The US study by John D Meeker et al measured urinary concentrations of BPA and compared them to levels of serum thyroid and reproductive hormone levels in 167 men from an infertility clinic.
BPA exposure and hormone levels
The paper, published in the journal Environmental Science and Technology, said BPA was detected in 89 per cent of urine samples with a media range of 1.3 ng/mL. It also found that men with higher urine BPA concentrations had higher blood levels of follicle-stimulating hormone (FSH) and lower levels of inhibin B. Raised FSH and depressed inhibin B have been associated with poorer sperm quality in humans.
The study also highlighted a fall in the ratio of estrogen to testosterone. This could reflect an anomaly in the production or elimination of these hormones. Lower thyroid-stimulating hormone (TSH) was also observed when data on multiple BPA measurements were used to assess exposure, suggesting excessive thyroid hormone.
The researchers noted that the number of human studies on the effects of the chemical, used in polycarbonate baby bottles and the epoxy linings of food and beverage cans, are limited.
The research team said that its overall conclusions were supported by findings from other studies on animals that have linked altered hormone levels with BPA exposure.
Study limitations
But the group pointed out that its work had “several limitations” as it said its findings need to be substantiated by further research. The most significant of these was that because levels of BPA and hormones were measured at the same time, there was the possibility that hormonal levels changed the concentration of BPA, rather than the reverse. Exposure measure error and the fact that all the subjects were recruited from an infertility clinic were factors that may also have skewed the results, said the study.
Despite these reservations, the study concluded: “Human exposure to BPA may be associated with alterations in circulating hormone levels.”
The continued safe use of BPA in food packaging is currently being scrutinised by both the US Food and Drug Administration and the European Food Safety Authority (EFSA). Presently, Canada and Denmark are the only two countries to have banned its use in food containers or packaging for children aged 0-3.
Urinary Bisphenol A concentrations in relation to serum thyroid and reproductive hormone levels in men from an infertility clinic by Meeker, JD, AM Calafat and R Hauser.
Source: Environmental Science and Technology