Pesticide Toxicity Hazard and Risk

Visual warning symbols on pesticide labels indicate the kind of harm that can result from pesticide misuse or mishandling. They alert the user to the degree of the hazard (by the shape of the border) and to the type of hazard (by the centre "picture"). .

Flammable
The "fire" symbol is a warning that the pesticide is flammable or easily ignited. Keep the pesticide away from heat, sparks, or open flames. Do not smoke while mixing or applying the product.

Explosive
The "exploding grenade" symbol indicates that the pesticide can explode, e.g., pesticide in pressurized cans. Explosive conditions may also be created by using Roundup or Rustler (glyphosate) in a galvanized steel spray tank.

Corrosive
The "corroded hand" symbol indicates that the pesticide is corrosive to the skin and eyes. The chemical is either acid or alkali (caustic) and can burn the skin. Protect the skin and eyes when using these products.

Poisonous
The "skull and cross bones" symbol warns that the chemical is poisonous if taken into the body. Keep the product out of reach of children. Use the appropriate safety measures when dealing with poisonous products.



Toxicity symbols

These symbols relate the oral LD₅₀ value (mg/kg) of a pesticide to its toxicity symbol.

Danger Poison
LD₅₀ less than 500 mg/kg indicates high toxicity.

Warning Poison
LD₅₀ 500 to 1,000 mg/kg indicates moderate toxicity.

Caution Poison
LD₅₀ 1,000 to 2,000 mg/kg indicates low toxicity.

LD₅₀ greater than 2,500 mg/kg indicates very low toxicity.

Pesticide Toxicity, Hazard and Risk

The terms "toxicity," "hazard" and "risk" do not all have the same meanings. Users of pesticides should understand the difference in meanings of these terms.

Pesticides vary in toxicity or the degree of being poisonous. How poisonous a pesticide is depends on its inherent chemical and physical properties.

The relative hazard of a pesticide is dependent upon the toxicity of the pesticide, the dose received and the length of time exposed. No hazard exists when the container of a pesticide is sealed, but once the seal is broken and the pesticide is handled, exposure can occur and a hazardous situation is created.

Risk of exposure is a function of how the individual handles the product. Although the hazard may be the same whenever a pesticide is being poured into the spray tank, the risk is different if one person wears a hard hat, goggles, respirator, nitrile gloves, waterproof apron and neoprene or rubber boots and the other person wears none of these. A knowledge of the toxicity of a product and the potential for personal exposure can be used to lower the risk of exposure. The user can control the risk by carefully managing the hazard. Even when highly toxic pesticides are used, if the degree of exposure is kept low enough, the risk can be kept at an acceptable level. The toxicity of the pesticide can't be changed, but the risk can be managed.

LD₅₀ values are used to rate the toxicity of the pesticides. The LD₅₀ is an abbreviation for the dose (expressed in milligrams per kilogram of body weight of the test animal) that is lethal to 50 per cent of the group of test animals. For example, if a pesticide has an oral LD₅₀ value of 10 mg/kg, and the test animals each weigh 1 kg, 50 per cent of the animals would die of poisoning if each ate 10 mg of the pesticide.

The smaller the LD₅₀ value, the more toxic the pesticide. The LD₅₀ value usually refers to the active ingredient in the pesticide formulation. The LD₅₀ of the formulated product is also given, when available.

Symptoms of Poisoning

Pesticide poisoning can be acute (due to an accident) or chronic (due to continued exposure over a long period of time). For example, chronic health problems may develop after long term exposure to pesticides low in toxicity. Accidental contact with a pesticide, however, will not necessarily lead to poisoning. Both types of poisoning can exhibit mild, moderate or severe symptoms as follows:

Mild poisoning symptoms: Mild symptoms may be vague and can be compared with sickness such as influenza. Typical symptoms include nausea, headache, tightness of chest, loss of appetite, stomach cramps. These can be immediate or be delayed by 12 to 24 hours.

Moderate poisoning symptoms:These symptoms are usually more pronounced than mild symptoms. They include nausea, trembling, muscular incoordination, excessive saliva, blurring of vision, tightness of chest, difficulty in breathing, flushed or yellow skin, abdominal cramps, vomiting, diarrhea, tearing from eyes, profound weakness, rapid pulse, cough.

Severe poisoning symptoms: Severe symptoms are often more specific and require immediate hospital treatment. They include vomiting, diarrhea, excessive sweating, inability to breathe, convulsions, fever, intense thirst and coma.