⚡ CHEAT SHEET
Ch.5: Pesticide Risks to People
High-yield exam facts: Risk, Toxicity, and Exposure; Hazard vs. Risk; The Dose Makes the Poison; Contact vs. Systemic Effects; Allergic Effects; The Four Routes of Entry; Acute vs. Delayed Effects; Measuring Toxicity; Signal Words & Symbols
National CORE · 2025 Third Edition · Ch.5
1. Risk, Toxicity, and Exposure
- Toxicity = the ability of a pesticide to cause injury. It's a characteristic of the chemical itself; you have very little control over it.
- Exposure = when a pesticide comes into contact with you. You have much more control (e.g., PPE). Concerns how much and which body part contacts it.
- Risk = the likelihood a person will be harmed by the pesticide and its particular use.
- Risk = Toxicity × Exposure.
- Very toxic + no exposure = no risk.
- Low toxicity + high exposure = you can still be harmed (e.g., spilling a large amount of concentrate).
- Any pesticide carries some toxicity, so there is always a potential for risk.
- Greatest risk is often while mixing and loading the concentrate (handled at its most concentrated). Application risk is often lower (diluted product) — but can still be substantial with a single high exposure (accident), a highly toxic product, or many small exposures over time.
- Best way to reduce risk: understand how to use it to minimize exposure — read the label and follow instructions.
2. Hazard vs. Risk
- Hazard = anything that can cause harm (a runaway car, a venomous snake, a pesticide).
- Risk = the potential that a hazard will cause harm. A hazard poses no risk unless you are exposed.
- Example: venomous snakes are a hazard, but pose little/no risk if you never go where they live.
3. The Dose Makes the Poison
- Toxicology = the study of poisons and their effects.
- The dose makes the poison: anything can be toxic with enough exposure; even highly toxic compounds do no harm without exposure.
- Aspirin: low toxicity per pill, but a whole bottle (large exposure) = high risk. Even water has been fatal when too much is drunk at once.
4. Contact vs. Systemic Effects
Contact effects
Systemic effects
Where
Only where the pesticide touches (skin, eyes, respiratory tract)
System-wide — absorbed into and circulated through the body
Examples
Itching, redness, rashes, blisters, burns; swelling/stinging/burning of eyes, nose, mouth, throat
Cholinesterase inhibition, kidney/liver damage, nerve damage, impaired clotting, some cancers, reproductive/hormonal effects, death
Duration
—
Can be acute (short) or chronic (long)
- Systemic effects depend on: the chemical's toxicity, the amount absorbed, and the body's ability to eliminate it.
- Spill on the forearm → blistering = contact effect; if absorbed and carried by blood to harm elsewhere → that harm is a systemic effect.
5. Allergic Effects
- A subset of systemic effects.
- Some people react, others don't; no way to predict who will. Sometimes takes more than one exposure to develop.
- Symptoms: red/itchy eyes, respiratory discomfort, asthma-like effects — up to life-threatening shock.
- An allergic reaction does not predict sensitivity to acute or delayed effects (different chemical reactions).
6. The Four Routes of Entry
Route
Meaning
Dermal
Pesticide on your skin — the most common route
Oral
Swallowing a pesticide
Inhalation
Breathing in vapors or dusts
Ocular
Pesticide in your eye
- You can be exposed whenever you handle pesticides: mixing/loading, applying, cleaning equipment, disposing.
Dermal details
- Absorption depends on: the chemical, extent of exposure, formulation, body area, skin condition (cuts), and how fast you decontaminate.
- Formulation: oil-based absorbs most easily → water-based less → dry materials least (but wet/sweaty skin increases dry-material absorption).
- Body area: moist areas (groin, armpits) absorb faster; cuts/scrapes easier than unbroken skin; hot, sweaty skin absorbs more than dry, cool skin.
Oral — relatively rare but very dangerous; almost always carelessness. Common cause: pesticides in food containers/unlabeled bottles; also not washing hands → transfer to mouth. Swallowing → poisoning + severe mouth/throat burns.
Inhalation — risky because lungs rapidly absorb pesticides (especially vapors and tiny particles); can damage nose, throat, lungs. High risk with dusts/powders or in a confined space.
Ocular — eye membranes absorb faster than any other external part; damage in minutes. Absorbed pesticide can reach other organs → serious illness or fatal.
7. Acute vs. Delayed Effects
- Acute effects = symptoms usually within minutes or hours after exposure (easier to study than delayed).
- Acute exposure = a one-time contact.
- Acute toxicity = the measure of harm from a single, one-time exposure.
8. Measuring Toxicity
- Active ingredients: tested for acute AND chronic toxicity.
- Other ingredients: tested for acute only (not chronic).
- Toxicity is typically measured on test animals (rats, mice, rabbits); human toxicity is derived. Companies also use non-animal methods (cell cultures, models).
9. Signal Words & Symbols
- Based on the highest measured toxicity (oral, dermal, or inhalation) + the amount an applicator could contact; eye/skin effects also count.
- A signal word = a one-word summary of relative potential acute toxicity to people. Relative scale only — Danger is more toxic than Caution, but not by how much.
- Don't be less careful with a Caution product — all pesticides can cause harm.
- Based on the total formulation, not just the a.i. → same a.i. can have different signal words.
Table 5.2 — the four signal words (highest → lowest)
Signal word
Toxicity
DANGER-POISON
Highly toxic; skull & crossbones required; fatal at a few drops to a teaspoon
DANGER
Highly toxic, corrosive; irreversible skin/eye damage
WARNING
Moderately toxic; moderate eye/skin irritation
CAUTION
Slightly to relatively non-toxic; slight eye/skin irritation
10. Delayed Effects
- Illnesses/injuries that don't appear soon after first exposure — a day, weeks, months, or years later.
- Caused by (1) a one-time exposure that reacts later, or (2) chronic exposure — repeated exposures over a long time (usually years).
- Kinds:
- Chronic effects — years after repeated exposures; cancer, tumors, mutations (harmful genetic changes).
- Developmental effects — injury/illness to a fetus in the womb (e.g., birth defect).
- Reproductive effects — injury to the reproductive system: infertility, sterility, impotence.
- Hard to pin the cause (time lapse, other exposures, lifestyle & genetics).
- EPA options when evidence is clear: cancel the product, require warning statements, change label directions, or classify as restricted use.
Key Vocabulary
Term
Meaning (per Ch.5)
Toxicity
The ability of a pesticide to cause injury (a chemical characteristic)
Exposure
When a pesticide contacts you (amount + body part)
Risk
The likelihood a person will be harmed (Risk = Toxicity × Exposure)
Hazard
Anything that can cause harm
Dose
The amount of a substance a person is exposed to
Absorb
To take a pesticide into the body
Contact effects
Local effects only where the pesticide touches
Systemic effects
System-wide effects after absorption and circulation
Allergic effects
A subset of systemic effects; vary by person
Acute effects
Symptoms within minutes or hours of exposure
Acute exposure
A one-time contact with a pesticide
Acute toxicity
Harm from a single, one-time exposure
Delayed effects
Effects appearing long after first exposure
Chronic exposure
Repeated exposures over a long time (usually years)
Chronic effects
Long-term effects (cancer, tumors, mutations)
Chronic toxicity
Harm from repeated exposures over time
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