Men concerned about their sperm count should steer clear of
Bisphenol-A, or BPA, a chemical created in the production of polycarbonated
plastics and epoxy resins found in baby bottles, plastic containers, the
linings of cans used for food and beverages, and in dental sealants.
A five-year study conducted by Kaiser Permanente concluded
that high exposure to BPA was significantly associated with decreased sperm
concentration, decreased total sperm count, decreased sperm vitality and
decreased sperm motility.
The study, which appears in the Journal ofFertility and
Sterility, recruited 514 workers in factories in China and compared workers
who had high urine BPA levels with those with low urine BPA.
Men with higher urine BPA levels had 2-4 times the risk of
having poor semen quality, including low sperm concentration, low sperm
vitality and motility.
Previous studies
Previous studies of BPA and sperm counts found a detrimental
association between BPA and male reproductive systems in mice and rats, but
this is the first study to report an adverse association between BPA and semen
quality in humans.
This study is the third in a series, published by Dr. Li and
his colleagues, that examines the effect of BPA in humans.
The first study, published in November 2009 in the Oxford
Journals Human Reproduction, found that exposure to high levels of BPA
in the workplace increases the risk of reduced sexual function in men.
The second study,
published in May 2010 in the Journal of Andrology, found that increasing
BPA levels in urine are associated with worsening male sexual function.
Funded by the U.S. National Institute of Occupational Safety
and Health, this new study adds to emerging human evidence questioning the
safety of BPA.
"Compared with men without detectable urine BPA, those
with detectable urine BPA had more than three times the risk of lowered sperm
concentration and lower sperm vitality, more than four times the risk of a
lower sperm count, and more than twice the risk of lower sperm motility,"
said the study's lead author. De-Kun Li, MD, PhD, a reproductive and perinatal
epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif.
He added that urine BPA was not associated with semen volume
or abnormal sperm morphology.
"Similar dose-response associations were observed among
participants with only environmental BPA exposure at levels comparable to men
in the general United States population," said Li.
Despite a markedly reduced sample size in this group of men
exposed only to low environmental BPA sources, the inverse correlation between
increased urine BPA level and decreased sperm concentration and total sperm
count remain statistically significant, the researchers explained.
"The consistency of the findings between the current
and the previous two studies, despite different exposure measurements (urine
BPA levels vs. BPA exposure in the workplace) and end points (semen quality vs.
sexual function), strengthens the validity of these findings," said Dr.
Li. "The finding of the adverse BPA effect on semen quality
illustrates two points: first, exposure to BPA now has been linked to changes
in semen quality, an objective physiological measure. Second, this association
shows BPA potential potency: it could lead to pathological changes of the male reproductive
system in addition to the changes of sexual function."
Highly suspect
The researchers explained that BPA is believed by some to be
a highly suspect human endocrine disrupter, likely affecting both male and
female reproductive systems. This new epidemiological study of BPA's effects on
the male reproductive system provides evidence that has been lacking as the
U.S. Food and Drug Administration and various other U.S. government panels have
explored this controversial topic.
These findings, Dr. Li also points out, may portend adverse
BPA effects beyond the male reproductive system. Semen quality and malesexual
dysfunction could be more sensitive early indicators for adverse BPA effects
than other disease endpoints that are more difficult to study, such as cancer
or metabolic diseases.
For this study, workers in participating factories with and
without BPA exposure in the workplace were identified and deemed eligible for
the study. Among 888 eligible workers, 514 (58 percent) agreed to participate
in the study. Of them, 218 participants provided both urine and semen specimens
and were included in the final analyses.
Through an in-person interview, participants provided
information on demographic characteristics; potential risk factors that may
influence semen quality including smoking, alcohol use, chronic diseases,
history of sub-fertility, exposure to other chemicals and heavy metals; and
recent exposure to heat sources such as a steam bath, as well as occupational
history.
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