Road Salts are Harming Our Waterways

Using road salts is necessary to ensure public safety during the cold weather seasons. Road Salts, or halite, is the mineral form of sodium chloride (NaCl) (LabNotes 2018). Unfortunately, it is relatively common to see too much or unevenly distributed salt on pavement. If it looks like you’re walking on marbles, there is way too much salt present. Overapplication of road salts is not only economically wasteful, but it poses severe threats to our freshwater systems.

Concentrations of road salts are becoming increasingly present in our waterbodies. According to the United States Geological Survey (USGS), between 16 and 35 million tons of salt are used each year on roads (Kelly, et al. 2019). Andrew Juhl, an aquatic ecologist and professor at Columbia Climate School, states that “once salt gets into the soil, or into a waterway, there really are no biological processes that will remove it” (Hinsdale 2018). Salt can be diluted by adding more freshwater to the system, but removing it requires human intervention and is not practical. Reducing our salt use is imperative to protecting Michigan’s most valuable natural resource, the Great Lakes.

In recent years, more studies have been conducted on road salts and their effects on freshwater systems. Scientists have found that elevated amounts of salts are toxic to fish, aquatic plants, aquatic insects, amphibians, zooplankton, and algae (Elgin 2018). Studies show that salts decrease biodiversity of aquatic animals and plants as well as favor the growth of cyanobacteria, which accelerates the eutrophication of freshwater systems (Szklarek, et al. 2022). Since salt is denser than freshwater, it will settle on lake bottoms, ultimately suffocating aquatic insects and other aquatic life (Elgin 2018).

Thankfully, most municipalities and road commissions have financial limitations, so they calibrate their equipment to disperse optimal amounts of road salt. They also have regulations and restrictions on salt application. Most of the over application of road salts is happening by private industries like businesses, plow companies, and residential areas. Educating the public on the consequences of overapplication of salt and providing tips on proper application techniques are imperative to reducing salt runoff into the Great Lakes and other local waterbodies.

If you are interested in taking the Salt Watch Pledge and testing your local lake, river, or streams for salt content, you may sign up and get Salt Watch kits mailed to you from the Izaak Walton League of America.  Each kit comes with four test strips, with the recommended testing regimen of once a month, December – March. If you would like a Salt Watch Kit immediately, you may contact Senci at senci.pace@gvmc.org to arrange a pickup at the GVMC office.

Fun Fact: Only a 12-ounce mug of salt-based de-icer is needed for a 20-foot driveway

Figure 1. Salt Watch Season 5 (2021-2022) results, West Michigan Specific. Salt Watch Findings (2021-2022) (iwla.org)

Works Cited:

Elgin, Erick. Feb. 22, 2018. “Salt runoff can impair lakes”. Michigan State University Extension. https://www.canr.msu.edu/news/salt_runoff_can_impair_lakes

Hinsdale, Jeremy. Dec. 11, 2018. “How Road Salt Harms the Environment”. State of the Planet, Columbia Climate School. https://news.climate.columbia.edu/2018/12/11/road-salt-harms-environment/

Kelly, V.R., Findlay, S.E.G., Weathers, K.C. 2019. “Road Salt: The Problem, The Solution, and How To Get There”. Cary Institute of Ecosystem Studies. https://www.caryinstitute.org/sites/default/files/downloads/report_road_salt.pdf

LabNotes. Mar. 16, 2018. “The Chemistry of Road Salt and How It Works”.  American Chemistry Council. https://www.americanchemistry.com/chemistry-in-america/news-trends/blog-post/2018/the-chemistry-of-road-salt-and-how-it-works#:~:text=Road%20salt%20%E2%80%93%20or%20rock%20salt,grey%20or%20brown%20in%20color.

Szklarek, S., Górecka, A., Wojtal-Frankiewicz, A.2022. “The effects of road salt on freshwater ecosystems and solutions for mitigating chloride pollution”. Science of The Total Environment, Volume 805. https://doi.org/10.1016/j.scitotenv.2021.150289