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Can road salt and other pollutants disrupt our circadian rhythms?

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13.01.2018

A pedestrian crosses the street in front of vehicles during a snowstorm, Sunday, Feb. 12, 2017, in Waltham, Mass. (AP Photo/Steven Senne) (Credit: AP)

Every winter, local governments across the United States apply millions of tons of road salt to keep streets navigable during snow and ice storms. Runoff from melting snow carries road salt into streams and lakes, and causes many bodies of water to have extraordinarily high salinity.

At Rensselaer Polytechnic Institute, my colleague Rick Relyea and his lab are working to quantify how increases in salinity affect ecosystems. Not surprisingly, they have found that high salinity has negative impacts on many species. They have also discovered that some species have the ability to cope with these increases in salinity.

But this ability comes at a price. In a recent study, Rick and I analyzed how a common species of zooplankton, Daphnia pulex, adapts to increasing levels of road salt. We found that this exposure affected an important biological rhythm: The circadian clock, which may govern Daphnia‘s feeding and predation avoidance behaviors. Since many fish prey on Daphnia, this effect could have ripples throughout entire ecosystems. Our work also raises questions about whether salt, or other environmental pollutants, could have similar impacts on the human circadian clock.

Daily biological rhythms and the circadian clock

In studying how road salt affects aquatic ecosystems, the Relyea lab showed that Daphnia pulex can adapt to handle moderate exposures in as little as two and a half months. These levels ranged from 15 milligrams of chloride (a building block of salt) per liter of water to a high of 1,000 milligrams per liter — a level found in highly contaminated lakes in North America.

However, an organism’s ability to adapt to something in its environment can also be accompanied by negative trade-offs. My lab’s collaboration with........

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