Slow, salty death: how our love for road salt is killing the environment
Ontarians have an affinity for water.
When the heat of summer arrives, residents flock to Grand Bend, Port Dover or Sauble Beach looking for a place to soak up the sun’s rays and escape the humidity in the refreshing waters of Ontario’s Great Lakes. Cottagers descend on small towns across the Muskoka and Kawartha regions, many of them looking for nothing more than a dock to jump off and a glistening lake to land in; and across the province’s urban centres, splash pads and community pools are filled with children running through hoses, sprinklers and jets.
We drink, swim, boat, fish, study, photograph, canoe, kayak, and sail, on many of Ontario’s 250,000 lakes and the 490,000 kilometres of rivers, streams and creeks that feed them. We harness the power of water to keep our lights on and appliances running—in 2019 nearly a quarter of Ontario’s power grid was fuelled by hydroelectricity.
All life on Earth relies on water to survive.
Ontario has the highest diversity of fish species anywhere in Canada with 154 different types; 13 species of frog and two species of toad; and the numerous salamanders, lizards, snakes and turtles that use lakes, wetlands or rivers to feed, breed or live at some point in their lifecycle.
Yet for decades we have known about an insidious threat to these lakes and waterways we rely on for so much.
Municipalities across the country rely on millions of tonnes of road salt every year to melt ice on local roadways. A large portion of this salt ends up running off into the local environment.
(City of Mississauga)
This is not breaking news. For more than two decades, governments have known that the liberal quantities of salt being splashed across highways and sidewalks throughout the cold winter months was not good for the environment. A study completed by the federal government in 2001 concluded that our dependency on road salt to melt ice was “having adverse effect on freshwater ecosystems, soil, vegetation and wildlife.”
In short, our salting of the Earth was slowly killing it.
While many could have guessed that pouring millions of tonnes of any chemical into the environment would have some kind of impact, they could not be blamed for a lack of understanding about the consequences for the natural world.
The same way people thought smoking was benign until science proved otherwise, or when Rachel Carson first exposed the widespread damage caused by DDT and other fertilizers (leading to the modern environmental movement) these reckonings left many asking, how could we let this happen?
It seemed the early 2000s would be a time of reckoning for sodium chloride.
The startling revelations from the 2001 study were met with a dismissive wave of the government’s hand. There was a lack of concern about the widespread use of a product the Environmental Protection Act defines as a toxic substance. It was not until 2004 that the Government of Canada released a “code of practice” that was meant to guide the public and private sector to optimize the use of road salt while maintaining safe driving conditions during the harsh winter months.
An analysis completed five years later found little had changed and gauging any successes, however small, was next to impossible because no targets or goals had even been set in 2004.
It wasn’t until 2014, a decade after the initial code of practice was created, that Ottawa released a set of performance indicators and targets. By then, chlorides from road salt had seeped from roadways into practically every single lake, river and stream around Canada’s major urban centres—causing salt levels considered harmful to aquatic life.
“The continued increase in chloride concentrations over the past 50 years at the majority of water quality stations are a cause for serious concern,” reads a report completed in 2021 by Watershed Planning and Ecosystem Science for the Toronto Region Conservation Authority (TRCA). “The number of stations with median chloride concentrations above the chronic effects guideline has increased over time from 4 out of 12 stations in 1991-1995 to 11 out of 13 stations in 2016-2020.”
Water quality guidelines put in place to protect wildlife state concentrations of chlorides higher than 120 milligrams per litre (mg/l) over a long period of time can cause harm to aquatic life. Levels above 640 mg/l are enough to cause acute harm as freshwater organisms are forced to try and survive in conditions more similar to a saltwater ocean than the freshwater ecosystems they’re adapted to.
An investigation by The Pointer of the 11 monitoring stations maintained by the Credit Valley Conservation authority in the months of June and July—when chloride concentrations are typically lower due to the reduction in salt use in summer months—found levels in the majority of stations were above what would cause long-term harm, and spikes were well above levels deemed to cause acute harm, sometimes nearly three times as high.
“Our reliance on salt is leading to negative environmental impacts,” the CVC said in response to the findings of The Pointer’s investigation. “While some efficiency has been created, salt application rates continue to be high.”
Without a viable alternative to chloride’s incredibly effective and cheap ability to melt ice, and as Peel continues to grow, salt will continue to be spread, putting the entire watershed at risk.
A new study has found that risk could be much higher than previously anticipated.
To keep roads safe in the winter months, healthy quantities of the white crystals known as sodium chloride are dumped onto pavement in a few different ways.
