With the trees budding and pollen counts seeing people reach for antihistamines and tissues, snow may be the last thought on people’s minds. Yet the end of the cold season means that environmentalists can begin analyzing the impact of a common wintry sight: the road salt used to keep roads and parking lots ice-free.
The most common kind of road salt is sodium chloride, the main component in table salt. Sounds harmless enough. However, a growing body of research points to negative impacts on human health and the natural environment when dissolved chloride trickles into freshwater systems.
In December 2020, the New Jersey-based Watershed Institute launched the NJ Salt Watch Program to monitor chloride levels in the state’s natural waterways. The study now has two years of data to analyze, with this past winter adding a third.
The study relies largely on volunteers, including regional nonprofits, schools and individuals. First, the group requests free test strips from the Watershed Institute’s website. Each person picks a freshwater spot to monitor, whether it be a river, creek or stream.
The goal is to visit that site four to six times per season in different conditions, both directly after rain or snow and in dry conditions. Participants can upload their results to the Watershed Institute’s data map, where all interested visitors can see the data as it’s gathered.
The institute classifies chloride levels into three categories. Low levels, marked by a green dot on the data map, indicate less than 100 mg of chloride per liter of water. Moderate levels, marked by a yellow dot, indicate measurements of 100 to 230 mg of chloride per liter. Impaired levels, marked by a dark orange dot, mean that there’s 230 mg of chloride or more per liter of water, a level that the EPA has designated unsafe for human health.
In a November 2022 webinar analyzing findings from the 2021/2022 season, Erin Stretz of the Watershed Institute explained that in the winter months, chloride levels climbed highest in February: statewide, about 20% of samples collected in February reflected impaired chloride levels.
That number might jump again just after snowfall, when municipalities dump fresh salt on the roads, or under snow melt conditions, when meltwater carries salt and sediment from the road into waterways.
Yet it’s in summertime that chloride levels reach dizzying– and worrying– heights. The Watershed Institute’s Summer StreamWatch program found that almost 100% of its samples reflected chloride levels of 230 mg/l or higher in August 2022.
It’s a counterintuitive but familiar finding for Christa Reeves, water quality program coordinator for the Musconetcong Watershed Association, one of the organizations participating in the Salt Watch Program.
“It actually gets worse over the summer because salt is one of those things in chemistry that, as the water temperature goes up, the lethal dose becomes less and less,” Reeves said. “So what was, you know, okay in winter has now become lethal in summer, because we have less flow, higher temperatures and the concentration becomes more acute.”
A river with unsafe levels of chloride isn’t a problem just for swimmers and fishermen, as Christine Dunbar knows. She is the coordinator for the Paulins Kill Watershed Association, another group participating in the Salt Watch Program.
“It’s hard to imagine that the surface water that becomes salty… is connected intimately with our groundwater,” she said. “And our well water comes from our groundwater.”
Dunbar points out that the Paulins Kill is the third largest supplier of water to the Delaware River from the Jersey side. According to the Delaware River Watershed Initiative, the Delaware River provides drinking water to 15 million people.
Elevated salt levels in drinking water provides a health risk to those with high blood pressure and heart problems, as well as anyone else required to adopt a low-salt diet.
Wildlife and plant life suffer as well. Recent studies have found that elevated chloride levels lead to an alarming die-off in freshwater organisms, even in waterways below the 230 mg/l threshold. Even a short period of acute chloride levels could lead to a die-off in plants, insects, and fish, a cascade of wildlife death.
The data from 2022/2023 isn’t done being collected and processed.
“I could say preliminarily that the Paulins Kill has generally elevated chloride levels upstream of the Marksboro area, and the Musconetcong River seems to be moderately elevated along the whole stretch,” Stretz said.
One positive development is increased awareness and participation in the Salt Watch Program, allowing for better data.
“The response has been tremendous this year,” she added, noting that 149 volunteers have submitted 1,019 data points since November 2022, almost as much as the last two years combined.
She credits project partners such as the Musconetcong Watershed Association and Foodshed Alliance, as well as participating community groups such as the Blairstown Enhancement Committee, Lake Hopatcong Foundation, Lake Owassa Community Association, Scenic Lakes Community Association, Wallkill Valley Girl Scouts, Sussex County Community College, Blair Academy and Ridge and Valley Charter School.
Over the next year, the aim of the NJ Watershed Watch Network will transition from raising awareness to creating advocacy tools, so volunteers can “engage with their municipalities and drive them toward more sustainable methods of winter road management.”
Chip O'Chang, Contributing Writer
Chip O'Chang is an educator, fiction writer, and lifelong resident of New Jersey. He has also written for My Life Publications and NJ Indy. He lives in the NJ Skylands with his partner, two cats, and and a bearded dragon.