Key Characteristics

The concept of ‘key characteristics’, properties of chemicals and other agents that confer potential hazard, was first developed for carcinogens and was based on properties of known human carcinogens as classified by the International Agency for Research on Cancer (IARC) (Smith et al., 2016; IARC, 2019; Smith et al., 2020). These key characteristics of carcinogens were applied in the evaluation of diverse carcinogens (Guyton et al., 2018) are now used as the basis for the evaluation of mechanistic data at IARC (2019 Preamble, Samet et al., 2019). They are also widely used by authoritative bodies and regulatory agencies, such as the National Toxicology Program Report on Carcinogens (Atwood et al., 2019), the U.S. EPA, and the California EPA. Recently the key characteristics of male and female reproductive toxicants (Arzuaga et al., 2019; Luderer et al. 2019) and of endocrine disrupting chemicals (La Merrill et al., 2020) have been described and those for other toxicant areas are in development.