Pass On the Salt

De-icers can hurt the environment, but there are other options.

By Thomas J. Fox

February 2006

In the northern United States, midwinter not only means snow, but some other white stuff—for instance, road salt, of which Americans use some 10 to 20 million tons each year. But for all the research that has been conducted on the effects of salt in people’s diets, surprisingly little has been done to examine its repercussions on the environment. 

“I’ve been concerned about it for many years,” says Daniel Hillel, senior research scientist at the Center for Climate Systems Research of The Earth Institute at Columbia Uni­versity, and one of the world’s foremost experts on soil and water. “Someone should really be looking into it.”
Although much remains unknown about the long-term effects of road salts, some facts are clear: Overuse of salts can damage concrete, corrode the metal in cars and other structures, destroy trees and shrubs, and kill fish and other wetlands creatures.

One group that has researched this situation is Environment Canada, that nation’s counterpart to the US Environmental Protection Agency (EPA). In 2001, Environment Canada determined that road salt containing inorganic chloride salts are “toxic” as defined by the Canadian Environmental Protection Act. They are still used in Canada, but the designation has highlighted the risks and led to a code of practice aiming to optimize their use and reduce waste. In the US, by contrast, de-icers such as road salt are not even regulated by the EPA, except at airports.

De-Ice Nicely

If you’re responsible for clearing snow and ice around your home this winter, your sidewalks and pathways may offer a great opportunity to first do no harm. About 90% of the salt used for de-icing in the US is sodium chloride, sometimes called halite or rock salt. It is readily available, effective and—most of all—cheap. That appeals to state and local agencies responsible for snow and ice removal. However, homeowners can opt for safer alternatives, which fall into two basic categories: abrasives such as sand, which make the ice less slippery, and non-salt based de-icers, which actually melt ice. Abrasives are often used in conjunction with de-icers.

Sand is probably the best solution for homeowners. It can be swept up and reused, which helps eliminate the risk of silting up waterways. Experts discourage the use of kitty litter or ashes, which often become soggy when wet.

De-icing products often contain blends, so look for the main ingredients. Two choices to consider over rock salt are calcium chloride and calcium magnesium acetate (CMA). Calcium chloride costs slightly more than sodium chloride to use; while it is about three to seven times as expensive per pound, it covers about three times as much ground. More significantly, it is effective at far lower temperatures than other choices—down to about -25ºF, compared with about +15ºF for rock salt.

CMA is effective to roughly +25ºF, making it somewhat less effective than sodium chloride. It is also significantly more expensive. Still, CMA is generally thought to be the safest de-icer, as it is biodegradable and free of chloride. It causes little or no damage to concrete or metal and is believed to carry few environmental risks.

Keep in mind that the price of your de-icing product is not the only cost. “People pay $1,000 to put in a tree,” notes Douglas Wilcox, branch chief of Coastal and Wetland Ecology at US Geological Survey’s Great Lakes Science Center, “and then kill it with salt.” This may be especially likely if you have a preference for white pines, hemlocks, dogwoods, American lindens and hornbeams, Douglas and balsam firs, or other plants especially sensitive to salt damage. Avoid using sodium chloride around these plants or consider choosing more salt-tolerant trees such as ponderosa pine, horse chestnut, white ash and honey or black locust. Tall fescue and perennial ryegrass are relatively salt tolerant for turfgrasses, so you might plant them where you know your lawn will be exposed to rock salt or calcium chloride.

Safe storage of de-icing chemicals is a must to protect children, pets and—in some cases—the product itself (left exposed to air, calcium chloride can actually absorb moisture and harden into a pillar of salt).  Teach your children to avoid playing with treated snow. If you find that they have eaten or become irritated by a de-icing product, contact your pediatrician or the National Poison Center at 1-800-222-1222, which will connect you with your local poison control center.

Prevent your pets from eating or walking on de-iced pavements and wipe off their paws with a damp cloth or in a bucket of water if they have any salt residue. This is especially important for exposure to calcium chloride, which actually produces a significant amount of heat. If your pet has eaten a de-icing product or suffered irritation, it’s best to call a veterinarian who knows your pet’s medical history. If you don’t have one, contact the ASPCA Animal Poison Control Center at 1-888-426-4435 (note that there may be a $50 consultation fee). Avoid treating the problem yourself without proper veterinary advice. According to the Animal Poison Control Center, human medications and preparations are the number-one reason for calls to the center, accounting for nearly 40,000 annually.

Start Shoveling

Of all the ice-handling alternatives, the best may be an honest sweat—yours if you’re healthy enough, or someone else’s if you’re not. If you live near a body of water, “the most important thing to use is a shovel or a snowblower,” says Wilcox. Shoveling away what you can before applying a de-icer will improve effectiveness and limit the accumulation of salty slush, which you might end up needing to shovel anyway. If you know ice-forming precipitation is coming, apply de-icers early as precipitation begins to prevent ice from bonding to pavement, as well as after shoveling to eliminate slick patches. A calcium chloride-based de-icer will be the most available, sensible choice for those in most parts of the nation’s snowbelt.

Buy your de-icers early in the season, so you’ll have the widest range of environmentally friendly choices. Choose spherical pellets if buying rock salt or calcium chloride; they work better than flakes. Avoid fertilizer de-icers, such as urea, potassium chloride or ammonium sulfate. They work no better than sodium chloride and can harm plants. And remember to water heavily in early spring to help flush out salt residue if you’ve used rock salt or calcium chloride near your lawn or plants.

Unfortunately, we can’t control how government agencies handle public snow removal. But taking precautions and making the extra effort to use environmentally friendly products on our own land can help make sure that a snow day remains a safe day.

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