CORE Ch5 Study Guide: Pesticide Hazards and First Aid

Learning Objectives

After studying this chapter, you should be able to:

Differentiate between types of harmful effects — allergic, acute, chronic, and delayed.
Identify common exposure routes for different pesticides and application methods.
Explain the hazard classification system and signal words.
Describe typical symptoms of pesticide exposure.
Give the appropriate first aid response to oral, ocular, dermal, and inhalation exposures.
List other health risks such as heat stress during pesticide application.

Toxicity vs Exposure vs Hazard — The Big Equation

HAZARD = TOXICITY × EXPOSURE

Toxicity: The capacity of a pesticide to cause injury or illness — a combination of its chemical properties and concentration. This is a fixed property of the chemical itself.

Exposure: How much pesticide actually gets onto/into the body through skin (dermal), lungs (inhalation), mouth (oral), or eyes (ocular).

Hazard (Risk): The probability of harm occurring — combines toxicity AND exposure. This is what applicators actually manage.

Classic Examples

Gasoline — extremely toxic, but gas pumps virtually eliminate exposure. Low hazard.
Aspirin — low toxicity, but easy to overdose (high exposure). High hazard.

🎯 Trick Spot: You can reduce hazard by either (1) choosing a less-toxic product, OR (2) reducing exposure — or both. When a less-toxic alternative isn't available, control exposure with PPE and engineering controls.

Highest-Exposure Activities

Handling opened containers
Mixing and loading concentrates (the most hazardous step)
Working around contaminated application equipment
Making spray, mist, or dust applications
Cleaning up spills
Re-entering a recently treated area before spray dries or dust settles

⚠️ Exam Tip: Mixing/loading concentrates presents the highest exposure risk — the pesticide is in its most concentrated, most toxic form. Diluted pesticide at application is much less concentrated.

Types of Harmful Effects

Local (Contact) Effects

Systemic Effects

Injury at the point of contact with skin, eyes, or respiratory tract. Examples: dermatitis, rashes, blisters, burns, eye irritation, nose/throat burning.

Poisoning effects at sites other than the entry point, after the pesticide is absorbed and distributed through the body. Examples: cholinesterase inhibition, organ damage, cancer, reproductive effects.

Four Categories by Time/Frequency

Acute toxicity: Injury or illness from a single exposure. Measured by LD50 and LC50.

Chronic toxicity: Injury or illness from small, repeated, prolonged exposure over time. No single measurement like LD50.

Delayed effects: Illness or injury that does NOT appear within 24 hours — may be delayed weeks, months, or years. Can result from acute OR chronic exposure.

Allergic effects: A hypersensitivity reaction in some individuals. May cause dermatitis, hives, asthma-like symptoms, or even life-threatening shock. Unpredictable — can't be known in advance who will react.

🎯 Trick Spot: Having an allergic reaction does NOT predict whether a person will also be more sensitive to chronic or delayed effects — different mechanisms. Allergies are unpredictable.

Common Systemic Effects

Cholinesterase inhibition or nerve damage (neuropathies)
Impairment of blood clotting
Some cancers
Reproductive problems
Impaired metabolism
Hormonal effects
Damage to kidneys, liver, or other organs

Exposure — How Pesticides Enter the Body

Dermal (Skin) Route

Up to 97% of body exposure during a spraying operation is through the skin. The most common route.

High-Absorbing Body Areas

Lower-Absorbing Body Areas

Groin, armpits, head, neck, backs of hands, tops of feet — warm, moist areas

Palms and forearms — but these get the most exposure so still need protection

🎯 Trick Spot: The groin, scalp, and ear canal absorb pesticides far more quickly than the palms. This is why washing hands BEFORE using the toilet matters and why head/neck protection is critical during overhead applications.

Factors That Increase Dermal Absorption

Contact time — the longer it stays, the more is absorbed
Cuts, abrasions, and skin rashes increase absorption
Oil-based liquid formulations (like ECs) are readily absorbed
Water-soluble liquids/powders, WPs, dusts, and granules don't easily penetrate skin

Ocular (Eye) Route

Eyes are extremely absorbent — blood vessels lie close to the surface so pesticides enter the bloodstream quickly. Some products are corrosive and can cause blindness.

