We may be on our way to a crisis in our supply of fresh water on Earth due to increased levels of salt. Deicers like road salt serve as one of the main sources of excess salt that pollutes fresh water in the United States.
While we often think water is abundant on Earth, the vast majority is salt water in our oceans. Only three percent is fresh water.
Chloride occurs naturally in the environment—in underground aquifers and coastal saltwater spray, for example. However, increased chloride concentrations nationwide are caused by humans, coming from road salt, water softener discharge, sewage effluent,
processing plants and fertilizers. In some regions, irrigation of crops increases the salinization of the soil, which can contribute to higher concentrations in waterways.
These higher concentrations of chloride in our water deliver a host of problems. The combination of physical, chemical and environmental harms from these salt sources is called “freshwater salinization syndrome.”
In a study published in October, 2023 in Nature Reviews Earth & Environment, the authors describe the “cascading direct and indirect human health impacts associated with salinization,” ranging from hypertension to cancers. And
the corrosive role of salt triggers the release of lead and other harmful chemicals in pipes that carry drinking water to American homes, schools and businesses. That was a factor in the toxic levels of lead in the drinking water in Flint, Michigan,
which triggered a public health emergency.
Data revealed by the U.S. Geological Survey also in October show sharp spikes in chloride pollution also in the groundwater in regions where a lot of road salt is applied, such as New England, the Midwest and the mid-Atlantic. In the Southwest, decades
of irrigation and evaporation have increased the salinization of the soil, which has leached salt into the groundwater.
Because there are remarkably few regulations about levels of salt in drinking water, and because there’s also low public awareness about harm caused by chloride pollution, the Izaak Walton League’s Salt Watch program plays an outsized role
in data collection, public awareness and advocacy for healthy, clean water in the U.S.
We like to say road salt can be too much of a good thing. Salt Watch encourages better application measures to reduce the concentration of salt in water while providing safety on roads, parking lots and sidewalks. In many cases, more salt than is needed
is applied to surfaces during icy weather.
When we use the term “salt,” we are often referring to sodium chloride, and chloride is the chemical that can be measured in water quality tests. This is the same salt that is used in our food, and it’s an essential nutrient for human
health.
Several types of salt are used on our roadways, parking lots and sidewalks including:
- sodium chloride
- magnesium chloride
- potassium chloride
- calcium chloride
Sodium chloride is the most common and least expensive. However, all of the other common products above have similar negative effects on our health and environment.
The costs of corroding water pipes
Chloride is incredibly corrosive. Although the initial cost of sodium chloride is low (about $80 per ton), the long-term associated costs of road salt are very high. Chloride can corrode metal, concrete, bridges, vehicles, drainage systems, highway fixtures
and drinking water pipes.
Although there are many factors to consider when creating a long-term damage estimate, Fortin Consulting (now Bolton and Menk, Inc.) in 2014 estimated that every ton of salt used in the U.S. costs about $800-$3,300 in infrastructure damage. If we use
approximately 20 million tons of road salt each year, that total in long-term associated costs of road salt pollution would be between $16-$66 billion.
Chloride not only damages infrastructure above ground, it also can corrode our pipes. Water treatment facilities deal with corrosion regularly. A scientist at WSSC Water (Washington Suburban Sanitary Commission, the utility for the Washington, DC region)
recently told us, “Water is corrosive. Increased chloride concentrations in waterways increase corrosion.”
And of course, as those chloride concentrations increase, corrosion only gets worse, which is why water treatment facilities regularly monitor for chloride and other factors that would increase water’s corrosivity.
As salt accelerates the corrosion of pipes in our water systems, it leaches metals, including dangerous metals like lead, into our drinking water. To prevent this, water providers routinely add a chemical to the water to prevent pipe corrosion. Utilities
must consider not just the disinfectants added at the water treatment plant but corrosive chemicals—such as chloride—that may already be in the source water.
The Flint water crisis is the tip of the iceberg
The water crisis in Flint, Michigan, that first made headlines in 2014, was caused by switching water sources and not adjusting water treatment accordingly. Starting around April of that year, the new source of water for residents was the Flint River.
The river at that time had high concentrations of chloride due to road salt runoff from the winter before. As water was being pumped to residents, the water was not adequately treated for the increased corrosivity caused by the high level of chlorides
in the river.
