Any Pennsylvania resident would agree that deicers (such as road salt) are a necessary tool for getting around safely throughout the winter. PennDOT maintains nearly 96,000 snow-lane miles — enough to circle the globe nearly four times! In the 2015-16 winter season, they used 1.1 million tons of salt on Pennsylvania roads.Two winters earlier, 63,095 tons of salt were used on Allegheny County roads alone. Not to mention the thousands of pounds of deicer used on sidewalks and driveways.
A road salt shipment arriving in Pittsburgh, PA(The Salt Factory, 2016).
While deicing is crucial in the winter months, what does this mean for our watersheds? How is the mass distribution of road salt affecting our local ecology?
In 2015, Rob Rossi, a former NMRWA intern and graduate student in the department of Geology and Environmental Science at the University of Pittsburgh, wrote a blog post describing the relationship between road salt and freshwater ecosystems such as Nine Mile Run.
Runoff from both rain events and snow/ice melt transports salt from roadways, driveways, and sidewalks to the surrounding landscape. Once it is free in the environment, salt participates in cation exchange reactions, which release metals — in the form of plant nutrients and trace elements — from the soil. These mobilized metals join salt as it flows through the groundwater. Eventually, both excess salt and metals reach surface waters, such as lakes, rivers, and streams.
In freshwater streams such a Nine Mile Run, the addition of salt poses a threat to native plants and animals, which are not adapted to saline conditions. When the salinity of their environment increases, these organisms struggle to regulate the water and salt content within their cells. Dissolved metals also pose a similar threat to aquatic organisms. When present in water, metals are taken up through the gills of fish, amphibians, and aquatic insects. Because many aquatic organisms cannot tolerate metals, this exposure can be toxic. In the long run, continuous exposure to salt and metals may depress the biodiversity of a stream.
Exposure to salt and metals threatens species within Nine Mile Run (Nine Mile Run Watershed Association, 2014).
So now comes the big question: how can we minimize the negative effects of deicers without sacrificing our safety?
As it turns out, there are several varieties of road salt, some more environmentally-friendly than others. Unfortunately, the least toxic varieties are also the least affordable. This explains why PennDOT — already spending over $32 million on road salt annually — uses sodium chloride, the cheapest and most toxic variety of road salt, available at 20 cents a pound.
While PennDOT may not be persuaded against using sodium chloride, we are free to use environmentally-friendly road salts around our homes and businesses. Luckily, there are several varieties available.
- At 60 cents a pound, calcium chloride contains less cyanide than sodium chloride, and is therefore a healthier choice for our environment.
- Magnesium chloride (52 cents/lb) contains less chloride than either of the two, making it safer for plants and animals, including pets.
- Calcium magnesium acetate (CMA) contains no chloride, and is therefore the least toxic choice. In the 1970’s, it was identified as the only road salt to meet a standard of low environmental damage.
- Because CMA costs 20 to 30 times more than sodium chloride, it is usually sold as part of an de-icer blend. Environmentally friendly blends like these can cost as much as $1.70 a pound. Visit the Environmental Protection Agency’s Safer Choice Standard website and select “Deicer” as the product type to learn about specific brands to choose from.
- An easy way to find less toxic deicer blends is to choose brands that are labeled as “pet safe” and do not list sodium chloride ( or NaCl) as an ingredient. These blends are not only easier on our watershed, but on your furry friend’s paws as well.
Another way to reduce our winter environmental impact is to reduce or eliminate the use of chemical deicers altogether. Be sure to shovel your walkways and sidewalks as soon as you can after it stops snowing, and before foot or vehicle traffic has packed down the snow – this helps prevent the snow from melting and refreezing, or hardening into immovable ice. This greatly reduces the amount of ice that forms and the amount of deicer that is needed. Next, always follow the instructions on the product’s container. Consider using a salt spreader. It will allow you to be more precise and even with your application. Want to make your own? Here is a great tutorial! You can also opt to put down sand or cinders in limited amounts to help with traction. A bonus: this will be easier on your landscaping and concrete and brick walkways in the long run, leading to less maintenance and replacement.
So, if these products are going to make a bigger dent in your wallet, is it really worth it? We would argue yes. Think of how much deicer you use at your home on an annual basis. Now multiply that by all the houses in your community. That’s a lot of chemical deicer! It is our job to make sure that we are using earth-friendly products and being responsible watershed stewards. For more information on the science behind salinity and freshwater, check out this great article from the Allegheny Front. Have questions? Please feel free to contact our Restoration Stewardship Coordinator, Lindsey-Rose Flowers, at .