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[Discussion]
Of the 30 reports reviewed, 22 (i.e. 73%) recognized some or
other effects on sperm. Pesticides were found relevant in 10 out
of 13 papers, which were mostly concerned with occupational
exposure at high levels. All of the six studies on
organochlorines found some or other effects (although not all of
them test significant differences). Since obvious exposure
sources do not exist for all of the subjects (young healthy men
and infertile men, except severely exposed yusho patients),
effects of organochlorine exposure on male fertility may be said
to have become manifest even in ordinary environment. To know
the exposure level in ordinary environment, however, more study
is needed on populations of ordinary healthy men (i.e. not
severely exposed people) or of men with some or other clearly
defined characteristics. Recently introduced measures of sperm
states, such as sperm motility, ratio of normal morphology,
sperm motility parameters determined by CASA, sperm nuclear
chromosome aneuploidy detected by FISH, and fragmentation ratio
of sperm nuclear DNA by comet assay, provide more sensitive
means of study than the conventional parameters (sperm
concentration and count). More precise analysis of sperm
parameters and development and application of new biomarkers
related to sperm formation are expected in future.
[Conclusions]
A survey of epidemiologic studies on effects of endocrine
disruptors on sperm was conducted. The number of papers
published has increased in the period 2001-2004. Most of them
recognize some or other effects of chemicals on sperm, while few
papers did so in earlier years. However, it is still difficult
to distinguish true endocrine disruption from usual testicular
toxicity as far as these studies are concerned. More systematic
evaluation methods of endocrine disrupting effects and
epidemiologic studies in more purposeful design are needed.
[Literature]
Table 2.11.1:
Cohort studies on the relationship of endocrine disruptors with
sperm count
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