Pesticide residues in food — 2007: Toxicological ... - ipcs inchem

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independent reviews (Neuberger, 1996; Sathiakumar & Delzell, 1997; IARC, 1999) have identified
ten case–control studies and two published cohort studies of workers exposed to triazines at
manufacturing plants.
Neuberger (1996) reported that of the ten case–control studies published, six of which considered
atrazine, none indicated any statistically significant association between atrazine and cancer. Two
studies indicated marginally significant associations between triazines and cancer (odds ratio, OR,
1.6; 95% confidence interval, CI, 1.0–2.6; and OR, 2.7; 90% CI, 1.0–6.9). The author concluded:
…on the basis of the data to date… there is no convincing evidence of a causal association between
atrazine and/or triazine(s) and colon cancer, soft tissue sarcoma, Hodgkin’s disease, multiple myeloma,
or leukaemia… There is a suggestion of a possible association between atrazine and/or triazine(s)
with ovarian cancer and non-Hodgkin’s lymphoma. However, the ovarian cancer study needs to be
replicated and the NHL studies fall short of providing conclusive evidence of risk because the results
could be due to chance, bias, or confounding.
Sathiakumar & Delzell (1997) assessed the relation between triazines and non-Hodgkin lymphoma
in four independent population-based case–control studies, reporting OR of between 1.2 and
2.5, and concluded that these weak statistical associations may have been produced by chance and/
or confounding by other agricultural exposures. Furthermore, a pooled analysis of three case–control
studies and the combined analysis of two retrospective follow-up studies did not demonstrate the
types of dose–response relationship or induction-time patterns that would be expected if triazines
were causal factors. The authors concluded that the available epidemiological studies, singly and
collectively, did not provide any consistent, convincing evidence of a causal relationship between
exposure to triazine herbicides and cancer in humans.
The International Agency for Research on Cancer (IARC, 1999) summarized their evaluation
of data on human carcinogenicity as follows:
A combined analysis of results of two cohort studies of agricultural chemical production workers in
the United States showed decreased mortality from cancers at all sites combined among the subset of
workers who had had definite or probable exposures to triazine. Site-specific analyses in this subset
of workers yielded no significant findings; a non-significant increase in the number of deaths from
non-Hodgkin’s lymphoma was seen, but was on the basis of very few observed cases.
A pooled analysis of the results of three population-based case–control studies of men in Kansas,
eastern Nebraska and Iowa-Minnesota, United States, in which the risk for non-Hodgkin’s lymphoma
in relation to exposure to atrazine and other herbicides on farms was evaluated, showed a significant
association; however, the association was weaker when adjustment was made for reported use of
phenoxyacetic acid herbicides or organophosphate insecticides. In all these studies, the farmers
tended to have an increased risk for non-Hodgkin’s lymphoma, but the excess could not be attributed
to atrazine
Less information was available to evaluate the association between exposure to atrazine and other
cancers of the lymphatic and haematopoietic tissues. One study of Hodgkin’s disease in Kansas,
one study of leukaemia in Iowa-Minnesota and one study of multiple myeloma from Iowa gave no
indication of excess risk among persons handling triazine herbicides.
In a population-based study in Italy, definite exposure to triazines was associated with a two to
threefold increase of borderline significance in the risk for ovarian cancer. The study was small (65
cases, 126 controls), and potential confounding by exposure to other herbicides was not controlled
in the analysis.
Therefore, on the basis of the findings described above the IARC (1999) concluded: “There is
inadequate evidence in humans for the carcinogenicity of atrazine.”
ATRAZINE 37–138 JMPR 2007