| |
[Discussion]
Findings before Dec. 31, 2000 can be summarized as follows: DES
cannot be established as a risk factor for thyroid cancer
according to prospective studies; chlorophenoxy herbicides cause
significant risk increases according to an analytical
epidemiology, and a risk increase by HCB is suggested by
ecological studies. No other epidemiologic study was found.
Search found two cohort studies on DES only for the period after
Jan. 1, 2001. No study has been conducted on a specific
organochlorine compounds, even major persistent ones such as
PCB, DDT, HCH or HCB. Substances other than organochlorine
compounds have scarcely studied, leaving much room for
elucidating correlation with thyroid cancer risk.
Epidemiologic knowledge on the relationship of thyroid cancer
with chemical substances other than DES is thus practically
lacking at present. Evaluation of the causality is consequently
impossible. Studies in future on this topic should, in addition,
determine whether thyroid cancer risk, if any, is associated
with endocrine system disruption.
[Conclusions]
Literature concerning epidemiology of endocrine disruptors and
thyroid cancer was surveyed for a period up to Oct. 31, 2004.
Only one epidemiologic study pertaining to organochlorine
compounds was retrieved. No report concluded that DES
significantly increases thyroid cancer risk. Correlation of
exposure to chemical substances and thyroid cancer has scarcely
been studied, and evaluation of the causality is impossible.
Experimental designs with high reliability are needed for future
studies on this problem.
[Literature]
Table 2.6 1: Cohort
studies on the relationship of endocrine disruptors with thyroid
cancer
|
