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"By denying scientific principles, one may maintain any paradox." – Galileo Galilei

Fix The Problem

Principles for the Reform of the IARC Monographs Program

The International Agency for Research on Cancer (IARC), an affiliate of the World Health Organization, is the principal international agency focused on cancer research. One of the Agency’s core elements, the IARC Monographs Program, places substances or behaviors into five classifications ranging from “carcinogenic” to “probably not carcinogenic,” after an abbreviated review by a small, handpicked group of researchers.

IARC’s review processes, the conclusions of the reviews (referred to as monographs), and the practices IARC uses to promote its findings have been widely criticized by scientists and government agencies. The IARC Monographs Program consistently lacks transparency and suffers from conflicts of interest. The Agency’s monographs do not consider the full weight of the scientific evidence and regularly rely on poor quality studies as the basis of conclusions. Most importantly, IARC conclusions cause significant public confusion, unwarranted marketplace de-selection, and regulatory action despite being of questionable relevance since IARC monographs do not reflect actual risks.

Though IARC uses the word “risk” in its monograph titles, it does not consider the actual risk of developing cancer based on exposure under real world circumstances. Rather, the Agency considers only a substance’s hazard —whether the substance could cause cancer in humans under any circumstances, such as doses and exposure levels far beyond what is typical. Unfortunately, this distinction is not widely known or understood. Consequently, IARC’s conclusions are widely misinterpreted. IARC must make key improvements to its Monographs Program to enhance the credibility and utility of its findings and prevent further public misunderstanding of its conclusions.


The following are principles for IARC reform:

  • Consider a Substances’ Risk, Not Just Hazard—IARC’s identification of substances as carcinogens must no longer ignore the essential elements of dose and exposure. Without this context, IARC’s conclusions are of little value in real world settings with potential adverse consequences in areas including health, safety, and nutrition in both developed and developing countries. This context should be provided at the point when IARC publishes and promotes its findings to the media and other stakeholders to prevent confusion.
  • Require Reliance on Weight of Evidence— When making determinations in its monographs, IARC should give the most weight to those studies that are of the highest quality and greatest relevance to humans. Currently, IARC relies on a limited view of the available scientific evidence, which considers only selected findings, ignores conflicting evidence, and fails to fully consider the quality of individual studies. A weight of the evidence approach evaluates each relevant study for its strengths and limitations before its conclusions are used as part of the review.
  • Establish Standard Criteria for Selecting Studies— IARC should establish clearly defined, transparent criteria for assessing the quality and reliability of studies for its monograph reviews. Currently it is unclear how IARC determines which studies it will consider and which it will disregard.
  • Increase Transparency and Utilize Input from Stakeholders—IARC should openly engage with and allow participation from stakeholders during monograph development, including meetings with experts. IARC should clearly articulate in its monographs how it considered stakeholder input and provide stakeholders an opportunity to comment on a draft monograph.
  • Explain Conflicts of Interest—IARC should disclose all conflicts of interest among the participants and advisors to its working groups, not just those affiliated with industry. For example, IARC has not disclosed instances when its advisors and monograph working group members from the academic or NGO community may have a personal or professional stake in the outcome of the monograph.
  • Improve Monograph Releases—IARC should release all monograph information at one time and do away with its current practice of releasing short summaries of its findings months before supporting information is made public. IARC’s current publication practice fails to provide the evidence and exposure levels used to support its classifications of substances as carcinogenic, causing misunderstanding by media and the public.