Document XzD3O41NQavqdZmYxRBEmN3by

Industrial Hygiene Digest une. Industrial Hygiene for Insulation V.'orkers. J. Occ Med. 10. 25-31 (Jar... 1963). L. Balzer. The asbestos worker is exposed to amosite and.chrysotile asbestos-containing materials, fib-e glass, cork, plastics, and adhesives. Working in industrial and commercial building proiecri and marine construction and repair, he is exposed to many other environmental hazards not created by his own trade. Although he works with asbestos-containing products 45"- of the time the over-all time-weighted average exposure to asbestos-containing materials is below the pr. sently recognized Threshold Limit Values (TLV) of 5 mppcf. The three work areas in which dust levels were above the TLV (prefabrication, tearing out, and mixing) account for less thar 20?o of his total work time. However, the incidence of radiographic changes indicative of asbestosis is over 25% in our men with 20 years or more of work. This and other evidence suggest that the present TLV is too high. Incidence of asbestosis and the risk of malignancies in the asbestos worker can be reduced by local and general ventilation, substitution of materia., changes in work habits and personal respiratory protection combined with education of the me: to reduce their own exposures to asbestos-containing dusts. There are 17 references. -- Author's summarv. 560 Asbestos as an Environmental Hazard. I. R. Tabershaw. J. Occ. Med. _lj>. 32-37 (Jan., 1968). In summary, if one accepts the assumptions (1) that asbestos minerals Increase the risk oi iur: cancer in occupational groups, (2) that they lead to an unusual risk of mesothelioma of the pie'.-: and peritoneum in occupational groups and those living near asbestos plants, (3) that such mak:- nancies usually result from exposures 30 to 50 years earlier, (4) that the "asbestos bodies found in from 25 to 50% of lung smears from routine autopsies are probably due to asbestos ir. most cases, (5) that these "asbestos bodies" may result from recent exposures as well as thoit many years earlier, (6) that world production and use of asbestos has increased from 500,00* tons to 3, 500, 000 tons in 30 years, it is Important to consider whether or not asbestos is a ' threat to public health. One is not yet justified in such a conclusion, in view of the fact thar is- of the world tonnage goes into uses that do not lead to air contamination; thatasbeatos is notac::a- Indestructible; that the effects are dose-dependent; and that low doses probably lead to lowrr rates and longer latency. Nevertheless, there is need for epidemiologic studies directed to " with intermediate exposures and for evaluation of the beneficial effects of cessation of smo*.-'- Another need is for experimental and industrial hygiene studies to determine the natureanc oi exposure. Biologic studies centered on the meaning of the "asbestos body" are crucial" understanding the clinicopathologic response. Strict control of Industrial and nelghborhooc ^ environments is essential, but it is premature to extrapolate from the effects of heavy expo*- to minor and low level exposures. There are 15 references. -- Author's summa.- 561 Research on Health Effects of Asbestos. L. J. Cralley, et al. J. Occ. Med. U), 38-41 (Jan., 1968). Asbestos is a general term applied to a group of fibrous crystalline hydrated siLicate rr.inr-4 Although a number of different types of asbestos minerals exist, only four or five are o* ^ commercial importance. Each differs somewhat from the others in chemical compos.t physical properties such as ability to withstand heat and chemical erosion, crystalline r<. fiber dimension, and degree of fiber harshness and brittleness. It has been known since ^ nineteen hundred's that excessive exposure to asbestos gives rise to the disabling Pul feJ. disease "asbestosis." More recently, evidence has been developed that the incidence ^ ,. plratory tract and other malignancies In asbestos workers is excessive. A major Pr0 ^ . studying the health effects of asbestos Is the long latent period of 20 or more years trt exposure to the onset of disease. Also in the mid-nineteen thirties ar.d earlier. :nere .. dust control and the workers were often exposed to massive levels of dust from aSkeS\.# a. other associated materials ir. the manufacture of asbestos products. Thus, the eau*8^. of the resultant disease are essentially unknown. Included in these potential s?urc^a,.. - causative agents, either alone or in combination, are asbestos fibers inemse:ve* ' _ . associated with the fibers in the ores such as trace minerals and polycyclic aroma*.- " materials added during processing such as metals, tars, and pitches, and concom- ^... exposures to tobacco smoke or other air pollutants. A strong supported lons-t*1"" . r needed tc provide the Information regarding the pathogenesis of asbestosis ar.d the^ _ . that appear associated with the inhalation of asbestos dust. More precise data o..