Health and Safety Facts for Rock and Slag Wool

The mineral wool form of man-made vitreous fiber (MMVF) was developed in the mid-1800s by melting slag and spinning it into the wool fibers that are used for insulation. Since their introduction, rock and slag wool insulation products have become two of the world’s most useful insulating materials, helping homeowners and industry increase energy efficiency, protect
the environment, and reduce energy costs. Rock and slag wool fall within a group of materials historically referred to as man-made vitreous fibers (MMVF’s), reflecting the glassy, non-crystalline nature of these materials.
NAIMA and its member companies are committed to ensuring that rock and slag wool products can be safely manufactured, installed and used. NAIMA member companies have funded tens of
millions of dollars of research at leading independent laboratories and universities in the United States and abroad. The weight of the scientific research shows no association between exposure to rock and slag fibers and respiratory disease or cancer in humans.

In October 2001, an international expert review by the International Agency for Research on Cancer (IARC) re-evaluated the 1988 IARC assessment of rock and slag wool fibers and removed rock and slag wools from its list of possible carcinogens by downgrading the classification
of these fibers from Group 2B (possible carcinogen) to Group 3 (not classifiable as to carcinogenicity in humans).
All rock and slag wool materials are included in this classification. IARC noted specifically:
“Epidemiologic studies published during the 15 years since the previous IARC Monographs review of these fibers in 1988 provide no evidence of increased risks of lung cancer or mesothelioma (cancer of the lining of the body cavities) from occupational exposures during manufacture of these materials, and inadequate evidence overall of any cancer risk.”
The IARC downgrade is consistent with the conclusion reached by the U.S. National Academy of Sciences, which in 2000 found “no significant association between fiber exposure and lung cancer or nonmalignant respiratory disease in the MVF [man-made vitreous fiber] manufacturing environment.”
The independent studies funded by NAIMA have provided substantial data upon which these comprehensive expert reviews were based.
The data from these evaluations demonstrate that:
1. No causal association has been found between either cancer or non-malignant pulmonary disease and human exposure to rock or slag wool.
2. Rock and slag wool fibers are biosoluble and therefore dissolve more rapidly in body fluids than
other fibers that have been associated with human disease.
3. Workplace levels of respirable rock and slag wool fibers in most settings are less than 1 fiber/cc; and airborne levels in insulated buildings are not significantly different than levels outside or in uninsulated buildings. Scientific evidence demonstrates that rock and slag wool are safe to manufacture, install and use when recommended work practices are followed. Following these work practices will help to reduce irritation.