Identifying occupational carcinogens: an update from the IARC Monographs

Abstract

The recognition of occupational carcinogens is important for primary prevention, compensation and surveillance of exposed workers, as well as identifying causes of cancer in the general population. This study updates previously published lists of known occupational carcinogens while providing additional information on cancer type, exposure scenarios and routes, and discussing trends in the identification of carcinogens over time. Data were extracted from International Agency for Research on Cancer (IARC) Monographs covering the years 1971–2017, using specific criteria to ensure occupational relevance and provide high confidence in the causality of observed exposure-disease associations. Selected agents were substances, mixtures or types of radiation classified in IARC Group 1 with ‘sufficient evidence of carcinogenicity’ in humans from studies of exposed workers and evidence of occupational exposure documented in the pertinent monograph. The number of known occupational carcinogens has increased over time: 47 agents were identified as known occupational carcinogens in 2017 compared with 28 in 2004. These estimates are conservative and likely underestimate the number of carcinogenic agents present in workplaces. Exposure to these agents causes a wide range of cancers; cancers of the lung and other respiratory sites, followed by skin, account for the largest proportion. The dominant routes of exposure are inhalation and dermal contact. Important progress has been made in identifying occupational carcinogens; nevertheless, there is an ongoing need for research on the causes of work-related cancer. Most workplace exposures have not been evaluated for their carcinogenic potential due to inadequate epidemiologic evidence and a paucity of quantitative exposure data.

Are we doing enough to identify and prioritise occupational carcinogens?

“…Siemiatycki et al 5 indicated that 16 more had been identified by 2004,5 and an additional 24 have been added since 2004 1. This pattern documents the success of epidemiological investigations in identifying cancer hazards in the workplace and may even indicate a quickening of the pace of discovery 1.…”

“…Loomis et al 1 use carcinogenicity evaluations completed by the International Agency for Research on Cancer (IARC) to characterise occupational exposures by tumour type, exposure scenarios and changing patterns of identification over time. Using the IARC classifications of occupational cancers, Marant Micallef et al 2 reviewed the literature to assemble the best-available relative risk estimates for each carcinogen–cancer site pair.…”

“…Siemiatycki et al 5 indicated that 16 more had been identified by 2004,5 and an additional 24 have been added since 2004 1. This pattern documents the success of epidemiological investigations in identifying cancer hazards in the workplace and may even indicate a quickening of the pace of discovery 1. The paper by Marant Micallef et al 2 illustrates that many of these occupational carcinogens have been sufficiently well studied to allow the IARC hazard identification process (by which an agent is deemed to be carcinogenic) to be translated into risk assessment (whereby the amount of risk associated with a carcinogen is defined).…”

“…The Loomis et al 1 tabulations underscore the widespread impact of workplace carcinogens. Twenty-three different types of cancer have been associated with workplace exposures.…”

“…Loomis et al 1 express the concern that funding for occupational research may have slowed in some countries and that this would diminish future progress. There is already evidence of such a curtailment on occupational cancer research efforts.…”