Since attending a seminar on Road Salt, sponsored by Toronto and Region Conservation Authority (TRCA) I’ve been more aware of oversalting of roads, streets, and sidewalks. This season in particular, I’m noticing excessive road salt on the sidewalks and pathways in my Beach neighbourhood.
But is salt really so bad? I started sleuthing for the answer.
My research uncovered a common theme - road salt is bad for the environment.
In a Great Lakes Now article, (Feb 17 2021), the author, Kathy Johnson, writes that “road salt places a heavy burden on freshwater ecosystems...Studies dating back to the 1970s have shown that road deicing salt has a negative impact on soil, vegetation, wildlife, surface water, groundwater and human health”.
The reason seems to be in its chemical ‘elements’. I’m not a chemist, or a marine biologist, or road maintenance specialist. I’m really nothing, except curious. So here is what I found out about salt.
One molecule of each element Sodium (Na) and Chlorine (Cl) bind together to form the mineral Sodium Chloride NaCl, a.k.a. Halite or Rock Salt.
In Environmental impacts of road salt and other de-icing chemicals published by the Minnesota Pollution Control Agency (MPCA), the author explains that when chloride-based deicers dissolve in runoff, the negative chloride anions and the positive sodium cations (elements) come apart. The chloride component is not biodegradable and is not easily absorbed into soil, so over time it will make its way to groundwater, vegetation, surface water, into the catch basin (i.e. to the lake), and if it dries up on the ground it gets blown around in the air. Once in the groundwater it persists for a long time.
As you can imagine, salt on the road will either runoff, or will be splashed, or sprayed up from the road’s edge. This can affect surrounding trees, gardens, and plants. Several studies were cited in the article regarding the adverse effects of chloride accumulation in soil including “reduced soil permeability and fertility, and increased soil alkalinity”...leading to... “negative effects on the chemical properties of the soil and its ability to retain water, both of which are important to plant growth and erosion control”.
To further support the work of the MPCA, Jeremy Hindsdale in his article How Road Salt Harms the Environment, Dec. 11, 2018, writes that “Chloride is toxic to aquatic life, and even low concentrations can produce harmful effects in freshwater ecosystems”.
Once again chemistry explains the problem. Saltier water is heavier than less salty water which means the salt water sinks to the bottom of the lake creating a dense layer. The dense layer prevents oxygen exchange with the layer above. Fish and aquatic organisms living near the bottom of the lake are deprived of oxygen. Salt can also be toxic to zooplankton thus reducing the fish’s food source.
Why do we use Salt and how does it melt ice?
Again the answer is elementary - it’s all about the chemistry.
When you sprinkle salt on top of ice, the salt dissolves into sodium and chloride. The ions prevent the water molecules from sticking together so it can't form ice. Essentially salt lowers the freezing point of water..."a concept known as freezing point depression.” (from How Road Salt Harms the Environment, by Jeremy Hindsdale, Dec. 11, 2018).
Where does Salt come from?
According to Wikipedia, the salt deposits from Goderich, Ontario form the largest underground salt mine in the world. Back in 1866, a fellow named Sam Platt was prospecting for oil when he found rock salt in the Goderich Harbour. I guess Sam was savvy enough to recognize the value in salt, and so he founded the Sifto Salt company. Sifto Canada was formed in 1950, and was later acquired by an American company, Compass Minerals in 1990.
Why do we use so much?
The biggest driver for oversalting (84% of respondents) is due to a concern for slip and fall liability. This is according to Toronto Remedial Action Plan
In Great Lakes Now, Claire Oswald, a hydrologist and associate professor at Ryerson University in Toronto is quoted as saying that “all types of agricultural alternatives have been tested so far including cheese brine, pickle juice and the runoff from brewing beer. Beet juice from sugar beet processing has emerged with the best potential as an alternative to sodium chloride”. But others say that replacing salt with beet juice is just replacing salt with sugar. Sugar is food for bacteria, and if found in water in high concentrations it reduces the oxygen level in the water. Chemistry again! As was mentioned earlier, deoxygenation is not good for the fish and their food.
What can we do?
I don’t think anyone is disputing that salt is a good option for de-icing. It works, and it seems to be cheap and abundant. I think the important thing is to keep its use to a minimum, while maintaining safety standards for preventing slips and falls.
Knowing how much is enough is key. The following photo shows how much salt should be enough for sidewalks. (from Toronto Remedial Action Plan).
Toronto has a very detailed Salt Management Plan and they are continuously reviewing and revising it. Personally I think our city does a great job of clearing snow and ice. I think sometimes there are just gaps in training or communication of the plan, leading to oversalting.
The city really is interested in minimizing the amount of salt used, while still maintaining a high level of safety, and minimizing the impact on the environment. One challenge is that they are bound by the provincial standards for maintaining safe highways and roads.
The Environment Canada website says “salting before a storm, instead of after, can prevent snow and ice from binding to the asphalt, making the post-storm cleanup a little bit easier and allowing road crews to use less salt overall. Mixing the salt with slight amounts of water allows it to spread more, and blending in sand or gravel lets it to stick more easily and improves traction for cars”.
The city has invested in new equipment and technology for spreading just the right amount of salt. However, for many applications it’s more practical to spread salt by hand. Walkways, sidewalks, stairs, and private property is usually where we find oversalting.
If you observe excess salt on a sidewalk or street in your neighbourhood it would be helpful to mention it to the shop owner or supervisor if it’s a public building. If it’s in a generic area managed by the city, you can take a photo and email it with the date, time and location to firstname.lastname@example.org.
The East York Civic Centre looks like they got it right in terms of salting the sidewalk. 👍
Now, when I salt, I try not to overdo it. I haven’t tried using brine or beet juice, and honestly I likely won’t because it’s not convenient, and it's time consuming to make enough to be useful, plus it may not be that effective in the long run.
What I find works best is to take the advice of Environment Canada and shovel early and shovel often. Don't let the snow melt and freeze. That way the snow does not have a chance to get compacted on the sidewalk, and turn to ice. I realize this is easier for those of us who are retired or work from home, but it’s not so easy if you are away all day at work.
The bottom line is to be aware of how much salt is actually required to do the job. A little really does go a long way. We just all have to do our part in any way we can.
Do not over-salt - a little goes a long way
I hope this little article leaves you thirsty for more information on salt and the environment.
Leave us a comment about the article or let us know what you are doing to improve the health of our freshwater lakes. We would love to hear from you.
Road Salt: Researchers look at vegetables and juices for alternatives to salt, Kathy Johnson, Feb. 17, 2021
Minnesota Stormwater Manual - Minnesota Polution Control Agency, Environmental impacts of road salt and other de-icing chemicals
University of Waterloo Earth Sciences Museum
Hesham Najiya and Jason Cole
About Sifto Salt/Compass Minerals https://en.wikipedia.org/wiki/Sifto_Canada
What Happens to All the Salt We Dump On the Roads?
Toxic substances list: road salts
How Road Salt Harms the Environment, by Jeremy Hindsdale, Dec. 11, 2018) https://blogs.ei.columbia.edu/2018/12/11/road-salt-harms-environment/
Salting the Earth: The Unintended Impacts and What We Can do to Prevent Them
Lake Ontario Evening November 22, 2018 Tim Van Seters, TRCA
Winter pollution: the environmental impacts of road salt
Published on November 27, 2017
Toronto salt management plan 2016
Road salt is bad for the environment, so why do we keep using it?
By Jamie Summers and Robin Valleau