Man-made Mineral Fibers Research Articles

Malignant mesothelioma in North America.

Ascertainment, through 7,400 pathologists, of all fatal malignant mesothelial tumors in Canada (1960-75) and the U.S.A. (1972) gave a total of 668 cases (272 in 1972). In Canada, the annual number of male cases rose from about 17 in 1966 to 25 in 1972 but the number of female cases remained fairly steady at a much lower level. The annual incidence in North America in 1972 was estimated at 2.8 per million males and 0.7 per million females aged 15 years and over. Occupational histories were obtained "blind" for 480 of the 557 cases through 1972, and their matched controls; relative risks were as follows: insulation work, 46.0 asbestos production and manufacture, 6.1, heating trades (other than insulation) 4.4. For nearly half the male cases and for about 5% of female cases, the tumor could be attributed to occupational exposure to asbestos, of which a fifth were in shipyards. No indication was found of other possible causes (including man-made mineral fibers, tobacco smoking, or residence near zeolite deposits). Four subjects were men who had been employed in Quebec chrysotile mines and 3 were children of employees, but no other subject had lived in the mining area. The findings remain consistent with a much greater mesothelioma-producing potential for crocidolite and amosite than for chrysotile; however, further studies of factory workers exposed to chrysotile only are needed to confirm this. Mineral fiber analysis of lung tissue from patients and controls is in progress.

Mesotheliomas, minerals, and man-made mineral fibres.

Mesotheliomas, minerals, and man-made mineral fibres.

Entrainment of fibers from air filters

This paper reports the results of a study in which the entrainment of man-made mineral fibers from commercially used modular filters was measured. The tests were performed on 42 modular filters representative of the most frequently used medium-efficiency air cleaning units which service health care facilities, banks, and general office spaces. The results of the study indicate that the fiber entrainment is a function of the broken and/or loose fibers present on the new filters and characteristically contribute insignificant amounts of fibers to the fiber concentration of the occupied spaces. The fiber concentration in the occupied spaces is in the order of 10 −3 fiber/cm 3 during the first day of operation and essentially zero during the remaining life of the filter (3 to 12 months).

Exposure of employees to man-made mineral fibers: Ceramic fiber production

Employee exposure to ceramic fibers in the ceramic fiber production industry was measured. Data were collected in three plants operated by three different corporations. The average exposure of employees was in the range 0.05 to 2 fibers/ml. Although there were major operational diversities among the plants investigated, the size and length distributions of airborne fibers in the facilities were consistent. Thus, 95% of the airborne fibers were less than 4 μm in diameter and 50 μm in length, with geometric mean diameter of 0.7 μm and geometric mean length of 13 μm. An excellent correlation was demonstrated between average exposure to total suspended particulate matter and fiber concentrations for the work activities in the plants.

Presumptive identification of asbestos in urban air

Chrysotile asbestos can be selectively stained with fluorochrome Coriphosphine O. The fluorescent staining technique positively distinguishes chrysotile from amosite, crocidolite and from man-made mineral fibers, like glass wool. As ubiquitous urban particulates do not interfere, the staining method allows the presumptive identification of asbestos fibers by light (fluorescent) microscopy in presence of a large excess of non-asbestos particles or fibers. Sometimes a slight interference from antigorite, a parent mineral of asbestos occurs. Investigations are in progress to establish if the few fluorescent points observed for this mineral may in fact correspond to asbestos fibers, in which case a link between fluorochrome uptake and physiological behaviour might be further sought. The current practice of sampling asbestos in occupational air, where asbestos represents a significant fraction of the particulates, is by collecting dust on organic membranes, mostly Nucleopore. The dust deposit is counted using phase contrast microscopy. Under these conditions, when asbestos is relatively abundant and overall samples of a few hundred micrograms can be collected, gravimetric evaluation using X-ray diffraction techniques is also possible.

Summary of measurements of employee exposure to airborne dust and fiber in sixteen facilities producing man-made mineral fibers.

The results of an industry-wide study to determine the exposure of workers to man-made mineral fibers are summarized. The purpose of the study was to determine current employee exposures to airborne fibers and to utilize results to estimate past exposures. Measured exposures of workers to airborne total particulate matter and fibers are presented; samples were evaluated by phase contrast and electron microscopy. Results of the three year study, which encompassed 16 facilities and over 1500 eight hour samples, show that although there is a wide variation in concentrations of airborne fibers and particulate matter between and within the facilities surveyed, the concentrations of airborne particulate matter and fibers are generally less than 2.5 mg/m3 and 0.5 fibers/cm3, respectively. The norminal fiber size of the fibers manufactured and average airborne fiber concentration were highly correlated.

Exposure of employees to man-made mineral fibers: Mineral wool production

This paper reports the results of a study in which employee exposure to mineral wool fibers in the mineral wool production industry was measured. Data for this study were collected in five plants operated by three different corporations. The results of the study indicate that the average exposure is about 0.1 to 0.5 fibers/ml. The results also indicate that despite operational diversities among the plants the size and length distributions of airborne fibers were consistent. It was also found that there is an excellent correlation between average total suspended particulate matter and average fiber exposure for types of work activity found in the plants.

