Human Toxicity, Exposure, and Personal Protective Equipment
Toxicity questions ask you to rank hazard, choose PPE, and recognize the exposure patterns that actually injure handlers. California adds a medical supervision program that is tested more heavily than the federal Worker Protection Standard alone.
Measuring toxicity
LD50 (mg/kg) and LC50 (mg/L of air or water) express acute toxicity; lower values mean more toxic. Dermal and oral LD50s can differ by orders of magnitude, which is why dermal exposure dominates for mixers and applicators. Toxicity Categories I through IV map to the signal words.
Acute versus chronic
Acute effects: cholinesterase inhibition, skin and eye burns, bronchospasm, nausea. Chronic effects: cancer, reproductive harm, neurotoxicity - found in the medical and precautionary statements, not in the signal word.
Organophosphates and carbamates
Both inhibit acetylcholinesterase. Symptoms include headache, blurred vision, salivation, sweating, pinpoint pupils, vomiting, diarrhea, muscle twitching, weakness, and respiratory failure in severe cases. Atropine is the antidote for both classes; pralidoxime (2-PAM) is used for organophosphate poisoning but is not indicated for carbamates. California requires written medical supervision, with baseline and periodic cholinesterase testing, for handlers working with cholinesterase-inhibiting pesticides.
PPE selection and use
Match the label: chemical-resistant gloves (nitrile, butyl, neoprene) - never leather or cloth; sleeves over glove cuffs; chemical-resistant apron for mixers; eye protection; coveralls. Respirators depend on formulation: dust/mist filters for particulates, organic vapor cartridges for solvents, supplied air for fumigants. Fit testing, medical clearance, and a written cartridge change schedule are required, and facial hair at the face seal disqualifies a user.
Decontamination and heat
Handlers need soap, water, and towels at the work site - at least 3 gallons per handler - plus prompt eye flush access. California's heat illness prevention standard (water, shade, rest, acclimatization) matters because full PPE in summer can disable a worker faster than the pesticide.
Worked example
A mixer handles an emulsifiable concentrate labeled Danger/Poison with a 12-hour REI and an organic vapor respirator requirement; the crew plans a 10-hour day. Reasoning: PPE follows label and task; the cartridge change schedule must exist in writing; the 12-hour REI blocks entry until it expires; and because the product inhibits cholinesterase, current testing should already be on file.
Traps that cost marks
Warning is not low risk. Solvent-soaked gloves fail faster than nitrile. A dust mask is not a cartridge respirator. Federal WPS rules are not the whole story in California.