U.S. EPA Pesticide Toxicity Classes
December 6, 2012
Most countries categorize pesticide toxicity by separating products into 3 or 4 groups. In the U.S., the Environmental Protection Agency uses the system below to indicate the environmental and human toxicity of registered products. To make these determinations, the EPA relies on several different toxicology tests conducted on mammals such as rats and mice, with the product administered orally, via inhalation, on the skin, and in the eye. The results of those tests are reported as LD50s or LC50s, which are abbreviations for “50% of the lethal dose, or 50% of the lethal concentration. The higher the LD50 or LC50 value, the safer the product is.
The decision to classify a product as Category I, II, III or IV is based on the test result that shows the highest toxicity, according to the scheme below. For more information on how the EPA categorizes pesticides, read here.
| LABEL SIGNAL WORD: | Danger | Warning | Caution | Caution* |
|---|---|---|---|---|
| TOXICITY CATEGORY: | I | II | III | IV |
| EXPLANATION: | High toxicity | Moderate toxicity | Low toxicity | Very low toxicity |
| ORAL TOXICITY LD50: | <50mg/kg | 50–500 mg/kg | 500–5000 mg/kg | >5000 mg/kg |
| INHALATION TOXICITY LC50: | <0.05mg/kg | 0.05–0.5 mg/kg | 0.5–2.0 mg/kg | >2.0 mg/kg |
| DERMAL TOXICITY LD50: | <200mg/kg | 200–2000 mg/kg | 2000–5000 mg/kg | >5000 mg/kg |
| EYE IRRITATION: | corrosive or lasting >21 days | clearing in 8–21 days | clearing in 7 days or less | minimal effects |
| SKIN IRRITATION: | corrosive | severe at 72 hrs | moderate at 72 hrs | mild or slight at 72 hrs |
*Signal word on label is not required for Category IV pesticides. Some manufacturers choose to print the CAUTION word on their Category IV products, while others do not.