Background: Recently, the International Agency for Research on Cancer (IARC) Programme for the Evaluation of Carcinogenic Risks to Humans has been criticized for several of its evaluations, and also for the approach used to perform these evaluations. Some critics have claimed that failures of IARC Working Groups to recognize study weaknesses and biases of Working Group members have led to inappropriate classification of a number of agents as carcinogenic to humans.

Objectives: The authors of this Commentary are scientists from various disciplines relevant to the identification and hazard evaluation of human carcinogens. We examined criticisms of the IARC classification process to determine the validity of these concerns. Here, we present the results of that examination, review the history of IARC evaluations, and describe how the IARC evaluations are performed.

Discussion: We concluded that these recent criticisms are unconvincing. The procedures employed by IARC to assemble Working Groups of scientists from the various disciplines and the techniques followed to review the literature and perform hazard assessment of various agents provide a balanced evaluation and an appropriate indication of the weight of the evidence. Some disagreement by individual scientists to some evaluations is not evidence of process failure. The review process has been modified over time and will undoubtedly be altered in the future to improve the process. Any process can in theory be improved, and we would support continued review and improvement of the IARC processes. This does not mean, however, that the current procedures are flawed.

Conclusions: The IARC Monographs have made, and continue to make, major contributions to the scientific underpinning for societal actions to improve the public’s health.

Citation: Pearce N, Blair A, Vineis P, Ahrens W, Andersen A, Anto JM, Armstrong BK, Baccarelli AA, Beland FA, Berrington A, Bertazzi PA, Birnbaum LS, Brownson RC, Bucher JR, Cantor KP, Cardis E, Cherrie JW, Christiani DC, Cocco P, Coggon D, Comba P, Demers PA, Dement JM, Douwes J, Eisen EA, Engel LS, Fenske RA, Fleming LE, Fletcher T, Fontham E, Forastiere F, Frentzel-Beyme R, Fritschi L, Gerin M, Goldberg M, Grandjean P, Grimsrud TK, Gustavsson P, Haines A, Hartge P, Hansen J, Hauptmann M, Heederik D, Hemminki K, Hemon D, Hertz-Picciotto I, Hoppin JA, Huff J, Jarvholm B, Kang D, Karagas MR, Kjaerheim K, Kjuus H, Kogevinas M, Kriebel D, Kristensen P, Kromhout H, Laden F, Lebailly P, LeMasters G, Lubin JH, Lynch CF, Lynge E, ‘t Mannetje A, McMichael AJ, McLaughlin JR, Marrett L, Martuzzi M, Merchant JA, Merler E, Merletti F, Miller A, Mirer FE, Monson R, Nordby KC, Olshan AF, Parent ME, Perera FP, Perry MJ, Pesatori AC, Pirastu R, Porta M, Pukkala E, Rice C, Richardson DB, Ritter L, Ritz B, Ronckers CM, Rushton L, Rusiecki JA, Rusyn I, Samet JM, Sandler DP, de Sanjose S, Schernhammer E, Seniori Costantini A, Seixas N, Shy C, Siemiatycki J, Silverman DT, Simonato L, Smith AH, Smith MT, Spinelli JJ, Spitz MR, Stallones L, Stayner LT, Steenland K, Stenzel M, Stewart BW, Stewart PA, Symanski E, Terracini B, Tolbert PE, Vainio H, Vena J, Vermeulen R, Victora CG, Ward EM, Weinberg CR, Weisenburger D, Wesseling C, Weiderpass E, Zahm SH. 2015. IARC Monographs: 40 years of evaluating carcinogenic hazards to humans. Environ Health Perspect 123:507–514;  http://dx.doi.org/10.1289/ehp.1409149

Address correspondence to N. Pearce, Department of Medical Statistics, London School of Hygiene and Tropical Medicine, Keppel St., London WC1E 7HT, United Kingdom. Telephone: 44-20-7958-8151. E-mail: neil.pearce@lshtm.ac.uk

This work was conducted with no direct funding, but was supported in part by the Intramural Research Program of the NIH (NCI and NIEHS).

The views expressed are those of the authors and do not necessarily reflect the official views of the Uniformed Services University of the Health Sciences, the Department of Defense, or the U.S. Food and Drug Administration. M. Stenzel is employed by Exposure Assessment Applications LLC (Arlington, VA, USA). P. Stewart is employed by Stewart Exposure Assessments LLC (Arlington, VA, USA). S.H. Zahm is employed by Shelia Zahm Consulting (Hermon, ME, USA), and she has served as an expert witness for the plaintiffs in U.S. litigation involving polychlorinated biphenyls and non-Hodgkin lymphoma. J. Huff has served as an expert witness for plaintiffs in U.S. litigation involving exposures to acrylamide and to styrene and carcinogenicity. B. Armstrong was formerly Deputy Director of IARC (1991–1993), and J. Huff and H. Vainio have previously served as head of the IARC Monographs Program. Most (but not all) other authors have served on IARC Monograph Working groups, and several have worked for IARC in the past. Although P. Bertazzi is Director of a Department that has research and consultancy contracts with industry (including petrochemical, plastics, iron, and steel, and other chemicals), as well as governmental, private, and nonprofit agencies, he has no affiliation with industry; he has served in Italy as an expert in medical legal cases involving asbestos exposure and asbestos-induced disease and prepared reports on causation and diagnosis of asbestos-related disorders for courts. D. Christiani, J. Dement, and A. Smith have served as expert witnesses in U.S. litigation involving asbestos exposure and disease outcomes, including cancer. E. Fontham is a Senior Research Fellow at the International Prevention Research Institute. P. Comba, P. Forastiere, E. Merler, F. Merletti, R. Pirastu, B. Terracini, and P. Vineis have acted as consultants to prosecutors and judges in a number of court case trials. F. Mirer has received compensation as a consultant to the AFL-CIO and the UAW in support of litigation. E. Weiderpass is currently a member of the IARC Scientific Council. The other authors declare they have no actual or potential competing financial interests.

Received: 14 September 2014 Accepted: 20 February 2015 Advance Publication: 24 February 2015 Final Publication: 1 June 2015

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