Meghan Hodges
Road salt pollution is an environmental issue that has emerged due to the increasing use of road salt for de-icing. Rock salt, similar in composition to table salt, is applied to roads, parking lots, and sidewalks during winters to prevent the formation of ice. While it is effective in maintaining road safety, the runoff from its application carries de-icing chemicals that contaminate nearby water bodies, including lakes, rivers, and streams. This contamination poses a significant threat to aquatic life and ecosystems, with elevated chloride levels endangering fish, bugs, amphibians, and plankton. Additionally, the accumulation of salt in the environment can impact soil health, plant life, and even drinking water sources, affecting both ecosystems and human health. As awareness of the environmental hazards of road salt grows, there is a pressing need to address this issue and explore alternative de-icing methods or techniques to reduce salt usage.
| Characteristics | Values |
|---|---|
| What is it? | Rock salt, chemically similar to table salt, is used to de-ice roads. |
| Origin | Mined from large underground deposits formed after prehistoric oceans evaporated. |
| History | Salt was first used to de-ice roads in New Hampshire in 1938. |
| Usage | About 20 million tons of salt are scattered on U.S. roads annually, roughly 123 pounds per person. |
| Environmental Impact | Salt accumulates in the environment, threatening ecosystems and human health. |
| Water Pollution | Salt runoff contaminates water sources, affecting drinking water quality and endangering aquatic life. |
| Soil Degradation | Salt washes into the soil, degrading soil health and harming plants. |
| Alternatives | Liquid brine can reduce salt usage by up to 70% but is less effective at lower temperatures. |
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What You'll Learn
Rock salt is chemically similar to table salt
Rock salt, also known as halite, is chemically similar to table salt. Both are primarily made of sodium chloride (NaCl) and contain about 40% of their weight in sodium. However, rock salt is typically mined directly from underground salt deposits that formed millions of years ago when ancient seas and lakes dried up and evaporated, leaving behind large salt deposits. These deposits can be hundreds of meters deep and are often found in salt mines. In contrast, table salt comes almost exclusively from evaporation ponds that remove salt from seawater.
Rock salt is not usually refined or processed, resulting in its coarse, crystal shape. The lack of processing allows rock salt to retain trace minerals like calcium, magnesium, and potassium, which give it a unique flavour profile and a slightly different taste compared to table salt. These minerals also influence the colour of rock salt, which can vary from clear to pink to dark brown, depending on the amount and type of impurities present.
Table salt, on the other hand, undergoes a refining process to remove additional minerals and add additives and chemicals, such as anti-caking agents. This process results in the fine, crystalline powder commonly associated with table salt, which is typically white or off-white in colour.
While rock salt is chemically similar to table salt, it is not typically used in the same way in cooking due to its larger crystal size and coarse texture. It takes longer to dissolve and is harder to measure, making it less practical for seasoning most dishes. However, rock salt is sometimes used as a finishing salt or in specific applications like salt crusts and ice cream making, where its large crystals provide a satisfying crunch and burst of flavour.
The use of rock salt as a de-icer on roads, parking lots, and sidewalks during winter has become an environmental concern. While it effectively lowers the freezing point of water, preventing the formation of ice, the exponential increase in its usage has led to water quality issues and infrastructure problems. The sodium chloride in rock salt dissolves into sodium and chloride ions, which can contaminate surface water and groundwater, posing risks to both ecosystems and human health.
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Salt harms aquatic ecosystems
Secondly, salt spray and salty runoff from roads and sidewalks can damage plants and trees, and high concentrations of chlorides can even kill them. Chlorides can also concentrate in the soil, causing harm to soil health and plants over time.
Thirdly, salt can change the way water mixes, leading to the formation of salty pockets near the bottom of lakes, creating biological dead zones. A study of North American lakes found that even a small amount of development, such as paving, within 500 meters of a lake, increased the risk of the lake becoming saltier over time.
Finally, salt can also impact the food web within aquatic ecosystems. For example, an increase in salt-tolerant zooplankton species has been observed, and this shift could potentially impact fish that feed on these zooplankton.
Overall, the use of road salt has a significant environmental impact, and it is important to consider alternative de-icing methods or ways to reduce salt use to protect aquatic ecosystems and water quality.
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Salt is a persistent pollutant
The sodium chloride in road salt dissolves into sodium and chloride ions, which interfere with water molecules' ability to form ice. However, these ions can find their way into the environment, causing issues for both surface and groundwater quality. Chloride is a persistent pollutant, and once it enters water sources, it remains there. As chlorides accumulate, drinking water is at risk of becoming salty, which can also lead to health issues for those requiring low-sodium diets.
The impact of road salt on aquatic ecosystems is significant. High concentrations of salt can be fatal to some aquatic animals, and it can alter the way water mixes, creating salty pockets near the lake bottoms that become biological dead zones. A study of North American lakes found that even a small percentage of development near a lake could lead to a significant amount of salt entering the water body. This has already been observed in the Muskoka region of central Ontario, where changes in lake sediments coincide with the onset of road salt applications.
