magnesium acetate, or CMA. The study concluded that a wholesale shift from salt to CMA was unwarranted, primarily because CMA was 20 to 30 times more expensive to purchase and use. Instead, it recommended pursuit of less expensive, targeted mitigation measures, including selective use of CMA in environmentally sensitive areas.

Since then, transportation agencies have learned how to reduce salt usage through improved spreading techniques, better timing and the use of other substances to aid in de-icing and provide traction. Meanwhile, engineers have figured out methods to reduce the impact of salt on cars and infrastructure. But the engineering has not come without a cost, and the environmental impacts remain. There is also a human health risk that has often been raised but never properly explored -- the effect of drinking water with higher salt concentrations on people with high blood pressure.

As home and business owners, we contribute to the salt overload directly when we salt our driveways, walkways and stoops. While there's no reason to leave the ice in place and risk a fall (or lawsuit), we can certainly learn better methods of de-icing. Here are the key ways:

Shovel snow before it can accumulate. De-icers are more effective with less snow in the way. And it's possible that by assiduous shoveling, you can avoid the need for de-icers altogether by preventing ice build-up.

Use the least toxic de-icers you can afford. The best choice is CMA. Though pricey compared to salt, new production methods may soon make it cheaper. Potassium acetate (KA) is another promising alternative. It has not been studied as extensively as CMA but appears to be similarly benign and to work at colder temperatures than either CMA or salt. Next best is calcium chloride. Though a salt with similar impacts to sodium chloride, it can be used in smaller amounts -- which is doubly good as it is also more expensive than sodium chloride. Urea is sometimes billed as a less toxic de-icer, but is a "nutrient" that can cause lakes to eutrophy -- so do not use it.

Many products are mixes of different de-icing agents. A mix of sodium chloride or calcium chloride and CMA or KA is better than one of the salts alone. Read the ingredients list on the label to know what you're getting, rather than relying on claims of environmental safety.

If you use sand for traction, collect it afterwards. Otherwise, it may end up causing sedimentation in wetlands and other water bodies, which could ruin habitat and impede water flow. It could also clog storm sewage systems. Do not bother with kitty litter or ashes. They are very messy and hard to sweep up.

Apply de-icers early -- and with restraint. Anti-icing (applying the de-icing agent in advance) is necessary with CMA and a good practice with salt as well. Do not use more than the amount recommended on the label. You will not get better or quicker results.

Here's hoping you won't have many occasions to try this advice this winter!

Family photos
Sheryl Eisenberg, a long-time advisor to NRDC, posts a new This Green Life every month. Sheryl makes her home in Tribeca (NYC), where—along with her children, Sophie and Gabe, and husband, Peter—she tries to put her environmental principles into practice. No fooling. Read more about Sheryl.


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Put Your Sidewalk and Driveway On a Low Salt Diet

What Is the Best Deicer?

Effects of Road Deicing on Enrivonment

Environmental Impacts of Road Salt and Alternatives in New York

Uses & Benefits

Cold Weather Protection for Pets

Salt-Tolerant Roadside Plants

Not news. Humans have known since ancient times that salt could be toxic to plants. Hence, combatants would "salt the earth" of their enemies -- to prevent crops from growing. The most famous example (possibly apochryphal) is the salting of Carthage by the Romans in the Third Punic War. Examples can also be found in the Bible.

Dog with booties
Protect your pooch. If your dog's paws have been exposed to de-icers on a winter walk, wash them when he returns home. Use a wet cloth or dunk them in a container of warm water. This is necessary not just to keep the paws in good condition, but to prevent ingestion of the de-icers through licking. Even better, equip your dog with booties before he goes out.

Salt-tolerant and salt-sensitive plants
Protect your lawn and garden. Avoid applying salt to paved surfaces near trees, shrubs, flowers and grasses that are sensitive to it. If you are considering new plantings near paved surfaces, pick salt-tolerant species. For instance, salt spray roses (top) tolerate salt whereas azaleas (above) don't. Among trees, red oak would be a good choice, where red maple would not be.

Your favorite nature spots and mine

This Green Life nature map

Been to any great nature spots lately? Add it to the This Green Life nature map. Here's how:

  1. Go to the map on Google.
  2. SIGN IN to your Google or Gmail account. (You need an account to edit the map.)
  3. Click the edit button in the panel to the left of the map.
  4. DON'T CHANGE the map title or description! INSTEAD, click the balloon icon near the map zoom controls.
  5. Move the balloon to your favorite spot and click.
  6. Tell us why you love it—and link to a picture if possible.
  7. Click OK.

Sheryl Eisenberg is a web developer and writer. With her firm, Mixit Productions (, she brought NRDC online in 1996, designed NRDC's first websites, and continues to develop special web features for NRDC. She created and, for several years, wrote the Union of Concerned Scientists' green living column, Greentips, and has designed and contributed content to many nonprofit sites. In between issues of This Green Life, she muses aloud on green issues at

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