Evidence of carcinogenicity in humans of water-soluble nickel salts

Our plain-English summary of Evidence of carcinogenicity in humans of water-soluble nickel salts, by T.K. Grimsrud, A. Andersen (Journal of Occupational Medicine and Toxicology, 2010).

The study

• Authors: T.K. Grimsrud, A. Andersen
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2010;5:7
• Type of article: Editorial
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Increased risks of nasal cancer and lung cancer in nickel refiners have been investigated scientifically and discussed since they were detected in the 1930s. Nickel compounds are considered to be the main cause of the cancer excess. Parts of the nickel producing industry and their consultants oppose the classification of water-soluble nickel salts as human carcinogens, and argue that the risk in exposed workers should be ascribed to other occupational exposures and smoking.

Discussion: Respiratory cancer risks in Welsh, Finnish, and Norwegian nickel refiners add to the evidence of carcinogenicity of water-soluble nickel. In Norwegian refiners, the first epidemiological study in 1973 identified high risks of lung cancer and nasal cancer among long-term electrolysis workers. Risk analyses based on exposure estimates developed in the 1980s supported the view that water-soluble nickel compounds were central in the development of cancer. Recently, new exposure estimates were worked out for the same cohort based on personal monitoring of total nickel and chemical determination of four forms of nickel. Additional data have been collected on life-time smoking habits, and on exposure to arsenic, asbestos, sulphuric acid mists, cobalt, and occupational lung carcinogens outside the refinery. After adjustment for these potential confounding exposures in case-control analyses, the risk pattern added to the evidence of an important role of water-soluble nickel compounds as causes of lung cancer. These Norwegian cancer studies rely on national Cancer Registry data, considered close to complete from 1953 onwards; and on National Population Register data continuously updated with mortality and emigration. Canadian mortality studies--perceived to offer the strongest support to the industry position not to recognise carcinogenicity of water-soluble nickel--appear to suffer from limitations in follow-up time, loss to follow-up, absence of risk analysis with individual exposure estimates, no confounder control, and a likely underestimation of cancer mortality.

Conclusions: Rejection to recognise water-soluble nickel as a human carcinogen seems to contradict material epidemiological evidence that demonstrates a strong association between water-soluble nickel compounds and risks of lung cancer and nasal cancer. Independent international scientific bodies have classified nickel compounds as carcinogenic to humans, inclusive of water-soluble nickel.

In plain English

This article was a commentary, not a new study. The authors responded to a 2009 paper by Heller and colleagues, and to a review by Goodman and colleagues, which questioned whether water-soluble nickel salts cause respiratory cancer. The authors described earlier research, much of it on workers at a Norwegian nickel refinery. They reported that the first Norwegian study, in 1973, estimated lung cancer and nasal cancer risks in long-term electrolysis workers at 20 and 200 times the expected values. They described later Norwegian analyses that took account of smoking, arsenic and acid mists. In one of these, adjusting for smoking changed the risk estimate for water-soluble nickel by around 15 percent. They criticised Canadian mortality studies, noting that vital status had been unknown for 40 percent of those workers. The authors acknowledged that estimating past exposures may introduce errors. The authors concluded that the industry position not to recognise water-soluble nickel as a human carcinogen appears to contradict material epidemiological evidence. Asbestos was mentioned only once, as one of several other exposures on which data were collected.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Commentary discussing published epidemiological evidence, written in response to an industry-funded paper (Heller et al.) and review (Goodman et al.); no new data were analysed
• Who was studied: No new population was studied. The commentary discussed published studies of nickel refinery workers in Norway, Wales, Finland and Canada, focusing on the Norwegian refinery cohort followed through national cancer registry data.
• Exposure: Water-soluble nickel salts in nickel refining, especially in electrolysis departments, compared with insoluble nickel compounds in roasting and smelting departments
• Main results:
  • As described by the authors, the first Norwegian study (1973) estimated risks in long-term electrolysis workers at 20 times the expected value for lung cancer and 200 times for nasal cancer, compared with the general population
  • As described by the authors, in an earlier Norwegian case-control study, adjusting for smoking changed the risk estimate for water-soluble nickel by around 15 percent
  • As described by the authors, a pulmonary fibrosis study among the same Norwegian workers found a low correlation between cumulative exposure to water-soluble nickel and pack-years of smoking (correlation coefficient 0.17)
  • As described by the authors, 2005 Norwegian analyses adjusted for historical arsenic exposure and found no more than a minor contribution to lung cancer incidence
  • As described by the authors, adjustment for acid mists in the 2005 Norwegian analyses had a negligible effect on lung cancer risk
  • For the Norwegian cohort, data were collected on other exposures, including asbestos, as potential confounders; the article gives no asbestos-specific results
  • The authors criticised the Canadian nickel worker mortality studies because vital status was unknown for 40 percent of the workers when follow-up stopped
• The authors' conclusion: The authors concluded that the industry position not to recognise water-soluble nickel as a human carcinogen appears to contradict material epidemiological evidence
• Limitations the authors state:
  • The authors acknowledged that retrospective exposure assessment may introduce errors
  • The authors stated that the commentary was not a complete presentation of nickel carcinogenicity

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Occupational Exposure, Habit, Confounding, Cancer Registry, Carcinogenic.

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