Inhalation (Lung) Route

Highest risk during mixing, loading, or applying in confined spaces.
Once in lungs, pesticides enter bloodstream very rapidly.
Aspiration of petroleum solvents (ECs) during vomiting is especially dangerous — another reason NOT to induce vomiting for EC ingestion.

Oral (Mouth) Route

Splashes into mouth during mixing or equipment cleaning.
Never use your mouth to clear a spray line or start siphoning pesticide.
Eating, drinking, or smoking without washing hands transfers product to mouth.
Children are most common victims of accidental oral exposure — usually from pesticides stored in unmarked food/beverage containers.

Acute Toxicity Measurements — LD50 and LC50

LD50 (Lethal Dose 50%): The dose of a toxicant required to kill 50% of a test animal population. Measured in mg/kg of body weight. Oral LD50 = fed; Dermal LD50 = skin exposure.

LC50 (Lethal Concentration 50%): The concentration in air or water required to kill 50% of the test population. Measured in parts per million or mg/L. Used heavily for aquatic toxicity and inhalation hazard.

🎯 Trick Spot: LOWER LD50 = MORE TOXIC. A product with oral LD50 of 5 mg/kg is far more toxic than one with 250 mg/kg — it takes less to kill 50% of the population.

Limitations of LD50 / LC50

They measure ONLY death — not other acute systemic effects, contact damage, or delayed effects.
They don't translate directly to humans (different body systems).
They reflect a SINGLE exposure — not cumulative effects of repeated exposures.

⚠️ Exam Tip: Signal words reflect acute toxicity only. Chronic and delayed effects come from different mechanisms and are NOT indicated by the signal word.

Signal Words & Hazard Classes

Signal Word

Hazard Class & Oral LD50

DANGER — POISON
(with skull & crossbones, in red)
Also: PELIGRO (Spanish)

Class I (highly toxic)
Oral LD50: trace to 50 mg/kg
A few drops can kill a 150-lb person

DANGER
(no skull/crossbones)

Class I due to severe contact damage (skin/eye/lung injury) — NOT necessarily systemic LD50
Common: "irreversible eye damage at low exposures"

WARNING
Also: AVISO (Spanish)

Class II (moderately toxic)
Oral LD50: 50 to 500 mg/kg
1 teaspoon to 1 ounce can kill a 150-lb person

CAUTION

Class III (slightly toxic)
Oral LD50: 500 to 5,000 mg/kg

(no signal word)

Class IV (very low toxicity) — not required to carry a signal word

🎯 Trick Spot: "DANGER" alone (without POISON or skull symbol) means severe contact damage — the LD50 may not even be Class I level. Always consult the "Hazards to Humans and Domestic Animals" section for details.

GHS (Globally Harmonized System)

An international system for hazard communication being integrated into US chemical labeling. Goal: consistent classification across paint, pesticides, cleaners, etc. Separate pictograms will distinguish acute from chronic hazards.

How the Body Handles Pesticides

Liver is the primary detoxification organ — transforms toxic substances to less-toxic, water-soluble forms.
Kidneys filter water-soluble substances into urine for elimination.
Substances that can't be made water-soluble get stored in fat deposits and breast milk.
Most modern pesticides (post-1970) are more water-soluble — eliminated in hours to days instead of months to years.
Continual or frequent exposure can overwhelm the body's breakdown capacity.

⚠️ Exam Tip: Having periods of non-exposure between applications of the same pesticide class reduces the chance of overwhelming your body's detoxification capacity.

Cholinesterase Inhibition

Cholinesterase is an enzyme needed for proper nerve impulse transmission. Organophosphate and carbamate insecticides reduce cholinesterase, disrupting nerve signals. Without treatment, severe inhibition can cause respiratory failure and death.

Cholinesterase Monitoring

Establish a baseline BEFORE starting to work with these chemicals, or during the off-season — at least 30 days from most recent exposure.
Baseline typically requires two tests at least 72 hours apart (but not more than 14 days apart).
Regular testing is compared to baseline. A significant drop suggests poisoning.
If poisoned, recovery usually requires 3 to 5 weeks with no exposure to rebuild cholinesterase.
Always use the same laboratory — methods vary slightly between labs.

