Workers Health & Safety Centre

Scientists conclude recent criticisms of IARC evaluations unfounded

A group of international scientists has concluded that recent criticisms of the International Agency for Research on Cancer’s (IARC) classification process are unfounded.
For the past 40 years the International Agency for Research on Cancer (IARC) Programme for the Evaluation of Carcinogenic Risks to Humans Monograph Programme has been identifying, and assessing carcinogenic hazards to humans from occupational, environmental and lifestyle exposures and agents.
The IARC Monographs are often the first evaluations of new and emerging threats to public health both in the workplace and in the community. They are widely used and referenced by governments, institutions, organizations, companies and the public around the world.
Although accepted internationally, IARC has been criticized recently for their classification of particular agents as human carcinogens and the general approach or process used to reach these conclusions. Critics have also claimed that IARC Working Groups have failed to recognize weaknesses in the studies on which they base their evaluations and have failed to take into account possible biases of some of the Working Groups’ members leading to inappropriate classifications of human carcinogens.
Concerned about these criticisms, a separate group of scientists from a variety of disciplines joined forces to review the history of IARC evaluations, including the IARC Monograph processes and examine the composition of the Working Groups to check for possible biases.
They concluded IARC “hazard assessment of various agents provided a balanced evaluation and an appropriate indication of the weight of evidence. Some disagreement by individual scientists to some evaluations is not evidence of process failure.”
In their paper, published in the June 2015 edition of Environmental Health Perspectives, the group of scientists explain, “Even if some scientists on the Working Group have performed research on some of the agents being considered, they make up a minority of the Working Group because several agents are usually evaluated in a single meeting, so the number of Working group members who have conducted research on any one agent is typically small.”
They further reason, Working Group members do not receive any fee for their work and IARC strictly requires that any conflict of interest is divulged and does not allow those with conflicts to serve on the Working Groups.
The evaluating scientists also point out, many exposures evaluated by IARC have also been independently evaluated by other institutions (e.g. ACGIH TLV/BEI threshold limit values; U.S. National Toxicology Program; U.S. Environmental Protection Agency; Bureau of Chemical Safety in Canada; and the Scientific Committee on Occupational Exposure Limits (SCOEL) to name a few) and assessments from these groups typically come to similar conclusions as those from IARC. This further indicates broad agreement within the scientific community regarding evidence on carcinogenicity in the scientific literature and expands the number of scientists who do not have a vested interest, but who have generally agreed with IARC’s conclusions.
At the end of their review the group of international scientists stated: “We have looked carefully at the recent charges of flaws and bias in the hazard evaluations by IARC Working Groups, and we have concluded that the recent criticisms are unfair and unconstructive.”
Moreover, they defend, “The IARC Monographs have made, and continue to make, major contributions to the scientific underpinning for societal actions to improve the public’s health.”
Want to read the complete evaluation of IARC Monographs, published in Environmental Health Perspectives?
Want to read about IARC’s 50 years of work?
Be sure to download another important resource explaining IARC’s classification system.

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