Epidemiology of malignant mesothelioma--an outline.

In the 1960s and 1970s, well designed case-referent studies put beyond doubt that exposure to airborne asbestos fibres was a cause of malignant mesothelioma. Some 35 cohort mortality studies in a large variety of industries during the 20-year period, 1974-1994, showed a wide range of outcomes, but in general that the risk was higher in exposures which included amphiboles rather than chrysotile alone. Real progress began, however, with discoveries along several lines: the link between pleural changes and mineralogy, the concept and importance of biopersistence, the developments in counting and typing mineral fibres in lung tissue, and data on amphibole mining in South Africa and Australia for comparison with that on chrysotile in Canada and Italy. This led to the recognition of the potential contamination in North America of chrysotile with tremolite. A survey in Canada in 1980-1988 and other surveys demonstrated that crocidolite, amosite, and tremolite could explain almost all cases of mesothelioma. Effective confirmation of this was finally achieved with data on vermiculite miners in Libby, Montana, in the years 1983-1999, where exposure was to tremolite-actinolite and/or other amphibole fibres alone.

Incidence and suspected cause of work-related musculoskeletal disorders, United Kingdom, 1996-2001.

BACKGROUND: Musculoskeletal conditions are the most common self-reported work-related disease, with high costs incurred from long-term disability. In the United Kingdom, occupational physicians and rheumatologists have been reporting new cases of work-related musculoskeletal disorders to voluntary surveillance schemes since 1996. AIMS: To estimate population incidence rates for work-related musculoskeletal disorders reported by rheumatologists and occupational physicians by occupation and industry, in relation to tasks and movements suspected as causal. METHODS: Estimated average annual incidence rates were calculated for nine main job categories and eight industrial groups; Labour Force Survey figures were used as the denominator for rheumatologists, and a special survey for the occupational physicians. These were then related to tasks and movements reported as causal. RESULTS: Between October 1997 and the end of 2001, an estimated 2,599 new cases/year were reported by rheumatologists, and from January 1996, 5,278 cases/year by occupational physicians. Average annual rates overall were 94 per million for rheumatologists and 1,643 per million for occupational physicians (a 17-fold difference). Jobs at highest risk for the upper limb were primarily clerical, craft-related and machine work. Tasks associated with upper limb disorders and with neck and back problems were predominantly keyboard work and heavy lifting, and in craft-related occupations with gripping or holding tools. CONCLUSIONS: Jobs at risk and the associate tasks were identified which should assist prevention, but the extent to which these factors were causal or aggravating previous injury requires further study. The much higher rates reported by occupational physicians reflect, in part, the type of industries they served.

Reported incidence and precipitating factors of work-related stress and mental ill-health in the United Kingdom (1996-2001).

BACKGROUND: Work-related mental ill-health appears to be increasing. Population-based data on incidence are scarce but in the United Kingdom occupational physicians and psychiatrists report these conditions to voluntary surveillance schemes. AIMS: To estimate the incidence of work-related stress and mental illness reported 1996-2001 by occupational physicians and 1999-2001 by psychiatrists. METHODS: Estimated annual average incidence rates were calculated by sex, occupation and industry against appropriate populations at risk. An in-house coding scheme was used to classify and analyse data on precipitating events. RESULTS: An estimated annual average of 3,624 new cases were reported by psychiatrists, and 2,718 by occupational physicians; the rates were higher for men in reports based on the former and for women on the latter. Most diagnoses were of anxiety/depression or work-related stress, with post-traumatic stress accounting for approximately 10% of cases reported by psychiatrists. High rates of ill-health were seen among professional and associated workers and in those in personal and protective services. Factors (such as work overload) intrinsic to the job and issues with interpersonal relations were the most common causes overall. CONCLUSIONS: The steep increase in new cases of work-related mental ill-health reported by occupational physicians since 1996 may reflect a greater willingness by workers to seek help but may also signify an increasing dissonance between workers' expectations and the work environment. Greater expertise is needed to improve the workplace by adjustment of job demands, improvement of working relations, increasing workers' capacities and management of organizational change.

Mortality from lung and kidney disease in a cohort of North American industrial sand workers: an update.

BACKGROUND: A previously published cohort study of some 2670 employees of the North American sand industry, followed through 1994, provided strong evidence of a causal relationship between quartz exposure and death from both silicosis and lung cancer, after allowance for cigarette smoking and in the absence of known occupational carcinogens. Unexpectedly, a significant excess mortality from chronic non-malignant renal disease [observed 16; expected 7.6; standardized mortality ratio (SMR) 212] was also found, whereas deaths from renal cancer at this stage were close to expectation (observed 6; expected 5.2). OBJECTIVES: Our primary aim was to discover whether death from chronic renal disease was related to the estimated intensity of crystalline silica exposure. A further aim was to determine whether or not our previous estimates of lung cancer and silicosis risk were confirmed by mortality in the cohort 6 years later. METHODS: With help from the US National Death Index, surviving members of the cohort, with the exception of employees of a small plant in Canada, were traced through 2000. The cause of death was determined for all who had died, for comparison against National and State mortality rates. Nested case-referent analyses were then undertaken, as previously, of deaths from lung cancer and silicosis, plus end-stage renal disease and kidney cancer, in relation to quantitative re-estimates of quartz exposure. RESULTS: The total number of deaths through 1994 was 990; there were 231 additional deaths during the period 1995-2000. The SMRs were significantly higher in the later than the earlier period, mainly due to a relative increase in heart disease and external causes. The updated odds ratios for lung cancer and silicosis were almost identical to those published previously, with lung cancer risk again related to average silica concentration and cumulative exposure, but not to length of employment. In contrast, risks of neither end-stage renal disease nor renal cancer were related to cumulative exposure, although now based on 19 cases (SMR 239), and 10 cases (SMR 202), respectively, in fact, opposite trends were apparent for both diseases. However, because of the small numbers there was only limited power to assess the statistical significance of these trends or of any separate relationship with the duration or intensity of exposure. CONCLUSIONS: Our findings support a causal relationship between lung cancer and quartz exposure after allowance for cigarette smoking, in the absence of other known carcinogens, but failed to find similar evidence to explain the excess mortality from either chronic renal disease or kidney cancer.

Reliability assessment of a coding scheme for the physical risk factors of work-related musculoskeletal disorders.

OBJECTIVES: This study assessed the reliability of a novel coding scheme for physical risk factors for musculoskeletal disorders reported to an occupational surveillance scheme. METHODS: Since 1997 new cases of musculoskeletal disease have been reported as part of a surveillance scheme by over 300 consultant rheumatologists in the United Kingdom; the rheumatologists also gave a short description of the tasks and activities they considered to be causal. With the use of a summary of the activities described, a coding scheme was developed comprising 16 categories of task codes and another 16 categories of movement codes. Four reviewers coded the work activities independently for 576 cases. The fourth rater coded the cases twice. With the use of a single summary kappa statistic and the matrix of kappa coefficients, both interrater reliability and intrarater reliability were assessed. RESULTS: The overall interrater agreement on the task codes was good (kappa = 0.73), with the best agreement for keyboard work (kappa = 0.96) and the worst for assembly work (kappa = 0.40, kappa = 0.37). The interrater agreement on movement codes was also good (kappa = 0.79), with the best agreement for kneeling (kappa = 0.94) and the worst for materials handling (kappa = 0.10). The intrarater agreement was somewhat better than the interrater agreement with both codes. CONCLUSIONS: The results suggest that the coding scheme was, on the whole, reliable for classifying the physical risk factors reported as causal.