Risk of lung cancer associated with quantitative beryllium exposure metrics within an occupational cohort

Our plain-English summary of Risk of lung cancer associated with quantitative beryllium exposure metrics within an occupational cohort, by M.K. Schubauer-Berigan, J.A. Deddens, J.R. Couch, et al (Occupational and Environmental Medicine, 2011).

The study

• Authors: M.K. Schubauer-Berigan, J.A. Deddens, J.R. Couch, M.R. Petersen
• Journal: Occupational and Environmental Medicine
• Published: 2011;68(5):354-60
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Beryllium has been identified as a human carcinogen on the basis of animal and epidemiological studies. The authors recently reported updated associations between lung cancer and beryllium exposure in a large, pooled occupational cohort. The authors conducted the present study to evaluate the shape of exposure-response associations between different exposure metrics and lung cancer in this cohort, considering potential confounders (race, plant, professional and short-term work status, and exposure to other lung carcinogens).

Methods: The authors conducted Cox proportional hazards regression analyses of lung cancer risk with cumulative, mean and maximum 'daily weighted average' (DWA) exposure among 5436 workers, using age-based risk sets. Different exposure-response curves were fitted to the exposure metrics, including categorical, power, restricted cubic spline and piecewise log-linear fits.

Results: The authors found significant positive associations between lung cancer and mean (p < 0.0001) and maximum (p < 0.0001) exposure, adjusting for age, birth cohort and plant, and for cumulative (p = 0.0017) beryllium exposure, adjusting for these factors plus short-term work status and exposure to asbestos. The best-fitting models were generally categorical or piecewise log-linear, with the steepest increase in lung cancer risk between 0 and 10 μg/m(3) for both mean and maximum DWA exposure and between 0 and 200 μg/m(3)-days for cumulative DWA exposure. The estimated mean DWA beryllium exposure associated with 10(-3) excess lifetime risk based on the piecewise log-linear model is 0.033 μg/m(3).

Conclusion: This study provides evidence that lung cancer risk is elevated at levels near the current US Occupational Safety and Health Administration beryllium exposure limit of 2.0 μg/m(3) DWA for workers.

In plain English

The authors studied lung cancer deaths among 5436 men who worked at three US beryllium-processing plants (Reading and Hazleton, Pennsylvania; Elmore, Ohio) before 1970, followed to 2005; 293 died of lung cancer. Each worker's beryllium exposure was estimated from plant air measurements and job records. Possible exposure to other lung carcinogens, including asbestos, was judged; 100 of the cases (34%) had potential asbestos exposure. Compared with average exposure under 0.6 micrograms per cubic metre, the hazard ratio was 2.29 (95% CI 1.29 to 4.30) at 0.6 to under 2.0 and 5.68 (2.66 to 12.4) at 8 to under 12. When professionals and asbestos-exposed workers were left out, the ratio for 0.6 to under 2.0 was 1.30 (0.59 to 3.11). The authors concluded that lung cancer risk was statistically significantly raised at 4 micrograms per cubic metre, near the US OSHA limit of 2. From one model excluding professionals and asbestos-exposed workers, they estimated that average exposure of about 0.033 micrograms per cubic metre carries a one-in-one-thousand excess lifetime risk of lung cancer death; models including all workers gave 0.0050 to 0.070.

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 occupational cohort study of lung cancer mortality, analysed with Cox proportional hazards regression using age-based risk sets
• Who was studied: 5436 male workers employed for at least 2 days before 1970 at three US beryllium-processing plants in Elmore, Ohio, and Hazleton and Reading, Pennsylvania. Vital status was followed to 31 December 2005.
• Exposure: Beryllium, measured as 'daily weighted average' (DWA) exposure and expressed as cumulative, mean and maximum exposure. Industrial hygienists judged potential exposure to other lung carcinogens (acid mist, asbestos, cadmium, chromium, nickel and silica), which was treated as a possible confounder.
• Main results:
  • The cohort included 293 lung cancer cases and 5143 non-cases; 74% of the cases occurred among Reading plant workers.
  • 100 of the 293 lung cancer cases (34%) had potential asbestos exposure.
  • Best-fitting categorical model, all workers, compared with mean exposure under 0.6 micrograms per cubic metre: at 0.6 to under 2.0 the hazard ratio was 2.29 (95% CI 1.29 to 4.30), based on 53 cases.
  • Same model, all workers: at mean exposure of 8 to under 12 micrograms per cubic metre the hazard ratio was 5.68 (95% CI 2.66 to 12.4), based on 19 cases.
  • Excluding asbestos-exposed workers and professionals: at mean exposure of 0.6 to under 2.0 micrograms per cubic metre the hazard ratio was 1.30 (95% CI 0.59 to 3.11), based on 20 cases.
  • In the initial categorical model for mean exposure, compared with under 2 micrograms per cubic metre, the hazard ratio at 2 to under 8 was 1.53 (95% CI 1.01 to 2.29).
  • For cumulative exposure, adjusted for age, birth cohort, short-term work status, plant and asbestos exposure, the power model coefficient was 0.094 (p = 0.0017).
  • In the categorical model for cumulative exposure, the hazard ratios were 1.11 (0.794 to 1.57) for 560 to under 2600 microgram-per-cubic-metre-days and 1.14 (0.789 to 1.64) for 2600 to under 10000, compared with under 560.
  • Exposures to the other lung carcinogens, with the possible exception of asbestos, had little impact on the beryllium risk estimates.
  • In models including all workers, the estimated hazard ratio at a mean exposure of 0.5 micrograms per cubic metre (the NIOSH recommended exposure limit) ranged from 1.11 (categorical model) to 1.68 (piecewise log-linear model).
  • Estimated lifetime excess absolute risk of lung cancer death at 0.5 micrograms per cubic metre ranged from 0.0061 to 0.049 across the models. The background lifetime risk for males was 0.0664.
  • In models including all workers, the mean exposure associated with a one-in-one-thousand lifetime excess risk of lung cancer death ranged from 0.0050 micrograms per cubic metre (power model) to 0.070 micrograms per cubic metre (categorical model).
  • Among workers excluding professionals and those potentially exposed to asbestos, the best-fitting piecewise log-linear model gave a mean exposure of 0.033 micrograms per cubic metre for a one-in-one-thousand lifetime excess risk.
• The authors' conclusion: The authors concluded that lung cancer risk is statistically significantly elevated at 4 micrograms per cubic metre DWA, very near the current US OSHA limit of 2 micrograms per cubic metre DWA. They estimated that a mean exposure of approximately 0.033 micrograms per cubic metre corresponds to a one-in-one-thousand excess lifetime risk of lung cancer death. This figure comes from the best-fitting piecewise log-linear model excluding professionals and asbestos-exposed workers.
• Limitations the authors state:
  • Smoking information was available only for a subset of the cohort, those employed in 1968.
  • The authors had no information on weekly or monthly variation in exposure.
  • The exposure estimates did not assume that respirators gave protection. This may have overestimated exposure, especially for more highly exposed workers.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer.

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