Study Shows How Road Salts and Other Man-Made Materials Actually Harms Freshwater Sources

As winter storms threaten to make driving risky, residents often use salt to melt snow and ice on roads, intersections, and sidewalks. Since thousands of people die or are hospitalized every year due to weather-related collisions, road salt is an effective safety tool.

However, a recent study led by the University of Maryland's Sujay Kaushal warns that injecting salt into the environment-whether for de-icing highways, fertilizing crops, or other reasons-releases toxic chemical cocktails that pose a major and increasing global danger to our freshwater source and human health.

Kaushal's latest work is the first to look at the complex and interconnected symptoms of Freshwater Salinization Syndrome and how they affect human health. Suppose a concerted management and control approach to human sources of salt is not implemented. In that case, the world's freshwater reserves could face significant challenges at local, regional, and global levels, according to this research.

The thesis was published in the journal Biogeochemistry on April 12, 2021, and calls on policymakers to treat salts with the same degree of urgency as acid rain, habitat destruction, and other high-profile environmental issues.

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Previously Ignored Problem

"We used to think that adding salts wasn't a big deal," said Kaushal, a professor in the Department of Geology and the Earth System Science Interdisciplinary Center at the University of Maryland. "We assumed that by putting it on the roads in the winter, it would be swept out. However, it remained and collected. We're now looking at both the immediate and long-term human, financial, and infrastructure impacts of all these chemical cocktails that result from adding salts to the atmosphere, and we're thinking, "This is becoming one of the most important threats to our freshwater supplies." And it's happening in a lot of ways in the United States and around the world, according to our research."

Kaushal and his colleagues discovered a global rise in chloride concentrations after comparing results and reviewing research from freshwater monitoring stations worldwide. Chloride is found in various salts, including sodium chloride (table salt) and calcium chloride (commonly used for road salt). They have discovered a 30-year pattern of rising salinity in areas like the Passaic River in northern New Jersey and a 100-mile-plus stretch of the Potomac River that provides drinking water to Washington, D.C., by drilling down into data from targeted regions.

Salt Contaminants

Road salts are the most common human-related salt source in the Northeast, but other sources include waste spills and discharges. Tracks, bridges, and structures that have weathered include limestone, concrete, or gypsum, both of which emit salt. The study adds to a growing body of evidence that both salt sources emit chemical cocktails that damage natural and built environments. Changes in salt levels, for example, may cause parasitic, salt-tolerant species to take over a stream.

Salts will corrode water pipes, releasing heavy metals into drinking water sources, according to the study. Salt's complicated relationships with the atmosphere are little known. According to the report, each lake, stream, and aquifer poses its own set of management challenges. According to the study, management methods must consider salt inputs from various sources. "The increasing complexity and severity of these problems astound me," says the study's co-author.

While technological advancements have helped to mitigate runoff, there are currently no safe and reliable alternatives to road salts.

Kaushal believes that policy, emerging technology, and a well-coordinated management strategy can mitigate the risks of Freshwater Salinization Syndrome on a large scale.

"In the end, we need higher-level oversight, and we still don't have enough safeguards for municipal jurisdictions and water bodies," Kaushal said.

Continuing Observation 

The study recommends that water monitoring activities be increased in the future and that new sensor equipment will collect continuous data. Scientists may use high-frequency sensor data to track peaks in salinity and water flow, which can help them predict the chemical structure and concentration of contaminants caused by Freshwater Salinization Syndrome.

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