Health and safety research on rock and slag wool has been ongoing for more than 50 years. NAIMA member companies have helped fund three areas of research involving rock and slag wool. These include exposure assessments of current production workers and end users, analyses of the rates and causes of death of former production employees, and animal test studies. Airborne levels of respirable rock and slag wool fibers have been demonstrated to be very low, less than 1 fiber per cubic centimeter of air in most instances. 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 wool. 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 wool. All these reviews concluded that inhalation of rock and slag wool fibers does not induce significant disease in animals.19
Various other studies have not established a link between casual exposure to rock and slag wool and lung cancer either; however, limited evidence does demonstrate an association between exposure to rock wool and cancer in manufacturing workers.
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.20 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, the International Agency for Research on Cancer (IARC) considered the animal evidence as limited for rock wool and inadequate for slag wool and, following its own guidelines, has classified both rock and slag wool as a “2B, possibly carcinogenic to humans.” For reference purposes, the IARC also has classified coffee, saccharin, gasoline engine exhaust, and more than 150 other common substances as “possibly carcinogenic to humans.” In general, IARC rules dictate that this designation be given if there is sufficient evidence of carcinogenicity in animals, even if the route of exposure is artificial (nonphysiologic) and human data are inadequate or limited.19
Rock and slag wool fibers are a catalyst for 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 gently rinsing the exposed skin with warm water. Hot water and scrubbing will exacerbate the condition.
Eye irritation occurs when rock or slag wool are deposited in the eye by the user’s fingers or through airborne 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 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 respiratory protection can effectively control upper respiratory tract irritation by limiting exposure to airborne fibers.
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 appear 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 manufacturers of these products remain confident that the risk associated with the use of rock and slag wool products, if there is any risk at all, can be effectively controlled via reduction of workplace exposures and adherence to simple recommended work practices.19
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. OSHA has expressed concern in situations where new insulation is installed over pre-1970 mineral wool and lead particulates are released into the air. Exposures will vary markedly from job site to job site because of such factors as the size of the space, the method of application, and the amount of lead dust in the mineral wool. Exposures are likely to be highest when insulation is blown into place in a confined space.21