Sodium chloride is currently being debated for its effects on human health, but the chemical compound commonly known as salt is also often questioned for its effects on the environment. Only a fraction of the sodium chloride produced in the United States is consumed as food, while the rest is used for road maintenance, water treatment, and manufacturing.
The debate over sodium in health stems from two papers and an editorial published in the New England Journal of Medicine which conflict with current medical practice guidelines advocating low sodium intake. The studies suggest that moderate amounts of sodium in the diet, as opposed to low amounts, pave the way to optimal health. The debates will continue until definitive clinical trials can determine how much salt is healthy and how much is not. Meanwhile, it is appropriate to consider the myriad ways in which chemical compound, NaCl, affects everyday life, most notably as a road deicer and a water softener.
Applying salt to melt ice on roadways saves lives and money, studies show. One study, by Marquette University, showed that road salt reduced vehicle crashes by 88 percent and vehicle-related injuries by 85 percent. An additional study performed for the American Highway Users Alliance found that snowstorms can cost states as much as $700 million per day when roads become impassable.
With compelling numbers like these, deicing becomes a necessary strategy for maintaining the welfare of communities, yet the environmental costs of using salt as a deicing agent are high. According to the Chesapeake Stormwater Network, one of the main problems with sodium chloride, or NaCl, as a deicer is that the chloride molecule is extremely soluble in water and easily contaminates groundwater and other bodies of water when the treated snow melts. Another problem with sodium chloride as a deicer is that high salt levels in roadside soils may cause many plants to die or fail to germinate.
While some winter road maintenance goals can be accomplished with abrasives such as sand, researchers are still seeking viable cost-effective alternatives to NaCl. Emerging substances of interest include methanol and calcium magnesium acetate (CMA). While both products are made from waste cellulose, CMA is preferred because, unlike NaCl, CMA inhibits corrosion, is beneficial to most soils, will not harm water supplies, and acts at the same rate and temperature as NaCl.
While the search continues for viable alternatives, proponents of sodium chloride as a deicing agent argue that safe and sustainable snowfighting practices can minimize road salt’s effects on the environment. Best practices for road salt management include appropriate salt storage facilities, calibrated spreaders for precise application and improved driver training. The American Public Works association trains snowfighters in safe and sustainable deicer storage and snowfighting techniques.
Sodium chloride cation exchange water softeners remove the calcium and magnesium ions found in hard water by exchanging them with sodium or potassium ions. Cation technology has been used to soften, or de-mineralize water, since the 1960’s. While the technology is often advertised as being outdated for household use, it is effective and is widely used in large-scale manufacturing. The presence of certain minerals in hard water, especially calcium and magnesium, causes production quality decline and undue wear and tear on machinery.
In household examples, hard water fades the colors of clothing, leaves cloudy films on dishes, and adds scaling, or mineral deposits, to water pipes and plumbing fixtures. The scaling from mineral deposits is unattractive, reduces the efficiency and shortens the life span of fixtures or appliances, and harbors microbes. Hot water heaters can lose up to 48 percent efficiency over 15 years if constantly exposed to hard water.
Water free of calcium and magnesium deposits is known as soft water, and creates better suds for washing, requires less energy for heating, and reduces microbe-friendly environments on plumbing fixtures. Soft water use studies have determined that dish washing and clothes washing machines using soft water require only half the detergent of those using hard water and can run effectively on cold water cycles.
Despite the benefits, salt-based cation water softening systems can use up to 25 gallons of water or more per day which translates into 10,000 gallons per year. However, the Environmental Protection Agency’s (EPA) WaterSense report is careful to indicate that water softening technology over all has reduced water consumption and demonstrated a great potential for water savings.
As the debates continue in medicine over the effects of sodium on health, debates are also ongoing in the environmental arenas of road maintenance and water quality about how best to manage salt. The overall message about sodium chloride in any area of inquiry seems to be that future studies must continue to explore the key question of what is the right amount.
By Lane Therrell