Toxicology of Industrial Compounds

92 CARCINOGENIC POTENTIAL OF MAN-MADE VITREOUS FIBERS
in the judgement that chronic inhalation studies of airborne fibers provide
the best model for assessing potential risk to man (McClellan et al., 1992).
In assessing the carcinogenic risks of exposure to any possible
occupational hazard, research is pursued through several different scientific
techniques. Studies of mortality (analysis of death rates) are used to
evaluate the potential carcinogenicity associated with direct human
exposure. Animal exposure studies are used to not only evaluate the
potential carcinogenicity but to also investigate the mechanisms of disease
development. Industrial hygiene and engineering studies are used for
quantifying exposures.
Epidemiological studies
By general agreement among experts (IARC, 1988; IPCS, 1988), two major
historical cohort studies are considered to have comprehensively addressed
the mortality experience of workers engaged in the production of FG, rock
wool and slag wool: a European study conducted by the International
Agency for Research on Cancer (IARC), and a University of Pittsburgh
study conducted in the USA. The discussion here will concentrate on those
two studies. For a summary of other studies, the reader is referred to the
IARC review (IARC, 1988). There are no published reports of the
mortality experience of RCF workers. Epidemiological studies of workers
engaged in the manufacture of all major classes of MMVF are underway or
are continuing. Morbidity studies of the respiratory health of workers are
not discussed here.
The IARC study
IARC researchers reported their study at the WHO Occupational Health
Conference on the Biological Effects of Man-Made Mineral Fibres at
Copenhagen in 1982, with a follow-up in 1986 (Simonato et al., 1987). The
updated study is also published in the Scandinavian Journal of Work,
Environment & Health, Volume 12, Supplement 1, 1986. The mortality of
23609 workers (2836 deaths) employed in 13 European factories engaged
in the production of MMVF (including 11 852 fibre glass production
workers at six plants in five countries and 10 115 rock wool/slag wool
production workers at seven plants in four countries) has been studied
(Saracci et al., 1984) and updated (Simonato et al., 1987). The authors
reported an ‘excess of lung cancer among rock-wool/slag workers
employed during an early technological phase before the introduction of
dust-suppressing agents’, and concluded that ‘fiber exposure, either alone or
in combination with other exposures, may have contributed to the elevated
risk’. The authors also reported that ‘no excess of the same magnitude was
evident for glass-wool production, and the follow-up of the continuous-