The most visible is rock salt. It’s the same type of salt that fills the shakers on dinner tables across the world, but it hasn’t been purified for human consumption. When dumped onto pavement, the sodium chloride works by disrupting the freezing process of snow into ice, melting the snow into a brine which then prevents ice from forming on the surface of the road. One of the largest criticisms of rock salt is it only begins to work once it gets wet. So dumping large quantities of rock salt onto the road prior to a storm, while a proactive step, can actually increase the amount that runs off into the local environment. It’s also a waste of money as this method can create a lot of waste. To avoid this, many municipalities have switched to using a brine, which mixes the rock salt and water in order to speed up the process. The Region of Peel uses this technique on regional roads. The implementation of prewetting and other electronic controls that help regulate the spread of salt has seen Peel’s road salt usage decline slightly since the early 2000s. The Region still dumps approximately 28,000 tonnes of the stuff on regional roads each year, coming at a cost of around $2.1 million, but this is down from just under 40,000 tonnes.
While the number of roads in Peel has increased, the Region has managed to reduce its total salt usage through different techniques and technologies.
(Region of Peel)
“All implemented best practices combined have helped staff make more informed decisions for salt usage while being mindful of the environment,” states Mark Crawford, Peel’s manager of roads, operations and maintenance. “Salt management is not only about salt reduction, it also benefits the community and travelling public. The safety of the travelling public is always top of mind during winter operations.”
The City of Mississauga has also managed to reduce its salt usage over the last five years, dropping from around 85,000 tonnes annually in 2017/2018 to just over 57,000 in 2020/2021. However, that number is most likely influenced by pandemic restrictions as the number has since surged 37 percent to nearly 79,000 tonnes for 2021/2022. The City’s annual salt budget is approximately $5.1 million.
The City of Brampton did not respond to requests for information from The Pointer.
Chlorides also impact Ontario’s bird populations which rely on creeks and waterways to drink, feed and bathe.
(Joel Wittnebel/The Pointer)
The troubling reality of road salt is that chloride is not easily removed from the environment once it has been dumped into it, and this persistence allows it to build up overtime. This is where the real harm lies.
“The only mitigation strategy to reduce chloride concentration in GTA streams is by reducing application of road salt. Unfortunately, once salt is applied, it cannot be economically taken out of the stream network,” explains Amanjot Singh, a senior engineer responsible for water and climate change science at CVC. “Winter road and sidewalk safety is necessary. But our reliance on salt is leading to negative environmental impacts. While some efficiencies have been created, salt application rates continue to be high.”
The future doesn’t look bright.
While Peel and Mississauga have managed to see some success in cutting the amount of salt they are dumping into the environment, Singh says any efficiencies achieved in this time could be offset by the growth Peel is experiencing in both its road network and commercial land. While municipalities play a large role in solving the chloride problem, residents and businesses must also take a look in the mirror and consider their own use of the dangerous compound.
To make matters worse, salt usage is not decreasing in Canada, quite the opposite. Despite the Government of Canada’s requirements for salt management plans to limit the spread of chloride into the environment, its usage has increased from approximately 5 million tonnes nationwide in 2004 to 7 million in 2021.
For the most part, Canada’s national targets for salt management set in 2014 are failing to reach even the most basic goals:
218 organizations, including 8 provinces, 1 territory and 194 municipalities (including Peel and Mississauga, but not Brampton), are a part of the national code of practice reporting on their progress to manage salt usage. The goal is for a membership of 220 organizations.
there was a goal to have 100 percent of member organizations report annually on their progress toward better salt management—only 56 percent of organizations reported in 2020
in terms of the number of organizations showing clear signs they are striving to “enhance their salt application techniques to optimize their use of salt”, there was a target for 95 parent of organizations to be showing such signs, but only 69 percent were doing so in 2020
only 66 percent of organizations were using the pre-wetting technique in 2020; the target was 75 percent by 2019
Perhaps most significantly, there has been little progress made in Canada toward identifying salt vulnerable areas, and preparing action plans to protect these sensitive ecosystems. There is a goal for 95 percent of member organizations to have finished this identification process and prepared action plans to protect them by 2024. As of 2020, only 30 percent had managed to do so after six years.
The small successes the national targets have achieved is seeing 100 percent of organizations storing their salt in a roofed location with an impermeable floor, and the use of electronic controllers to monitor salt use.
A recently released study could provide a much needed kick to these organizations as the troubling findings indicate that harm to the environment is happening at much lower chloride concentrations than what current safety guidelines indicate.
The international study, conducted at 16 sites in four countries, found that harms to zooplankton in freshwater lakes—a critical source of food for fish and an organism that keeps algal blooms at bay—was happening at concentrations at or below the established Canadian government thresholds.
