Got an Environmental Science Question? Ask an EPA Scientist!

By Kacey Fitzpatrick


Front loader loads road salt into a large dump truck.

What happens to all that salt? Image courtesy of Maryland State Highway Administration

Have you ever had a question about something you saw and wished you had an expert you could ask? This happens to me all the time, so I decided to take advantage of working at EPA and start a new blog series called ‘Ask an EPA Scientist.’

I’m kicking off the series with a question that’s been on my mind recently.

Walking in a winter wonderland can be magical – but what about driving in one? Not so great. As I was driving (very slowly) through a snowstorm last week, I started wondering: What happens to all that road salt after the snow melts? Is it bad for the environment?

To find out, I asked EPA ecologist Paul Mayer, Ph.D. who conducts research on riparian zones and stream restoration. He and two Agency colleagues recently published a paper (Cooper et al. 2014) looking at the effects of road salt on a local stream.

Below is what he told me.

EPA Ecologist Paul Mayer, Ph.D. at a stream restoration research site.

EPA Ecologist Paul Mayer, Ph.D. at a stream restoration research site.

Paul Mayer: Road salts are an important tool for making roads safer during ice and snowstorms. Every winter about 22 million tons of road salt and other de-icers are used nationwide. Some washes from roadways into nearby bodies of water. This is a growing concern for the health of our urban watersheds because it can affect water quality and aquatic organisms.

I’ve been part of a study collecting surface and ground water data in Minebank Run, an urban stream in Maryland, since November 2001. We found that salt levels (chloride and sodium) there are chronically elevated throughout the year.

Road salts can accumulate and persist in our waterways, often even into the summer months. We found that the levels are significantly higher downstream of a major nearby road (I-695 beltway), suggesting that this roadway is a significant source of salts in the watershed.

This is a concern for Minebank Run because such salinization may reduce the benefits of restoration work that has been done, limiting the benefits the stream provides the local community and across the watershed. Increased salinity in freshwater systems can also damage or kill vegetation. Other research has indicated that road salts represent a risk to the safety of drinking water sources in the Baltimore area and elsewhere (Kaushal et al. 2005).

The implication of our research and others’ is that stream ecosystems in areas where road salts are routinely applied are at risk of environmental damage and that human health may also be at risk if water supplies are affected.

Kacey: I’m glad I asked! I also found some additional information that includes what we can do to reduce the impact of road salt:


Ask an EPA Scientist!
Do you have your own environmental science questions you’d like to see featured on our blog? Please email them to, post them in the comments section below, or tweet them to @EPAresearch using #EnvSciQ. We’ll pick as many as we can to pass along to our scientists, get them answered, and share the Q&A here on this blog. Stay tuned!
About the Author: Curious science writer Kacey Fitzpatrick is a student contractor working with EPA’s Science Communication team, and a frequent contributor to It All Starts with Science.

References Cited

Cooper, CA, PM Mayer, BR Faulkner. 2014. Effects of road salts on groundwater and surface water dynamics of sodium and chloride in an urban restored stream. Biogeochemistry 121:149-166. DOI: 10.1007/s10533-014-9968-z (Accessed at

Kaushal, et al. 2005. Increased salinization of fresh water in the northeastern United States. PNAS 102:13517-13520. (Accessed at