A number of Canadian cities have exceeded acceptable chloride levels in watersheds in recent years, raising concerns about the impact on freshwater wildlife and other species.
The problem largely stems from road salt and saline solutions, which have a chemical compound of chloride to keep roadways safe during winter weather.
Chloride has both long- and short-term impacts on wildlife, and some experts believe it is adversely affecting fish, frogs and aquatic ecosystems across Canada.
"In the spring, where we might have amphibians, frogs, salamanders, coming into small, shallow pools of water along ponds, along roadways or in the forest, they may end up in salty water. That really limits their ability to survive," Donald Jackson, professor in the department of ecology and evolutionary biology at the University of Toronto, told CTVNews.ca in an interview.
Humans sometimes use the same water we are polluting as well, but the to remove unnecessary toxins and salt for consumption.
Even with these objectives, drinking water may be a problematic source of salt – but only for those with certain conditions.
"Although the average intake of , the intake from this source could be significant for persons suffering from hypertension or congestive heart failure who may require a sodium-restricted diet," the Guidelines for Canadian Drinking Water Quality report reads.
For freshwater species that live their entire lives in water, removing excessive chloride is not an option.
The in order to keep rivers, streams and lakes healthy for plants and animals.
According to research from DataStream, a number of cities across Canada had heightened periods of chloride in their watersheds in the past.
The CCME says if chloride content exceeds 120 milligrams per litre (mg/L) of water, it can become a chronic issue to aquatic life. If chloride exceeds 640 mg/L, it is categorized as acute, and can severely impact water species immediately.
In an analysis by CTVNews.ca, data from some cities show chloride levels have surpassed (at times) 1,000 mg/L, far exceeding guidelines to maintain healthy waterways.
WHERE IN CANADA IS CHLORIDE AN ISSUE?
Data shows in many municipalities, the areas where roadways are concentrated are where chloride levels are too high for freshwater species.
The data, collected between 2020 and 2023, shows cities like Ottawa, Toronto, Calgary, Edmonton and St. John's are seeing chloride levels exceed 640 mg/L, enough to have an acute effect on species.
Often the waterways are located within subdivisions or along major roads, where salting occurs regularly in the winter.
Researchers in Nova Scotia determined that urbanization without proper waterway planning is hurting ecosystems
That study, , showcases an analysis of the chloride concentrations in 57 lakes around the Halifax-Dartmouth area.
Using data from the Energy and Environment division of the Halifax Regional Municipality gathered between 2006 and 2011, researchers were able to categorize which watersheds were under greater stress.
The data was collected three times a year and from there, researchers determined a mean for the chloride levels. The highest mean concentration of chloride was found in Dent's Punch Bowl, a small lake found in the middle of a subdivision in Halifax.
According to the article, there was a mean chloride concentration over 120 mg/L, meaning chronic living conditions for species in the lake.
Russel Lake in Dartmouth, N.S., had similar concentrations, with a mean over 120 mg/L and was also located within a subdivision.
Researchers were able to determine lakes along expressways and major collector roads had high mean concentrations of chloride in them.
Recently, the province launched a new water monitoring program to track fluctuating chloride levels in lakes, rivers and streams, among other things.
WHAT HAPPENS WHEN CHLORIDE LEVELS ARE TOO HIGH?
Jackson says the information on which species are harmed by increased chloride levels is minimal. The guidelines for how high the concentration can be before it harms the ecosystems are based on about 30 different organisms with ranging resistance to chloride.
The , last updated in 2011, lists a number of species of fish, amphibians, plants and algae and how long they can survive before their "endpoint" in high chloride concentrations.
Some species, like the rainbow trout in laboratory testing, can withstand a concentration of 8,634 mg/L for 96 hours before they will die. Other species, like the freshwater mussel, have only 24 hours to survive at a chloride concentration of 709 mg/L.
Others severely impacted by rising chloride levels include the northern riffleshell mussel (), the chorus frog, the spotted salamander and fingernail clams.
For each species to survive, Jackson says it is about maintaining a careful balance.
If a scientist were to put a freshwater fish in distilled water, Jackson says, it would die because it lacks the "ions and chloride" that help it maintain the balance of water in and outside its body.
"If you were to put that fish into saltwater, it's also going to die, because it can't balance those ions properly inside the bloodstream and outside the bloodstream," he said.
'EVENTUALLY… WE’LL KILL IT'
Despite the dangers, there is hope in that ecosystems and species have proven to be resilient.
Over time, Jackson says, these organisms have learned to adapt to the increased chloride concentration.
But as the levels get higher at a rapid pace it becomes more difficult for the organisms to reproduce.
"As we start increasing those (chloride compounds), really what we're doing is we're making it more difficult for the organism that fish or the plants to maintain that balance," he said. "And eventually we'll overwhelm it and we'll kill it."
Although relatively unseen to the human eye, some of these species are used as food, like mussels and fish, while others provide a balance within ecosystems to keep other species in check.
The largest issue with chloride is that once in the waterway it can not be removed easily. Instead of seeing what Jackson calls a "die off" these species will disappear.
"If it takes a long time, we often don't even recognize that (they are) disappearing," he said.
WHAT CAN BE DONE?
There are some cities across Canada that showed lower levels of chloride in their waterways. Despite being located on an island in the Atlantic Ocean, Charlottetown was one of the municipalities curbing salt.
A spokesperson from the city told CTVNews.ca that it has taken steps to limit salt usage in the winter.
"For example, sidewalks will not be salted when snow can be scraped to reveal mostly bare sidewalks, sunny weather conditions and rising temperatures are forecast for after the snow has been plowed, another weather event is expected in the next 24-36 hours or temperatures are too low for salt to be effective," the spokesperson said.
Some municipalities use more sand or small gravel to ensure traction without chloride.
The City of Winnipeg has used beet juice to help lower the amount of salt used on its roadway since 2020, and according to a city spokesperson, it can improve the "adhesion of the sand and salt to the roadway surface at colder temperatures."
"Beet juice can make up to 60 per cent of the solution we are applying to the roads and is combined with a traditional sodium chloride-based brine. This lessens our chloride loading on infrastructure and the environment while producing a good quality melting solution effective to temperatures below -30 C," the spokesperson wrote in an email to CTVNews.ca.
In the northern parts of the country, chloride is not used often in the winter because it isn’t effective below temperatures of -10 C.
Data from Great Slave Lake near the Northwest Territories shows chloride levels hovered around 10 mg/L in 2021. Since 2014, the information from DataStream shows,
