Heavy metals, welding fumes, and other occupational exposures, and the risk of kidney cancer: A population-based nested case-control study in three Nordic countries

Our plain-English summary of Heavy metals, welding fumes, and other occupational exposures, and the risk of kidney cancer: A population-based nested case-control study in three Nordic countries, by I.M. Michalek, J.I. Martinsen, E. Weiderpass, et al (Environmental Research, 2019).

The study

• Authors: I.M. Michalek, J.I. Martinsen, E. Weiderpass, J. Hansen, P. Sparen, L. Tryggvadottir, E. Pukkala
• Journal: Environmental Research
• Published: 2019;173:117-123
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To determine whether occupational exposure to heavy metals (chromium (VI), iron, nickel, lead) and welding fumes is associated with the risk of kidney cancer and to describe whether other occupational exposures included in the Job Exposure Matrix of the Nordic Occupational Cancer (NOCCA) study are associated with the risk.

Materials And Methods: Nested case-control study among individuals registered in population censuses in Finland, Iceland, and Sweden in 1960-1990. A total of 59,778 kidney cancer cases, and 298,890 controls matched on sex, age, and country. Cumulative occupational exposures to metals (chromium (VI), iron, nickel, lead), welding fumes, and 24 other occupational exposure covariates, lagged 0, 10, and 20 years.

Results: Overall, there was no or very little association between kidney cancer and exposures studied. The risk was elevated in individuals with high exposure to asbestos (OR 1.19, 95%CI 1.08-1.31). The risk was significantly decreased for individuals characterized with high perceived physical workload (OR 0.86, 95%CI 0.82-0.91), high exposure to ultraviolet radiation (OR 0.85, 95%CI 0.79-0.92), and high exposure to wood dust (OR 0.82, 95%CI 0.71-0.94). The risk of kidney cancer under the age of 59 was elevated in individuals with high exposure to nickel (OR 1.49, 95%CI 1.03-2.17). The risk of kidney cancer in age 59-74 years was elevated for individuals with high exposure to iron (OR 1.41, 95%CI 1.07-1.85), and high exposure to welding fumes (OR 1.43, 95%CI 1.09-1.89).

Conclusions: The only markedly elevated risks of kidney cancer were seen for the highest exposures of nickel and iron/welding fumes in specific age strata.

Copyright © 2019 Elsevier Inc. All rights reserved.

In plain English

This nested case-control study compared 59,778 people in Finland, Iceland and Sweden diagnosed with cancer of the kidney or renal pelvis with 298,890 controls matched on birth date, sex and country. Occupations reported in population censuses from 1960 to 1990 were turned into estimated cumulative exposures to 29 agents using a job-exposure matrix. The agents included asbestos, chromium (VI), iron, nickel, lead and welding fumes. Smoking was not measured. For none of the metals or welding fumes was the dose-response trend statistically significant. In the highest asbestos exposure group, the odds ratio for kidney cancer was 1.19 (95% CI 1.08–1.31). The lower asbestos groups showed no clear increase. In people diagnosed under age 59, high nickel exposure had an odds ratio of 1.49 (1.03–2.17). In those aged 59–74, high iron exposure had 1.41 (1.07–1.85) and high welding fume exposure 1.43 (1.09–1.89). Lower odds were seen with high physical workload, ultraviolet radiation and wood dust. The authors described a positive association between asbestos exposure and kidney cancer.

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: Population-based nested case-control study within the Nordic Occupational Cancer Study (NOCCA) cohort, analysed with conditional logistic regression
• Who was studied: 59,778 people diagnosed with cancer of the kidney or renal pelvis (Sweden 1961-2005, Finland 1971-2005, Iceland 1982-2004) and 298,890 controls matched on birth date, sex and country. 58.3% were male. Mean age at diagnosis was 66.
• Exposure: Cumulative occupational exposures estimated from census-reported occupations with the NOCCA Job Exposure Matrix. The 29 agents included asbestos (in f/cm3-years; fiber type not specified), chromium (VI), iron, nickel, lead and welding fumes. Results were presented for a 10-year lag.
• Main results:
  • All cases and controls, highest asbestos exposure category (above 1628.47 f/cm3-years; 953 cases, 4448 controls): OR 1.19, 95% CI 1.08–1.31.
  • Lower asbestos categories: OR 0.97 (0.93–1.01) for low exposure and OR 1.04 (0.98–1.10) for moderate exposure. The p-value for trend for asbestos was 0.36.
  • Across both sexes and all ages, the dose-response trend was not statistically significant for any of the heavy metals or for welding fumes.
  • People diagnosed under age 59, high nickel exposure: OR 1.49, 95% CI 1.03–2.17.
  • People aged 59–74 at the index date: high iron exposure OR 1.41 (1.07–1.85), moderate welding fume exposure OR 1.27 (1.02–1.56), and high welding fume exposure OR 1.43 (1.09–1.89).
  • All cases and controls: lower odds with high perceived physical workload (OR 0.86, 0.82–0.91), high ultraviolet radiation (OR 0.85, 0.79–0.92), high wood dust (OR 0.82, 0.71–0.94) and high aliphatic and alicyclic hydrocarbon solvents (OR 0.81, 0.69–0.95). The trend test for ultraviolet radiation was p less than 0.001.
  • The authors interpreted the asbestos finding as a positive association between asbestos exposure and kidney cancer.
• The authors' conclusion: The authors concluded that there was no association between chromium (VI) or lead exposure and kidney cancer. They reported elevated risk for high nickel exposure under age 59, and for high iron and for moderate and high welding fume exposure at ages 59–74. They noted that concurrent exposure to iron and welding fumes hinders interpreting their separate roles.
• Limitations the authors state:
  • No data on tobacco smoking.
  • Hereditary tumors such as von Hippel-Lindau syndrome were not taken into account.
  • Work history came only from censuses. The authors assumed no job changes between age 20 and the first census occupation, or between the last census occupation and age 65.
  • Industry codes were not available for all countries, so exposure estimates could not distinguish types of welding work.
  • Cadmium could not be studied because it is not in the job-exposure matrix.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Welders.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, nested case-control study.

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