Assignment to a toxicity class is based typically on results of acute toxicity studies such as the determination of LD50 values in animal experiments, notably rodents, via oral, inhaled, or external application. The experimental design measures the acute death rate of an agent. The toxicity class generally does not address issues of other potential harm of the agent, such as bioaccumulation, issues of carcinogenicity, teratogenicity, mutagenic effects, or the impact on reproduction.
Regulating agencies may require that packaging of the agent be labeled with a signal word, a specific warning label to indicate the level of toxicity.
The system is based on LD50 determination in rats, thus an oral solid agent with an LD50 at 5 mg or less/kg bodyweight is Class Ia, at 5–50 mg/kg is Class Ib, LD50 at 50–2000 mg/kg is Class II, and at LD50 at the concentration more than 2000 mg/kg is classified as Class III. Values may differ for liquid oral agents and dermal agents.[1]
The Indian standardized system of toxicity labels for pesticides uses a 4-color system (red, yellow, blue, green) to plainly label containers with the toxicity class of the contents.
requires signal word: "Danger-Poison", with skull and crossbones symbol, possibly followed by:
"Fatal if swallowed", "Poisonous if inhaled", "Extremely hazardous by skin contact--rapidly absorbed through skin", or "Corrosive--causes eye damage and severe skin burns"
Class I materials are estimated to be fatal to an adult human at a dose of less than 5 grams (less than a teaspoon).
Furthermore, the EPA classifies pesticides into those anybody can apply (general use pesticides), and those that must be applied by or under the supervision of a certified individual. Application of restricted use pesticides requires that a record of the application be kept.
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