A study in mice has found prostate cancer is more likely to develop when exposure to BPA levels matches that typical for pregnant women, according to researchers from the University of Illinois at Chicago (UIC) investigating concerns over the chemical used in water bottles.
Gail Prins, professor of physiology and director of the andrology laboratory at the UIC College of Medicine, says BPA levels are almost impossible to avoid - the plasticizer is found in water bottles, soup can liners and paper receipts.
Her study - using human prostate cells in the rodents, and published in the journal Endocrinology - suggests that exposure of male fetuses to BPA (bisphenol A) could lead to a later-life higher risk of prostate cancer.
Dr. Prins, who specializes in basic research into hormonal control of the prostate gland's development, and is interested in its growth and function, says other research proves the difficulty of avoiding BPA:
"Previous studies have shown that people who avoided all contact with plastics or other BPA-containing objects for up to a month or more still had BPA in their urine, which means they must have come into contact with BPA in the last 24 to 48 hours, since it clears the body rather quickly. It's very hard to avoid."
The UIC research has investigated pregnancy exposure to BPA "because the chemical, which mimics the hormone estrogen, has been linked to several kinds of cancer, including prostate cancer, in rodent models."
Dr. Prins says: "Our research provides the first direct evidence that exposure to BPA during development, at the levels we see in our day-to-day lives, increases the risk for prostate cancer in human prostate tissue."
Study used human stem cells to create model of prostate
The use of human stem cells implanted into mice allowed the study to investigate whether prostate cancer develops in direct response to BPA exposure.
The cells had been taken from deceased young men, allowing any cancer cause-and-effect comparisons to be made in the animal models. One group of mice with human-tissue prostates was exposed to BPA while another was not.
The exposed mice were given feed containing BPA "equivalent to levels ingested by the average person" for 2 weeks after stem cell implantation. A control group was not fed BPA.
The prostate tissue was allowed to mature for 1 month, after which the mice were given the hormone estrogen. This was designed to mimic the estrogen levels that naturally rise as men age - which the researchers say is known to be a factor in prostate cancer.
Finally, after 2-4 months, the prostate tissue from both groups of mice was analyzed for cancer.
Dr. Prins found pre-cancerous lesions or full prostate cancer in tissue samples from a third of the mice that had been fed BPA, compared with just over a tenth of the control group of oil-fed mice.
Dr. Prins says the US government should act over exposure to BPA:
"The findings of adverse effects of BPA in human tissue are highly relevant and should encourage agencies like the Food and Drug Administration to re-evaluate their policies in the near future."
Links between the plasticizer and cancer are related, Dr. Prins believes, to effects on hormone sensitivity. She explains: "We believe that BPA actually reprograms the stem cells to be more sensitive to estrogen throughout life, leading to a life-long increased susceptibility to diseases including cancer."
The FDA has explained its policy on BPA. The regulator has allowed the chemical in food-contact materials since 1960 and has found no evidence to support the requests it has received to ban it.
How to reduce exposure to BPA
While Dr. Prins points out that avoiding BPA is difficult, the FDA says in its advice to consumers that some measures reduce exposure to the chemical:
- Avoid plastic containers that have recycle codes 3 or 7 on them (some may be made with BPA)
- Do not use plastic bottles for hot liquids
- Discard scratched bottles.
The Natural Hydration Council, UK, made the following statement:
"The plastic material used to contain naturally sourced bottled waters found on supermarket shelves is made of PET (Polyethylene Terephthalate). There is no Bisphenol A (BPA) in PET plastic. PET is the main packaging used for beverages, it is completely safe and complies with all European and national legal requirements."
In other medical research, BPA was linked to childhood obesity in a study published in the Journal of the American Medical Association in September 2012, and to the same problem in girls aged 9 to 12 in a PLoS ONE study in June 2013. Other 2013 research suggested links between BPA and female infertility, and childhood asthma.