Acute toxicity of a pesticide refers to the effects from a single dose or repeated exposure over a short time (e.g. one day), such as an accident during mixing or applying pesticides. Acute toxicity is measured by LD50 and LC50 values. The smaller the LD50, the more toxic the pesticide.
Signal words are found on pesticide product labels, and they describe the acute (short-term) toxicity of the formulated pesticide product. The signal word can be ei- ther: DANGER, WARNING or CAUTION. Products with the DANGER signal word are the most toxic. Products with the signal word CAUTION are lower in toxicity.
Chronic exposure to certain pesticides has been suspected to cause various detrimental effects on health [37]. The severity of acute toxicity is classified into four categories: extremely toxic, highly toxic, moderately toxic, and slightly toxic.
The Science of Toxicology
Toxicological testing evaluates whether short-term exposure to a pesticide will produce acute effects (e.g., eye and skin irritation, death) and whether long-term, continual exposure will cause chronic effects (e.g., impaired liver function, reproduc- tive abnormalities, cancer).
One such population-level measure is the median lethal dose, LD50 (lethal dose, 50%). This is defined as the dose required to kill half the members of a specific animal population when entering the animal's body by a particular route. LD50 is a general indicator of a substance's toxicity within a short space of time.
Acute toxicity is measured by LD50 and LC50 values. The smaller the LD50, the more toxic the pesticide. Example: a pesticide with an LD50 of 5 mg/kg is 100 times more toxic than a pesticide with an LD50 of 500 mg/kg Page 2 2 values are given in milligrams per kilogram of body weight of the animal (mg/kg body wt.).
A product's toxicity is determined by its chemical composition – how the atoms and molecules it is made of interact with living tissues. Substances with similar chemical structures often cause similar health problems.
Pesticides with a high LD50 are the least toxic to humans if used according to the directions on the product label. The chronic toxicity of a pesticide is determined by subjecting test animals to long-term exposure to the active ingredient.
Fungicides were the most toxic from concentrations 300–600 times lower than agricultural dilutions, followed by herbicides and then insecticides, with very similar profiles in all cell types. Despite its relatively benign reputation, Roundup was among the most toxic herbicides and insecticides tested.
Toxicity category I is highly toxic and severely irritating, Toxicity category II is moderately toxic and moderately irritating, Toxicity category III is slightly toxic and slightly irritating, Toxicity category IV is practically non-toxic and not an irritant.
Classification of insecticide
Based on toxicity, it is classified into four types: Extremely toxic – Colour: red, symbol: skull and poison, oral LD50: 1-50. Moderately toxic – Colour: blue, symbol: danger, oral LD50: 501 – 5000. Highly toxic – Colour: yellow, symbol: poison, oral LD50: 51 – 500.
Acute toxicity makes it possible to classify pesticides into five classes: class I - highly toxic, class II - toxic, class III - moderately toxic, class IV - slightly toxic, class V - virtually non-toxic.
People should stay out of the treated area for a minimum of 12 hours after the pesticide has been applied, unless a longer time is specified on the label. Pregnant women may be more sensitive to the strong smell of some pesticides.
Illness may occur quickly or be delayed a few hours. However, if signs or symptoms start more than 12 hours after exposure to the pesticide, it is probably some other illness.
Pesticide Toxicity Index (PTI) is a tool to assess pesticide mixtures. PTI is an indicator of potential toxicity of pesticide mixtures to aquatic life.
In most cases, your family, including children and fur children, should be able to return home between 30 minutes and a few hours after spraying. In some cases, your exterminator may recommend keeping pets and small children away for a few hours longer. When in doubt, ask the professionals.
Signal words generally fall into four categories, from greatest to least toxic: DANGER ‐ POISON, DANGER, WARNING and CAUTION (see table below). DANGER – POISON are the signal words used for the most toxic compounds.
With chronic toxicity, gastrointestinal symptoms are common. Nausea, vomiting, and diarrhea are generally seen. The toxidrome known as cinchonism can occur in chronic toxicity.
EPA recommends using rats for subchronic, chronic, carcinogenicity, and reproduction studies; mice for carcinogenicity studies; and dogs for subchronic and chronic studies. Rats are routinely used for acute oral and inhalation studies and rabbits for eye and skin irritation studies and acute dermal studies.
Toxicity refers to the ability of a chemical to cause harmful effects to the body. As was described by Paracelsus (1493-1541):
A substance is considered extremely toxic if it has an LD50 of less than 5 mgs/kg of animal body weight. To humans, this is the equivalent of a taste (less than 7 drops). It is Highly toxic if it has an LD50 of between 5 and 50 mg/kg of animal body weight to a human, this would be about a teaspoon.