Chlorophenols, associations with exposure

Several studies have assessed the plausibility of the association between soft tissue sarcomas and exposure to phenoxy herbicides and chlorophenols. Table VI lists two case-control studies conducted in Sweden, which selected controls from the general population and concluded that exposure to the herbicides or to chlorophenols resulted in a greater than 5-fold excess in soft tissue sarcomas (38-39). A New Zealand study found no association with exposure to phenoxy herbicides (40). This study drew controls from other cancer cases in the National Cancer Registry of New Zealand. However, in the New Zealand study, a 5-fold excess of STS was noted in persons who handled animal pelts, which are sometimes preserved with trichlorophenols containing isomers of dioxin. 

In summary, studies of STS have reported both positive and negative findings. All of the studies had limitations in statistical power or assessment of exposure. To date, no definitive answer exists as to whether STS is associated with exposure to phenoxy herbicides or chlorophenols. The situation is similar for lymphoma, stomach and nasal cancer. 

Associations with chlorophenols were, however, analysed in two case-control studies nested within 24 of the 36 cohorts of the lARC study. These compared 11 cases of soft-tissue sarcoma and 32 cases of non-Hodgkin lymphoma with 55 and 158 controls, respectively (Kogevinas et al., 1995). Exposure to chlorophenols, phenoxy acid herbicides, dibenzodioxins and -furans and other agents was assessed by a team of industrial hygienists (Kauppinen et al., 1994). Odds ratios for non-Hodgkin lymphoma, not adjusted for exposure to other agents, were 1.3 (95% CI, 0.5-3.1) for any chlorophenol, 2.8 (0.5-17.0) for pentachlorophenol and 1.0 (0.3-3.1) for 2,4-dichlorophenol. No excess risk was found in relation to other chlorophenols, but the munber of exposed cases was small. The odds... 

As described in an earlier monograph (lARC, 1986), a case-control study in Sweden found a significant association between nasal and nasopharyngeal cancer and exposure to chlorophenols, independent of exposure to wood dust (Hardell et al., 1982). The same group of researchers also reported positive associations with high-grade exposure to chlorophenols in case-control studies of colon cancer (odds ratio, 1.8 95% CI, 0.6-5.3) and primary liver cancer (odds ratio, 2.2 95% CI, 0.7-7.3) (Hardell, 1981 Hardell et al., 1984). 

A, To date, exposure to phenoxy herbicides and chlorophenols has been shown in some studies to be associated with soft tissue sarcoma, lymphoma, stomach cancer, and nasal cancer, but no outcome has been conclusively established or rejected. 

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