LD50 Testing - Is It On The Way Out?

Lethal doses are expected kill 50 percent of animals tested

White rats
Rats are funny, happy, intelligent creatures. Getty Images

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’ AssociationU.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.

 

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

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Rivera, Michelle A. "LD50 Testing - Is It On The Way Out?" ThoughtCo, Sep. 1, 2016, thoughtco.com/ld50-testing-on-the-way-out-4041541. Rivera, Michelle A. (2016, September 1). LD50 Testing - Is It On The Way Out? Retrieved from https://www.thoughtco.com/ld50-testing-on-the-way-out-4041541 Rivera, Michelle A. "LD50 Testing - Is It On The Way Out?" ThoughtCo. https://www.thoughtco.com/ld50-testing-on-the-way-out-4041541 (accessed November 19, 2017).