home edit2 whole TSD November 2002 PDF format - OEHHA

Table 1 (continued):
A Summary of Epidemiologic Data for Occupationally Exposed Vinyl Chloride
Workers
LAS = angiosarcoma of the liver; f/u = follow-up
1 The studies of Cooper and EEH are reanalyses of the Tabershaw and Gaffey Cohort
2 SMR subjects also in the Tabershaw and Gaffey Cohort
3 SMR is for the “digestive system cancer”, not liver cancer
4 SMR is for “other and unspecified cancer”, 40% of which were brain cancer
5 SMR is for cancer of CNS, not brain
a b
p < 0.05 p < 0.01
The association between VC exposure and increased risk for other cancers is not as clear as that for liver
cancer. Some evidence associates exposure to VC with increased mortality ratios for brain cancer, lung
cancer, and lymphoma. Since these cancers appear more commonly in the general population than LAS and
primary liver cancer, it becomes more difficult to show increased risk.
Workers exposed to VC appear to be at greater risk for brain cancer than do non-exposed
populations. Of the six studies that assessed the risk of brain cancer, five showed a positive trend for
increased risk of this cancer type following exposure to VC, with four demonstrating statistical
significance (p < 0.05). Cancer risk increased an average of four times above that expected in the
general population in those studies that exhibited a significantly increased risk. Of the two studies not
showing a significant increase in risk for brain cancer, statistical power in the Bertazzi and associates
study was only about 35% (Bertazzi et al., 1979), while that of Fox and Collier (1977) was
approximately 80% (Beaumont and Breslow, 1981). In the Fox and Collier study, the number of
deaths overall was low and, most importantly, a large percentage of workers in the cohort was very
recently employed in the VC industry and thus had a short follow-up time. These factors may partially
explain why this study failed to detect an association between VC exposure and brain cancer.
The evidence linking VC exposure with lung cancer remains inconclusive. Analyses of SMRs for cancer
of the lung were performed in 12 studies. Of these, seven studies showed an increased risk for lung
cancer, but only one was statistically significant at the 5% level (Buffler et al., 1979). This increased
risk persisted after adjusting for personal smoking habits (for this particular cohort). However, this
cohort was small and the study was unable to demonstrate an increased risk for any other cancer. The
Waxweiler et al. (1976) cohort (which had a follow-up period greater than 15 years) also used a small
group.
An association between VC exposure and lymphoma has not been established. Five studies evaluated
the risk of lymphoma development among workers occupationally exposed to VC. Four of the studies
showed a positive trend for lymphoma among VC workers, but statistical significance was noted only
by Weber et al. (1981). However, the statistical power in all of these studies was less than 80% to
demonstrate a relative risk of two, and less than 40% to show a relative risk of 1.5.