Signal Words and Toxicity Classes
Understanding DANGER, WARNING, CAUTION signal words indicating acute toxicity levels and associated precautions.
Detailed Overview
EPA assigns toxicity categories based on acute toxicity tests. Signal words required on labels: (1) DANGER - POISON: Category I - Highly toxic. Lethal dose less than 50 mg/kg. Skull and crossbones symbol. May be fatal if swallowed, inhaled, or absorbed through skin. Requires extensive PPE. Used mainly in restricted-use products - fumigants, some rodenticides. PCOs rarely use. (2) WARNING: Category II - Moderately toxic. Lethal dose 50-500 mg/kg. May be harmful if swallowed, inhaled, or absorbed. Requires PPE (usually gloves, eye protection). Many professional insecticides in this category. (3) CAUTION: Category III & IV - Slightly toxic or relatively non-toxic. Lethal dose over 500 mg/kg. Harmful if swallowed, inhaled, or absorbed. Minimum PPE. Most ready-to-use consumer products. Signal word based on most toxic exposure route (oral, dermal, inhalation, eye/skin irritation). Product may have different toxicities by different routes. Toxicity refers to acute (short-term high dose) effects, not chronic (long-term low dose). Chronic effects listed separately. Lower toxicity does not mean safe to misuse - all pesticides require careful handling per label.
When to Use
Check signal word when selecting products. Understand toxicity level. Use appropriate PPE and precautions. Choose lower toxicity products when options available for same pest.
Required Skill Level
Requires some training and experience in pest management
Benefits
- Quickly identifies product toxicity level
- Guides appropriate precautions and PPE
- Helps select safer products when available
- Standardized system across all pesticides
- Warns of most hazardous products
Limitations
- Acute toxicity only - does not reflect chronic effects
- Does not indicate environmental toxicity
- Low toxicity to humans may be high to fish/bees
- Signal word alone does not determine safety
Related Concepts
Other principles that may be useful
Integrated Pest Management (IPM)
A prevention-based pest management method that provides long-lasting pest control, improves building conditions, and is less harmful to residents and pets than traditional pest control.
Pest Triangle
The four essential requirements pests need to survive: food, water, shelter, and ways to get around. Eliminating any of these makes an environment inhospitable to pests.
Threshold Levels
The point at which pest populations or damage reaches a level that requires action. IPM uses threshold levels to determine when treatment is necessary rather than treating on a schedule.