Chemical-based weed killers contain substances that are potentially dangerous to humans, wildlife and the environment. Glyphosate, an active ingredient in popular brands of herbicides, is highly toxic if swallowed. Weed killer manufacturers advise keeping animals and children away from treated areas until the weeds are dry. Take care using weed killers near ponds and fish and check the safety label for suitability.
Toxicity to humans
Weed killers may contain the chemical glyphosate which is poisonous to humans when ingested. If someone swallows a glyphosate-based herbicide call 999 immediately and give the operator the poisons information in the safety panel on the label. Do not make the patient vomit unless you are given specific instructions to do so by the emergency call centre.
The active chemicals in weed killers can cause burns and rashes on your skin. Always wear gloves, eye protection and a dust mask when working with weed killers and wash your hands immediately after use. If you suffer from hayfever, your safety gear can become irritating, but don't be tempted to wipe your nose, rub your eyes or touch your face when applying the treatment.
Manufacturers develop weedkillers to target particular types of plants according to their biological make up. Use them near similar leafy plants or grasses in your garden, and you may damage those as well. Apply weedkiller precisely to avoid accidental contamination of other plants. Never use spray treatments when it's windy or raining. The product may drift to other parts of your garden or blow back into your face.
Wildlife, pets and children
Domestic weed killers for garden use are generally safe for the wildlife in your garden. If not, there will be a warning on the packaging. Weed killers are dangerous when wet and freshly applied, however many popular brands claim to be safe for wildlife, pets and children only when dry. The RSPCA warns that phenoxy acid herbicides are highly dangerous to horses and donkeys when ingested from newly treated grass.
Ponds and fish
Overspill from chemical weed killers can be toxic to aquatic creatures, so keep it away from the edge of garden ponds, unless it claims to be fish-friendly. Even if you don't have fish, wildlife such as hedgehogs and birds often drink from ponds, so check the safety information. Never empty or wash weed killer bottles in streams, rivers or natural water courses.