The long-term application of road salt has negative consequences on soil health as well. Salt spray and salty runoff from roads can damage plants, and high concentrations of chlorides can even kill them. Additionally, chloride pollution can concentrate in the soil, causing harm to soil health and plants over time. The impact of road salt pollution is a growing concern, and there is a need for greater awareness and the development of alternative de-icing methods to minimize its environmental impact.
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Salt is an emerging threat to human health
The practice of using salt for deicing roads, which began in the 1940s and 1950s with approximately 5,000 tons used annually, has now grown exponentially. Today, about 20 million tons of salt are scattered on US roads each year, amounting to roughly 123 pounds per American. This excessive use of road salt has led to various problems with water quality and water-related infrastructure.
Salt, or sodium chloride, works by lowering the freezing point of ice. When sprinkled on ice, it separates into sodium and chloride ions, interfering with water molecules' ability to bond and form ice. However, these ions then make their way into the environment, causing issues for both surface water and groundwater quality. Chloride is a persistent pollutant, and as it accumulates, our drinking water is at risk of becoming salty. Excessive sodium in drinking water can be detrimental to those who require low-sodium diets, and it is a well-known risk factor for hypertension or high blood pressure, which increases the risk of heart disease, stroke, and premature death.
In addition to the direct impact on drinking water, the runoff from roads and sidewalks containing salt and de-icing chemicals damages plants and can even lead to their death. This runoff also affects soil health over time. Furthermore, a study released in 2023 found that the application of chloride de-icers in Colorado more than tripled between 2015 and 2019, resulting in the pollution of a commercial potable water supply to the extent that freshwater had to be trucked in.
The excessive use of salt, particularly in de-icing practices, has led to its accumulation in the environment, threatening both ecosystems and human health. While salt is necessary for bodily functions, its overuse has been linked to increased blood pressure and a higher risk of heart disease, stroke, and other health issues. Therefore, it is essential to address this emerging threat and explore alternatives to traditional road salt, such as liquid brine, to reduce the environmental and health hazards associated with road salt pollution.
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Alternatives to road salt
The use of road salt, or rock salt, has been a common method to prevent or eliminate ice formation on roads and sidewalks since the 1930s. While it is effective and inexpensive, the exponential increase in its usage has led to various environmental concerns, such as water quality degradation, infrastructure damage, and threats to ecosystems and human health. As a result, there is a growing interest in exploring alternatives to road salt. Here are some of the alternatives that have been proposed and implemented:
Liquid Salt Brine
Liquid salt brine is a technique that involves spreading a solution of salt and water instead of traditional rock salt. This method allows for more even and efficient distribution and immediate effectiveness. Switching to liquid brine can significantly reduce the amount of salt applied to roadways, lowering environmental hazards and costs. However, one drawback is its reduced effectiveness at lower temperatures.
Pickle Brine, Cheese Brine, and Other Natural Brines
In some regions, such as Bergen County, New Jersey, and Wisconsin, natural brines like pickle brine and cheese brine have been used instead of road salts. These brines are effective in preventing snow and ice accumulation and are significantly cheaper than road salts. Additionally, they can be used to make productive use of waste products, such as the large volumes of cheese brine generated by cheese-makers.
Sugar Beet Juice
Sugar beet juice is another popular alternative to road salt. It lowers the freezing point of ice and helps deicers adhere better to the ground. It is considered safer for pets and vehicles than conventional deicers. While it may not be as potent as other deicers on its own, it can reduce the amount of conventional deicer needed. However, more research is needed to fully understand its environmental impact, as a 2018 study suggested it may cause psychological stress in mayflies.
Coffee Grounds
The city of Krakow, Poland, inspired by its sister city Lviv in Ukraine, has implemented an innovative approach by collecting used coffee grounds from local cafes and using them instead of salt or sand to combat slippery winter conditions. This method provides an ecological and cost-effective solution to maintaining safe walkways during winter.
Public Awareness and Research
In addition to these practical alternatives, there is a growing emphasis on raising public awareness about the excessive use of road salt and its detrimental effects on watersheds, human health, and economics. Involving students and the community in nature walks, workshops, and citizen science programs can foster a deeper understanding of the impact of road salt on the environment and explore alternative solutions. Furthermore, creating research and advocacy groups to study the economic, environmental, and social costs associated with road salt use can help hold governments accountable for preserving our natural world.
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Frequently asked questions
Road salt pollution is the contamination of the environment by road salt, specifically rock salt, which is used to de-ice roads in winter.
Road salt enters waterways through runoff, leaching, and surface water runoff via stormwater sewer systems. This increases the salinity of water, which can be toxic to aquatic life and endanger wildlife in freshwater ecosystems. It also affects soil health and plants.
High levels of chloride in drinking water can cause health problems for those who need low-sodium diets.
Liquid brine can be used instead of traditional road salt. It can be spread more evenly and efficiently and works immediately. However, it is less effective at lower temperatures.
