Pesticide Toxicology and Human Health Effects
Toxicology questions test whether you can distinguish exposure routes, dose-response, and types of toxicity. The four exposure routes are dermal, inhalation, oral, and ocular. For most agricultural pesticides, dermal exposure is the most common route, which is why PPE selection emphasizes skin protection. Acute toxicity describes effects from a single or short-term exposure and is expressed as an LD50 (dose lethal to 50% of test animals, usually mg/kg) or LC50 (concentration in air or water). Lower LD50 means more toxic. Chronic toxicity describes effects from repeated long-term exposure, such as cancer, reproductive effects, or organ damage.
Know the difference between local effects (irritation, burns at the contact site) and systemic effects (effects after absorption, e.g., cholinesterase inhibition from organophosphates and carbamates). Recognize cholinergic crisis signs: salivation, lacrimation, urination, diarrhea, sweating, and pinpoint pupils. Understand that inert ingredients and formulants can also cause harm, and that signal words reflect acute toxicity only.
Traps: Confusing LD50 with LC50; assuming a low-toxicity product is harmless with chronic exposure; assuming all organophosphates and carbamates have identical effects. Also watch for questions about sensitization (allergic response) and delayed effects.
Rule of thumb: Dermal is the dominant route for most handlers; protect skin first, then inhalation, then eyes. LD50 is a relative ranking, not a guarantee of safety.
Worked example: Product A has an oral LD50 of 50 mg/kg; Product B has 5,000 mg/kg. Product A is far more acutely toxic. If a worker reports sweating, salivation, and blurred vision after mixing a carbamate, treat as possible cholinergic poisoning and seek immediate medical care with the label in hand.