Government regulations in many countries require toxicity testing on animals as a condition for the importation or sale of pesticides, industrial chemicals, drugs, medical devices, vaccines, genetically modified foods, and some consumer products. Depending on the product type, its likely toxicity, and the degree of anticipated human or environmental exposure, tests using hundreds or thousands of animals may be required by law.1 In these tests, animals—including birds, dogs, fish, guinea pigs, mice, rabbits, rats, and monkeys—are forced to swallow or inhale a test substance, or a chemical is applied to their skin or eyes. These tests and the non-animal methods that can replace them are described below. Animal-free methods and strategies are often less expensive, faster, and more predictive of human health outcomes.
Most countries do not keep detailed public records of the numbers of animals used in experiments or what tests they are used in. Therefore, it is not possible to know the number used in government-required testing worldwide. However, one study estimated that more than 115 million animals were used for scientific purposes in 2005, and the authors acknowledge that this is likely an underestimate because of the incomplete records kept in many countries.2
The U.S. Department of Agriculture’s fiscal year 2017 annual report of animal usage indicates that more than 932,954 animals were used in or held for experiments nationwide.3 However, this is just a fraction of the number actually used in testing. Mice, rats, birds, and cold-blooded animals make up more than 95% of animals used, but because they’re not covered by even the minimal protections of the federal Animal Welfare Act—the only law that governs the use and treatment of animals in U.S. laboratories—they’re not counted.4
Canada, which does count mice, rats, and fish, reported the use of more than 3.5 million animals in experiments in 2015, including approximately 20,000 dogs, cats, and primates. Additional animals were used in experiments at facilities that are not certified by the Canadian Council on Animal Care.5 In the European Union, which also counts the number of mice, rats, and fish used, 11.5 million animals were used in 2011.6
In the U.S., there are no laws protecting animals from physical and psychological pain and suffering once the testing has been approved by in-house committees. Experiments can cause paralysis, swelling and ulceration of the skin and eyes, convulsions, bleeding from the nose or mouth, severe pain, self-mutilation, and ultimately death.7 There is no requirement to provide animals with pain-relieving drugs during these experiments, and animals who have not died by the end are usually killed. In 2017, hundreds of thousands of animals were subjected to painful experiments, and many did not receive any form of pain relief.8
Animals in laboratories endure not only pain and distress in experiments but also inhumane living conditions. For example, social animals are often isolated for long periods of time; food and/or water may be withheld; mothers and babies are separated; animals are confined to small, barren cages bearing no resemblance whatsoever to their natural environment; and animals are subjected to loud noises and bright lights, which are unnatural and stressful to them.
Most animal tests in use today have never been scientifically validated according to internationally agreed-upon criteria in order to demonstrate that they are predictive of human health outcomes or environmental hazards.9 The reliability, accuracy, and relevance of their results are always questionable and subject to vastly differing interpretations, as explained here.
Recognition of the scientific limitations—as well as the cost, inefficacy, and ethical issues—of testing on animals has led to significant interest within the scientific community in implementing animal-free test methods. The 2007 landmark National Academy of Sciences report Toxicity Testing in the 21st Century presented a strategy for moving away from testing on animals toward human-relevant, non-animal testing approaches. Dr. Melvin Andersen, coauthor of the report and former director of the Division of Computational Biology at The Hamner Institutes for Health Sciences, stated, “The reason we use animal tests is because we have a comfort level with the process … not because it is the correct process, not because it gives us any real new information we need to make decisions. Animal tests are no longer the gold standard.”10 The former head of the European Centre for the Validation of Alternative Methods, Dr. Thomas Hartung, echoed Dr. Andersen’s statement when he said, “Some animal tests haven’t changed in 60 years. The tests are frozen in time. This is not science. Science is always moving ahead.”11
Some commonly conducted animal tests and the non-animal test methods that have been scientifically validated to replace them include the following:
- Acute systemic toxicity: To determine the toxic consequences of a single, short-term exposure to a product or chemical, the substance is administered to animals in extremely high doses via forced inhalation, feeding, and/or skin contact. One international study examined the results of rat and mouse “lethal dose 50” (LD50) tests, which determine the amount of a test substance that kills 50% of the animals, and found that human cell–based tests were better able to predict human outcomes than the LD50.12 Among strategies that can be used to avoid testing on animals, the cell-based neutral red uptake phototoxicity test can determine if a substance is not toxic, and three-dimensional reconstructed human skin models can predict if a substance will penetrate the skin.13,14 There are also computational models, such as the Collaborative Acute Toxicity Modeling Suite (CATMoS), which can predict toxicity following oral consumption of a substance. The PETA International Science Consortium Ltd. has cosponsored workshops and webinars with the goal of developing strategies to replace animal use in acute systemic toxicity testing.
