Salt guide
for responsible salt use that reduces chloride
pollution into our water.
Our Water.
Our Responsibility.
This resource guide provides information about how the choices we make each winter can keep our freshwater healthier for people, pets, and wildlife.
Winter Sources
Across much of the United States, winter maintenance relies heavily on salt products to keep roads, parking lots, driveways, and sidewalks safe. Millions of tons of these materials are applied each year, especially in colder regions such as northern Michigan where snow and ice are frequent and persistent. While effective for public safety, widespread salt use has unintended consequences beyond the pavement.
Most deicing products are made from chloride-based salts, including sodium, magnesium, and potassium compounds. When snow and ice melt, these salts dissolve and move with runoff into nearby streams, lakes, and groundwater. Once dissolved, chloride does not readily break down or settle out and cannot be filtered out, making it extremely difficult to remove from freshwater systems. As a result, particularly in developed areas with large amounts of pavement and hard surfaces, this process can rapidly increase chloride levels in local waterways.
While winter salt application is a major source of chloride, it is not the only way it enters our freshwater systems.
Everyday Sources
Water Softeners
Many homes use water softeners to reduce hard water minerals like calcium and magnesium. These systems periodically flush the trapped minerals using a salt solution, creating salty wastewater. In communities with municipal sewer systems, this water passes through wastewater treatment plants that are not designed to remove salt before it enters rivers and lakes. In rural areas, water softener discharge moves through septic systems and into groundwater. Over time, this can add a steady source of salt to local waterways.
Dust Suppressants
Salt is not only used in winter. During warmer months, calcium chloride is often applied to gravel roads to reduce dust by holding moisture on the road surface. While effective for dust control, these salts can be washed into nearby streams or soak into groundwater during rain events.
Fertilizers
Some commonly used fertilizers contain chloride, including potassium chloride and magnesium chloride. Once it breaks down, chloride does not bind to soil and can move easily with water through the soil and into groundwater, especially after a heavy rainfall.
Why We Care
Salt Builds Up in Water
Once chloride from salt dissolves into water and enters the environment, it is difficult to remove. Chloride moves easily with water and accumulates in lakes, rivers, streams, wetlands, and groundwater. Even small amounts can cause harm – just one teaspoon of salt can contaminate five gallons of water to levels that are toxic to many freshwater organisms. Over decades of widespread salt use, this buildup has led to steadily rising chloride levels in surface water and groundwater, threatening freshwater ecosystems and drinking water supplies.
Impacts on Aquatic Plants and Animals
Freshwater plants and animals are adapted to low-chloride conditions, and many are highly sensitive to increases in chloride. Exposure to high concentrations of chloride can disrupt growth, reproduction, and survival – even before chloride concentrations reach lethal levels.
Damage to Infrastructure
Salt does not just affect the environment; it also takes a toll on our built surroundings. Salt accelerates the deterioration of concrete, brick, stone, and metal, weakening roads, bridges, sidewalks, vehicles, and buildings. Each ton of salt applied can cause hundreds to thousands of dollars in damage, contributing to billions of dollars in repair costs nationwide every year.
Risks to Pets and Wildlife
Salt left on sidewalks and roads can irritate pets’ paws and skin, and swallowing salt either directly or by licking paws can lead to serious health problems. Salt residue can also affect birds, small mammals, and other wildlife that come into contact with salt on surfaces, drink water with elevated salt concentrations, or forage on vegetation and other food sources contaminated with salt.
Changes to Lakes and Aquatic Systems
In lakes, elevated chloride levels can interfere with natural seasonal mixing, which affects how oxygen and nutrients move through the water. These changes can alter food webs, reduce habitat quality, and increase stress on aquatic life over time.
Understanding Chloride Standards
In 2019, the State of Michigan established chloride water quality standards to better protect freshwater systems from salt pollution. These standards are based on concentrations known to harm aquatic organisms and disrupt aquatic ecosystems.
- Chronic chloride standard (150 mg/L) – chloride concentrations are high enough to cause stress to sensitive aquatic organisms. Prolonged exposure with chloride at or above this level can affect behavior, growth, and reproduction.
- Acute chloride standard (320 mg/L) – chloride concentrations may be lethal to some aquatic organisms. Even short-term exposure to chloride at or above this level can impair mobility and survival.
Learn more about how chloride standards were developed and how the state is implementing them to help protect our waters from chloride pollution.
While these limits help define conditions needed for healthy freshwater and are used by resource managers to assess water quality conditions, chloride continues to enter lakes, streams, and groundwater through everyday salt use. Without meaningful changes in how and how much salt is used, many freshwater systems are expected to reach or exceed these protective standards in the coming decades.
Learn more about responsible salt use that will protect our freshwater systems.
This project has been funded wholly through the Michigan Department of Envrionment, Great Lakes and Energy’s Nonpoint Source program.