Running head: EXPOSURE TO BISPHENOL A
Human Exposure to Bisphenol A
Jainam Shah
Wayne State University
Abstract
Bisphenol-a (BPA) is an environmental toxin that has recently been at the forefront of
health issues. It is believed to mimic the hormone estrogen and cause adverse health
affects. Many studies have been conducted in vivo to observe the effects in animals like
rodents. These studies reveal that exposure to BPA can lead to early onset of puberty,
obesity, decrease in sperm quality, polycystic ovary syndrome, miscarriage and other
health effects. Many studies also measure levels of BPA in human tissues and fluids. It
is evident that humans are exposed to this chemical, but there are few studies conducted
to explain possible health outcomes that may arise from exposure to it. Understanding
the effects of BPA is critical because of its effects on human health. In this paper, I will
discuss health effects observed in animals, levels of BPA found in human samples and
how high levels of BPA during pregnancy is associated with miscarriage/adverse
pregnancy outcomes. With this research, I propose that more funding be provided to
conduct research on human cells/fluids (in vitro) in order to determine the effects BPA
has on human health.
Human Exposure to Bisphenol A
In today’s society, humans are exposed to a variety of chemicals in the
environment. They can be in the air we breathe, in the water we drink, or the foods we
eat. Some of these chemicals act as endocrine disruptors which can mimic hormones
found in the body and disrupt the endocrine system. This leads to many abnormalities
and adverse health effects to those exposed to these chemicals (Lee, Chattopadhyay,
Gong, Ahn, Lee, 2003). One such chemical is 2, 2 bis (4-hydroxyphenyl) propane,
commonly known as bisphenol-a (BPA). An article written in the Environmental Health
Perspectives reports that over 6 billion pounds of BPA is consumed every year (Vom
Saal, Claude Hughes, 2005). This chemical is widely produced and is found in baby and
water bottles made from polycarbonate plastic, food can liners made from epoxy resins
and in dental sealants. Even the water we use to take showers and to drink, along with
many other sources, may contain BPA (Vom Saal et al., 2005, Dash, Marcus, Terry,
2006). BPA is a cause for concern since it has been found to leech into the food we eat
and drink. The ester bonds that link the molecules in plastics and resins are easily broken
by heat, repeated washing of polycarbonates, or in the presence of acid/bases making it
easier for the chemical to leech into our system (Vom Saal et al., 2005). With this high
exposure, it is important to know what effects BPA has on our health. Many studies have
been conducted in vivo with animals to observe the effects of exposure to BPA. There
have been few in vitro studies conducted with human tissues and fluids that try to observe
and explain the effects of BPA exposure. Bisphenol A exhibits toxic properties and
further research must be conducted in order to understand the adverse health effects that
can occur in humans.
Studies conducted in vivo with animals have shown that BPA is toxic and that it
causes many delirious health effects. It has been reported that in utero exposure to BPA
results in early onset of puberty and increased body weight (Honma, Suzuki, Buchanan,
Katsu, Watanabe, Iguchi, 2002, Nikaido et al., 2004). These studies report that early
exposure to BPA results in reproductive abnormalities and other developmental problems
in mice. Nikaido and Shizuka observed that female mice exposed to BPA had earlier
vaginal openings which caused puberty at a younger age. It was also observed that
exposure to BPA resulted in increased fetal body weight which progressed into
adulthood. The latter effect is also noted in male rodents. Studies conducted on male
rodents’ show that exposure to BPA leads to a decrease in serum testosterone levels
which continues on into adulthood (Richter et al., 2007, Chitra, Latchoumycandane,
Mathur, 2003). Because BPA mimics the female hormone estrogen, high levels of this
chemical in males is found to decrease sperm production and levels of testicular
testosterone (Chitra et al., 2007). The above studies also report that exposure to BPA
causes an increase in prostate size and other male reproductive abnormalities. It is
evident that BPA mimics the hormone estrogen and displays toxic properties which cause
adverse affects in animals. What’s vexing is that humans are exposed to this endocrine
disruptor from many pathways and little is known about its effects on human health.
BPA levels have been measured in humans and are detected in many fluids and
tissues. Research by Osamu Tsutsumi (2005) reported at 15 weeks of gestation (critical
developmental period in humans) showed that BPA was detected in amniotic fluids at
concentrations five times higher than normal. Some studies also found that women with
polycystic ovary syndrome (PCOS) and some healthy men have higher levels of serum
BPA when compared with normal women (Osamu Tsutsumi. 2005, Vandenberg, Hauser,
Marcus, Olea, Welshons, 2007). Vandenberg et al report that BPA is measured in human
urine samples, serum blood and plasma, and breast milk. Of major concern are the high
levels of BPA found in maternal serum and amniotic fluids during pregnancy, especially
since the fetus can be exposed to the chemical during critical periods of development
(2007). Many studies have been conducted in order to measure levels of BPA in humans
to show that humans are exposed to this dangerous chemical.
In the few studies that are conducted in vitro with human fluids and tissues,
experimenters have hypothesized that BPA causes adverse effects in mankind. In one
study, experimenters report that increased exposure to BPA can result in recurrent
miscarriages in humans.
Forty-five patients who had 3 or more first-trimester
miscarriages were observed and compared to 32 healthy non-pregnant females who had
no history of miscarriage (Sugiura-Ogasawara, Ozaki, Sonta, Makino, Suzumori, 2005).