Symptoms of Organophosphate/Carbamate Poisoning

Mild

Moderate

Fatigue, headache, dizziness, blurred vision, excessive sweating/salivation, nausea, vomiting, stomach cramps, diarrhea

Inability to walk, weakness, chest discomfort, constricted pupils, mild symptoms more severe

Severe: Unconsciousness, severe pupil constriction, muscle twitching, running nose and drooling, breathing difficulty, coma, death.

Symptoms by Pesticide Class

Pesticide Type

Common Symptoms

Borates (insecticides)

Irritate skin, nose, respiratory system

Some fungicides

Skin, eye, mucous membrane irritation

Anticoagulant rodenticides

Affect blood clotting — bloody noses, bleeding gums

Organophosphate & carbamate insecticides

Cholinesterase inhibition — may lead to respiratory failure

Synthetic pyrethroids

Nausea, dizziness, weakness, nervousness, eye/skin irritation

Chlorophenoxy herbicides (2,4-D, dicamba, MCPA, MCPP)

Skin/mucous membrane irritation, vomiting, headaches, diarrhea, confusion

First Aid — General Rules

🎯 Trick Spot — Critical: Seek medical advice IMMEDIATELY for unusual symptoms within 24 hours of pesticide exposure. Don't wait until severe illness. Take the pesticide label (or a copy, or at minimum the EPA registration number) with you to the medical professional.

Protect Yourself First

Ensure the victim is breathing and is no longer being exposed BEFORE you call for help if you're alone.
Wear appropriate PPE (including a respirator if indicated) before entering a contaminated area.
Never become a second victim.

Key Emergency Contacts

American Association of Poison Control Centers (AAPCC): 800-222-1222 — 24/7
National Pesticide Information Center (NPIC): 800-858-7378
Animal Poison Control Center: 888-426-4435

General Principles

For oral or dermal exposure, rinse with water to dilute and prevent absorption.
Never give anything by mouth to an unconscious person.
Do NOT induce vomiting unless the label tells you to.
For inhalation exposure, get the victim to fresh air immediately.

First Aid by Exposure Route

Skin Exposure

Remove all contaminated clothing immediately.
Wash affected area — including hair — with water and soap. Rinse well.
Shower rather than bathe to avoid prolonged contact with residue.
Avoid harsh scrubbing — it damages skin and increases absorption.
Gently dry and wrap loosely in clean cloth or blanket.
For chemical burns: cover loosely; do NOT use ointments, greases, powders unless directed by medical authority.

Eye Exposure

Hold eyelid open and gently wash with drips of clean water.
Drip water across — not directly into — the eye, or use an eyewash dispenser.
Rinse continuously for 15 minutes.
Flush under the eyelid to remove debris.
Don't use chemicals or drugs unless directed by a medical professional.
Be careful not to contaminate the other eye if only one is affected.
Cover the eye with clean cloth and seek medical attention immediately.

🎯 Trick Spot: You drip water across the eye, NOT directly into the eye. Direct streams cause additional injury.

Inhalation Exposure

Carry (don't walk) the victim to fresh air.
Don't attempt rescue in contaminated enclosed areas without proper PPE.
Warn others in the area.
Have victim lie down; loosen clothing.
Keep warm and quiet — neither chilled nor overheated.
If convulsing: protect head, turn head to the side, watch breathing. Do not put anything in the victim's mouth.
Keep chin up to keep airway open.
Administer artificial respiration if breathing stops or becomes irregular.

Oral Exposure (Swallowed)

If pesticide is in the mouth but NOT swallowed: rinse with plenty of water, then give up to 1 quart of milk or water.
If swallowed: the critical question is whether to induce vomiting — only if the label tells you to.

NEVER induce vomiting if the victim:

Is unconscious or convulsing
Has swallowed a corrosive poison (strong acid or alkali) — it burns as severely coming up
Has swallowed an emulsifiable concentrate or oil solution — aspiration of petroleum solvents into the lungs can be fatal

🎯 Trick Spot: Ipecac syrup is no longer recommended for routine use — too slow (20 min) and only voids about one-third of stomach contents.

