Mortality Among Hardmetal Production Workers: US Cohort and Nested Case-Control Studies

Research Recommendations for Selected IARC-Classified Agents: Impact and Lessons Learned

BACKGROUND

The International Agency for Research on Cancer (IARC) Monographs program assembles expert working groups who publish a critical review and evaluation of data on agents of interest. These comprehensive reviews provide a unique opportunity to identify research needs to address classification uncertainties. A multidisciplinary expert review and workshop held in 2009 identified research gaps and needs for 20 priority occupational chemicals, metals, dusts, and physical agents, with the goal of stimulating advances in epidemiological studies of cancer and carcinogen mechanisms. Overarching issues were also described.

OBJECTIVES

In this commentary we review the current status of the evidence for the 20 priority agents identified in 2009. We examine whether identified Research Recommendations for each agent were addressed and their potential impact on resolving classification uncertainties.

METHODS

We reviewed the IARC classifications of each of the 20 priority agents and identified major new epidemiological and human mechanistic studies published since the last evaluation. Information sources were either the published Monograph for agents that have been reevaluated or, for agents not yet reevaluated, Advisory Group reports and literature searches. Findings are described in view of recent methodological developments in Monographs evidence evaluation processes.

DISCUSSION

The majority of the 20 priority agents were reevaluated by IARC since 2009. The overall carcinogen classifications of 9 agents advanced, and new cancer sites with either "sufficient" or "limited" evidence of carcinogenicity were also identified for 9 agents. Examination of published findings revealed whether evidence gaps and Research Recommendations have been addressed and highlighted remaining uncertainties. During the past decade, new research addressed a range of the 2009 recommendations and supported updated classifications for priority agents. This supports future efforts to systematically apply findings of Monograph reviews to identify research gaps and priorities relevant to evaluation criteria established in the updated IARC Monograph Preamble. https://doi.org/10.1289/EHP12547.

Site-specific cancer risk following cobalt exposure via orthopedic implants or in occupational settings: A systematic review and meta-analysis

In 2020, the European Commission up-classified metal cobalt as Class 1B Carcinogen (presumed to have carcinogenic potential) based primarily on data from rodent inhalation carcinogenicity studies. This up-classification requires an assessment under the Medical Device Regulations of cobalt cancer risk from medical devices. We performed a systematic review and meta-analysis to evaluate site-specific cancer risks with cobalt exposure from either total joint replacement (TJR) or occupational exposure (OC). Results were stratified by exposure type (OC or TJR), exposure level (metal-on-metal (MoM) or non-MoM), follow-up duration (latency period: <5, 5-10 or >10 years), and cancer incidence or mortality (detection bias assessment). From 30 studies (653,104 subjects, average 14.5 years follow-up), the association between TJR/OC and cancer risk was null for 22 of 27 cancer sites, negative for 3 sites, and positive for prostate cancer and myeloma. Significant heterogeneity and large estimate ranges were observed for many cancer sites. No significant increase in estimates was observed by exposure level or follow-up duration. The current evidence, including weak associations, heterogeneity across studies and no increased association with exposure level or follow-up duration, is insufficient to conclude that there exists an increased risk for people exposed to cobalt in TJR/OC of developing site-specific cancers.

Concise Review of Nickel Human Health Toxicology and Ecotoxicology

Nickel (Ni) metal and Ni compounds are widely used in applications like stainless steel, alloys, and batteries. Nickel is a naturally occurring element in water, soil, air, and living organisms, and is essential to microorganisms and plants. Thus, human and environmental nickel exposures are ubiquitous. Production and use of nickel and its compounds can, however, result in additional exposures to humans and the environment. Notable human health toxicity effects identified from human and/or animal studies include respiratory cancer, non-cancer toxicity effects following inhalation, dermatitis, and reproductive effects. These effects have thresholds, with indirect genotoxic and epigenetic events underlying the threshold mode of action for nickel carcinogenicity. Differences in human toxicity potencies/potentials of different nickel chemical forms are correlated with the bioavailability of the Ni2+ ion at target sites. Likewise, Ni2+ has been demonstrated to be the toxic chemical species in the environment, and models have been developed that account for the influence of abiotic factors on the bioavailability and toxicity of Ni2+ in different habitats. Emerging issues regarding the toxicity of nickel nanoforms and metal mixtures are briefly discussed. This review is unique in its covering of both human and environmental nickel toxicity data.

Mortality among United States aerospace materials manufacturing workers

OBJECTIVES

To evaluate long-term mortality rates among aerospace material manufacturing workers as follow-up to an earlier observed excess of nephritis/nephrosis.

METHODS

Subjects were 2020 workers ever employed in the facility during 1963-2014. Vital status through 2014 was determined for all subjects and cause of death for 99.2% of 492 deaths. We computed standard mortality ratios (SMR) and internal relative risks.

RESULTS

SMRs for nephritis/nephrosis were unremarkable. We observed statistically significant elevated SMRs for kidney cancer among all workers and for the category "other lymphatic hematopoietic tissue cancer" (4/5 deaths from multiple myeloma) among long-term workers with potential plant exposure.

CONCLUSIONS

We found no evidence of elevated mortality rates for nephritis/nephrosis. Study limitations precluded robust evaluation of whether the elevated rates for kidney cancer and other lymphatic hematopoietic tissue cancer were related to occupational factors at the study site. Our findings for these two cancers warrant continued mortality follow-up.

Mortality Among Hardmetal Production Workers: Pooled Analysis of Cohort Data From an International Investigation

OBJECTIVES

Based on a pooled analysis of data from an international study, evaluate total and cause-specific mortality among hardmetal production workers with emphasis on lung cancer.

METHODS

Study members were 32,354 workers from three companies and 17 manufacturing sites in five countries. We computed standardized mortality ratios and evaluated exposure-response via relative risk regression analysis.

RESULTS

Among long-term workers, we observed overall deficits or slight excesses in deaths for total mortality, all cancers, and lung cancer and found no evidence of any exposure-response relationships for lung cancer.

CONCLUSIONS

We found no evidence that duration, average intensity, or cumulative exposure to tungsten, cobalt, or nickel, at levels experienced by the workers examined, increases lung cancer mortality risks. We also found no evidence that work in these facilities increased mortality risks from any other causes of death.