home edit2 whole TSD November 2002 PDF format - OEHHA

To confirm these findings, Ericksson et al. (1981) replicated this study in Southern Sweden, using cases
from a cancer registry. Similar study methods were used, including matching controls from a population
registry (at a 2:1 ratio), and determining exposure by mail and telephone questionnaires. The
investigators calculated separate odds ratios for exposure to phenoxy acids known to be contaminated
with PCDD and PCDF (OR-17.0; 95% CI 2.1-140.0) and for exposure to phenoxy acids thought to
be free of PCDD and PCDF (OR-4.2; 95% CI 1.2-14.9). When exposure was dichotomized into
categories of 30 days or less, or more than 30 days, the ORs were 5.7 and 8.5, respectively, possibly
indicating a dose-response trend.
One of the drawbacks of this study is that, exposure histories were provided by the study subjects;
therefore, the results may be influenced by recall bias. Cases (or their next of kin) may be more likely to
recall an exposure than a healthy person. In order to investigate this possible bias, Hardell (1981)
duplicated the study methods using cases of colon cancer. Here there was no significant association
with exposure to herbicides. Therefore, Hardell concluded that the association with STS was not due
to reporting differences between diseased cases and healthy controls.
Smith et al. (1984) reported a similar case/control study in New Zealand. Here, male cases of STS
were gathered from a national cancer registry, with controls also being selected from the same registry.
This method of control selection was designed to avoid differential recall. Unlike the Swedish studies,
however, the New Zealand study showed no significant associations with reported phenoxy herbicide
spraying. The authors suggested that if dioxin were the necessary agent, that Swedish herbicides may
have been more contaminated than New Zealand herbicides. However, Smith et al. (1984) note that
the Swedish investigators also found a significant association between STS and
non-dioxin-contaminated herbicides, indicating that if the association were true, dioxin would not be the
sole agent.
Another case/control study reported in brief by Olsen and Jensen (1984) of cases from the Danish
Cancer Registry failed to show an association between nasal cancer and chlorophenol exposure,
although nasal cancer was associated with occupational exposure to wood dust.
In a letter to Lancet, Milham (1982) reported proportionate mortality data from Washington state
indicating that farmers suffered a significantly larger proportion of deaths due to STS. No other group
occupationally exposed (foresters, orchardists, tree farmers) showed an excess of STS; however, the
exposure assessment was based on occupations taken from death certificates. Furthermore, Milham
indicated that 2,4-D was the predominant herbicide used, and 2,4-D is not generally contaminated with
2,3,7,8-TCDD.
A cohort study of phenoxy acid herbicide applicators in Finland was reported by Riihimaki et al.
(1983). A historical cohort of 1926 herbicide applicators was assembled from the records of four large
employers, including the Finnish Highway Authority and State Railways. These male workers had used
chlorinated phenoxyacids for at least two weeks between 1955 and 1971. Their mortality between
1972 and 1980 was studied by comparing their names against population registers. National mortality
figures provided expected age-standardized numbers of deaths. Deaths from all causes, and for all
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