Toxicology of Industrial Compounds

filament cohort was too short to allow for an evaluation of possible longterm
effects’. It was also noted that ‘there was no evidence of an increased
risk for pleural tumors or non-malignant respiratory diseases’. An update of
this study is underway.
The University of Pittsburgh study
This study was also reported at the WHO Occupational Conference on
Biological Effects of Man-Made Mineral Fibres at Copenhagen in 1982 and
the follow-up Conference in 1986 (Simonato et al., 1987). Subsequent to
the 1986 Conference, additional analyses were completed and included in
the manuscript published for the proceedings (Enterline et al., 1987). The
study has been updated and published (Marsh et al., 1990). The University
of Pittsburgh researchers’ comprehensive mortality review of more than
16000 workers— many with long-term exposure up to 40 years—was
undertaken at 17 US fiber-glass, rock-wool and slag-wool manufacturing
plants, including 14800 fiber-glass workers in 11 plants. The original
report, given in 1982, covered the mortality experience from the 1940s to
the end of 1977. The same group of workers was followed through 1982
(reported in October 1986, with additional analyses available in June
1987). The June 1987 report contained, for the first time, local area
mortality statistics for each of the plants as the basis for studying the
mortality experience. Experts agree that, barring unusual circumstances,
local area comparisons are most appropriate. The study has been further
updated through 1985, with publication in 1990. For respiratory cancer, in
the latest update there was a small but statistically significant increase for
fiber glass production workers. However, aside from the issue of
uncontrolled potential confounding, the study provides no evidence to date
that respiratory cancer mortality is related to fiber glass exposure. There
was a somewhat larger statistically significant excess of respiratory cancer
mortality reported for slag wool and rock wool production workers. The
absence of any clear exposure-response relationship for any of the fiber
groups studied led the authors to conclude that ‘overall, the evidence of a
relationship between exposure to man-made mineral fibers and respiratory
cancer appears to be somewhat weaker than in the previous update’.
Consistent with the IARC study, no increase in the occurrence of
mesothelioma has been observed in this cohort. This study has now been
expanded to include well over 30000 workers from 14 fiber-glass and six
rock wool and slag wool facilities.
Other epidemiological studies
T.W.HESTERBERG ET AL. 93
In addition to the two major studies highlighted above, a number of other
studies have been conducted as well. Many of them widely overlap these