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Monitoring should also be conducted on diseases possibly related
to chemical exposure. The Vital Statistics is the most reliable
national data source for diseases, but it is not sufficient for
the present purpose because cancer in the breast, uterus,
prostatic gland, testicle and thyroid gland, which are possibly
under the influence of chemical exposure, have high five-year
survival rates. Although the ongoing Regional Cancer Registry
programs provide some information, a survey and monitoring
scheme on the national level is indispensable. In fact, the
Ministry of Health, Labor and Welfare supports the Regional
Cancer Registry as an important item in its 10-year anticancer
program and is planning its improvement in precision and
standardization at a national level. Monitoring systems at the
national level should also cover endometriosis, sperm count and
organ malformation.
(2) Promotion of epidemiological studies (case-control studies
and cohort studies)
Evaluation of chemical exposure level for only patients of a
disease does not provide information on the association of the
chemical agent and the disease. A disease possibly related to a
chemical agent found in an individual does not mean that the
agent caused the disease. The relationship of the two factors
can be verified only by a quantitative representation obtained
through the epidemiologic method and minimization of possible
errors due to incidental factors, biases or confounding of
factors. This document has performed relevant reports of this
kind to check causal relationships of chemical substances
including organochlorines and several diseases. Studies from
Europe and the U.S. have provided many evidences that a causal
relationship between residual pesticides and breast cancer
incidence is not supported. This conclusion can, however, not
directly applied to Japanese populations who have lifestyle and
genetic factors different from those for Caucasians. Other
diseases and chemicals are still poorly understood, and require
reliable, large-scale epidemiologic studies.
Examples of specific research subjects in need are listed below.
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