“We were so shocked by the results,” says Shelley Arnott, a researcher and professor of aquatic biology at Queen’s University. Arnott was one of the lead researchers of the study alongside Bill Hintz from the University of Toledo.
At 11 of the 16 sites, chloride levels that caused more than a 50 percent reduction in zooplankton were at or below established water quality thresholds put in place to reduce harm to aquatic life. Arnott says her team observed high mortality and reductions in zooplankton reproduction at concentrations ranging from 5 to 40 mg/l. At half of these sites, as the zooplankton died off, algae began to increase. It’s safe to assume that should chlorides cause disruption to zooplankton, the ripple effects could hurt other levels of the food web.
“If you lose a lot of the abundance, it would be hard to imagine that it is not going to have an impact on other trophic levels,” Arnott says. “That’s speculation, but I think it’s something that’s worth considering.”
This new study puts the CVC data recorded by The Pointer in a startling new context.
If Arnott and her team were seeing impacts at just 40 mg/l of chloride, what exactly is happening to the wildlife in Cooksville Creek, where a monitoring station on June 6 recorded levels of 1,802.5 mg/l? Or 867.8 mg/l recorded in the same location a month later? Overall, for the weeks of June 6 and July 6, the average chloride readings were 643.8 mg/l and 689.8 mg/l respectively.
Over the 16 days across 11 monitoring locations, The Pointer recorded 15 readings above levels that can cause acute harm to aquatic life and 113 readings above levels that can cause harm through long-term exposure.
Natural chloride concentrations are typically between 1 and 10 mg/l.
The vast majority of monitoring stations around Peel’s dense urban areas recorded chloride levels deemed harmful to aquatic life. These were not just spikes, but a consistent reality for these waterways.
This is a critical issue for Peel’s wildlife.
After years of build up within a waterbody, chloride creates a “dead zone” within the creek, stream or lake. Heavier than water, salt brine sinks. On the lake or creekbed, it forms a smothering blanket that prevents the exchange of oxygen and nutrients from the lakebed through other levels of the water table.
For wildlife, over-salted water can interfere with a process called osmoregulation, the process aquatic species rely on to regulate and control the concentrations of salt and other fluids in their body. When this process is disrupted it can impact growth, reproduction and the animals eventual survival.
Without alternatives for melting ice, as Peel’s road network expands, the reach of chlorides in the environment will continue to increase.
(Alexis Wright/The Pointer)
Arnott hopes the results of the recent study are able to get policy makers to realize new regulations are required to protect aquatic life across the province.
“To take that next step sometimes you just need the science behind it and so that’s really what we’re doing, we’re just filling in that knowledge gap,” she says.
For starters, this change could come in a refreshed commitment from the federal government to enforce its own national targets. It could mean searching for alternatives to road salt to try and eliminate our reliance altogether. Municipalities within the jurisdiction of the CVC have been experimenting with things like pickle brine, potato juice, beet juice and cheese brine to melt ice. Although, these alternatives need to be properly studied to ensure they don’t make the problem worse. At the very least, Arnott says action needs to come in the form of increased education for businesses and homeowners.
“Where I think we’re running into trouble is all the private parking lots, sidewalks and that because people are just throwing down salt,” she says.
For homeowners, the typical advice is more is less. If spread correctly, it only takes a pill bottle of rock salt to melt an area the equivalent of a sidewalk slab.
The CVC is attempting to lead by example when it comes to the salting of large parking lots in Peel. In the late winter months, it’s not uncommon to see unmelted piles of rock salt sitting on the brine-streaked pavement; a clear signal of improper usage.
At the CVC headquarters in Mississauga, the organization used this past winter to work with its winter maintenance contractor to track the timing and amount of salt being applied.
“Through this study we hope to learn how different application rates can still achieve a safe result and how liquid anti-icing works on permeable versus non-permeable surfaces,” a March 2022 blog post reads. The goal is to create an example for others to use.
“There are so many things that are impacting biodiversity in general. Whether it’s salt or climate change or changes in nutrients, invasive species. All of these things are interacting and just making things worse,” Arnott says. “The salt actually seems like a pretty easy thing for us to deal with.”
Email: [email protected]
COVID-19 is impacting all Canadians. At a time when vital public information is needed by everyone, The Pointer has taken down our paywall on all stories relating to the pandemic and those of public interest to ensure every resident of Brampton and Mississauga has access to the facts. For those who are able, we encourage you to consider a subscription. This will help us report on important public interest issues the community needs to know about now more than ever. You can register for a 30-day free trial HERE. Thereafter, The Pointer will charge $10 a month and you can cancel any time right on the website. Thank you
Submit a correction about this story