Baby male monkeys act more like female infants after BPA exposure in the womb.
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Nakagami A, T Negishi, K Kawasaki, N Imai, Y Nishida, T Ihara, Y Kuroda, Y Yoshikawa and T Koyama. Alterations in male infant behaviors towards its mother by prenatal exposure to bisphenol A in cynomolgus monkeys (Macaca fascicularis) during early suckling period. Psychoneuroendocrinology doi:10.1016/j.psyneuen.2009.03.005. |
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| Erik K Veland/flickr |
| The behavior of infant male cynomolgus monkeys is feminized by fetal exposure to BPA |
A new study finds that exposure to bisphenol A in the womb causes infant male monkeys to behave more like infant females, highlighting a new and potentially important consequence of exposure to low doses of BPA. The species of monkey used in this study was chosen due to its similarity to humans. People are exposed to BPA–a chemical found in hard plastics–through food, water and some medical instruments.
Context
Bisphenol A, or BPA, is a chemical used in many plastics. Polycarbonate plastic, which is clear and often shatterproof, is used in many consumer products including baby bottles, water bottles and plastic toys. Most food cans on US supermarket shelves today are lined with an epoxy resin made from BPA.
Humans are exposed to BPA through plastic’s contact with food, or by contact with BPA containing products or devises such as dental sealants and medical equipment.
Many of our body’s processes are controlled by hormones. Some chemicals can mimic hormones and disrupt normal body functioning. Processes involving reproduction and development appear to be especially vulnerable.
Concerns about BPA’s ability to act like estrogen hormones have received a great deal of scientific and media attention. Many scientific studies from laboratories across the world have uncovered a host of negative health effects associated with BPA exposure.
Of recent concern, are studies reporting changes in behavior and brain function in laboratory animals exposed to BPA. Male rats exposed to BPA have shown female-like behaviors in some studies. Female rats have been shown to be more cautious and less explorative of their environment than unexposed females (Adriani et al. 2003).
Many of these studies use standard lab animals–such as rats and mice–and have been criticized because of the difficulty in making direct links to human health. Although many of the physiological systems investigated using rats and mice are similar to humans, there are nonetheless clear differences.
Both humans and monkeys are primates, and are more physiologically similar than typical lab animals. Therefore, research with monkeys is generally easier to extrapolate to human health.
What did they do?
Researchers in Japan exposed female cynomolgus monkeys to BPA throughout most of their pregnancy.
The BPA was delivered to the monkeys through a small implanted devise designed to release small amounts over time. Control monkeys received BPA-free implants.
The daily dosage of BPA given to the monkeys was 10 micrograms per kilogram of body weight. This dose is comparable to exposures used in prior rat studies.
Once her infants were born, researchers observed both mother and infant behaviors every two weeks when the infants were 2 and 3 months of age. Common monkey behaviors were placed into categories. These categories included clinging to the mother, environmental exploration, social exploration, outward looking and others.
The frequency of behaviors was tallied in each behavior category and compared between male and female infants.
What did they find?
The behaviors of the BPA exposed male infants was similar to that of female infants in several categories.
The major areas in which the male infants acted like normal female infants included clinging and social exploration. Male infant monkeys whose mothers were exposed to BPA didn’t cling to their mothers like normal male monkeys and their level of social exploration was also greatly reduced.
Outward looking, in which the monkeys look away from their mother and observe the area around them, could be an indication of the monkey’s concern or interest in the environment. Both exposed mothers and their male infants showed significantly more “outward looking” than unexposed monkeys.
Female infants exposed to BPA had more outward looking behaviors than unexposed females, although differences were less dramatic than for males. Other categories were not affected by BPA exposure in females.
What does it mean?
This study shows strong evidence that BPA has the ability to cause significant behavior changes in nursing monkeys. The male infants acted like female infants when their mothers were exposed to low doses of BPA during pregnancy.
Normally, the infant monkeys used in this study would show distinct behavior differences between males and females. BPA exposure caused the males to act like females for several common behaviors.
This work supports other findings in common lab animals such as rats, indicating responses to BPA could have similar consequences across many groups of animals.
Although it is uncertain what this could mean for humans exposed to BPA, this study highlights a new and important consequence of BPA exposure in human health. The species of monkey used in this study was chosen due to its similarity to humans.
The BPA dose given to the mother monkeys in this study was about 10 times higher than the daily amount to which humans are thought to be exposed. However, the actual concentration of BPA measured in the monkey’s blood was similar to levels commonly observed in people. This suggests that either monkeys metabolize BPA differently than do people, or that current estimates of human exposure are low. This has been suggested by previous research.
Human mothers at time of delivery have been shown to have plasma BPA levels ranging from less than 1 to about 22 nanograms per mililiter (Padmanabhan et al. 2008). The monkeys in this study had plasma BPA levels of about 12 nanograms per milliliter.
ResourcesAnimal behavior. Soceity for Integrative and Comparative Biology. Adriani W, D Della Seta, F Dessi-Fulgheri, F Farabollini and G Laviola, 2003. Altered profiles of spontaneous novelty seeking, impulsive behavior, and response to D-amphetamine in rats perinatally exposed to bisphenol A. Environmental Health Perspectives 111: 395-401. BPA Overview. Envrionment Canada. Clotfelter, ED, AM Bell and KR Levering. 2004. The role of animal behaviour in the study of endocrine-disrupting chemicals. Animal Behavior 68:665-676. Padmanabhan V, K Siefert, S Ransom, T Johnson, J Pinkerson, L Anderson, L Tao and K Kannan, 2008. Maternal bisphenol-A levels at delivery: a looming problem? Journal of Perinatology 28: 258-263. Zala, SM and DJ Penn. Abnormal behaviours induced by chemical pollution: a review of the evidence and new challenges. Animal Behavior 68:649-664. |
Scientific studies of BPA
