September 24, 2012

expert reaction to bisphenol A and reproductive health in monkeys

Pregnant rhesus monkeys exposed to the chemical bisphenol A (BPA) during the equivalent of the human third trimester developed altered mammary glands, according to a study in PNAS. 

Prof Richard Sharpe, MRC Centre for Reproductive Health at The University of Edinburgh, said:

“This study in pregnant rhesus monkeys shows that (extremely high) exposure to bisphenol A  is associated with subtle changes in oocytes (eggs) in the developing fetal ovary.  In rhesus monkeys, as in humans, the number of oocytes becomes fixed during fetal life and determines reproductive lifespan and fertility in adulthood.  Therefore, any effects of environmental chemicals during fetal development on oocyte development are of potential concern.

“Although most humans are exposed to bisphenol A (mainly via food/drink), including pregnant women, the levels of exposure are extremely low and most bisphenol A is inactivated immediately in the gut or liver with the result that exposure of body tissues is likely to be minimal; in fact, contrary to what the authors of this article state, the levels of free (biologically active) bisphenol A are too low to measure in normal humans.  The levels of exposure used by the authors in the present study are far in excess of human exposure (by many 100-fold*), so raise minimal health concerns for pregnant women and their babies.

“In addition, the effects on oocytes that are described are subtle and animal numbers are very small; and the implications, if any, for later oocyte function and fertility are unknown.  The most disconcerting aspect of this publication is that the authors claim that the levels of exposure they use ‘are analogous to those reported in humans’, a statement that bears no relationship to the extensive amount of human exposure data.”

*For example, in their study 1 they exposed to 400ug/kg/day whereas human exposure is estimated to be <1ug/kg/day. Exposure in their study 2 was via an implant which would have bypassed normal bisphenol A inactivation in the gut and thus resulted in inordinately higher levels of exposure than would occur in humans

‘Bisphenol A alters early oogenesis and follicle formation in the fetal ovary of the rhesus monkey’ by Patricia Hunt et al. published in PNAS  on Monday 24^th September.