Published: Jan 1983
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Medical-scientific studies relating to man-made vitreous fibers (MMVF) date from the early 1930s. Extensive health research since that time has dealt with the effects of MMVFs on humans, animals, and the environment. Results to date indicate that MMVFs do not produce any chronic adverse health effects in man.
Animal inhalation studies demonstrate no appreciable alteration of lung architecture, minimal pleural change, no significant fibrosis, and no tumor development in animals as a result of exposure to man-made vitreous fibers. Even injection of the fibers into the trachea of animals has not produced malignant tumors. When massive doses of varied materials—including specially produced fibers—were surgically implanted into the pleural and peritoneal cavities of animals, mesotheliomas have been produced. However, the major study cautions that application of the findings to humans “would be unwise because the method of application and high doses used are remote from the usual exposure of man to fibers…”
Studies of workers exposed to man-made vitreous fibers (fibrous glass) demonstrate no significant difference in lung fiber content or fiber dimensions than shown in nonexposed persons. Such studies further demonstrate no significant malignant respiratory disease. Preliminary results of a current study encompassing 17 man-made vitreous fiber manufacturing facilities and over 16 000 production workers with exposure up to 40 plus years do not indicate any evidence of an excess of malignancies caused by man-made vitreous fibers.
Man-made vitreous fibers differ significantly from asbestos fibers. There are data suggesting that very fine man-made vitreous fibers that may be respired have a marked tendency to disappear, whereas some types of asbestos fibers can survive within tissues for the full life span of exposed animals and humans. Asbestos fibers split longitudinally into progressively thinner components that have been shown to be associated with chronic, progressive nonmalignant and malignant disease in humans. Asbestos fibers fragment transversely with much less frequency. In sharp contrast, man-made vitreous fibers do not split longitudinally; they only fragment transversely into shorter pieces. Short fibers have been shown to be nonpathogenic.
In summary, no chronic progressive disease, either malignant or nonmalignant, has been demonstrated to date by inhalation of man-made vitreous fibers in animal studies. Airborne exposures of man-made vitreous fibers observed during fabrication and installation are extremely low. Asbestos fibers and man-made vitreous fibers differ in durability, fate, and ability to cause disease. In man, asbestos is known to be associated with malignant and nonmalignant disease. In man, there is no credible evidence of malignant or chronic progressive nonmalignant disease resulting from exposure to manmade vitreous fibers.
thermal insulation, man-made vitreous fibers, health and safety
Chairman, Health-Safety Group, Thermal Insulation Manufacturers Association, Brick Town, N.J.