After leaving the water treatment facility, water was being dispersed to residents through old pipes made of lead and copper. The added chloride in the water corroded those metals from the pipes after leaving the facility, tragically pumping water laden
with heavy metals into the drinking supplies of residents across the city.
The EPA reports that lead in water poses cardiovascular, kidney and reproductive health risks to adults and even low levels of lead in the blood of children can result in:
- behavior and learning problems
- lower IQ and hyperactivity
- slowed growth
- hearing problems
- anemia
Across the U.S., there are between 6 and 10 million water service lines containing lead, according to the EPA. Major cities have investigated replacing these pipes. Cost estimates have averaged $400 million per city and a decade of work. Because of this
high cost and time, the pipes are often left in place.
With millions of lead water lines still delivering water to American homes, schools and businesses, the public has a right to know about these lines so they can advocate for investments that will ensure their water is safe. Congress has approved funds
to help states and localities accelerate efforts to replace these lines.
By October 2024, the EPA will require all community water systems to submit an initial inventory of lead service lines. Americans will soon be able to visit the agency’s website and see where these lines are.
The corrosive effect of road salt on these water pipes in Flint, Michigan contributed to dangerous levels of lead leaching into the city’s drinking water.How chloride harms the environment
In the environment, chloride can dry out and kill vegetation, compact soil and become toxic to freshwater aquatic life. Because organisms that live in fresh water aren’t adapted to sudden chemistry changes (especially those that make water salty),
increased chloride in waterways can be deadly to aquatic life.
Chloride is naturally present in the environment. Chloride concentrations between 1 and 100 ppm (mg/L) are “normal” in most freshwater waterways. (100 parts per million, or ppm, is roughly equal to 100 milligrams per liter, or mg/L.) The Stroud
Water Research Center in Avalon, Pa., has been conducting surveys of waterways throughout the region for many years and has determined that for some areas, like Maryland, chloride naturally occurs at much lower concentrations, even below 50 ppm.
In areas with large amounts of impervious surfaces (pavement and concrete), chloride concentrations in streams, lakes and drinking water reservoirs tend to be higher. These areas are often heavily salted during the winter months and the impervious surfaces
don’t allow chloride to soak into the ground before entering nearby waterways. This causes the chloride concentrations in local waters to be elevated. If you look at the map on our Salt Watch results webpage,
you’ll notice that northern cities often display higher salt concentration.
In general, larger organisms like fish seem to be less sensitive to chloride than smaller organisms including macroinvertebrates and daphnia (sometimes called water fleas). Those smaller organisms play a vital role in the health of the ecosystem by controlling
algae and being a food source for larger organisms. If they are removed from the environment due to road salt pollution, the entire food web can be destabilized and algae can be left unchecked, leading to eutrophication events that end up depleting
waterways of oxygen.
If chloride is present in freshwater systems at 230 ppm over a period of a few days, that concentration is high enough to be toxic to freshwater aquatic life. At 860 ppm or above, chloride can be toxic to freshwater life in just a few hours.
But at lower concentrations, chloride can still be harmful to freshwater life. A 2007 study published in Ecological Indicators by Meador and Carlisle found chloride tolerance to be as low as 3.1 ppm for some species of brook trout. Sensitive
species like amphibians can also be affected, especially as they often breed in waterways formed by seasonal snowmelt that have no drainage or discharge point for the water. If road salt enters those waterways, the chloride will be trapped in those
depressions and will only increase over time.
Rising levels of salt and radium in groundwater
Data presented by the U.S. Geological Survey (USGS) in October 2023 show sharp spikes in groundwater salinization. Assessing a large sample of data from more than three decades, USGS hydrologist Bruce Lindsey said, “Chloride and sodium had statistically
significant increases more frequently than any other [potential pollutants] that we have on our list.” The fact that the increase has accumulated over decades means it may also take decades to recover, he said.
Hot spots for salt pollution were found in Northeastern and Midwest regions, “particularly around urban areas where there’s cold weather and a lot of road salt,” Lindsey said. “We obtained data on road salt application and
found correlations between these increases in chloride and sodium… [and] the road salt application rates.”
Reporting from an October 18 conference, the Geological Society of America said Lindsey and his colleagues also uncovered a new and alarming danger. A mixture of low pH and high salinity in a southern New Jersey aquifer has “mobilized the radium—a
radioactive element which is harmful to humans."