- Skin sensitization: The guinea pig test involves injecting a substance under the skin of guinea pigs and watching for an allergic response. This test may cause their skin to become itchy, inflamed, ulcerated, or otherwise painful as a result of an allergic reaction. In another animal test, the murine local lymph node assay, a test substance is applied to the ears of between 16 and 32 mice per test, who are ultimately killed so that the lymph node near the ear can be removed and the mice’s immune response measured. Several non-animal replacements for the skin sensitization animal tests are widely available and are accepted by regulatory agencies including the U.S. Environmental Protection Agency (EPA).15,16,17
- Skin irritation and corrosion: A substance is smeared onto animals’ shaved skin, and the resulting irritation or skin damage—which can include inflamed skin, bloody scabs, and ulcers—is observed. Significant differences between the skin of humans and that of rabbits, who are often used in these tests, have been documented for almost 50 years, and the qualitative scoring of skin damage using this animal test is highly subjective.18 Non-animal methods for assessing skin irritation and corrosion, including three-dimensional human skin models such as EpiDerm, have been validated and accepted around the world as replacements for animal tests.19,20,21
- Eye irritation and corrosion: A substance is dropped or spread into the eyes of rabbits, and the level of irritation or corrosion—which can include swollen eyelids, irritated and cloudy eyes, and blindness—is subjectively assessed. Because of differences in ocular anatomy and physiology between humans and animals, this Draize eye test “exaggerates the eye irritancy response reported in humans,” making this painful test unreliable.22 Human-based non-animal methods can replace animal use in eye irritation and corrosion tests.23,24,25
- Phototoxicity: Animals are fed a test substance, or it is smeared onto their skin, then they are exposed to ultraviolet light to see if sunlight-induced skin irritation occurs. However, the differences in physiology between humans and other animals, including in drug metabolism and skin penetration, make this test unreliable.26 The cell-based neutral red uptake phototoxicity test is a widely accepted alternative to using animals to assess phototoxicity.27
- Pyrogenicity: In the rabbit pyrogen test, a substance is injected into the veins of rabbits and the animals’ temperature is monitored to see if bacteria or other contaminants cause a fever. The human cell–based monocyte activation test is a replacement for pyrogenicity testing in animals, and the Science Consortium held a workshop on this topic in 2018.28
- Reproductive and developmental toxicity: Hundreds to thousands of animals per test are forced to inhale or ingest a substance and then are bred so that experimenters can observe any damage that it causes to reproductive abilities or to the offspring. Progress is being made in advancing non-animal methods for examining specific stages of reproductive or developmental toxicity. For example, one test uses cells to detect chemicals that have the potential to cause the malformation of developing embryos.29,30
- Carcinogenicity: In the rodent cancer bioassay, hundreds of rats or mice per test are forced to ingest or inhale a substance, or it is injected into or spread onto their skin. The animals are exposed to it for up to two years before they are killed and examined for signs of cancer, such as abnormal cells or tumor formation. A review of existing data suggests that experiments using mice or rats often do not accurately predict whether a substance will cause cancer in humans.31 In vitro tests that examine known stages of cancer progression have been developed to assess the risk of a substance’s potential carcinogenicity. For example, cell transformation assays measure the tumor-initiating activity and tumor-promoting activity of a substance and serve as reliable indicators of carcinogenicity without using animals.32,33 The Science Consortium is leading a collaborative research effort that brings together experts from government and industry to reduce carcinogenicity testing on animals.
For more detailed information on non-animal test methods, see here.
The Way Forward
PETA is persuading world governments, both individually and as part of international organizations such as the Organisation for Economic Co-operation and Development, to become more involved in developing and using sophisticated animal-free test methods. For example, after decades of involvement by PETA scientists and other organizations, the EPA announced that it will end its reliance on and funding of toxicity testing on mammals by 2035 and provide researchers working on the development of non-animal methods with funding.
Where non-animal methods are not yet available or fully validated, PETA encourages others to provide funding for the development and validation of test methods. Additionally, PETA and its international affiliates have provided millions of dollars in funding for promising non-animal test methods. More information on the ways in which PETA is helping to promote, fund, and validate non-animal testing methods can be found here.
What You Can Do
Use this form to ask the U.S. Food and Drug Administration to take the following steps:
- Amend test guidelines to omit animal tests and replace them with non-animal methods and strategies that are currently available.
- Devote more resources to the development and validation of non-animal test methods.
- Provide additional training for its reviewers on the interpretation of data from non-animal tests.
1See, e.g., “Death Toll From Pesticide Testing” at http://www.peta.org/issues/animals-used-for-experimentation/death-toll-pesticide-testing/.
2Katy Taylor et al., “Estimates for Worldwide Laboratory Animal Use in 2005,” Alternatives to Laboratory Animals, 36.3 (2008): 327-342.
3U.S. Department of Agriculture, “Annual Report Animal Usage by Fiscal Year,” 2017.
4Justin Goodman et al., “Trends in Animal Use at US Research Facilities,” Journal of Medical Ethics, 41.7 (2015): 567-569.
