What is the LD50 Test?

young female lab assistant takes care about laboratory rats into plastic cages
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Updated and edited on May 20, 2016 by Michelle A. Rivera, About.com Animal Rights Expert

The LD50 test is one of the most controversial and inhumane experiments endured by laboratory animals. “LD” stands for “lethal dose”; the “50” means that half the animals, or 50 percent of the animals forced to endure testing the product, will die at that dose.

LD50 value for a substance will vary according to the species involved.

The substance may be administered any number of ways, including orally, topically, intravenously, or through inhalation. The most commonly used species for these tests are rats, mice, rabbits, and guinea pigs. Substances tested might include household products, drugs or pesticides. These particular animals are popular with animal testing facilities because they are not protected by the Animal Welfare Act which states, in part:

            AWA 2143 (A)  “…for animal care, treatment, and practices in experimental procedures to ensure that animal pain and distress are minimized, including adequate veterinary care with the appropriate use of anesthetic, analgesic, tranquilizing drugs, or euthanasia;…”

The LD50 test is controversial because the results have limited, if any, significance when applied to humans. Determining the amount of a substance that will kill a mouse has little value to human beings.

Also controversial is the number of animals frequently involved in an LD50 trial, which may be 100 or more animals. Organizations such as the Pharmaceutical Manufacturers’ Association, U.S. Environmental Protection Agency, and the Consumer Product Safety Commission, among others, have all spoken out publicly against the use of too many animals in order to reach that 50 percent number.

Approximately 60-200 animals are used even though the above organizations have indicated that these same tests could be successfully concluded by using only six to ten animals. The tests involved testing for “,,,toxicity of gases and powders (the inhalation LD50), irritancy and internal poisoning due to skin exposure (the dermal LD50), and toxicity of substances injected directly into animal tissue or body cavities (the injectable LD50),” according to the New England Anti-Vivisection Society, whose mission it is to end animal testing and supporting alternatives to testing on live animals. The animals used are almost never given anesthesia and suffer tremendous pain during these tests.

Because of public outcry and advances in science, the LD50 test has been largely replaced by alternative test measures. In “Alternatives to Animal Testing, (Issues in Environmental Science and Technology)” a number of contributors* discuss alternatives that have been adopted by laboratories around the world including the Acute Toxic Class method, the Up and Down and Fixed Dose procedures.  According to the National Institute of Heath, the Consumer Product Safety Commission "strongly discourages" the use of the LD50 test, while the Environmental Protection Agency discourages its use, and, perhaps the most unnerving, the Food and Drug Administration does not require the LD50 test for cosmetic testing.

Merchants have used the public outcry to their advantage. Some have added the words “cruelty free” or some other indication that the company does not use animal testing on their finished product. But beware of these claims because there is no legal definition for these labels. So the manufacturer may not test on animals, but it’s entirely possible that the manufacturers of the ingredients which comprise the product are tested on animals.

International trade has also added to the confusion. While many companies have learned to avoid testing on animals as a public relations measure, the more the United States opens trades with other countries, the higher the chance that animal testing will again be part of the manufacture of a product previously deemed "cruelty free." For example, Avon, one of the first companies to speak out against animal testing, has begun selling their products to China.

China requires some animal testing be done on certain products before being offered to the public. Avon chooses, of course, to sell to China rather than stand on ceremony and stick to their cruelty-free guns. And while these tests may or may not involve LD-50, the fact is that all the laws and regulations that have been so hard fought and won by animal-rights activists over the years won't mean a thing in a world where global trade is the norm. 

If you want to live a cruelty-free life and enjoy following a vegan lifestyle, you have to be part detective and research the products you use every day.

*R E Hester (Editor), R M Harrison (Editor), Paul Illing (Contributor), Michael Balls (Contributor), Robert Combes (Contributor), Derek Knight (Contributor), Carl Westmoreland (Contributor)

Edited by Michelle A. Rivera, Animal Rights Expert