How safe is bottled water?
Believe it or not, the Safe Drinking Water Act does not apply to bottled water. Municipal or public tap water is regulated by the EPA and bottled water is regulated by the FDA (Food and Drug Administration). The EPA has tighter restrictions and inspection
regimens. Public tap water regulations also require disclosure of consumer information, and promptly notifies consumers about any drinking water standard violations.
The FDA requires water-bottling plants to implement water quality standards followed by suppliers of tap water. In contrast to the EPA regulations of public drinking water utilities, the FDA does not require disclosure of consumer information for
bottled water on packaging, cannot require bottled water to be analyzed by certified labs and in the past has fallen short in keeping up with EPA regulations for new contaminants. However, many brands of bottled water are sourced from tap water,
so they were initially regulated by the EPA, and later they were regulated by the FDA.
The impact of 20 million tons of salt
Even if we quit using road salt today, the salt already in the ground can endure for decades, and the salt content in our streams will rise as salt continues to percolate through the soil.
In some areas, chloride has infiltrated groundwater, giving high chloride results year-round. In other areas, chloride is so present in the soil that spikes can occur during drought conditions when water levels are low and there isn’t as much water
to dilute the chloride infiltrating the waterway.
Road salt was first used in the United States in New Hampshire in 1938 as an experimental treatment for ice on roadways. After World War II, the U.S. greatly expanded highway systems across the country and to reduce ice, the use of salt began to soar.
By the mid-1950s, the U.S. was using roughly one million tons of road salt every year. This number increased to 10 million tons by 1970. Today, we apply about 20 million tons of road salt to pavement each year, depending on the winter conditions. Road
salt has become a vital part of keeping northern communities safe during the winter.
A strain on drinking water utilities
Let’s keep pollutants out of waterways in the first place. Treatment plants, like this one in northern Virginia, can only do so much.
When chloride concentrations in source water used for drinking reach or exceed 250 mg/L (250 ppm), EPA requires public water suppliers to reduce chloride below this level before pumping it to the consumer.
So when too much salt is applied during the winter, the high concentration puts huge strains on our public drinking water utilities. Chloride and sodium cannot simply be filtered out of our water with the filtration equipment or processes commonly used
by water utilities—they need to go through a specialized process like reverse osmosis, which is incredibly expensive and requires specialized equipment.
At the current rate of road salt application, chloride concentrations have been increasing each year. In the Washington DC region, WSSC Water, which serves nearly two million residents, has determined that chloride concentrations over the past 30 years
have increased considerably in two waterways that supply WSSC’s drinking water. The Potomac River has seen a 200 percent increase over the past 30 years and the Patuxent River Reservoir has seen a 260 percent increase in chloride over the same
period.
What You Can Do
The Izaak Walton League created Salt Watch in 2018 to enable volunteers to test chloride levels in local waterways, report the results to a national database and advocate for policies and practices that reduce the use of salt as a de-icer.
Go to saltwatch.org to sign the Salt Watch pledge and request a free Salt
Watch kit. It’s easy to check how much salt is in your local stream using chloride test strips, which provide an instant reading. Start collecting data now to get a long-term look at chloride levels and the health of your water. By testing
with Salt Watch, you will join thousands of other clean water advocates across the country in road salt monitoring and learning more about what is happening in your own back yard.
On the League’s Salt Watch website, you can download our advocacy guide to learn more about some of the different groups involved in road salt in your community. The guide provides examples of how transportation professionals are trying to reduce
road salt pollution while maintaining public safety during winter weather. You will also find sample letters to your government officials and information you can use to get the conversation started in your community, including flyers, yard sign
templates and fact sheets. Educating yourself and your neighbors also makes a big impact.
For residents in the snow belt, there are many ways to make a difference in your own home or your community. One easy way is to Shovel, Scatter, and Sweep!
- Shovel early and often to prevent snow from turning into ice.
- Scatter salt judiciously. One 12-oz. mug holds enough salt to treat a 20-foot-long driveway or 10 sidewalk squares (about two parking spaces).
- Sweep up any excess salt that was spilled or left behind after a storm. This salt can be stored in a closed container and reused during the next storm event.
