Bisphenol A (BPA) is a widely-used synthetic compound which has been the subject of public health concern since it has been shown that continuous daily exposure to the chemical is widespread. The main cause for concern is the use of BPA in food containers such as polycarbonate drinks bottles and epoxy resins lining food containers.
BPA has a chemical structure similar to the hormone oestrogen, and this has led to concerns that it may cause adverse health effects by mimicking the actions of oestrogen and similar sex hormones in the body.
EFSA concludes BPA is safe
A toxicology report by the European Food Safety Authority in 2008 concluded that exposure to BPA was unlikely to cause adverse health effects. This is due to the efficient conversion of BPA to an inactive metabolite by the liver, its rapid removal from the body via urine, and the results of scientific investigations such as one by Snyder et al (2000) suggesting that BPA does not have any effect on hormonal regulation in the body.
BPA can cause hormone changes in rat models
Research by Steinmatz et al (1997) suggested that BPA could mimic the effects of oestrogen in rats genetically predisposed to hyperprolactinaemia. The rats treated with BPA demonstrated an increase in the release of the hormone prolactin. The study concluded that BPA exposure may have important implications in women suffering from hyperprolactinaemia. However, the absence of any effect of BPA on normal lab rats suggests these effects may be limited to individuals with pre-existing hormonal imbalances.
In 2001, Tohei et al demonstrated that BPA inhibits the testicular function of male rats, but the researchers administered a much higher sub-cutaneous dose of BPA to the rats than humans are likely to be exposed to.
New study suggests BPA is linked with testosterone
Galloway et al published a new population-based study in August 2010 in which they examined the relationship between urinary BPA levels and the levels of testosterone and oestrogen in more than 700 adults. They found no association between BPA levels and hormone levels in women; but in the men studied, those with higher urinary BPA were also more likely to have higher total testosterone levels.
BPA may increase risk of disease
In an earlier population-based study by Lang et al (2008), researchers found a link between higher urinary BPA levels and an increased incidence of cardiovascular disease and diabetes. However, in the later study by Galloway et al, an incidental finding showed urinary BPA to be increased in subjects with a higher waist circumference and increased weight, so this association may well be incidental.
Lang et al also found a significant association between urinary BPA levels and abnormally high concentrations of some liver enzymes. It is unclear whether this association is causal, or whether the two are both raised as a result of some other underlying change.
More research is needed
In order to establish whether exposure to BPA does result in any significant hormonal changes likely to cause adverse effects in humans, more research is needed. No epidemiological studies have so far been able to identify any causal relationships between BPA exposure and human disease.
Sources
- "Toxicokinetics of Bisphenol A" The EFSA Journal 759 (2008)
- RW Snyder, SC Maness, KW Gaido "Metabolism and Disposition of Bisphenol A in Female Rats" Toxicology and Applied Pharmacology 168: 225-234 (2000)
- R Steinmetz, NG Brown, DL Allen "The Environmental Estrogen Bisphenol A Stimulates Prolactin Release in Vitro and in Vivo" Endocrinology 138:1780-1786 (1997)
- A Tohei, H Koibuchi, K Tamura "Bisphenol A Inhibits Testicular Functions and Increases LH Secretion in Male Rats" Experimental Biology and Medicine 226:216-221 (2001)
- T Galloway, R Cipelli, J Guralnik "Daily Bisphenol A Excretion and Associations with Sex Hormone Concentrations: Results from the InCHIANTI Adult Population Study" Environmental Health Perspectives 118:1603-1608 (2010)
- IA Lang, TS Galloway, A Scarlett "Association of Urinary Bisphenol A Concentration with Medical Disorders and Laboratory Abnormalities in Adults" Journal of the American Medical Association 300:1303-1310 (2008)