The Environmental Impact of Road Salt
2 minute read
Road salt has been used across the US since the 1930s to prevent ice from forming on roads, sidewalks, driveways, and parking lots
While road salt does make driving and walking during winter weather safer, it also has negative effects on human health, the environment, and infrastructure
Applying a salt brine solution can lessen the amount of road salt that needs to be applied, reducing its negative consequences
Did you know that about 20 million metric tons of road salt is applied to U.S. roads every year? Road salt, or sodium chloride, prevents water molecules from joining together to form ice by mixing with the water and causing this new solute to have a lower freezing point. By preventing ice formation, it makes roads, sidewalks, driveways, and parking lots much safer for both drivers and pedestrians.
Road salt has likely prevented many car accidents and saved thousands of lives, making it an essential part of preparation for winter weather. However, it also has negative effects on people, the environment, and both public and private property. So while road salt is necessary, there are ways that its impact can be mitigated and alternative solutions can also be used.
Harm to Humans
Sodium chloride can enter surface water and groundwater, contaminating drinking and well water. Higher levels of sodium in drinking water is harmful for people with high blood pressure.
One study in 2018 found that wells in Dutchess County, New York had sodium levels as high as 860 milligrams per liter. The federal and state recommendations are that sodium levels not surpass 20 milligrams per liter for someone on a very low-sodium diet and 270 milligrams per liter for someone on a moderately restricted sodium diet. So while a person is monitoring their sodium intake from food, they might not know that they are receiving a lot of sodium from their drinking water.
Harm to the Environment
High levels of chloride in surface water can be toxic to some fish, insects, and amphibians. When road salt accumulates on the sides of roads it kills vegetation and harms animals that consume it. Deer and moose love licking road salt, so they are more present on roads after salting, resulting in more collisions and roadkill.
Researchers have found in the contiguous U.S., 37% of drainage areas have an increased level of salinity compared to 50 years ago. Salt can only leave an ecosystem by transport or can be diluted by the addition of more freshwater.There are no natural biological processes that will reduce salt concentrations in ecosystems.
The Great Lakes are one of the largest surface freshwater ecosystems in the world. Gradually, the salinity levels in these lakes have increased due to the use of road salt starting in the 1940s. In the 1800s, Lake Michigan’s water contained about 1 to 2 milligrams of chloride per liter (road salt is sodium chloride, so chloride levels are used to measure sodium as well). Today the level is close to 15 milligrams per liter. While being under the threshold of 250 milligrams per liter at which freshwater plants and animals are harmed and drinking water is contaminated, it can cause stress to some freshwater organisms. This trend is concerning to scientists and activists who want to preserve this large freshwater resource.
Damage to Property and Infrastructure
Every year $5 billion in repairs must be made to cars, trucks, bridges, and roads due to damage caused by corrosive road salt. Because of its corrosive nature, the chloride in road salt is suspected to have played a role in the corrosion of Flint, Michigan’s water pipes. This process allowed lead to leach out into the water supply, having serious consequences for public health.
Reducing Its Impact
A liquid salt brine solution is a great way to drastically reduce the amount of road salt that needs to be applied prior to a storm. Brine spreads more evenly than road salt and begins to work immediately. Applying this solution has been found to reduce the need for road salt by 75%. This reduction also lowers costs for municipalities managing brine and road salt applications. In about two years the cost of salt brine equipment is recouped and after that the savings continue to stack up.
One Last Thing
Road salt is absolutely necessary for keeping roads, sidewalks, driveways, and parking lots safe during winter weather. However, due to the impacts to human and ecosystem health, along with damage to property and infrastructure, we should encourage the utilization of practices that reduce the demand for road salt.
