As discussed in Chap. 7, human epidemiologic studies have not demonstrated evidence of a dose-related causal association between lung cancer or nonmalignant respiratory disease and occupational exposure to rock and slag wools. Animal inhalation studies using massive doses of rock and slag wool fibers, hundreds to thousands of times greater than human exposures, have not shown a relationship between inhalation of rock and slag wool fibers and lung cancer either. Since 1987, several major reviews have been undertaken on the health and safety of rock and slag wools. All these reviews concluded that inhalation of rock and slag wool fibers does not induce significant disease in animals.14
With publication of the OSHA hazard communication standard in 1983 and the IARC decision in 1987 to classify rock and slag wool as “possibly carcinogenic to humans,” rock and slag wool manufacturers have added cancer warnings to their product labels. While this may be alarming to an uninformed user of rock and slag wool products, the primary purpose of the labels is simply to identify a potential hazard. The labels do not signify that there is any real risk to humans at actual levels of exposure.
The use of injection/implantation studies as the sole determinant of the carcinogenic hazard of a fibrous material is not generally accepted for human health hazard assessment. These studies, however, have not produced significant tumors except for one injection test at an exceedingly high concentration.15 However, the fact that rock wool fibers, when intentionally inserted into animals, have produced tumors may not be a practical analysis for casual exposure. Based primarily on these studies using nonphysiologic routes of exposure, IARC considered the animal evidence as limited for rock wool and inadequate for slag wool and, following its own guidelines, classified both rock and slag wool as a “2B, possibly carcinogenic to humans.”14
Some of the mineral wool insulation manufactured before about 1970 has been found to contain lead particles. According to industry sources, lead slag is no longer used in the manufacture of mineral wool, although lead can be present as a trace impurity.16
Rock and slag wool fibers are a source of skin irritation. This irritation is a mechanical reaction of the skin to the ends of rock and slag wool fibers that have rubbed against or become embedded in the skin’s outer layer. Workers in contact with mineral wool during manufacturing processes or installation are susceptible to this temporary nuisance. It can be relieved by washing the exposed skin gently with warm water and mild soap.
Eye irritation occurs when rock wool or slag wool are deposited in the eye by the user’s fingers or through airborne mineral wool fibers. If this occurs, the eyes should not be rubbed but rinsed thoroughly with warm water. A doctor should be consulted if the irritation persists.
If sufficient amounts of rock wool and slag wool are released into the air during manufacture or handling, some workers may experience temporary upper respiratory tract irritation. Such exposures to high concentrations of airborne rock and slag wool fibers may result in temporary coughing or wheezing, a mechanical reaction. These effects will subside after the worker is removed from exposure. The use of approved National Institute of Occupational Safety and Health (NIOSH) respiratory protection can effectively control upper respiratory tract irritation by limiting exposure to airborne fibers.
Rock and slag wool fibers are noncombustible.
Certified contractors, if available, should install a proprietary wet – spray rock wool insulation product. It is still prudent, whether installing or observing an installation, to follow a number of general work practices during spraying. These general work practices, applicable to all work involving synthetic vitreous fibers (SVFs) such as rock wool and slag wool, have been established by OSHA.
These are listed in the sprayed-in-place fiberglass section of this chapter.