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Road salt (sodium chloride) is everywhere during winter months. It keeps us safe on roads and sidewalks, but it can also pose a threat to fish and wildlife as well as human health.

Fish and bugs that live in freshwater streams can't survive in extra salty water. And many of us (more than 118 million Americans) depend on local streams for drinking water. Water treatment plants are not equipped to filter out the extra salt, so it can end up in your tap water and even corrode your pipes.

This past winter, people from around the country tested their streams for salt. The maps at the right show what they found: 31 watersheds tested by citizen scientists always showed normal, safe chloride levels, but high levels of chloride were found in 8 other watersheds that include metropolitan areas.

Repeated testing demonstrated that these metropolitan watersheds had consistently high levels of salt: 25% of test results were above the maximum level of salt considered tolerable for freshwater organisms (230 ppm), and an additional 31% were noticeably higher than levels of salt normally found in freshwater. Of the watersheds that tested high in chloride, the Lower Delaware and the Schuylkill in the Philadelphia metro area, the Middle Potomac-Anacostia in the Washington, DC, metro area, and the Clinton in the Detroit area showed abnormally high salt levels on more than half of their results.

Read more about what was learned from the 2018-2019 Winter Salt Watch season.

Though winter is now over, the danger salt poses to stream life has not passed: summer rainstorms can wash last season's salt out of the ground and into streams, and new research shows that salt is even more harmful to stream life when the water is warm.

You can take action.

  • If you live in one of the watersheds with high salt levels, or if you noticed salt piles sitting on roadsides last winter, call your city or county department of environmental protection to make sure they are aware of these issues.
  • Write a Letter to the Editor of your local newspaper or other news outlet to educate your community about how road salt harms stream health. You can start with our sample letter and adapt it for your use. (Download the Word file or PDF.)
Thank you for keeping our streams safe from salt!



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Want to know more about what you can do year-round to protect stream health? Sign up for the Clean Water Challenge. We'll send periodic emails with tools and tips to improve water quality in your community.

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What Impacts Chloride graph info


WINTER SALT WATCH MAP