Many known or suspected carcinogens appear on both organization’s lists however, if a substance or exposure is only on one agency’s list, this it does not necessarily mean there is a controversy, as one agency may not have evaluated it. To learn more about these agencies and how they study and classify cancer causes, see Determining if Something Is a Carcinogen.

More information on each of these known and probable human carcinogens can be found on their websites. Instead, we rely on the determinations of other respected agencies, such as the International Agency for Research on Cancer (IARC, part of the World Health Organization) and the US National Toxicology Program (NTP). In general, the American Cancer Society does not determine if something causes cancer (that is, if it is a carcinogen).