If you are part of an HOA or condo association or hire contracted road salt applicators, you can look at the agreement you have with your applicators and make sure that they aren’t being paid by the bag or number of pounds of salt that they
are applying each year. You can also encourage contracted “for hire” road salt applicators to take a road salt certification course that some states offer.
You can also alert someone (like a local watershed group or your Department of Environmental Protection) if you see a salt spill or too much salt being applied in an area. It’s good to also let them know about uncovered piles of salt. According
to an article by the University of Rhode Island, “uncovered salt piles lose about 20 percent of their salt each year, much of which finds its way into nearby waterways.” Something similar can occur for salt piles that are covered but
not contained.
A Brief History of Water Treatment
Water treatment began as early as 4000 B.C. in Ancient Greece as a means of improving the taste, appearance and odor of drinking water by methods of filtering and boiling. Ancient Greeks wanted to reduce turbidity or “visible cloudiness”
of the water. By 1500 B.C., the Egyptians started using alum to settle particles out of water. Filtration was established in the 1700s to achieve some level of water clarity.
By the 1800s, filtration with sand was widely used across Europe. It wasn’t until 1855 that waterborne illnesses were discovered after Dr. John Snow linked a cholera outbreak to a sewage-contaminated public well. By the late 1880s, Louis Pasteur
demonstrated “germ theory” that explains how diseases could be spread by microbes in water. In the early 1900s, drinking water treatment systems were built across the United States to remove particulates, thereby removing disease-causing
microbes.
Chlorine was introduced in 1908 to disinfect drinking water leaving water treatment facilities, drastically reducing waterborne disease outbreaks. Federal regulation of drinking water began in 1914 with a limited number of systems.
Water standards were revised and expanded by the Public Health Service in 1925, 1946 and 1962. In the 1962 revision and expansion, 28 substances were regulated.
In 1974, with enactment of the Safe Drinking Water Act (SDWA), all 50 states adopted (as either regulations or guidelines) the Public Health Service standards. Today, the EPA has legal limits set for more than 90 contaminants in drinking water including
microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals and radionuclides.
While not addressing drinking water directly, the Izaak Walton League has served as a leader in clean water advocacy from its earliest years. During the 1920s and ‘30s, the League led a national push to build sewage treatment plants in every
community, and chapters across the U.S. helped to make that happen. For instance, the Sioux Falls Chapter in South Dakota persuaded voters to approve a bond to create the city’s water treatment plant. In 1927, President Calvin Coolidge commissioned
the League to conduct the nation’s first survey of water pollution, which found that raw sewage was commonly dumped into waterways. Responding to the findings, seven states passed laws designed to reduce water pollution.
Where Does Your Drinking Water Come From?
At a time when we have access to so much information at our fingertips and the ability to connect with most anyone across the globe, in many ways we are more disconnected than ever before. Simple concepts like where our food and water come from do
not always have simple answers. Asking students, “where does your drinking water come from?” elicits answers such as “from the faucet,” “from the drinking water fountain” or “from bottled water.”
While those answers might be the last stage before we put a glass or bottle of water to our lips, the journey of water to our tap is more complex.
At the most basic level, our drinking water comes from the water cycle—from rain, streams and groundwater. Water is then pulled from large water bodies, such as lakes, rivers and aquifers, by water treatment facilities to treat and pump to the
consumer.
As water reaches a water treatment plant, that water goes through several steps to make sure it is safe for the consumer. Coagulation, flocculation, sedimentation, filtration and disinfection are some of those steps.
Coagulation is a process that involves injecting positively charged chemicals to neutralize any negatively charged particles in the waterways. Flocculation involves mixing the water to form heavier particles. Sedimentation separates solids from the
water. Filtration filters out any remaining solids from the water. Disinfection usually involves adding chemical disinfectants, such as chlorine, to kill any remaining parasites, bacteria and viruses. Obviously, this is a very simplified explanation
of what is involved at a water filtration plant, but you get the picture. Water goes through a lot of steps before it arrives in your spigot.
But not everyone gets water from a water treatment facility. Many receive their water via wells or springs. Those water sources are not regulated by the EPA, and people who get water from those sources are responsible for doing their own water testing.
This can leave millions of people each year at risk of contaminants they may not even know exist!
Top photo: The amount of salt used to treat icy pavement has grown enormously in recent decades creating a crisis for drinking water supplies, infrastructure and human health. Credit: iStock.