Pesticide Safety, Human Health, and Personal Protective Equipment
Reading toxicity from the label
Signal words summarize acute toxicity across all routes. Category I is "DANGER - POISON" (with skull and crossbones) for the most toxic oral, dermal, or inhalation values, or "DANGER" alone for severe eye/skin irritation or corrosivity; Category II is "WARNING"; Categories III and IV are "CAUTION." The word reflects the most severe route, so a product can be relatively safe orally yet still labeled DANGER for skin effects.
LD50 and LC50
LD50 (mg/kg body weight) and LC50 (mg/L air or water) are the doses lethal to half a test population. Lower numbers mean greater toxicity. Acute effects appear soon after exposure; chronic effects (cancer, birth defects, nerve damage) appear after repeated low doses. Organophosphates and carbamates inhibit cholinesterase; early poisoning looks like flu - headache, nausea, sweating, blurred vision - and is easily mistaken for heat stress.
Exposure routes and PPE
Dermal exposure is the most common route for applicators, especially hands, forearms, and head. The label's PPE section is a minimum; employers may require more. Use chemical-resistant gloves (butyl, nitrile, neoprene, barrier laminate) - never leather or cotton - plus the labeled coveralls, apron, eyewear, footwear, and respirator. Respirators require a medical evaluation, fit testing, and a written cartridge change schedule. Wash PPE separately from family laundry, and wash hands before eating, drinking, or smoking.
Worked example: Product A has an oral LD50 of 1,200 mg/kg; Product B, 12 mg/kg. Product B is 100 times more toxic per unit of body weight, so a spill of B demands a far more aggressive response.
Rule of thumb: diluting a concentrate dilutes the concentration, not the PPE requirement - the label's PPE applies to the tank mix as handled.