4.2 Signal Words and Precautionary Statements
Key Takeaways
- Signal words are DANGER–POISON (with skull-and-crossbones) for Category I oral, dermal, or inhalation toxicity; DANGER without that symbol when Category I is driven by eye or skin corrosion; WARNING for Category II; and CAUTION for Category III (optional on Category IV).
- EPA acute oral LD50 bands are Category I at or below 50 mg/kg, II greater than 50 through 500, III greater than 500 through 5,000, and IV greater than 5,000 mg/kg. Dermal and inhalation bands use different numeric cutoffs from the Label Review Manual / 40 CFR 156.62.
- The skull-and-crossbones and the word POISON in red are required for Category I acute oral, dermal, or inhalation toxicity of the formulated product—not merely for severe eye irritation.
- The signal word reports acute toxicity of the formulated product, including inerts. It is not a chronic cancer classification, not an RUP classification, and not an environmental-hazard grade.
- Precautionary statements, labeled PPE as a minimum, first aid, Note to Physician, environmental hazards (including pollinator and aquatic language), and physical/chemical hazards are separate blocks you must read after the signal word.
Why the signal word is an acute-toxicity headline
The signal word is the one-word acute-toxicity headline for the formulated product. It is not a chronic-toxicity grade, not a cancer classification, not an environmental-hazard score, and not a use-classification (Restricted Use Pesticide versus general use). A product can be CAUTION on acute oral, dermal, inhalation, eye, and skin results and still carry a chronic or oncogenicity advisory elsewhere on the labeling. A product can be DANGER–POISON and still be classified general use. Read the signal word for immediate handler hazard; then read the rest of the label for everything else.
EPA assigns toxicity categories I through IV from the acute studies on this formulation: oral, dermal, inhalation, primary eye irritation, and primary skin irritation. Dermal sensitization is a sixth study (positive or negative for allergic contact dermatitis). It does not receive a I–IV category and does not set the signal word by itself, but a product that is Category IV on every categorized route and negative for sensitization is the rare case where a signal word is not required. If a signal word is used in that case, it must be CAUTION. A Category IV sensitizer still needs a signal word.
The signal word is the most severe of the five categorized studies (40 CFR 156.64). Formulations with 4 percent or more methanol are a special review case because of blindness risk; EPA label-review practice uses DANGER and commonly adds POISON and the skull-and-crossbones.
The four signal words
All required front-panel warnings are grouped so they will not be overlooked. The signal word is in all capital letters, on the front panel, near Keep Out of Reach of Children, and it is repeated with the human-precautionary heading (except when first aid and hazards already occupy the front panel). It must also appear on supplemental labeling that accompanies the product.
| Signal word | Acute toxicity category | What you should expect |
|---|---|---|
| DANGER–POISON with skull-and-crossbones | Category I for oral, dermal, or inhalation | Highest acute systemic or inhalation hazard of the product as sold |
| DANGER without the POISON symbol | Category I driven by eye or skin corrosion or severe irritation | Can permanently damage eyes or skin even if swallowing data are milder |
| WARNING | Category II | Moderate acute toxicity or irritation |
| CAUTION | Category III, or optional on Category IV | Lower acute toxicity; still not a safety claim |
POISON in red on a contrasting background, with the skull-and-crossbones in immediate proximity, is required when the product is Category I for acute oral, acute dermal, or acute inhalation toxicity (40 CFR 156.64(a)(1)). Severe eye damage alone gives DANGER without that poison symbol. That split is a favorite exam item.
EPA acute toxicity bands
These bands are the EPA Label Review Manual / 40 CFR 156.62 standard used to classify the product in the jug. LD50 is the single dose that kills 50 percent of test animals, in milligrams of product per kilogram of body weight. LC50 is the air concentration that kills 50 percent, in milligrams per liter for inhalation. Lower numbers mean higher acute toxicity.
| Study | Category I | Category II | Category III | Category IV |
|---|---|---|---|---|
| Acute oral LD50 | ≤ 50 mg/kg | > 50 through 500 mg/kg | > 500 through 5,000 mg/kg | > 5,000 mg/kg |
| Acute dermal LD50 | ≤ 200 mg/kg | > 200 through 2,000 mg/kg | > 2,000 through 5,000 mg/kg | > 5,000 mg/kg |
| Acute inhalation LC50 | ≤ 0.05 mg/L | > 0.05 through 0.5 mg/L | > 0.5 through 2 mg/L | > 2 mg/L |
| Eye irritation | Corrosive, or irritation persisting more than 21 days | Clearing in 8–21 days | Clearing in 7 days or less | Minimal effects clearing in less than 24 hours |
| Skin irritation | Corrosive into the dermis and/or scarring | Severe irritation at 72 hours | Moderate irritation at 72 hours | Mild or slight irritation at 72 hours |
Worked examples you should be able to run on paper:
- Oral LD50 400 mg/kg → Category II → at least WARNING, unless another route is worse.
- Oral LD50 2,000 mg/kg but corrosive to eyes → Category I eye → DANGER without POISON, unless oral, dermal, or inhalation is also Category I.
- Oral LD50 20 mg/kg → Category I oral → DANGER–POISON and the skull.
- Oral LD50 8,000 mg/kg, all other categorized routes IV, not a sensitizer → signal word not required, optional CAUTION.
These bands describe acute lethality or irritation of the formulated product, not lifetime cancer slope factors. Do not pick WARNING because a fact sheet mentioned a chronic endpoint if the front panel says CAUTION.
