Road Salt: Safety vs. the Environment

By: Gwen Roth

Is that really the question? Around this time of year many questions come up about using salt to melt the ice on our roads and bridges. Road salt (sometimes called rock salt) is mostly sodium chloride, the same as our table salt, but in a much coarser form. Sodium chloride, in small amounts is actually important for people to consume, but in larger amounts can be harmful to people, wildlife and aquatic ecosystems.
So where does rock salt come from and why do we use it? Interestingly, according to the American Geosciences Institute, Ohio is the 3rd largest producer of rock salt (5.4 million metric tons), behind Louisiana and New York and 2nd highest consumer of rock salt (3.5 million metric tons), behind only New York. Rock salt is used by many communities to make travel safer. It is spread on roads to help lower the freezing temperature of water, thereby not allowing ice to form. Over the years, the use of road salt has increased dramatically in the US.

Image: American Geosciences Institute

With this increased use of rock salt, comes increased environmental issues as well. While the rock salt is designed to keep roads from becoming slippery, as the snow and ice melts it mixes with the salt and runs off. This stormwater runoff often goes directly to creeks and streams where it can wreak havoc on local aquatic ecosystems. A 2017, study of 371 lakes in North America (mostly in Northern US and Southern Canada) showed chloride levels rose in over 30% of the lakes and more than two dozen were approaching chloride levels harmful to aquatic wildlife. When salt gets into our local waterbodies, it can alter the water’s temperature, dissolved oxygen levels and cause stratification - the inability to mix water vertically in the water column. This can lead to fish kills, algal blooms and an increase in non-native species, who are traditionally more able to adapt to changing environments.
Our local governments are doing many things to decrease salt runoff, including pre-treating roadways with a mixture of salt and water (called brine which uses significantly less salt than traditional treatments), using alternative solutions (like beet juice mixtures) and making sure salt is stored in a covered area to prevent runoff.
So, what can you do to help out? When it snows, first shovel your driveway or sidewalk before adding salt and make sure to use the minimum amount to do the job. You can always add more later if needed. If you just want to get traction and not to melt the ice, you can always add sand, but try to sweep up later to avoid clogging storm drains. Research alternatives to rock salt. Many ‘environmentally friendly’ or ‘green’ products that people use to replace salt might not be that green at all, so do your homework. In 2019, Olivia and Sophia Dick from Wyoming High School won the Caring For Our Watersheds competition because they had researched an alternative to rock salt, made up samples and distributed them to their local community members. What was their alternative? Used coffee grounds and alfalfa meal and it really works! ​

Bottom line, we live in a climate where we have to deal with snow in the winter (at least some of the time) and while there is no perfect answer to get rid of the snow, we can all do a little to help protect our local ecosystem by not over using salt. ​

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Sources:
Dugan, Hillary A., et al. “Salting our Freshwater Lakes.” PNAS vol. 114, no.17, 2017, 4453-4458. https://www.pnas.org/content/114/17/4453.full
Lilek, Joseph, “Roadway Deicing in the United States.” American Geosciences Institute. 2017. https://www.americangeosciences.org/sites/default/files/CI_Factsheet_2017_3_Deicing_170712.pdf