Toxicology

• A. The shelf life of a pesticide in days
• B. The dose of a substance required to kill 50% of a test population ✓
• C. The amount of active ingredient in a formulation
• D. The time it takes for a pesticide to degrade by 50%

LD50 (Lethal Dose 50) is the dose of a chemical that kills 50% of a test animal population. It is expressed in milligrams per kilogram of body weight (mg/kg). A lower LD50 indicates a more toxic substance.

• A. Practically non-toxic
• B. Highly toxic — a small dose can be lethal ✓
• C. Moderately toxic
• D. Slightly toxic

An oral LD50 of 10 mg/kg means only 10 milligrams per kilogram of body weight is enough to kill half the test animals. The lower the LD50, the more toxic the substance. Products with oral LD50 of 0-50 mg/kg are in Toxicity Category I (DANGER/POISON).

• A. Acute means mild; chronic means severe
• B. Acute effects occur from a single short-term exposure; chronic effects develop from repeated long-term exposure ✓
• C. Acute applies to animals; chronic applies to plants
• D. There is no difference

Acute toxicity refers to harmful effects from a single exposure or short-term exposure (within 24 hours). Chronic toxicity refers to effects that develop from repeated or prolonged exposure over weeks, months, or years.

• A. Eating, sleeping, breathing, touching
• B. Oral (ingestion), dermal (skin absorption), inhalation (breathing), and ocular (eyes) ✓
• C. Injection, digestion, circulation, elimination
• D. Contact, vapor, solution, suspension

Pesticides can enter the body through four routes: oral (ingestion through the mouth), dermal (absorption through the skin), inhalation (breathing vapor, dust, or spray mist), and ocular (absorption through the eyes). Dermal is the most common for applicators.

• A. Palms of the hands and soles of the feet
• B. Groin, armpits, eyes, and forehead ✓
• C. Back and chest
• D. Elbows and knees

Absorption rates vary dramatically across body areas. The groin, armpits, and forehead absorb pesticides many times faster than forearms or palms. The eyes are also extremely absorptive. This is why full-body PPE is important.

• A. Dry mouth, dilated pupils, and constipation
• B. Excessive salivation, pinpoint pupils, nausea, difficulty breathing, and muscle twitching ✓
• C. Skin rash only
• D. Swollen joints and fever

Organophosphates inhibit cholinesterase, causing acetylcholine buildup. The classic symptoms (SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis) include pinpoint pupils, sweating, chest tightness, and muscle fasciculations.

• A. The relationship between pesticide price and effectiveness
• B. The principle that the severity of toxic effects increases as the dose (amount of exposure) increases ✓
• C. The time between dose and response
• D. The response of pests to bait

The dose-response relationship is a fundamental toxicology principle stating that as the amount of a substance absorbed increases, the severity of the toxic effect increases. This relationship is used to establish safe exposure levels and LD50 values.

• A. Herbicides
• B. Organophosphates and carbamates ✓
• C. Pyrethroids
• D. Rodenticides

Cholinesterase blood tests measure the activity of cholinesterase enzymes, which are inhibited by organophosphate and carbamate insecticides. Regular monitoring helps detect overexposure before clinical symptoms appear.