Information on Test Methods

A toxicity test is designed to generate data concerning the harmful effects of a substance on human health or the environment. Many toxicity tests examine specific types of harmful effects, known as "endpoints," such as eye irritation or cancer. Other tests are more general in nature, ranging from single-exposure ("acute") studies to multiple-exposure ("repeated dose") studies, in which animals are administered daily doses of a test substance to determine whether one or more organ or system is harmfully affected following exposures of up to one-month ("subacute"), three-months ("subchronic"), and/or two-years ("chronic") duration. Tests aimed at identifying hazards to humans are generally referred to as "safety" or "health effects" studies, whereas wildlife-oriented tests are known as "ecotoxicity" studies.

Common types of toxicity tests are listed below. Many have been in use for between 40 and 80 years, and virtually all inflict suffering and death on animals. [An asterisk (*) indicates a test for which animal reduction, refinement or replacement methods are currently available; visit the Alternatives to Animal Testing section for details.)

• Acute systemic toxicity: Death or evident toxicity occurring within a short time after administration of a single, extremely high dose of a substance via oral force-feeding, forced inhalation and/or application to the skin*
• Skin irritation/corrosion: Chemically induced skin damage that is reversible (irritation) or irreversible (corrosion)*
• Eye irritation/corrosion: Chemically induced eye damage that is reversible (irritation) or irreversible (corrosion)*
• Skin sensitization: The induction of allergic contact dermatitis following repeated exposure to a chemical agent*
• Skin absorption: The extent and rate by which a chemical is able to enter the body via the skin*
• Repeated dose toxicity: General toxicological effects occurring as a result of repeated daily exposure to a substance (via oral, inhalation and/or skin routes) for a portion of the expected life span (i.e., 1 to 3 months) or for the majority of the life span (i.e., 14 to 24 months)
• Reproductive and developmental toxicity: Chemically induced harmful effects on sexual function, fertility and/or normal offspring development (e.g., spontaneous abortion, premature delivery and birth defects), generally determined through the breeding of one or more generations of offspring
• Genetic toxicity: Chemically induced genetic mutations and/or other alterations of the structure, information content or segregation of genetic material*
• Carcinogenicity: Chemically induced cancer, whether through genotoxic or non-genotoxic (i.e., growth-promoting) mechanisms
• Immunotoxicity: Chemically induced harmful effects on the immune system (e.g., thymus, white blood cell number and viability)
• Neurotoxicity: Chemically induced harmful effects on the brain, spinal cord, and/or peripheral nervous system (e.g., deficits in learning or sensory ability
• Toxicokinetics: The study of the absorption, distribution, metabolism, and elimination of chemicals in the body
• Ecotoxicity: Chemically induced harmful effects on wildlife populations, including mammals, birds, fish, amphibians, crustaceans, and other aquatic invertebrates; common study designs include acute systemic, dietary, and reproductive (also known as "life-cycle") toxicity*

In addition to the "conventional" toxicity tests listed above, which are used in many different sectors (e.g., cosmetics, chemicals, food additives and pesticides), various types of specialized tests are also used in the pharmaceutical and vaccine sectors (e.g., to detect the fever-inducing "pyrogenic" effects of injectable drugs or the potential for sunlight-induced "phototoxicity"). In addition, a wide range of new and revised tests are under development to address concerns such as "endocrine disruption" and the unique hazards posed by ultra-tiny "nanomaterials." A comprehensive listing of sector-specific animal testing requirements is available in our Fact Sheets.