Human Health, Toxicity, and Personal Protective Equipment
Measuring toxicity
Toxicity is the ability of a substance to injure; hazard = toxicity × exposure. Acute toxicity is measured by LD50 (dose killing 50% of test animals, usually mg/kg) or LC50 (concentration in air or water). Lower numbers mean more toxic.
Signal words reflect acute toxicity only:
- DANGER / POISON - Category I. Oral LD50 up to 50 mg/kg; also required for severe eye or skin damage.
- WARNING - Category II. Oral LD50 50–500 mg/kg.
- CAUTION - Category III and IV. Oral LD50 above 500 mg/kg.
Chronic effects (cancer, reproductive harm, nerve damage) do not raise the signal word; they appear in the precautionary and hazard statements instead.
Routes of exposure and PPE
Dermal exposure is the most common route for applicators. Protect against inhalation with the respirator type the label specifies - often a particulate filter, sometimes a cartridge respirator or supplied air. Chemical-resistant gloves, footwear, coveralls, and eye protection must match the label; "waterproof" is not the same as "chemical-resistant." Respirators require fit testing and medical evaluation under OSHA. Never store PPE with pesticides; wash separately from family laundry.
Poisoning and heat
Organophosphate and carbamate insecticides inhibit cholinesterase; symptoms include sweating, salivation, pinpoint pupils, vomiting, weakness, and blurred vision. Atropine is a medical treatment given by professionals - not something an applicator administers. Heat stress mimics some of these symptoms; ask about heat, not just chemicals.
Trap and rule of thumb
A product labeled CAUTION can still be hazardous - signal words cover acute toxicity, not all risk. Rule of thumb: when the label lists PPE, wear it for the entire task, including mixing, loading, cleanup, and equipment repair.