Coolant, also known as antifreeze, is toxic to grass and other plants, and it can kill them quickly. This fluid is designed to regulate engine temperature by changing the freezing and boiling points of water within the cooling system. Because of its chemical composition, any spill requires swift and careful action to prevent extensive soil and plant damage. Understanding the toxicity of this common automotive product is necessary for safe cleanup.
Toxic Ingredients in Coolant
The primary components of automotive coolant are glycols, which are alcohols that serve as the main agents for temperature regulation. Most traditional formulations contain ethylene glycol, a sweet-tasting, viscous liquid that is highly poisonous to all forms of life, including grass and soil microorganisms. Ethylene glycol is metabolized into corrosive acids, such as glycolic and oxalic acid, which directly interfere with cellular processes in plant roots and leaves. Its presence in the soil creates a hostile chemical environment that prohibits the healthy functioning of the grass.
A less toxic, though still damaging, alternative is propylene glycol, which is often used in “safer” or RV-specific antifreeze products. While propylene glycol is less acutely poisonous than ethylene glycol, it still presents a significant environmental hazard to plants. Both glycol types can slow plant growth and cause necrosis, or tissue death, if left untreated in the soil.
Used coolant is often contaminated with various heavy metals and other substances picked up from the engine’s cooling system as it circulates. These secondary contaminants, which include lead, zinc, and tin, are highly toxic and persist in the soil, compounding the poisoning effect. Corrosion inhibitors and dyes, added to the formula, also contribute to the overall chemical burden on the lawn.
How Coolant Damages Grass and Soil
The damage to grass from a coolant spill occurs through two distinct, yet simultaneous, mechanisms: chemical toxicity and osmotic stress. The chemical compounds, particularly the glycols and heavy metal contaminants, are absorbed by the grass roots, directly poisoning the plant from the inside. This chemical interference can disrupt photosynthesis and other metabolic functions, leading to chlorosis, which is an abnormal loss of the green color, followed by plant death.
The high concentration of glycol in the spill creates an immediate osmotic imbalance in the soil surrounding the grass roots. The concentrated coolant solution effectively draws water out of the grass cells in the roots, causing severe desiccation or “chemical burn.” This rapid dehydration starves the plant of the water it needs to survive, resulting in the characteristic brown, dead patch of lawn often seen after a spill.
The soil itself also suffers, as the high concentration of chemicals can kill the beneficial microorganisms that are essential for nutrient cycling and soil health. Although the glycols can eventually break down into less harmful byproducts like carbon dioxide and water, this process can take several days to weeks depending on environmental conditions. During this time, the soil remains largely sterile and unable to support healthy grass growth.
Immediate Steps After a Coolant Spill
Controlling the spill quickly is the most important step to minimize damage to the grass and prevent the toxin from spreading into the surrounding environment. The first action should be to keep all pets and children away from the area, as the sweet smell and taste of glycol can be attractive but deadly if ingested. Immediately contain the fluid by creating a small berm or barrier around the spill using garden soil, sand, or old towels to stop it from flowing further across the lawn.
Once contained, the liquid must be absorbed rather than washed away. Hosing down the spill only spreads the contamination and pushes the toxic chemicals deeper into the soil and potentially into storm drains. Cover the entire affected area with a highly absorbent material like clay-based kitty litter, sawdust, or a commercial oil-absorbent product. Allow this material to sit for a few hours to ensure maximum absorption of the concentrated liquid.
After the absorbent material has done its work, carefully scoop up all of the saturated material and the top inch or two of contaminated soil. Place this waste into a heavy-duty, sealed container. This waste must be disposed of as household hazardous waste (HHW) at a local facility, not simply placed in the regular trash. Following the removal of the most contaminated soil, lightly watering the spot over several days can encourage the remaining soil microbes to break down trace residues.