Dustiness of different high-temperature insulation wools and refractory ceramic fibres.
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Recent regulations are encouraging the replacement of older types of man-made mineral fibre by more soluble and, thus, less biopersistent compositions. In order for there to be any health benefits from this policy and to gain maximum benefit from such substitutions, the use of the new materials should not increase exposure. The work reported here was undertaken to investigate the use of new high-temperature glass insulation wools in place of refractory ceramic fibres (RCF). Airborne fibre levels occurring during the manufacture of both RCF and calcium magnesium silicate wools (CMS) were compared using measurements of genuine workplace exposure from a routine monitoring operation on the same plant. Exposures during use were compared in one customer facility where RCF and CMS blankets were used for the same task. Further comparisons were made in a laboratory test of dustiness using a "shaking box test". For some manufacturing tasks there are only a few workplace samples and there are few opportunities for genuine comparisons with both RCF and CMS in identical uses. However, both materials produced very similar exposure levels during manufacture, use and in the laboratory test. The novel magnesium silicate fibre was significantly dustier in the laboratory test. (+info)
The role of environmental and occupational exposures in Turkish immigrants with fibre-related disease.
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Environmental exposure to tremolite and erionite causes endemic diseases of the lung and pleura in Turkey. This study aimed to evaluate the impact of these exposures and further occupational exposures on fibre-related diseases in Turkish immigrants living in Belgium. The study included 51 males and 17 females that emigrated < 1-38 yrs ago. Most of them (n=46) had nonmalignant pleural lesions, one had asbestosis and one had mesothelioma. Environmental asbestos exposure was likely for the majority of patients (60%), but there were also reports of possible occupational asbestos (n = 14) and erionite (n = 2) exposure. Tremolite was the main fibre type in bronchoalveolar lavage fluid (BALF). Elevated concentrations of amosite or crocidolite were detected in only two patients. The delay elapsed since the end of the environmental exposure had no influence on the asbestos body or the tremolite fibre concentrations in the BALF of Turkish immigrants. Most fibre-related diseases in Turkish immigrants are probably due to environmental rather than occupational exposure. Precise information about geographical origin and occupation should be obtained when investigating these patients. Mineralogical analysis of bronchoalveolar lavage fluid gives valuable information on the type and intensity of exposure, especially in patients with both environmental and occupational exposure. (+info)
A proposal for harmonising laboratory performance assessment criteria in national asbestos fibre counting schemes.
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Four European national asbestos fibre counting proficiency testing schemes have been studied in order to compare their criteria for the assessment of laboratory performance. Performance assessment is based on each laboratory's results after counting a certain number of samples. Two methods are currently being applied. To be classified 'satisfactory' laboratories must obtain at least 75% of normalised counts lying within defined performance limits (in three schemes), or the median and coefficient of variation of normalised counts must be within performance limits (in the fourth scheme). Differences in the numbers of test samples mean that the schemes are operating with different selectivity in assessing their laboratories' performances. Differences in the percentage of laboratory results falling within performance limits indicate that the schemes do not operate the same confidence probability in correctly assessing individual counts. It means that some schemes may be more lenient than others. This paper discusses two proposals to move towards harmonisation of the asbestos fibre counting proficiency testing schemes: (i) standardisation of the number of samples used for laboratory assessment and (ii) changes to the criteria to establish the limits of satisfactory performance. (+info)
Asbestos lung fibre concentrations in South African chrysotile mine workers.
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Mesothelioma has not been found in South African chrysotile miners and millers despite decades of producing about 100000 tons of the mineral per year. One possible explanation for the scarcity or absence of the cancer may be a relative lack of contaminating fibrous tremolite, an amphibole that variably occurs with chrysotile ores. The fibre content in the lungs of nine former chrysotile mine workers was ascertained by transmission electron microscopy. Despite fairly long service in most cases (median 9.5 yr; range 32-4 yr) the concentrations of chrysotile fibres were relatively low: only two cases exceeded 1.14 million fibres/g dried lung. Tremolite fibre levels were even lower: less than 1 million fibres/g dried lung in all but one case. Tremolite fibre concentrations exceeded those of chrysotile in only two cases. These results support the contention that South African chrysotile is not heavily contaminated by tremolite. (+info)
Case-referent survey of young adults with mesothelioma: I. Lung fibre analyses.
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OBJECTIVES: Our study aimed to determine the lung tissue concentration of asbestos and other mineral fibres by type and length in persons with mesothelioma aged 50 yr or less at time of diagnosis, compared to controls of similar age and geographical region. In this age group it was thought that most, but not all, work-related exposures would have been since 1970, when the importation of crocidolite, but not amosite, was virtually eliminated. METHODS: Eligible cases were sought from recent reports by chest physicians to the SWORD occupational disease surveillance scheme. Lung tissue samples were obtained at autopsy from 69 male and four female cases, and mineral fibres identified, sized and counted by electron microscopy. Fibre concentrations per microg dry tissue were compared with similar estimates from a control series of autopsies of sudden or accidental deaths. Unadjusted, and adjusted odds ratios calculated by logistic regression, assessed relative risk in relation to fibre type, length and concentration. RESULTS: Unadjusted and adjusted odds ratios increased steadily with concentration of crocidolite, amosite, tremolite and all amphiboles combined. There was also some increase with chrysotile, but well short of statistical significance. Incremental risk examined in a linear model was as highly significant for all amphiboles together as individually. Short, medium and long amphibole fibres were all associated with increased risk in relation to length. Mullite and iron fibres were significant predictors of mesothelioma when considered without adjustment for confounding by amphiboles, but, after adjustment, were weak and far from statistically significant. CONCLUSIONS: In this young age group, amosite and crocidolite fibres could account for about 80% of cases of mesothelioma, and tremolite for some 7%. The contribution of chrysotile, because of low biopersistence, cannot be reliably assessed at autopsy, but to the extent that tremolite is a valid marker, our results suggest that it was small. The steep linear trend in odds ratio shown by amphiboles combined indicates that their effects may be additive, with increased risk from the lowest detectable fibre level. Non-asbestos mineral fibres probably made no contribution to this disease. Contrary to expectation, however, some 90% of cases were in men who had started work before 1970; this was so whether or not amosite or crocidolite was found in lung tissue. (+info)
Case-referent survey of young adults with mesothelioma: II. Occupational analyses.