Man-made Mineral Fibres

Insulation wools from glass fibres have been in production for over 40 years and similar products made from slag wool have been made since the 1880s. These products contain a significant proportion of fibres of respirable diameter. Continuous filaments for textile fibres have been made since the 1940s and contain only extremely small quantities of respirable fibres. The relatively high falling speed of large diameter fibres means that high gravimetric estimations may be associated with very small quantities of airborne respirable fibres in production plants. Fibres above 5 μm in diameter act as a primary irritant on the skin but continued exposure leads to hardening and a cessation of symptoms, sensitization does not occur. Prevalence studies of groups of workers exposed for lengthy periods to glass fibres in several countries produced evidence of the absence of pulmonary fibrosis, respiratory impairment and symptoms of bronchitis. Epidemiological studies have failed to show an excess risk of lung or other cancers. Reports of a small number of individual cases with respiratory disease and an exposure to glass fibres have not demonstrated a causal effect. Postmortem studies of workers with long-term exposure to glass fibres have shown no evidence of lung damage. Animal inhalation studies, in general, show that man-made mineral fibres elicit a macrophage response and the reaction is typical of a nuisance dust, significant fibrogenic reaction is not produced and carcinogenesis has not been demonstrated by inhalation. Injection of fibres into the pleura produces an incidence of tumours related to the number, diameter and length of fibres. The order of diameter of biological significance is believed to be between 0.5 and 1 μm in diameter. Such effects have not been observed in man and are obtained with all durable fibres, asbestos being the only substance for which a similar effect is known to occur in humans. Cell culture work suggests the mechanism of tumorigenesis differs from that of most carcinogens and may resemble the Oppenheimer effect.

HEALTH ASPECTS OF MAN-MADE MINERAL FIBRES<subtitle>A REVIEW</subtitle>

Man-made mineral fibres (MMMF) have been in production for over 40 years. The diameter of the fibres has in general been too large to cause a high concentration of respirable fibrous dust during manufacturing or use. Medical studies in several countries of groups of workers exposed for lengthy periods to glass fibre have produced evidence of the absence of lung fibrosis or respiratory impairment, and have not shown an excess risk of lung or other cancers. Reports of a few individuals with respiratory disease and an exposure to MMMF have not clearly indicated the fibres as a cause of the disease. Limited pathological studies of lungs of workers with long term exposures to glass fibre have shown no evidence of lung damage. Animal inhalation studies in general confirm that MMMF are not fibrogenic. Following injection of fibres into the pleura, the incidence of tumours produced is related to the dose, diameter and length of the fibres. Further research is needed to enlarge the number and diversity of the epidemiological studies; also to look more critically at the biological effects of small diameter fibres which may arise as a result of changes in technology of production and use of MMMF.

Man-made mineral fibres: what needs to be known and done.

Man-made mineral fibres: what needs to be known and done.

THE BIOLOGICAL EFFECTS OF MAN-MADE MINERAL FIBRES (MMMF)<subtitle>Proceedings of a Workshop sponsored by the Scientific and Technical Committee of the Joint European Medical Research Board<xref ref-type="fn" rid="fn1"><sup>*</sup></xref> at the WHO Regional Office for Europe, Copenhagen, Denmark, 26–27 October 1976</subtitle>

THE BIOLOGICAL EFFECTS OF MAN-MADE MINERAL FIBRES (MMMF)<subtitle>Proceedings of a Workshop sponsored by the Scientific and Technical Committee of the Joint European Medical Research Board<xref ref-type="fn" rid="fn1"><sup>*</sup></xref> at the WHO Regional Office for Europe, Copenhagen, Denmark, 26–27 October 1976</subtitle>

Man-made mineral fibres: medical research--CIRFS/EURIMA initiative.

The Joint European Medical Research Board (JEMRB) was formed following discussions between the Comité International de la Rayonne et des Fibres Synthétiques (CIRFS) and the European Insulation Manufacturers' Association (EURIMA) to initiate reasearch into the biological effects of man-made mineral fibres (MMMF). It is the policy of JEMRB to promote research into the safety of the industry's products by providing financial support and access to all facilities within its power whilst preserving the total independence of the scientists involved.

Medicine and mineralogy

The article deals with the health hazards caused by mineral dusts, and by asbestos fibres in the induction of cancers in particular. Mineral dusts cause damage by inhalation, rarely by ingestion or ingress into the skin. In the lung, bronchitis, fibrosis (pneumoconiosis), and cancers may result. Few mineral dusts cause cancers, and asbestos is unique in causing two separate types within the lung. Epidemiological and other studies of groups of asbestos workers have shown important differences in risk with the type of fibre and the type of job. All types of asbestos cause fibrosis and an excess of bronchial cancers which are, however, also closely cigarette related. Crocidolite is especially related to cancers of the surface of the lung (mesotheliomas). Mining and milling of chrysotile, the most used type of asbestos, have caused few mesotheliomas, despite heavy dust exposures in the past. The diseases induced by asbestos are dose-related* Where it has been possible to divide the groups of asbestos workers into those with different levels of past exposure, the least exposed groups have shown small or no excess of asbestos-related diseases despite their exposures having been considerably higher than that likely to have been encountered by the general public. Present evidence indicates that the general public have not been at risk of asbestos-related diseases, but more evidence is required about the proportion of all mesotheliomas which are related to asbestos. The new techniques of mineralogy when applied at a micro level to the dust in tissues, and particularly in the lung, may be of great help in answering this important problem. Some comparisons of the mortality from occupationally related cancers, accidents, smoking habits, and general diseases are given. Current research into the biomedical effects of natural fibrous mineral dusts is likely to be of great value in ensuring that the new man made mineral fibres now being developed are manufactured and used under circumstances which will cause no ill effects to health.