This study found that patients who had miscarried had higher levels of BPA. Because of
this relationship, it is believed that exposure to high levels of BPA can lead to recurrent
miscarriage in humans. Surprisingly, in a recent study it was found that even low doses
of BPA can trigger cell apoptosis which can lead to adverse pregnancy outcomes
including miscarriage (Nora Benachour, Aziz Aris, 2009).
In this study, 5 placentas
were obtained from healthy women who had no medical conditions.
The
cytotrophoblasts (placental cells) were then isolated and exposed to varying levels of
BPA. This study was conducted in vitro on human cells and tries to explain what effects
could be observed in vivo with placental cells when they are exposed to BPA.
Interestingly, these findings were also observed in animal studies conducted on mice
(Hunt et al. 2003). In this study, the mice were exposed to BPA and the experimenters
observed abnormal metaphase configurations. It was observed that high exposure to
BPA leads to meiotic aneuploidy (abnormal number of chromosomes) which is said to be
a leading cause of miscarriage.
These in vitro and in vivo studies are useful in
understanding what effects can be observed in humans when cells are exposed to BPA.
Many studies have been published that discuss the effects varying doses of BPA
has on health outcomes in animals. It is unethical to conduct in vivo experiments in
humans in order to understand what effects BPA exposure poses. Even so, very few in
vitro studies have been conducted with human fluids and tissues to observe effects on
certain cells in humans. Additional research is needed in the area concerning the effects
BPA has on human health.
This area has largely been unexplored even with the
extensive knowledge available on effects of endocrine disruptors in animals. Further
research needs to be conducted to understand the exact role BPA plays in humans. I
propose that more funding be provided so that research can be conducted in vitro with
samples in human fluids and tissues.
These epidemiological studies will be important in establishing a connection with
BPA exposure and adverse health outcomes in humans. Effects seen in animals are
widely researched and understood. By understanding the effects this chemical poses on
humans, measures can be taken to control the amount of BPA humans are exposed to on
a daily basis. This can be done by banning the production of BPA in products that are
known to leech the chemical. The first step is to understand what role BPA plays in
human health especially since the chemical has been correlated with pregnancy loss in
humans. Once we have concluded the effects BPA has on our health, we will be able to
create a healthier environment for future generations.
References
Hyun Ju Lee, Soma Chattopadhyay, Eun-Yeung Gong, Ryun Sup Ahn, Keesook Lee.
(2003). Antiandrogenic Effects of Bisphenol A and Nonylphenol on the Function
of Androgen Receptor. Toxilogical Sciences, 75. pp 40-46.
Frederic S vom Saal, Claude Hughes. (2005). An Extensive New Literature Concerning
Low-Dose Effects of Bisphenol A Shows the Need for a New Risk Assessment.
Environmental Health Perspectives, 113. pp. 926-933.
Chiranjeev Dash, Michele Marcus, Paul D. Terry. (2006). Bisphenol A: Do recent
studies of health affects on humans inform the long standing debate? Reviews in
Mutation Research, 613. pp. 68-75.
Shizuka Honmaa, Atsuko Suzukib,c, David L. Buchananb,c, Yoshinao Katsub,c,
Hajime Watanabeb,c, Taisen Iguchi. (2002). Low Dose effect of in utero
exposure to bisphenol A and diethylstilbestrol on female mouse reproduction.
Reproductive Toxicology, 16. pp. 117-122.
Yasuyoshi Nikaido, Katsuhiko Yoshizawa, Naoyuki Danbara, Miki Tsujita-Kyutoku,
Takashi Yuri, Norihisa Uehara, Airo Tsubura. (2004). Effects of maternal
xenoestrogen exposure on development of the reproductive tract and mammary
gland in female CD-1 mouse offspring. Reproductive Toxicology, 18. pp. 803811
Catherine A. Richter , Linda S. Birnbaum , Francesca Farabollini , Retha R. Newbold
,Beverly S. Rubin , Chris E. Talsness , John G. Vandenbergh ,
Debby R. Walser-Kuntz, Frederick S. vom Saal. (2007). In vivo effects of
bisphenol A in laboratory rodent studies. Reproductive Toxicology, 24. pp 199224.
K.C. Chitra, C. Latchoumycandane, P.P Mathur. (2003). Induction of oxidative stress by
bisphenol A in the epididymal sperm of rats. Toxicology, 185. pp. 119-127.
Osamu Tsutsumi. (2005). Assessment of human contamination of estrogenic endocrinedisrupting chemicals and their risk for human reproduction. Journal of Steroid
Biochemistry and Molecular Biology, 93. pp. 325-330.
Laura N. Vandenberg, Russ Hauser, Michele Marcus, Nicolar Olea, Wade V. Welshons.
(2007). Human Exposure to bisphenol (BPA). Reproductive Toxicology, 24. pp.
139-177.
Mayumi Sugiura-Ogasawara, Yasuhiko Ozaki, Shin-ichi Sonta, Tsunehisa Makino,
Kaoru Suzumori. (2005), Exposure to bishphenol A is associated with recurrent
miscarriage. Human Reproduction, 20. pp. 2325-2329.
Patricia A. Hunt, Kara E. Koehler, Martha Susiarjo, Craig Hodges, Arlene Ilagan, Robert
C. Voigt, Sally Thomas, Brian F. Thomas, Terry J. Hassold. (2003). Bisphenol A
Exposure Causes Meiotic Aneuploidy in the Female Mouse. Current Biology, 13.
pp. 546-553.