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Road Salt is Polluting Fresh Water

It’s Time to

Cut the Salt

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Measure chloride levels in a local stream, lake, or river and contribute to our research.

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Salt keeps us safe on icy roads — but it’s also quietly harming waterways. Every winter, millions of tons of salt are spread on roads, sidewalks, and driveways to combat snow and ice. While it’s effective at reducing slippery conditions, the consequences for freshwater ecosystems, infrastructure, and drinking water are profound, especially as winter salt use has risen dramatically over the past 50 years.

A graph showing how the use of winter salt for deicing more than doubled between 1940 and 2023.
Figure 1. Metric tons of deicing salt used in the U.S. from 1940 to 2023.
Graph showing rising chloride levels in streams due to winter salt use across different land use types.
Figure 2. The rise in salt use is strongly correlated with urbanization.

Why Is Winter Salt an Issue?

The Impact on Freshwater Ecosystems
Dorothea mayfly photo by David H. Funk.

Winter salt runoff harms aquatic life, turning sections of some streams as salty as the ocean (see Figure 3). When salt levels rise in freshwater ecosystems, sensitive species, like mayflies and amphibians, can disappear. Even the chloride levels recommended by the U.S. Environmental Protection Agency (EPA) may not be enough to protect these vital species.

Graph showing chloride concentration in Shoemaker Creek Pennsylvania, compared to chloride concentration in seawater.
Figure 3. Chloride concentration in Shoemaker Creek, Pennsylvania, during winter storms compared to seawater. Data courtesy of Tookany-Tacony/Frankford Watershed Partnership.
Salt and Drinking Water
A glass of drinking water.

Salt also infiltrates groundwater and rivers, which supply most drinking water. Once contaminated, it’s costly and difficult to remove.

Water treatment facilities struggle to filter out salt, and advanced systems like reverse osmosis are expensive to install and maintain.

Protecting shared water sources is critical for both the environment and public health.

How Bad Is It? Rising Salt Levels in Fresh Water

Since 2016, Stroud Water Research Center has led efforts to monitor salt contamination, collaborating with hundreds of community scientists and volunteers. By measuring chloride and specific conductivity — key indicators of salt pollution — the Stroud Center and partners such as the Tookany-Tacony/Frankford Watershed Partnership have documented alarming levels of contamination in streams like Shoemaker Creek, Pennsylvania, which often exceed EPA safety thresholds (see Figure 4).

Graph showing chloride concentration in Shoemaker Creek, Pennsylvania, in early 2022 far exceeding EPA criteria.
Figure 4. Chloride concentration in Shoemaker Creek, Pennsylvania, as shown in Figure 3, is expanded and compared with the U.S. EPA’s recommended criteria for freshwater chloride concentrations. Data courtesy of Tookany-Tacony/Frankford Watershed Partnership.

Data collected by community scientists and volunteers indicates an alarming trend: salt concentrations in many or most streams remain elevated year-round — even in summer. Worse yet, Stroud Center research shows salt is more toxic to aquatic life as temperature rises.

These findings highlight the urgent need to address winter salt use. 

Learn more in “Salty Streams,” episode 5 in the WHYY TV12 series Stories From the Streams. 

John Jackson, Ph.D.

Learn about scientist John Jackson’s testimony on road salt’s impact on fresh water at a hearing held by the Philadelphia City Council Committee on Streets and Services.

How You Can Help

By implementing best practices and new technologies, we can reduce salt use by 30 to 50 percent.

Five ways you can Cut the Salt.
Reducing salt use doesn’t mean sacrificing safety — it means making smarter choices for roads and waterways. Here are five easy ways to Cut the Salt this winter.
Cut the salt graphic: a snow shovel with the text, shovel or plow first.
Remove snow and ice first. Shovel, sweep, or use a blower to clear surfaces before salting.
Cut the salt graphic: a measuring cup with the text, use only what you need.
Use just enough salt. Check your deicer’s instructions to avoid overuse. After storms, clean up leftover crystals.
Cut the salt graphic: icon of a clock face at the center of a snowflake with the text, be proactive.
Watch the weather and treat walkways before ice forms. Be proactive with each unique storm.
Cut the salt graphic: a snow boot with the text, get some traction.
Use sand, grit, or natural materials to improve traction without polluting water. Wear snow boots or ice cleats to stay safe.
Cut the Salt: Educate Yourself and Others.
Talk to neighbors and local contractors about reducing salt use. Small changes by many people can make a big difference.

Take Action

Want to make a difference? Here’s how you can help protect fresh water from salt contamination:

Order a Free Freshwater Test Kit 

Measure chloride levels in a local stream, lake, or river and contribute to our research. Request a kit.

Participate in Winter Salt Week

Join a stream sampling event to measure salt concentrations in your region. January 27-31 is Winter Salt Week, a multistate effort to raise awareness about the harms of road salt, and the Stroud Center is leading the charge in the mid-Atlantic region, helping dozens of organizations sample streams and tell the story of road salt in their communities. The Stroud Center will also host an event in partnership with West Chester University and West Chester Borough in Pennsylvania. Visit the Winter Salt Week website to find an event near you. Results will be posted to this page after the event.

A poorly protected pile of road salt.
Headshot of Carol Armstrong, Ph.D., in a riparian forested buffer.

Spread the Word

Share what you’ve learned with your community. Carol Armstrong, Ph.D., a community science volunteer, has reached out to local businesses as well as local and state agencies to address documented cases of improperly stored road salt, which can pollute nearby streams. She also convinced her township to start an environmental advisory council, offering to share what she’s learned.

Resources

Winter Salt Week Results

Stay tuned! Results from our Winter Salt Week stream sampling events will be shared here after January 31. These findings will highlight salt concentrations across various sites, providing valuable insights into the scope of salt pollution and guiding future action.

Learn More

  • Listen to an NPR Interview: Dr. John Jackson discusses the impact of road salt on freshwater ecosystems.
  • Learn From a Local Success Story: Discover how multiple communities rallied to protect waterways from salt pollution.
  • Get More Details About Salt Contamination: The intense use of salt threatens streams and rivers, marshes and ponds, and even groundwater — freshwater resources that were never meant to be so salty.

Stay in Touch

Subscribe to UpStream Newsletter for monthly updates on freshwater research, tips for protecting waterways, and opportunities to support watershed restoration.

Together, we can reduce the harmful impacts of winter salt and safeguard precious freshwater ecosystems.

Support Science That Leads to Solutions

Stroud Water Research Center produces the trusted science needed for successful stream and river conservation. Your donation of any amount supports this crucial work. Donate now.