The toxicity of any compound is related to the dose. A highly toxic substance causes severe symptoms of poisoning with small doses. A substance with a low toxicity generally requires large doses to produce mild symptoms. Even common substances like coffee or salt become poisons if large amounts are consumed.
EPA Acute Toxicity Rankings
EPA gives a warning label of Category 1 to pesticide products with the highest acute toxicity levels and Category 4 to the least acutely toxic pesticide products.
A toxic LOC tells you what level (threshold concentration) of exposure to a chemical could hurt people if they breathe it in for a defined length of time (exposure duration). Generally, the lower the toxic LOC value for a substance, the more toxic the substance is by inhalation*.
Category 1, the highest toxicity category, has cut off values of 5 mg/kg by the oral route, 50 mg/kg by the dermal route, 100 ppm for gases or gaseous vapours, 0.5 mg/l for vapours, and 0.05 mg/l for dusts and mists.
Category 1 is always the greatest level of hazard (that is, it is the most hazardous within that class).
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.
It may be chemical, physical, or biological in form. Toxic agents may be: chemical (such as cyanide), physical (such as radiation) and biological (such as snake venom).
Lethal dose (LD50)
LD50 is a general indicator of a substance's toxicity within a short space of time. It is a measure of acute toxicity. Most users of a substance will want to know the toxicity of that substance. The information for an LD50 must include the substance, the route of entry and the animal species.
LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material.
It is safest to keep exposure to any toxic substance as low as possible. Since some chemicals are much more toxic than others, it is necessary to keep exposure to some substances lower than others. The threshold level is the lowest concentration that might produce a harmful effect. It is different for every chemical.
There are generally five types of toxicities; chemical, biological, physical, radioactive and behavioural. Disease-causing microorganisms and parasites are toxic in a broad sense but are generally called pathogens rather than toxicants.
Toxicity is a measure of the poisoning strength of a chemical. Chemicals with low toxicity require large doses or amounts to cause poisoning. Chemicals with high toxicity only need small doses to cause poisoning.
The GHS has five categories for acute toxicity.
1 Toxic Effects. Toxic effects are generally classified as acute toxicity or chronic toxicity. Acute toxicity is generally thought of as a single, short-term exposure where effects appear immediately and are often reversible.
Grade 3: severe toxicity; Grade 4: life-threatening toxicity; and. Grade 5: death.
Category 1 hurricane: Very dangerous winds will produce some damage. In a Category 1 hurricane, winds range from 74 to 95 mph. Falling debris could strike people, livestock and pets, and older mobile homes could be destroyed. Protected glass windows will generally make it through the hurricane without major damage.
Category 1 is always the greatest level of hazard within its class. – If Category 1 is further divided, Category 1A within the same hazard class is a greater hazard than category 1B. Category 2 within the same hazard class is more hazardous than Category 3, and so on. There are a few exceptions to this rule.
To be classified as a hurricane, a tropical cyclone must have one-minute-average maximum sustained winds at 10 m above the surface of at least 74 mph (64 kn, 119 km/h; Category 1). The highest classification in the scale, Category 5, consists of storms with sustained winds of at least 157 mph (137 kn, 252 km/h).
Eating a lot of food that contains metals (fish). Drinking water from older water supply systems. Working with metals on the job. Taking medications or supplements with high amounts of metallic elements.
The NOEL (no observable effect level) is the highest dose or exposure level of a substance or material that produces no noticeable (observable) toxic effect on tested animals.
It relies on the concept that a dose, or a time of exposure (to a chemical, drug, or toxic substance), will cause an effect (response) on the exposed organism. Usually, the larger or more intense the dose, the greater the response, or the effect. This is the meaning behind the statement “the dose makes the poison.”
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.
When a chemical causes a defined form of toxicity, the threshold is the maximum exposure when this toxicity does not occur. It is an operational parameter and is limited in its interpretation and applicability.