Study of two cohorts of workers exposed to methyl methacrylate in acrylic sheet production

Abstract

Objectives-To study mortality among 4324 workers at two United Kingdom factories, Darwen, Lancashire and Wilton, Cleveland, producing polymethyl methacrylate (PMMA) sheet. The Darwen factory is still active, but the Wilton one was closed in 1970. Also, to investigate patterns of mortality after exposure to methyl methacrylate; in particular, mortality from colon and rectal cancer. Results-In the Darwen cohort, 622 deaths were identified and a further 700 deaths in the Wilton cohort. Mortalities for the cohort were compared with national and local rates and expressed as standardised mortality ratios (SMRs). In the subcohort of Darwen workers with more than minimal exposure to MMA, reduced mortalities compared with national and local rates, were found for all causes (SMR 94), and colorectal cancer (SMR 92), but mortality from all cancers was slightly increased (SMR 104). No relations were found with cumulative exposure to MMA. In the subcohort of Wilton workers, mortality from all causes of death was significantly reduced (SMR 89), but mortality from all cancers (SMR 103) and colorectal cancer (SMR 124) were increased. The excess of colorectal cancer was confined to employees with less than 1 year of employment. Conclusion-The study provided no clear evidence that employment at the factories or exposure to MMA had adversely affected the mortalities of workers. (Occup Environ Med 2000;57:810-817)

Critical review of the epidemiology literature on the potential cancer risks of methyl methacrylate

“…The highest occupational exposures to MMA occur during acrylic sheet manufacture and the two primary studies are retrospective cohort studies of workers engaged in the manufacture of acrylic sheet at two US (Walker et al 1991) and two UK facilities (Tomenson et al 2000). Both studies incorporated a comprehensive assessment of cumulative exposure to MMA and the cohorts include a high proportion of workers who experienced high levels of exposure during the earliest days of acrylic sheet production.…”

“…It concluded that there is evidence suggesting the lack of carcinogenicity of MMA in experimental animals but inadequate evidence in humans. New epidemiological information has recently become available following the publication of a cohort study of workers at two UK plants involved in the manufacture of poly methyl methacrylate (PMMA) sheet (Tomenson et al 2000). This study is of particular interest because it includes workers at one plant who were employed during the war years when exposure conditions would have been similar to those at the Bristol and Knoxville plants, although EA was never an ingredient of the acrylic sheet produced at the UK plants.…”

“…The studies of Walker et al (1991), Tomenson et al (2000) and an unpublished study by Lucas (1995) include the majority of workers who will have experienced high and well-documented exposure to MMA. Hence, it is very unlikely that any new cohorts of workers with significant exposure to MMA will be assembled and it is considered an appropriate time to collect together all the epidemiological literature relating to MMA and synthesise the evidence for an association between MMA exposure and cancer endpoints.…”

Proportionate Cancer Mortality in Methyl Methacrylate-Exposed Orthopedic Surgeons Compared to General Surgeons

“…All other studies have been retrospective, descriptive, observational studies; standardized mortality rate (SMR) studies comparing observed to expected death rates; or meta-analyses, which have simply lumped prior studies for analysis, including ones by the same authors (Table 5) [4][5][6][7][8]. The design of this study permitted the exact confirmation of professional lifetime occupations and underlying causes of death.…”

“…Most MMA carcinogenicity studies in humans have been combined retrospective cohort studies from the 1930s through the 1990s, or meta-analyses of the same and similar studies [4][5][6][7][8][9][10]. In addition, most of the negative cancer studies were authored by epidemiologists employed by major chemical manufacturers of MMA in the USA (American Cyanamid Company, Wayne, NJ; Rohm and Hass Co., Croydon, PA) and in the UK (Imperial Chemical Industries; Lucite International UK Ltd.) [6][7][8].…”