Background: The International Agency for Research on Cancer (IARC) Monographs programme assembles expert Working Groups that publish a systematic review, synthesis, and evaluation of existing data on the carcinogenicity of various agents. These comprehensive reviews provide a unique opportunity to identify research gaps and needs to address classification uncertainties. Currently, 135 agents have been classified as carcinogenic to humans (Group 1), 97 agents as probably carcinogenic to humans (Group 2A), and 324 agents as possibly carcinogenic to humans (Group 2B). For most of the Group 2A and 2B agents, there is sufficient evidence for carcinogenicity in animals but limited or inadequate evidence in humans. There are also another 499 Group 3 agents, that are not classifiable as to their carcinogenicity to humans. There is a need for further research on occupational and environmental agents to address such evaluation uncertainties.

Objectives: A Workshop on Research Recommendations for Priority Occupational and Environmental IARC-Classified Agents is being planned at IARC in Lyon, France. The aim of the Workshop is to select 20 occupationally and environmentally relevant agents and to convene 30 international experts in cancer epidemiology, human mechanistic research, and exposure assessment to develop and discuss research recommendations for these agents in order to resolve classification uncertainties and strengthen the human evidence base in their potential hazard re-evaluation. The Workshop will build upon a previous multidisciplinary expert review that was held in 2009 that identified research gaps and needs for 20 priority occupational chemicals, metals, dusts, and physical agents, that helped to stimulate advances in epidemiology studies of cancer and carcinogen mechanisms.

Methods: A total of 20 new priority occupational and environmental agents will be reviewed during the upcoming Workshop including bio-agents, chemicals, metals/particles/fibres, physical agents, and tobacco-related agents. Agents will largely focus on those with human exposure for which the evidence of carcinogenicity is less-than-conclusive (Group 2A or 2B with sufficient evidence for cancer in animals). Agents with emerging evidence that have not previously been evaluated by the Monographs are also being considered. Overarching issues will be identified. Research recommendations will apply findings of previous Monographs reviews of each agent to the identification of research priorities and also consider recent methodological advancements in evidence synthesis and cancer hazard identification, including in exposure assessment quality, bias assessment, consideration of mechanistic evidence and key characteristics of carcinogens, and integration of evidence from different streams.

Results: Specific research gaps and needs will be outlined for each of the 20 new agents and overarching issues. Research recommendations arising from the upcoming workshop are anticipated to stimulate important new research initiatives in occupational and environmental cancer in the coming decade leading to resolving of classification uncertainties and supporting of updated classifications, as did the previous 2009 review where carcinogen classifications of nine agents have since advanced, and new cancer sites with either sufficient or limited evidence of carcinogenicity identified. 

Conclusions: Efforts to stimulate new research in occupational and environmental cancer are needed to address key evaluation uncertainties to ultimately support occupational and environmental cancer prevention.