Cancer morbidity and quartz exposure in Swedish iron foundries

Our plain-English summary of Cancer morbidity and quartz exposure in Swedish iron foundries, by H. Westberg, L. Andersson, I.L. Bryngelsson, et al (International Archives of Occupational and Environmental Health, 2013).

The study

• Authors: H. Westberg, L. Andersson, I.L. Bryngelsson, Y. Ngo, C.G. Ohlson
• Journal: International Archives of Occupational and Environmental Health
• Published: 2013;86(5):499-507
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: The aim of this study was to determine cancer morbidity amongst Swedish iron foundry workers with special reference to quartz exposure. In addition to respirable dust and quartz, phenol, formaldehyde, furfuryl alcohols, polycyclic aromatic hydrocarbons (PAHs), carbon black, isocyanates and asbestos are used or generated by foundry production techniques and exposure to any of these substances could have potentially carcinogenic effects.

Methods: Cancer morbidity between 1958 and 2004 was evaluated in a cohort of 3,045 male foundry workers employed for >1 year between 1913 and 2005. Standardised incidence ratios (SIRs) with 95 % confidence intervals (95 % CI) were determined by comparing observed numbers of incident cancers with frequencies in the Swedish cancer register. Exposure measures were assessed using information from the personal files of employees and modelling quartz measurement based on a database of 1,667 quartz measurements. Dose responses for lung cancer were determined for duration of employment and cumulative quartz exposure for latency periods >20 years.

Results: Overall cancer morbidity was not increased amongst the foundry workers (SIR 1.00; 95 % CI, 0.90-1.11), but the incidence of lung cancer was significantly elevated (SIR 1.61; 95 % CI, 1.20-2.12). A non-significant negative dose response was determined using external comparison with a latency period of >20 years (SIR 2.05, 1.72 1.26 for the low, medium and high exposure groups), supported by internal comparison data (hazard ratios 1, 1.01, 0.78) for the corresponding groups. For cancers at sites with at least five observed cases and a SIR > 1.25, non-significant risks with SIRs > 1.5 were determined for cancers of the liver, larynx, testis, connective muscle tissue, multiple myeloma plasmacytoma and lymphatic leukaemia.

Conclusions: A significant overall risk of lung cancer was determined, but using external and internal comparison groups could not confirm any dose response at our cumulative quartz dose levels.

In plain English

This retrospective cohort study compared cancer incidence from 1958 to 2004 among 3,045 men employed over one year at ten Swedish iron foundries with general Swedish population rates. The authors estimated workers' cumulative respirable quartz exposure from 1,667 measurements; asbestos and other foundry agents were not estimated. Overall cancer incidence was as expected (347 cases; SIR 1.00, 95% CI 0.90 to 1.11), but bronchus and lung cancer was significantly elevated (52 cases; SIR 1.61, 1.20 to 2.12). More than 20 years after first exposure, lung cancer SIRs were 2.05 (95% CI 1.32 to 3.02), 1.72 (1.00 to 2.75) and 1.26 (0.26 to 3.69; three cases) in the low, medium and high quartz groups. Internal comparison gave hazard ratios of 1.01 (0.55 to 1.84) for medium and 0.78 (0.24 to 2.57) for high versus low exposure, showing no clear dose response. One malignant pleural mesothelioma occurred (1.3 expected). Smoking was surveyed only in 500 randomly selected persons born before 1980 (60% responded). The authors concluded lung cancer risk was increased but could not confirm a dose response at their cumulative quartz dose levels.

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: Retrospective cohort study of cancer incidence. Observed cancers were compared with expected numbers from the general Swedish population (standardised incidence ratios). For lung cancer, the authors also ran an internal Cox regression comparison of quartz exposure groups.
• Who was studied: 3,045 male workers employed for more than 1 year at ten Swedish iron foundries, drawn from an initial 3,996 employees after women and others were excluded. Cancer follow-up ran from 1958 to 2004.
• Exposure: Cumulative exposure to respirable quartz, estimated for each worker from 1,667 air measurements and grouped as less than 1, 1 to 2, and more than 2 mg per cubic metre-years. Duration of employment was also used. The authors note that phenol, formaldehyde, furfuryl alcohols, PAHs, carbon black, isocyanates and asbestos are also used or generated in foundry production, but the exposure estimates were for quartz only.
• Main results:
  • Overall cancer incidence in the cohort was close to expected: 347 observed cases, SIR 1.00 (95% CI 0.90 to 1.11).
  • Bronchus and lung cancer was significantly elevated in the cohort: 52 observed against 32.24 expected, SIR 1.61 (95% CI 1.20 to 2.12). For lung and pleura combined, the SIR was 1.58 (95% CI 1.18 to 2.06).
  • With a latency of more than 20 years, lung cancer SIRs by cumulative quartz exposure were 2.05 (95% CI 1.32 to 3.02; 25 cases) for less than 1 mg per cubic metre-years, 1.72 (95% CI 1.00 to 2.75; 17 cases) for 1 to 2, and 1.26 (95% CI 0.26 to 3.69; 3 cases) for more than 2. No clear dose-response relationship was noted.
  • In the internal comparison (Cox regression, with the low exposure group as reference), lung cancer hazard ratios were 1.01 (95% CI 0.55 to 1.84) for the medium group and 0.78 (95% CI 0.24 to 2.57) for the high group.
  • One case of malignant pleural mesothelioma was found in the cohort, compared with 1.3 cases expected from the general population.
  • No other cancer showed a significant excess. Non-significant SIRs above 1.5 were reported for liver 1.59 (95% CI 0.82 to 2.78), larynx 1.77 (0.65 to 3.85), testis 1.54 (0.56 to 3.35), connective tissue and muscle 1.94 (0.63 to 4.52), multiple myeloma plasmacytoma 1.58 (0.68 to 3.11) and lymphatic leukaemia 1.51 (0.61 to 3.11).
  • A smoking questionnaire was sent to 500 randomly selected persons born before 1980, and 60% responded. Among respondents, ex-smokers and smokers made up 68%, 65% and 84% of the low-, medium- and high-exposed groups.
• The authors' conclusion: The authors concluded that the results indicate an increased lung cancer risk for Swedish foundry workers exposed to quartz (overall SIR 1.61). However, neither the external nor the internal comparison could confirm a dose response at the cumulative quartz dose levels in this cohort.
• Limitations the authors state:
  • Individual smoking data were not available for the whole cohort. A questionnaire sent to 500 randomly selected persons born before 1980 was used only to illustrate smoking habits.
  • Other lung carcinogens in the foundry environment, in particular PAHs and asbestos, could be confounders in the analysis.
  • The authors suggested that the elevated bladder and larynx cancer SIRs may reflect differences in smoking habits between the foundry workers and the general population, or some other occupational exposure.
  • There were no exposure data on nitrosamines and aromatic amines, which the authors discuss as possible causes of bladder and liver cancer.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Standardized Incidence Ratio (SIR), confidence interval, Lung Cancer, Latency, Hazard Ratio, Myeloma.

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• Cancer incidence among mild steel and stainless steel welders and other metal workers — K.S. Hansen, J.M. Lauritsen, et al. (1996)
• Past asbestos exposure levels in foundries and cement-asbestos factories — S. Mattioli, D. Nini, et al. (2002)
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