Show Identifying a carcinogenic hazard is an important first step in cancer prevention. The International Agency for Research on Cancer (IARC) – a specialized agency of the World Health Organization – plays a key role in this step because it reviews scientific evidence to identify and classify causes of cancer. Impact of IARC classificationsWhen IARC determines that something causes cancer, the classification can trigger many actions by government, industry, public health organizations and advocacy groups :
For example, Ontario introduced restrictions on tanning bed use by youth after IARC announced that using tanning beds increases the risk of melanoma., IARC’s Monograph ProgramIARC’s Monograph Program classifies many potentially cancer-causing agents, including:
The IARC classifications describe the likelihood that an agent causes cancer, rather than the strength of the carcinogen. For example, when IARC first classified processed meat as “carcinogenic to humans,” which is the same classification as tobacco smoking, many news stories wrongly claimed that “bacon is as bad as cigarettes.” However, the IARC classification does not mean that the level of risk is the same – it simply indicates that both agents cause cancer. How IARC evaluates carcinogensIARC updated the way it classifies carcinogens in 2019. The key changes include:
However, overall the process remains the same. Agents are recommended to IARC for review, and chosen based on whether there is some evidence of human exposure and cancer hazard. Each evaluation is done by a Working Group of scientists from around the world, chosen for their expertise and lack of any conflicts of interest. These scientists carefully consider 3 types of data to make classification decisions:
The final evaluation is done by integrating the 3 evidence streams. IARC uses the 4 classification categories described below and as of spring 2020, it has reviewed 1,017 agents. More detail on the classification process is available in the IARC Monographs Preamble. Carcinogenic to humans (Group 1) – Agents in this group are known causes of cancer. Very strong, clear evidence is needed for an agent to be classified in Group 1. If the evidence from studies of cancer in humans is strong enough, the agent is automatically placed into Group 1. Otherwise, a combination of strong animal studies and mechanistic evidence in humans is needed. Probably carcinogenic to humans (Group 2A) – Agents generally need to fulfill 2 of the following 3 requirements to be placed in Group 2A: some evidence of cancer in humans, strong animal evidence and strong mechanistic evidence. Possibly carcinogenic to humans (Group 2B) – Agents that only have some evidence of cancer in humans or strong animal evidence or strong mechanistic evidence are placed in this category. Not classifiable (Group 3) – More research is needed on the agents in this group to determine whether they cause cancer. Agents classified by the IARC Monographs
Source: International Agency for Research on Cancer [Internet]. Lyon: Agents Classified by the IARC Monographs, Volumes 1–125 [updated 2020 Feb 18; cited 2020 Mar 5]. Notes: Before 2019, IARC also used to include “Group 4 (probably not carcinogenic to humans).” However, because IARC only reviews agents if there is some evidence that they may cause cancer, this group was rarely used and has been removed. How Ontario Health (Cancer Care Ontario) uses IARC classificationsOntario Health (Cancer Care Ontario) used the IARC evaluations to identify cancer-causing substances that have a large impact in Ontario for its reports on cancer burden:
Read the reports to learn about cancers caused by common infections and exposures at work or in the environment, as well as policy changes that could help prevent these cancers. How many carcinogenic agents are there?To date, IARC has classified 120 agents as carcinogenic to humans. Over 40 agents have more than one target organ site, with up to 17 sites for tobacco smoking and 14 sites for X-radiation and gamma-radiation.
What is a Class 3 carcinogen?IARC definition and list of compounds. Group 3: "Unclassifiable as to carcinogenicity in humans" There is no evidence at present that it causes cancer in humans.
What is IARC classification?The International Agency for Research on Cancer (IARC) have devised a system of categories to evaluate the carcinogenicity of an agent to humans. An agent is classified based on scientific evidence derived from human and experimental animal studies and from mechanistic and other relevant data.
Which is a list of potential carcinogens?Common Carcinogens You Should Know. Tobacco.. Radon.. Asbestos.. Crispy, Brown Foods.. Formaldehyde.. Ultraviolet Rays.. Alcohol.. Processed Meat.. |