Antifreeze, a mixture of glycol and water used to regulate engine temperatures, is harmful to plants when spilled onto soil. Its chemical composition directly interferes with a plant’s ability to absorb water and nutrients necessary for survival. Because antifreeze properties are disruptive to biological processes, any spill should be treated seriously to prevent damage to your garden or lawn.
Understanding the Toxicity of Antifreeze Types
Antifreeze products use one of two primary glycol compounds, each presenting a different hazard level to plant life. Ethylene glycol (EG) is the compound most commonly used in conventional automotive coolants. EG is highly toxic and can severely stunt a plant’s growth or cause rapid death even in small concentrations.
The second type is Propylene Glycol (PG), sometimes marketed as “safer.” While PG is less acutely poisonous than EG, it remains harmful to plants in high concentrations. PG vapor can cause chlorosis (yellowing of leaves) and subsequent cellular death (necrosis) in plant species.
The danger is also posed by contaminants in used coolant. Both EG and PG become contaminated with heavy metals, including lead, copper, and zinc, after cycling through an engine. These metals are toxic to soil health and plant roots. The overall risk is proportional to the concentration and volume of the spill.
The Mechanisms of Plant Damage
The main way antifreeze harms plants is through osmotic stress. Antifreeze has a high concentration of dissolved solutes (glycol), creating a hypertonic solution when it enters the soil. This high solute concentration reverses the natural process of water absorption by the roots.
Instead of water moving into the roots, the glycol solution draws water out of the plant cells, causing rapid dehydration. This cellular dehydration, or plasmolysis, prevents the roots from absorbing moisture and nutrients. The plant essentially dies of thirst, even when surrounded by liquid.
A secondary, long-term mechanism is the direct chemical toxicity of the glycol and its contaminants. Heavy metals and residues picked up from the engine can cause chemical burn to the root system. Furthermore, as antifreeze breaks down, it can form corrosive organic acids that destroy beneficial soil microorganisms and inhibit fertility.
Immediate Steps for Contaminated Soil
If an antifreeze spill occurs on soil, immediate action is necessary to minimize the spread and impact.
Containment and Removal
Contain the spill by applying an absorbent material, such as kitty litter, sand, or specialized oil absorbent pads, directly onto the liquid. Allow the material to soak up the visible antifreeze before carefully scooping it up and placing it in a secure, sealed container.
Contaminated absorbent material and used antifreeze must never be put into regular trash or poured down a storm drain, as they are hazardous waste. Contact your local municipality or a hazardous waste disposal facility for proper collection and handling instructions.
Soil Excavation
For spills involving ethylene glycol, or any large spill, the safest procedure is the physical removal of the contaminated topsoil. Dig out the affected soil to a depth of several inches, place it in a heavy-duty container, and arrange for its disposal as hazardous waste.
After removing the contaminated soil, the area should be flushed thoroughly with water to wash away any remaining chemical residue. Affected plants should then be monitored for signs of recovery or permanent damage.