
Photo by InnerPeaceSeeker / Getty Images
High levels of chloride in Ottawa’s waterways due to road salt is putting wildlife and ecosystems at risk, a new report shows.
Ottawa Riverkeeper, a charitable organization dedicated to protecting the health and future of the Ottawa River and its tributaries, this week released their report, 5 Years of Road Salt Monitoring in the National Capital Region. It summarises the data of their ongoing project to monitor chloride levels in waterways.
Here are the quick facts:
- Road salt is used to make walkways and roads safer during winter months.
- Road salt contains chloride, which quickly breaks down and seeps into soil and waterways.
- Ottawa Riverkeeper and their community scientists took more than 500 samples from across 45 locations in the National Capital Region.
- Their results indicate that only 10% of samples collected were below thresholds for chronic chloride toxicity, and about 45% of samples exceeded the threshold for acute toxicity.
- Even during summer months, chloride levels remained above the chronic toxicity threshold, showing that the impact of road salt on ecosystems is year-round and not seasonal.

Graphic provided by Ottawa Riverkeeper
What is Acute and Chronic Toxicity?
The Ottawa Riverkeeper report explains that “‘acute’ and ‘chronic’ chloride toxicity thresholds refer to the water quality guidelines published by the Canadian Council for Ministers of the Environment. These guidelines establish two ranges where chloride concentrations could be harmful to freshwater aquatic organisms. Chronic toxicity occurs when chloride concentrations are between 120mg/L and 640mg/L for an extended period (more than 4 days). After prolonged conditions of these high concentrations, there can be a significant loss in biodiversity within freshwater ecosystems. Acute toxicity occurs when chloride concentrations are above 640mg/L. Exposure to acute chloride toxicity can be fatal to freshwater aquatic organisms, even if the high concentrations are not prolonged.”
The impact of drinking or exposure to water with toxic levels of chloride can be severe on wildlife. According to the Merck Veterinary Manual, salt toxicosis’ “clinical signs vary between species, and between acute and chronic exposure, but may include depression, weakness, ataxia, muscle tremors, gastroenteritis, and seizure-like activity.”
Further, high levels of sodium or chloride in the waterways can significantly impact organisms throughout the food web, creating cascading impacts across species. As per the report, “Unfortunately, the impact of road salt on aquatic ecosystems can only be described as devastating.”
Fortunately, there are solutions.

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What can we do?
Ottawa Riverkeeper has four primary recommendations for municipalities and property owners:
- Municipalities and large property owners need to take advantage of available resources to ensure road salt applications is effective.
- Develop and regularly update road Salt Management Plans.
- Identify areas to restrict the application of road salt.
- Become informed about appropriate road salt use to reduce the harm to local streams.
The also have four tips that can help reduce or eliminate road salt use:
- Don’t use road salt at temperatures colder than -7°C
- Use alternatives for traction, such as sand or gravel
- Shovel often to prevent ice buildup
- Use only as much salt as you need
And, according to the report, The City of Ottawa is looking to do more to reduce their impact, as well. In it, Ottawa Riverkeeper notes the City has been, “actively looking to make sure it is spreading salt optimally and sustainably” and has invited the group to share data and participate in a training video for municipal staff.
You can read more about the study, including its methodology and more detailed results and recommendations by clicking here or use the PDF viewer below. You can get more information about Ottawa Riverkeeper and their salt monitoring program at http://ottawariverkeeper.ca/salt.