Pleural mesothelioma risk by industry and occupation: results from the Multicentre Italian Study on the Etiology of Mesothelioma (MISEM)

Our plain-English summary of Pleural mesothelioma risk by industry and occupation: results from the Multicentre Italian Study on the Etiology of Mesothelioma (MISEM), by E. Migliore, D. Consonni, S. Peters, et al (Environmental Health, 2022).

The study

• Authors: E. Migliore, D. Consonni, S. Peters, R.C.H. Vermeulen, H. Kromhout, A. Baldassarre, D. Cavone, E. Chellini, C. Magnani, C. Mensi, E. Merler, M. Musti, A. Marinaccio, D. Mirabelli
• Journal: Environmental Health
• Published: 2022;21(1):60
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The Italian mesothelioma registry (ReNaM) estimates mesothelioma incidence and addresses its etiology by assessing cases' exposures but cannot provide relative risk estimates.

Objectives: i) To estimate pleural mesothelioma relative risk by industry and occupation and by ReNaM categories of asbestos exposure; and ii) to provide quantitative estimates of the exposure-response relationship.

Methods: A population-based mesothelioma case-control study was conducted in 2012-2014 in five Italian regions. Cases and age and gender frequency-matched controls were interviewed using a standard ReNaM questionnaire. Experts coded work histories according to international standard classifications of industries/occupations and assigned asbestos exposure according to ReNaM categories. Job codes were further linked to SYN-JEM, a quantitative job-exposure matrix. Cumulative exposure (CE, f/mL-years) was computed by summing individual exposures over lifetime work history. Unconditional logistic regression analyses adjusted by gender, centre and age were fitted to calculate odds ratios (OR) and 95% confidence intervals (CI).

Results: Among men we observed increased risks of mesothelioma in many industries and associated occupations, including: asbestos-cement (OR = 3.43), manufacture of railroad equipment (OR = 8.07), shipbuilding and repairing (OR = 2.34), iron and steel mills (OR = 2.15), and construction (OR = 1.94). ORs by ReNaM exposure categories were as follows: definite/probable occupational exposure (OR = 15.8, men; OR = 8.80, women), possible occupational (OR = 2.82, men; OR = 3.70, women), sharing home with an exposed worker (OR = 2.55, men; OR = 10.3, women), residential (OR = 2.14, men; OR = 3.24, women). Based on SYN-JEM, mesothelioma risk increased by almost 30% per f/mL-year (OR = 1.28, CI 1.16-1.42).

Conclusions: Out study involved five regions with historically different types and levels of industrial development, encompassing one third of the Italian population and half of Italian mesothelioma cases. As expected, we found increased pleural mesothelioma risk in the asbestos industry and in trades with large consumption of asbestos materials. Clear associations were found using both qualitative (ReNaM classifications) and quantitative estimates (using SYN-JEM) of past asbestos exposure, with clear evidence of an exposure-response relationship.

© 2022. The Author(s).

In plain English

This population-based case-control study (MISEM) compared 626 people with pleural mesothelioma (463 men, 163 women) with 718 population controls in five Italian regions, October 2012 to March 2015. Experts classified asbestos exposure into registry (ReNaM) categories; a job-exposure matrix (SYN-JEM) estimated cumulative work exposure in fibres per millilitre-years. Among men, odds ratios (ORs) for ever versus never employment were raised in railroad equipment manufacture (8.07), shipbuilding and repairing (2.34), construction (1.94) and a group covering asbestos-cement, other asbestos products and non-asbestos industries (3.43). Their confidence intervals are in a figure and supplementary table missing here. Against unlikely or unknown exposure, definite or probable work exposure gave ORs of 15.8 (95% CI 10.5–23.8) in men and 8.80 (3.66–21.2) in women. Sharing a home with an exposed worker gave 2.55 (1.15–5.62) in men and 10.3 (4.10–26.1) in women. The OR per f/mL-year was 1.28 (1.16–1.42). The authors concluded that risk was raised in the asbestos industry and heavy asbestos-using trades, with an exposure-response relationship. They noted unblinded interviews in two regions, more proxy respondents among cases and lower control response.

