Safe Use of Pesticides

The Four Hazard Categories

Herbicides, fungicides and insecticides are classified according to the use hazard and risk involved.

The categories of hazard are:

Degree of Risk

The degree of risk is represented by symbols taken from common traffic signal sign shapes represented by the

Stop Sign


Signal word is danger (high risk)

Caution Sign


Signal word is warning (moderate risk)

Yield Sign


Signal word is caution (low risk).

The label on the container will carry the appropriate signs for the protection of the user.

Oral LD50 Values

As They Relate to

Risk - Hazard symbols

LD50 values are used to rate the toxicity of pesticides.

The LD50 refers to the dose of pesticide(in mg per kg of the test animal's body weight) that is lethal to 50 percent of the group oftest animals.

For example, if a pesticide has a LD50value of 10 mg/kg, and the test animals each weigh 1kg.

Then 50 percent of the animals would die if they each ate 10 mg of the pesticide.

Risk - Hazard Symbols and their LD50 values:

Danger Poison

symbol for Danger poison

LD 50 less than 500 mg/kg

Indicates high toxicity

Warning Poison

symbol for warning poison

LD50 500-1000 mg/kg

Indicates moderate toxicity

Caution Poison

symbol for caution poison

LD50 1000-2500 mg/kg

Indicates low toxicity

No Symbol

LD50 > 2500 mg/kg

Indicates very low toxicity

Protective Equipment

Different types of protective equipment are required for pesticides that differ in toxicity.

Special equipment requirements are described on the product label.

But in general, the following precautions must be taken when using pesticides of dierent hazard ratings.

The absence of a hazard symbol on a pesticide label indicates low toxicity to mammals. Never - theless, protective clothing should be worn when using pesticides that do not have a hazard symbol