Inducing Vomiting (when appropriate)

Position victim kneeling forward or on their side (prevents aspiration).
Give at least two glasses of water. Do NOT use carbonated beverages. Do NOT use salt water.
Use finger or blunt end of spoon at back of throat. Never use anything sharp or pointed.
Collect some vomitus — doctor may need it for chemical analysis.

Activated Charcoal

Can adsorb many swallowed chemicals. Seek advice from a medical professional or poison control center before administering.

Heat Stress

Heat stress symptoms closely resemble poisoning symptoms — both can cause dizziness, nausea, weakness, confusion. PPE can contribute to heat stress by blocking sweat evaporation.

Heat Stress Symptoms

Fatigue, exhaustion, muscle weakness
Dizziness and fainting
Clammy, OR hot dry skin
Altered behavior — confusion, slurred speech, irrational conduct
Headache, nausea, chills
Severe thirst, dry mouth
Heavy sweating that eventually stops — lack of sweat is a key symptom of heatstroke

Heatstroke (Severe)

Body temperature may exceed 105°F (normal is 97–99°F).
Staggering, loss of consciousness, convulsions.
More than 10% of severe heat stress victims die.
Victims may remain sensitive to heat for months.

🎯 Trick Spot: Wearing PPE does NOT prevent heat stress — it can actually increase the risk by blocking sweat evaporation. Cooling vests, ice-pack headbands, frequent water breaks, and shade breaks help prevent heat stress.

Prevention

Drink plenty of water.
Take breaks in the shade.
Use cooling vests/headbands under PPE.
Watch for symptoms in yourself AND coworkers.
If under a physician's care, consult before working in hot/humid conditions.

Antidotes

Antidotes are available for only a few classes of pesticides: anticoagulant-type rodenticides and organophosphate / carbamate insecticides. They can be dangerous if misused — only a qualified medical professional should administer them. Never use antidotes preventively.

Key Terms Cheat Sheet

Hazard = Toxicity × Exposure

Toxicity: Capacity of a pesticide to cause injury.

Exposure: Amount that actually enters the body.

Hazard (risk): Probability of harm — what we actually manage.

Acute toxicity: Harm from a single exposure; measured by LD50/LC50.

Chronic toxicity: Harm from repeated small exposures over time.

Delayed effects: Don't appear within 24 hours; can be weeks, months, or years later.

Allergic effects: Hypersensitivity reaction — unpredictable.

Local (contact) effects: At point of contact — dermatitis, eye irritation.

Systemic effects: After absorption, anywhere in the body — organ damage, cancer, etc.

LD50: Dose to kill 50% of test animals, in mg/kg body weight.

LC50: Concentration in air/water to kill 50%. ppm or mg/L.

Lower LD50 = more toxic.

DANGER–POISON: Class I, oral LD50 trace–50 mg/kg. Skull & crossbones. A few drops can kill.

DANGER: Class I due to severe contact damage — irreversible eye/skin/lung damage.

WARNING: Class II, oral LD50 50–500 mg/kg. 1 tsp–1 oz can kill.

CAUTION: Class III, oral LD50 500–5,000 mg/kg.

Cholinesterase inhibitors: Organophosphate and carbamate insecticides — disrupt nerve signals.

Cholinesterase baseline: Established off-season, at least 30 days from last exposure; 2 tests 72 hours apart.

Poison Control: 800-222-1222 (AAPCC).

National Pesticide Info Center: 800-858-7378.

Animal Poison Control: 888-426-4435.

Skin exposure = 97% of body exposure during spraying.

Ipecac: no longer recommended.

Never induce vomiting for: unconscious victim, corrosive poison (acid/alkali), emulsifiable concentrate / oil solution.

Eye flush: 15 minutes, drip ACROSS the eye, not into it.

Heatstroke: Body temp over 105°F; lack of sweat is a key sign; more than 10% fatality rate.

Chapter 5 — Pesticide Hazards and First Aid