IARC MONOGRAPHS PROGRAMME RE-EVALUATES
CARCINOGENIC RISKS FROM AIRBORNE MAN-MADE VITREOUS FIBRES
A scientific working group of 19 experts from 11 countries convened
by the Monographs Programme of the International Agency for Research on Cancer (IARC) has
concluded its re-evaluation of the carcinogenic risk of airborne man-made vitreous fibres.
Man-made vitreous fibres in the form of wools are widely used in thermal and acoustical
insulation and in other manufactured products in Europe and North America. These products,
including glass wool, rock (stone) wool, and slag wool, have been in use for decades and
have been extensively studied to establish whether fibres that are released during
manufacture, use, or removal of these products present a risk of cancer when inhaled.
Epidemiologic studies published during the 15 years since the previous IARC Monographs
review of these fibres in 1988 provide no evidence of increased risks of lung cancer or of
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.
Beside this, much industrial effort has gone into development of newer materials that have
similar insulation properties to the older products, but which disappear from body tissues
much more rapidly. The reason for this effort is that asbestos, a known human carcinogen
which causes both mesothelioma and lung cancer and had been used as insulating material
for several decades, is extremely slow to decompose and disappear from body tissues in
which it has been deposited. This characteristic, known as high biopersistence, is
correlated with the high carcinogenic potency of asbestos fibres. Some of these newer
materials have now been tested for carcinogenicity and most are found to be
non-carcinogenic, or to cause tumours in experimentals animals only under very restricted
conditions of exposure.
The Monographs working group concluded that only the more biopersistent materials remain
classified by IARC as possible human carcinogens (Group 2B). These include refractory
ceramic fibres, which are used industrially as insulation in high-temperature environments
such as blast furnaces, and certain special-purpose glass wools not used as insulating
materials. In contrast, the more commonly used vitreous fibre wools including insulation
glass wool, rock (stone) wool and slag wool are now considered not classifiable as to
carcinogenicity to humans (Group 3). Continuous glass filaments, which are used
principally to reinforce plastics, are also considered not classifiable as to
carcinogenicity to humans.