OAKLAND, Calif., -- In utero exposure to Bisphenol-A may adversely affect male genital development, according to a Kaiser Permanente study published online in the journal Birth Defects Research.
The observational study found that the sons of BPA-exposed Chinese workers had a shortened distance between their genitals and anus -- known as anogenital distance -- compared with sons whose parents were not exposed to workplace BPA.
The association between BPA exposure during pregnancy and anogenital disease also showed a dose-response relationship, meaning the greater the BPA exposure a mother had during her pregnancy, the shorter her son’s AGD measured, according to researchers.
“Although the finding needs to be confirmed by additional research, this study provides the first epidemiological evidence that parental exposure to BPA in the workplace during pregnancy is associated with shortened AGD in male offspring,” said De-Kun Li, MD, PhD, the principal investigator of the study and a reproductive and perinatal epidemiologist at the Kaiser Permanente Division of Research in Oakland, Calif. “This finding indicates that BPA may interfere with testosterone function during fetal development because the shortened AGD indicates under-developed male genitalia, likely due to an abnormal testosterone function.”
This study is the fifth in a series published by Dr. Li and his colleagues that examine 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.
• The third study published in Fertility and Sterility showed that an increasing urine BPA level was significantly associated with decreased sperm concentration, decreased total sperm count, decreased sperm vitality and decreased sperm motility.
• The fourth study, published in 2011 in the Journal of Reproductive Toxicology showed that parental exposure to BPA during pregnancy was associated with decreased birth weight in offspring.
For this study, workers in participating factories with and without BPA exposure in the workplace were identified. They were divided into three groups: unexposed (neither parents exposed to BPA in workplace), father directly exposed (representing maternal indirect exposure through the father), and mother directly exposed during the index pregnancy. Then 153 sons, age ranging from infancy to 17 years old with 81 percent being less than 10 years old, were examined. The study found that maternal exposure to BPA in the workplace during pregnancy was associated with a 2.8 millimeter (approximately 0.11 inch) shortened AGD in sons if the mother was indirectly exposed through the father’s direct exposure, and 8.1 millimeter (approximately 0.32 inch) shortened AGD in sons if the mother was directly exposed, compared to unexposed parents.
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, a chemical created in the production of polycarbonated plastics and epoxy resins found in baby bottles, plastic containers, the linings of cans used for foods and beverages, and in dental sealants.
The researchers explained that BPA is considered to be a highly suspect human endocrine disrupter with estrogen-like effect.
“This new epidemiological study of in utero BPA’s effects on the fetal male reproductive system provides direct evidence from human studies that is urgently needed as the U.S. Food and Drug Administration and various other U.S. government panels are evaluating this controversial topic,” Li said.
This new finding is also consistent with a recent report from animal studies that in-utero exposure to BPA made male offspring less attractive to female mating counterparts.
Other authors on this study include: M. Miao, MD, PhD, J. Wang, PhD, E. Gao, MD, MPH, PhD, and W. Yuan of the Shanghai Institute of Planned Parenthood Research and National Population and Family Planning Key Laboratory of Contraceptive Drugs and Devices; Guohong Li, Institute for the Prevention and Treatment of Occupational Diseases, Baling Petrochemical Company, Yueyang, China; and Z. Zhou, MD, PhD and Y. He, PhD of the Department of Occupational Health and Toxicology, School of Public Health and WHO Collaborating Center for Occupational Health, Fudan University, Shanghai.