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 case-control study, analysed with unconditional logistic regression (odds ratios with 95% confidence intervals)
• Who was studied: Cases were 626 people with histologically confirmed pleural mesothelioma: 463 men and 163 women. Controls were 718 people (490 men, 228 women), drawn at random from regional National Health Service rosters and frequency matched on age and gender. The study covered five Italian regional centres: Piedmont (Turin province and Casale Monferrato district only), Lombardy, Veneto (Venice and Padua provinces only), Tuscany and Apulia. The study period ran from October 2012 to March 2015. Direct interviews were obtained for 450 of 626 cases (71.8%) and 671 of 718 controls (93.5%); for the rest, relatives were interviewed.
• Exposure: Lifetime occupational and non-occupational asbestos exposure, collected by the standard ReNaM questionnaire. Local experts classified exposure into these categories: definite, probable or possible occupational; familial (living with an occupationally exposed person); residential (near asbestos sources); other non-occupational; and unlikely or unknown. Jobs were also linked to SYN-JEM, which gave cumulative occupational exposure in f/mL-years using Southern-Western European estimates. Fiber types (e.g. chrysotile, crocidolite) were not specified.
• Main results:
  • Among men, the article's abstract reports these ORs for ever versus never employment: asbestos-cement 3.43 and manufacture of railroad equipment 8.07. Confidence intervals for these are shown in Figure 1 and Supplementary Table S2, which are not in the supplied text. The body of the article describes the asbestos group as ISIC code 3699, a broader 'non-metallic mineral products' group that also includes non-asbestos industries, with a more than three-fold risk in men.
  • Among men, the abstract also reports ORs of 2.34 for shipbuilding and repairing, 2.15 for iron and steel mills and 1.94 for construction. Construction was the largest exposure group among men, with 119 exposed cases.
  • Among men, employment in water transport gave an OR of 3.31 (CI 1.12–9.84).
  • Among women, charworkers, cleaners and related workers was the job code with the largest mesothelioma risk. Most of the relevant employment periods were in cleaning services, often described as industrial cleaning.
  • By ReNaM category, compared with unlikely or unknown exposure (10-year lag):
• Definite or probable occupational exposure: OR 15.8 (CI 10.5–23.8) in men (306 cases, 96 controls); OR 8.80 (CI 3.66–21.2) in women.
• Possible occupational exposure: OR 2.82 (CI 1.68–4.72) in men; OR 3.70 (CI 1.34–10.3) in women.
  • For familial exposure (sharing a home with an exposed worker), the OR was 2.55 (CI 1.15–5.62) in men and 10.3 (CI 4.10–26.1) in women. For residential exposure, the OR was 2.14 (CI 1.07–4.28) in men and 3.24 (CI 1.33–7.86) in women. In women, familial exposure had the highest OR, although the authors noted wide, overlapping confidence intervals.
  • For 'other non-occupational' exposure, the OR was 4.67 (CI 1.49–14.6) in men. In women the OR was 2.16 (CI 0.64–7.29); this interval includes 1, so the result was not statistically significant.
  • Using SYN-JEM, men and women combined who had ever been exposed had about double the odds of pleural mesothelioma compared with the unexposed. The unlagged OR was 2.22 (CI 1.70–2.91), based on 333 exposed cases and 262 exposed controls.
  • At a 20-year lag, men and women combined showed rising ORs by tertile of cumulative exposure:
• below 0.34 f/mL-y: 1.45 (CI 0.96–2.21)
• 0.34 to 1.62 f/mL-y: 2.59 (CI 1.80–3.73)
• above 1.62 f/mL-y: 2.69 (CI 1.88–3.83)
  The trend test gave p less than 0.001.
  • Treated as a continuous measure, each 1 f/mL-year of cumulative exposure gave an OR of 1.28 (CI 1.16–1.42) in men and women combined.
  • Spline modelling showed the OR rising steeply up to about 1 f/mL-year and more slowly after that. The authors described the relationship as sub-linear.
  • When the analysis was restricted to blue-collar workers, ORs by cumulative exposure were reduced, but a positive trend with increasing exposure remained.
• The authors' conclusion: The authors concluded that pleural mesothelioma risk was increased in the asbestos industry and in trades with large consumption of asbestos materials. They found clear associations using both the ReNaM expert classifications and the SYN-JEM quantitative estimates, with evidence of an exposure-response relationship in which risk was sub-linearly proportional to cumulative exposure. They also reported increased risk from familial, residential and other non-occupational exposures.
• Limitations the authors state:
  • The ISIC group used for asbestos manufacturing also includes non-asbestos industries. The authors say this lack of specificity most likely underestimated the true risk for asbestos workers.
  • By the time of recruitment, many former Italian asbestos workers had already died. This left few exposed subjects, giving a wide confidence interval for men and no exposed controls among women in that group.
  • Assigning individual exposure levels from a job-exposure matrix introduces random error. The authors note this can distort the shape of the exposure-response curve.
  • Quantitative exposure estimates were available only for occupational exposures. Models were adjusted for non-occupational exposures.
  • In Lombardy and Tuscany, interviewers were not blinded to whether a person was a case or a control.
  • Cases more often had proxy respondents (relatives), who are expected to give less detailed descriptions. The authors adjusted for this.
  • Controls had a lower response rate. Because response depends on education and socio-economic status, this may have biased the findings; blue-collar status was used as a proxy to address it.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Etiology, Mesothelioma, Relative Risk, Asbestos Exposure, Case-Control Study, Cumulative Exposure, Work History.

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• Mesothelioma Risk among Construction Workers According to Job Title: Data from the Italian Mesothelioma Register — L. Vimercati, D. Cavone, et al. (2023)
• Pleural mesothelioma risk in the construction industry: a case-control study in Italy, 2000-2018 — S. Stella, D. Consonni, et al. (2023)
• Mesothelioma Risk Among Maritime Workers According to Job Title: Data From the Italian Mesothelioma Register (ReNaM) — L. Vimercati, D. Cavone, et al. (2023)
• Malignant mesothelioma due to non-occupational asbestos exposure from the Italian national surveillance system (ReNaM): epidemiology and public health issues — A. Marinaccio, A. Binazzi, et al. (2015)

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