Toxicity class

Indian toxicity label system
Toxicity symbol for European Toxicity Class I and II

Toxicity class refers to a classification system for pesticides that has been created by a national or international government-related or -sponsored organization. It addresses the acute toxicity of agents such as soil fumigants, fungicides, herbicides, insecticides, miticides, molluscicides, nematicides, or rodenticides.

General considerations

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.

By jurisdiction

World Health Organization

The World Health Organization (WHO) names four toxicity classes:

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 III, at 5–50 mg/kg Class II, at 50–2000 mg/kg Class I-b, and at more than 2000 mg/kg Class I. Values may differ for liquid oral agents and dermal agents.[1]

European Union

There are eight toxicity classes in the European Union's classification system, which is regulated by Directive 67/548/EEC:

Very toxic and toxic substances are marked by the European toxicity symbol.


Main article: Toxicity label

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.

United States

The United States Environmental Protection Agency (EPA) uses four toxicity classes. Classes I to III are required to carry a signal word on the label. Pesticides are regulated in the United States primarily by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).

Toxicity Class I

"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).

Toxicity Class II

"Harmful or fatal if swallowed", "Harmful or fatal if absorbed through the skin", "Harmful or fatal if inhaled", or "Causes skin and eye irritation"

Class II materials are estimated to be fatal to an adult human at a dose of 5 to 30 grams.

Toxicity Class III

"Harmful if swallowed", "May be harmful if absorbed through the skin", "May be harmful if inhaled", or "May irritate eyes, nose, throat, and skin"

Class III materials are estimated to be fatal to an adult human at some dose in excess of 30 grams.

Toxicity Class IV

General versus restricted use

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.

See also


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