In 1927, J.W. Trevan attempted to find a way to estimate the relative poisoning potency of drugs and medicines used at that time. Since Trevan's early work, other scientists have developed different approaches for more direct, faster methods of obtaining the LD50. Acute toxicity is the ability of a chemical to cause ill effects relatively soon after one oral administration or a 4-hour exposure to a chemical in air. In nearly all cases, LD50 tests are performed using a pure form of the chemical. Mixtures are rarely studied.
Researchers can do the test with any animal species but they use rats or mice most often.
Other species include dogs, hamsters, cats, guinea-pigs, rabbits, and monkeys. Inhalation and skin absorption are the most common routes by which workplace chemicals enter the body. Thus, the most relevant from the occupational exposure viewpoint are the inhalation and skin application tests. Despite this fact, the most frequently performed lethality study is the oral LD50. This difference occurs because giving chemicals to animals by mouth is much easier and less expensive than other techniques.