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OBJECTIVES: Our study aimed to identify occupations at increased risk of developing mesothelioma in persons aged 50 yr or less, and to relate these occupations to lung tissue concentration of asbestos fibres by type. In this age group it was thought that most, but not all, work-related exposures would have been since 1970, when the importation of crocidolite, but not amosite, was virtually eliminated. METHODS: Eligible cases were sought from recent reports by chest physicians to the SWORD occupational disease surveillance scheme. Work histories were obtained for 115 men and 13 women, usually with the help of the chest physicians or coroners. Jobs were coded by the Office of National Statistics, so that the observed years spent in each occupation could be compared with expected values from census data, 1960-90. Lung tissue samples were obtained at autopsy from 69 male and four female cases, and mineral fibres identified, sized and counted by electron microscopy. RESULTS: Of 37 industrial occupations analysed, odds ratios were significantly raised in eight: five in the construction industry and the others in shipbuilding, the manufacture of cement products and the manufacture of non-metallic mineral products (including asbestos). The concentrations in lung of crocidolite and amosite fibres, which together could account for 80-90% of cases, did not differ between occupational categories; those for amosite were appreciably higher than for crocidolite. Tremolite fibres were rarely found. CONCLUSION: Mesothelioma in this young age group is dominated by carpenters, plumbers, electricians and insulators in the construction industry, and is mainly attributable to amphibole exposure. Work in shipbuilding and manufacture of mineral products was less important than in earlier studies. Contrary to expectation, however, some 90% of cases were in men who had started work before 1970. (+info)
Effect of size of man-made and natural mineral fibers on chemiluminescent response in human monocyte-derived macrophages.
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Fiber size is an important factor in the tumorigenicity of various mineral fibers and asbestos fibers in animal experiments. We examined the time course of the ability to induce lucigenin-dependent chemiluminescence (CL) from human monocyte-derived macrophages exposed to Japan Fibrous Material standard reference samples (glass wool, rock wool, micro glass fiber, two types of refractory ceramic fiber, refractory mullite fiber, potassium titanium whisker, silicon carbide whisker, titanium oxide whisker, and wollastonite). We determined how fiber length or width might modify the response of cells. We found that the patterns of time-dependent increase of CL (sigmoid type) were similar for each sample except wollastonite. We observed a strong correlation between geometric-mean length and ability to induce CL in seven samples > 6 microm in length over the time course (largest r(2) = 0.9760). Although we also observed a close positive correlation between geometric-mean width and the ability to induce CL in eight samples < 1.8 microm in width at 15 min (r(2) = 0.8760), a sample of 2.4 microm in width had a low ability to induce CL. Moreover, the relationship between width and the rate of increase in ability to induce CL had a negative correlation at 30-60 min (largest r(2) = 0.7473). Our findings suggest that the release of superoxide from macrophages occurs nonspecifically for various types of mineral fibers depending on fiber length. (+info)
An epidemiological study of the respiratory health of workers in the European refractory ceramic fibre industry.
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OBJECTIVES: To investigate possible relations between respiratory health and past airborne exposure to refractory ceramic fibres (RCFs) and respirable dust in workers at six European factories, studied previously in 1987. METHODS: The target population comprised all current workers associated with RCF production, plus others who had participated in 1987 "leavers". Information was collected on personal characteristics, chest radiographs, lung function, respiratory symptoms, smoking, and full occupational history. Regression analysis was used to study relations between indices of health of individual workers and of cumulative exposure to airborne dust and fibres, and likely past exposure to asbestos. RESULTS AND DISCUSSION: 774 workers participated (90% of current workers, 37% of leavers). Profusion of small opacities in exposed workers (51% 0/1+; 8% 1/0+) was similar to that among an unexposed control group but higher than in new readings of the 1987 study films (11% 0/1+, 2% 1/0+). The large difference between 1987 and recent films may be, at least in part, a reading artefact associated with film appearance. Small opacities of International Labour Organisation (ILO) category 1/0+ were not associated with exposure. An association of borderline significance overall between 0/1+ opacities and exposure to respirable fibres was found for some exposure periods only, the time related pattern being biologically implausible. Pleural changes were related to age and exposure to asbestos, and findings were consistent with an effect of time since first exposure to RCFs. Among men, forced expired volume in 1 second (FEV(1)) and forced vital capacity (FVC) were inversely related to exposure to fibres, in current smokers only. FEV(1)/ FVC ratio and transfer factor (TL(CO)) were not related to exposures. The estimated restrictive effect was on average mild. Prevalence of respiratory symptoms was low. Chronic bronchitis and its associated symptoms (cough, phlegm) showed some association with recent exposure to respirable fibres. This could be due to an irritant effect of RCFs. (+info)