Winter road salt may corrode plumbing and contaminate water for nearby well owners

Road salt helps keep roads from icing up in the winter, but it also seeps into groundwater, raising its chloride levels. High levels of chloride in water can corrode plumbing and leach harmful metals into drinking water, posing health risks, particularly for people using well water. A new study involving citizen science predicts that nearly a quarter of private wells in New York state could be influenced by road salt application and its consequences to plumbing and health (Environ. Sci. Technol. 2018, DOI: 10.1021/acs.est.8b04709).

Chloride causes corrosion when it reacts with metals in plumbing, including iron, lead, and copper. In Flint, Michigan, this phenomenon caused the neurotoxin lead to contaminate drinking water when the city switched its water supply to a river with elevated chloride levels.

In the upstate New York town of Orleans, residents living near a storage barn for road salt had private wells with elevated chloride levels, according to a 2012 report by environmental and geological consulting firm Alpha Geoscience. In the past few years, Stephanie Weiss and her family, who have a private well about 3 km from the storage barn, noticed some of their appliances failing. Two new dishwashers stopped working in short succession, and the spindle of their washing machine disintegrated. They got their water tested and found high levels of lead.

When the news about Flint broke, Weiss, who has a bachelor’s degree in chemistry and is a coauthor of the new study, began to “put two and two together, in terms of what happened chemically in Flint and what was happening chemically here.” She called Virginia Tech’s Marc A. Edwards, an environmental engineer who helped uncover the Flint water crisis, to ask if he would investigate the problem.

Edwards, postdoctoral associate Kelsey J. Pieper, and their colleagues designed a study to look into the issue. They provided over 100 water testing kits to residents with private wells in Orleans, with directions for taking water samples at home. The researchers analyzed the samples they received from 90 residents for chloride and metals and found trends consistent with the 2012 report: chloride levels were highest for wells near the salt barn, elevated but less high for those near major roads, and lowest for those near minor roads. Overall, 21% of wells had chloride levels over the U.S. Environmental Protection Agency’s recommended level of 250 mg/L. And 20% had levels of lead or copper over the EPA’s action levels of 15 µg/L and 1.3 mg/L, respectively.

Because plumbing composition varied among the homes, the researchers could not use the citizen science data to link the road salt with metal release. Instead, in the lab, they produced simulated well water with the range of chloride levels they found in homes and applied it to metal wires and simulated lead solder joints. As chloride levels increased to 250 mg/L, more lead leached from simulated lead solder joints, with no difference in leaching at higher chloride levels. Copper leaching from lead solder joints was greatest at lower levels of chloride.

Finally, through modeling, the team estimated that 24% of private wells in New York state could be affected by road salt application and 2% by salt storage facilities.

Sujay S. Kaushal, a biogeochemist at the University of Maryland, calls the study “really interesting and important,” noting that its citizen science component provides rare insight into the impact of road salt on private wells. Well owners don’t usually test their water frequently, he says, but this study shows that it’s important to do so in the winter, especially where road salt is commonly used, such as in the northeast or midwestern US.

In Orleans, 70% of those surveyed by the Virginia Tech team had already stopped drinking their well water by 2016. About a year ago, Weiss says, the state began providing her and other affected residents with free bottled water, and a water main is now under construction. “For decades residents have been trying to get the state to step up and do the right thing,” she says. After the study, she says, the dialogue changed. “This is real science. It couldn’t be ignored anymore.”