Precautionary statements and PPE
Under Precautionary Statements and Hazards to Humans and Domestic Animals, EPA places route-specific hazard language ("Fatal if swallowed," "Causes irreversible eye damage," "Harmful if absorbed through skin") plus the practical steps that go with that category: wash, remove clothing, wear specified PPE. Statements are typically ordered with the most severe route first. The heading may omit "and Domestic Animals" if domestic animals will not be exposed.
Personal protective equipment on the label is the minimum for the tasks named—often split among mixers/loaders, applicators, and early-entry workers. Coveralls, chemical-resistant gloves, protective eyewear, mix/load aprons, and respirators appear only when required for that product and task. You may wear more protection. You may not wear less. Chapter 7 treats glove materials and respirators in depth; here, the skill is to find the PPE block and treat it as a work order. A cotton-field aerial label may list different PPE for flaggers than for mixer-loaders. A restaurant 7a aerosol may list goggles for crack-and-crevice work in a confined restroom. The turf label's "long-sleeved shirt, long pants, shoes, socks, and chemical-resistant gloves" is still mandatory even if the signal word is only CAUTION.
If the Agricultural Use Requirements box lists early-entry PPE, that is what Worker Protection Standard early-entry workers wear during the REI—not permission to ignore the REI.
First aid and Note to Physician
First aid (statements of practical treatment) is required when systemic toxicity is Category I, II, or III, or when skin or eye irritation is Category I or II. Category I first aid belongs on the front visible panel unless EPA allows a front-panel referral such as "See side/back panel for first aid." Category II–IV first aid may sit on another panel with a referral near the signal word. Category IV first aid is not required but is often present.
Typical blocks: If swallowed, If on skin or clothing, If inhaled, If in eyes. Follow this product's first aid, not a generic memory. Some labels say not to induce vomiting because of petroleum distillates or aspiration risk; others give different oral instructions. Organophosphate and N-methyl carbamate labels carry extra first-aid and physician language about cholinesterase. Zinc phosphide and petroleum distillate products have their own first-aid notes in EPA's Label Review Manual.
Have the EPA Registration Number and the label with you when you call Poison Help (1-800-222-1222) or emergency medical services.
The Note to Physician is written for the emergency clinician: antidote clues, aspiration warning, "contains petroleum distillate," "cholinesterase inhibitor—treat symptomatically," corneal-damage follow-up. It is not a handler how-to. Do not skip transporting a poisoned mixer because you already read the Note to Physician.
Environmental hazards, including pollinators and aquatic life
Environmental Hazards protect fish, aquatic invertebrates, wildlife, pollinators, and sometimes groundwater. Typical agricultural language: toxic to fish and aquatic invertebrates; do not apply directly to water except as labeled; drift and runoff warnings; wellhead and sinkhole caution. Pollinator statements may say the product is highly toxic to bees exposed to direct treatment or residues on blooming crops and weeds, and they may restrict applications during bloom or when bees are foraging. Those sentences still have to be followed even though they sit under a hazard heading rather than inside a rate table.
A pasture insecticide labeled highly toxic to bees is not cleared for a midday spray on blooming clover just because the pasture is "not a crop." A cotton insecticide with a fish-toxicity statement is not a pond treatment. A turf product with a groundwater advisory still needs the mixing and loading setbacks you will study in the environmental-stewardship chapter; the label sentence is the first gate.
Physical and chemical hazards
Physical or Chemical Hazards address fire, explosion, oxidizers, and materials compatibility: "Do not use or store near heat or open flame," "Contents under pressure," or similar. An emulsifiable concentrate can be a combustible liquid even when the signal word is only WARNING. Do not store that jug next to a welding cart in a Harmon County barn. Do not put a strong oxidizer in a spray tank that just held an incompatible concentrate because a mixing-order chart (Chapter 5) and this hazard block both forbid it.
Oklahoma scenarios
Caddo County wheat. A hopper-box or seed-treatment product marked DANGER–POISON is Category I by oral, dermal, or inhalation toxicity. Gloves and a respirator listed on that label are not optional because "it is only seed."
Tillman County cotton. A WARNING defoliant with an oral LD50 in the Category II band can still be a Restricted Use Pesticide for groundwater or other reasons. Classification and signal word are separate reads.
Osage County pasture. CAUTION on a herbicide does not erase "toxic to fish" if you spray across a stock pond.
Stillwater turf. Optional CAUTION on a Category IV ready-to-use product does not waive Keep Out of Reach of Children or "keep people and pets out until sprays have dried."
Oklahoma City restaurant. A 7a pyrethroid aerosol can be CAUTION and still require covering food, shutting off air handlers, and wearing labeled eye protection. The signal word is not a food-handling exemption, and the three-foot category boundary is not a first-aid substitute.
Exam traps for this section
- Equating DANGER with DANGER–POISON.
- Using a chronic cancer classification to pick the signal word.
- Assuming Category IV means no child-hazard warning.
- Treating other ingredients as non-hazardous because they are not "active."
- Wearing less PPE than the label because the crew always uses this product.
A Harmon County cotton insecticide is Toxicity Category I for primary eye irritation and Category III for oral, dermal, and inhalation studies. There is no methanol issue. Which front-panel signal marking is correct?
An Osage County pasture product has an acute oral LD50 of 400 mg/kg. Other categorized routes are no worse than that oral result. Using EPA Label Review Manual oral bands, which signal word applies?
A Caddo County wheat fungicide front panel says CAUTION. A fact sheet discusses a chronic cancer classification for the active ingredient. Which statement about the signal word is accurate?
When must a pesticide label bear the skull-and-crossbones and the word POISON in red?