PubMed · 5196242
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C H Brown. 1969. Chronic bronchitis.. https://pubmed.ncbi.nlm.nih.gov/5196242/
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In 1997, the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area set a new MAK value ("Maximale Arbeitsplatz-Konzentration") governing worker exposures to general airborne dust. The new values limit worker dust exposures to concentrations not exceeding 1.5 mg/m3 for respirable dust and 4 mg/m3 for inhalable dust, and are substantially lower than corresponding standards in other western industrialized nations. The purpose of this document is to critically review the science behind the MAK Commission's new threshold limit value standards. The Commission relied heavily upon a re-analysis of data from the Deutsche Forschungsgemeinschaft (DFG) Chronic Bronchitis study (1965-1977). We have reservations about the scientific merit of the DFG study and the validity of data used as the basis for establishing a new MAK value for dust. In particular: (1) Assessing the potential role of inert dust in the development of chronic bronchitis in worker cohorts with extremely high cigarette smoking prevalences is scientifically implausible. (2) It is unlikely that the dust in the industries studied, including steel works, foundries and cement works, was in fact "inert", and any effects of the dust on chronic bronchitis rates may have been increased by the presence of free crystalline silica and other toxic agents. (3) The study made use of area- rather than personal-exposure monitoring, thereby correlating the prevalence of chronic bronchitis with lower dust exposure levels than actually existed and significantly overstating the health effects of the dust exposures. (4) Inappropriate statistical methods were used to estimate threshold limit values. Results of three additional epidemiological studies are cited as providing evidence of chronic lung effects due to insoluble dust exposure. All three studies suffer from extremely poor documentation of the study methodology, particularly regarding lung function testing, and they provide little evidence that exposure to insoluble non-fibrogenic dusts leads to chronic lung obstruction. In summary, it is our opinion that the studies evaluated by the MAK Commission and the methods used do not provide the scientific basis to support the lower threshold limit values for dust. We recommend that an appropriate prospective morbidity study be conducted to address the concerns detailed in this critical examination.
To evaluate the mortality and causes of death in monoclonal gammopathy of undetermined significance (MGUS), we identified 1324 cases of MGUS in the period 1978-93 in North Jutland County, Denmark. Data on mortality were obtained by record linkage to the Danish Death Registry. There were 868 deaths in the MGUS cohort during 7785 years of follow-up vs. 409.6 expected, giving a standardized mortality ratio (SMR) of 2.1 (95% confidence interval 2.0-2.3). Malignant transformation was the cause of death in 97 patients vs. 4.9 expected, yielding a SMR of 20.0 (16.2-24.4), which explained about 20% of the excess mortality in the cohort. The mortality was increased for several other malignant and non-malignant causes of death during the first 4 years of follow-up. For late follow-up, 5-18 years after detection of the M-component, the overall SMR was 1.7 (1.5-1.9), and malignant transformation was the only cause of death with a substantial increase of SMR. Although malignant transformation is an important cause of death in MGUS patients, it did not entirely explain the increased mortality. MGUS patients often suffer from coexisting clinical conditions that increase the mortality, especially during the first years after detection of the M-component.