5Canadian Council on Animal Care, “Animal Data Report,” 2015.
6European Commission, “Seventh Report on the Statistics on the Number of Animals Used for Experimental and Other Scientific Purposes in the Member States of the European Union,” 2013.
7Organisation for Economic Co-operation and Development, “No. 19: Guidance Document on the Recognition, Assessment, and Use of Clinical Signs as Humane Endpoints for Experimental Animals Used in Safety Evaluation,” OECD Environmental Health and Safety Publications, Series on Testing and Assessment, 2000.
8U.S. Department of Agriculture.
9John J. Pippin, “Animal Research in Medical Sciences: Seeking a Convergence of Science, Medicine, and Animal Law,” South Texas Law Review, 54 (2013): 469-511.
10Gilbert M. Gaul, “In U.S., Few Alternatives to Testing on Animals,” The Washington Post, April 12, 2008.
12B. Ekwall, “Overview of the Final MEIC Results: II. The In Vitro–In Vivo Evaluation, Including the Selection of a Practical Battery of Cell Tests for Prediction of Acute Lethal Blood Concentrations in Humans,” Toxicology In Vitro, 13.4 (1999): 665-673.
13European Union Reference Library for Alternatives to Animal Testing, “EURL ECVAM Recommendation on the 3T3 NRU Assay for Supporting the Identification of Substances Not Requiring Classification for Acute Oral Toxicity,” 2013.
14Joseph R. Manuppello et al., “Avoiding Dermal Systemic Toxicity Testing,” Applied In Vitro Toxicology, 1.3 (2015): 173-174.
15Organisation for Economic Co-operation and Development, “Test No. 442C: In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA),” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2019.
16Organisation for Economic Co-operation and Development, “Test No. 442D: In Vitro Skin Sensitisation: ARE-Nrf2 Luciferase Test Method,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2018.
17Organisation for Economic Co-operation and Development, “Test No. 442E: In Vitro Skin Sensitisation: Human Cell Line Activation Test (h-CLAT),” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2018.
18Methodius J. Bartek et al., “Skin Permeability In Vivo: Comparison in Rat, Rabbit, Pig and Man,” Journal of Investigative Dermatology, 58.3 (1972): 114-123.
19Organisation for Economic Co-operation and Development, “Test No. 431: In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2019.
20Organisation for Economic Co-operation and Development, “Test No. 439: In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2019.
21Organisation for Economic Co-operation and Development, “Test No. 435: In Vitro Membrane Barrier Test Method for Skin Corrosion,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, 2015.
22L.A. Lambert et al., “The Use of Low-Volume Dosing in the Eye Irritation Test,” Food and Chemical Toxicology, 31.2 (1993): 99-103.
23Organisation for Economic Co-operation and Development, “Test No. 460: Fluorescein Leakage Test Method for Identifying Ocular Corrosives and Severe Irritants,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2017.
24Organisation for Economic Co-operation and Development, “Test No. 491: Short Time Exposure In Vitro Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2018.
25Organisation for Economic Co-operation and Development, “Test No. 492: Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2019.
26Marcella Martignoni et al., “Species Differences Between Mouse, Rat, Dog, Monkey and Human CYP-Mediated Drug Metabolism, Inhibition and Induction,” Expert Opinion on Drug Metabolism & Toxicology, 2.6 (2006): 875-894.
27Organisation for Economic Co-operation and Development, “Test No. 432: In Vitro 3T3 NRU Phototoxicity Test,” OECD Environmental Health and Safety Publications, OECD Guidelines for the Testing of Chemicals, Section 4, last updated 2019.
28European Centre for the Validation of Alternative Methods. “Statement on the Validity of In Vitro Pyrogen Tests,” 2006.
29Elke Genschow et al., “The ECVAM International Validation Study on In Vitro Embryotoxicity Tests: Results of the Definitive Phase and Evaluation of Prediction Models,” Alternatives to Laboratory Animals, 30.2 (2002): 151-176.
30Andrea E.M. Seiler and Horst Spielmann, “The Validated Embryonic Stem Cell Test to Predict Embryotoxicity In Vitro,” Nature Protocols, 6 (2011): 961-978.
31Fanny K. Ennever and Lester B. Lave, “Implications of the Lack of Accuracy of the Lifetime Rodent Bioassay for Predicting Human Carcinogenicity,” Regulatory Toxicology and Pharmacology, 38.1 (2003): 52-57.
32Organisation for Economic Co-operation and Development, “Guidance Document on the In Vitro Syrian Hamster Embryo (SHE) Cell Transformation Assay,” OECD Environmental Health and Safety Publications, Series on Testing and Assessment No. 214, 2015.
33Organisation for Economic Co-operation and Development, “Guidance Document on the In Vitro BHAS 42 Cell Transformation Assay,” OECD Environmental Health and Safety Publications, Series on Testing and Assessment No. 231, 2017.