Chlorophenols, associations with

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). 

These investigations have shown significant associations with several types of cancer, but the most consistent findings have been for soft-tissue sarcoma and non-Hodgkin lymphoma. Although the odds ratios in some case-control studies may have been inflated by recall bias, this cannot explain all of the findings. Nor are they likely to have arisen by chance. It is not possible, however, to exclude a confounding effect of polychlorinated dibenzo-para-dioxins which occur as contaminants in chlorophenols. 

TCDD is a possible human carcinogen when considered alone and a probable human carcinogen when considered in association with phenoxy herbicides and/or chlorophenols. The EPA has determined also that a mixture of CDDs with six chlorine atoms (4 of the 6 chlorine atoms at the 2, 3, 7, and 8 positions) is a probable human carcinogen. 

Utility telecommunication and railway right-of-ways may be contaminated by leaching of CDDs associated with chlorophenol-treated railway ties and utility poles. A study in British Columbia showed that CDDs and CDFs were not detected in parkland ditch water (control area), but were detected in farmland, utility, and railway right-of-way ditch water (Wan and van Oostdam 1995). Total mean CDD concentrations (mainly OCDD and HpCDD) measured in farm ditch water, and railway ditch water, without and with utility poles were 2.22 g/L, 45 g/L, and 9,627 g/L respectively. Mean total concentrations of CDDs were much higher in ditch water adjacent to utility poles (13,142 ng/L) than in ditch water 4 meters downstream (4,880 ng/L) or 4 meters upstream of the utility poles (2.72 ng/L). 

PCP is more non-polar than 2-CP and it may have remained associated with methanol after addition to water, even though there was no apparent emulsion. This may accoimt for its lack of reactivity with the enzyme, compared to the 2-CP. However, these data suggest that the enzyme may be specific for certain types of structures and that this may limit its applicability. Other compoimds which have reported removal efficiencies less than 90% include 3-chlorophenol, 2,6-dimethylphenol, aniline, 4-chloroaniline, 4-l omoaniline, 4-fluoroaniline, and... 

Some compounds absorbing close to 231 nm may be present in raw samples and thus may interfere with sulphide spectra. Several compounds, such as, for example, p-chlorophenol (absorption at 227 nm), anionic surfactant, RBS commercial product (absorption at 223 nm) and 1-propanthiol (absorption at 239 nm), were tested, and the results show low interference values to the studied compounds [34]. The error of restitution by deconvolution is 5% at maximum with the highest interference associated with anionic surfactant (leading to an error of 4.3%). 

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. 

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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