Sidewalk salt enhances safety on wintry surfaces by melting ice and snow. Concerns persist regarding its potential effects on pets, plants, and water systems. Understanding these de-icing agents and their broader consequences is important for informed choices.
Common Types of Sidewalk Salt
Sidewalk salts primarily consist of various chemical compounds designed to lower the freezing point of water, a process known as freezing point depression. Sodium chloride (NaCl), often referred to as rock salt or table salt, is the most common and economical option. Other widely used compounds include calcium chloride (CaCl2), magnesium chloride (MgCl2), and potassium chloride (KCl). These salts dissolve into ions in the thin layer of water present on ice, disrupting the water molecules’ ability to form a solid crystalline structure, thereby melting the ice.
Each type of chloride salt offers different melting efficiencies at various temperatures. Calcium chloride, for instance, melts ice down to -25°F (-32°C), while sodium chloride is less effective below 15°F (-9°C). Magnesium chloride works down to about -5°F (-15°C) and potassium chloride to around 12°F (-11°C). These varying chemical properties lead to differing environmental and biological impacts.
Risks to Pets and Children
Sidewalk salt poses risks to pets through direct contact and ingestion. Salt crystals irritate paw pads, causing dryness, cracking, chemical burns, and pain. This discomfort often leads pets to lick their paws, ingesting the salt. Topical irritation symptoms include redness, swelling, limping, or persistent paw licking.
Ingestion of de-icing salts can cause gastrointestinal upset, including drooling, vomiting, diarrhea, and abdominal pain. Larger quantities of sodium chloride can lead to sodium ion poisoning. This condition causes dehydration, lethargy, increased thirst, tremors, disorientation, and potentially seizures or coma. Fatal outcomes can occur if a dog consumes 4 grams of sodium chloride per kilogram of body weight.
Children are also susceptible to harm from sidewalk salts, primarily through accidental ingestion or direct contact. Young children may be curious about the pellets and put them in their mouths. Ingesting even small amounts can irritate the mouth and stomach, causing upset stomach, nausea, and diarrhea. Direct skin contact can cause irritation or burns, and eye contact can cause chemical burns.
Environmental Consequences
Salt runoff from sidewalks and roads can significantly affect plants and soil. Dissolved salts directly contact plant foliage, leading to “salt burn” or desiccation, resulting in browning of leaves, stunted growth, and premature leaf drop, particularly on plants nearest to salted surfaces. In the soil, salt ions, especially sodium, compete with essential plant nutrients like potassium and phosphorus, disrupting nutrient uptake and causing physiological drought.
Salt alters soil chemistry and structure, increasing salinity and compaction while reducing aeration and water infiltration. It harms beneficial soil microorganisms and reduces soil fertility. Long-term accumulation can lead to vegetation decline or death, contributing to ecological shifts.
Beyond terrestrial impacts, dissolved road salt enters waterways through storm drains and runoff, affecting aquatic ecosystems. Freshwater organisms, including fish, amphibians, and invertebrates, are adapted to low salt concentrations. Increased salinity disrupts their osmoregulation, affecting growth, reproduction, and survival. Sensitive species may perish, while others experience reduced growth or reproductive capacity. This alters biodiversity and food webs, potentially increasing salt-tolerant invasive species and harmful algal blooms.
Road salt runoff contaminates local drinking water sources, particularly groundwater and wells. Elevated chloride and sodium levels in water supplies affect taste and pose health concerns for individuals on sodium-restricted diets. Increased chloride concentrations also accelerate plumbing corrosion, potentially leaching metals into drinking water.
Protecting Against Salt Exposure and Safer Options
Protecting pets from sidewalk salt exposure involves several practical measures. After walks, wipe or rinse paws with warm water to remove salt and prevent ingestion. Apply a protective paw balm or wax before going outside to create a barrier against salt and chemicals, moisturizing paw pads and preventing cracking. Pet booties offer comprehensive protection, shielding paws from direct contact with salt, ice, and cold. Discourage pets from eating snow or drinking meltwater from salted areas.
Homeowners have several alternatives to traditional chloride-based salts. Sand or kitty litter provide traction without melting ice, making them safer for pets and plants. Calcium Magnesium Acetate (CMA) is a chloride-free de-icer, less corrosive and safer for pets, plants, and concrete. While biodegradable, CMA may be less effective at very low temperatures and is generally more expensive.
Potassium acetate is another alternative, less corrosive to steel and faster degrading than sodium chloride. However, its breakdown can lead to high biochemical oxygen demand (BOD) in water bodies, potentially depleting oxygen for aquatic life.
Some products incorporate beet juice, often mixed with salt, to lower the freezing point and reduce overall salt needed. While less corrosive and potentially more eco-friendly, beet juice can stain surfaces and its sugar content may promote bacterial growth in waterways, affecting oxygen levels.