The chemical Bisphenol A (or BPA) is hard to avoid. It is used to make the clear, hard plastic containers so many foods and beverages come in; it's found in the linings of cans and the thermal paper in every credit card receipt.
The problem is that BPA is an endocrine disruptor and has been associated with obesity, diabetes, and neurological disorders, as well as some cancers. As a chemical that subtly disrupts hormones in the body, it is also suspected in fertility problems and birth defects.
So the news from a recent study that BPA appears to be strongly associated with the risk of prostate cancer in men is not completely unexpected, but men may want to make note of the connection and do what they can to avoid exposure, which isn't easy.
Men with prostate cancer had levels of urinary BPA about four times higher than those who did not have prostate cancer.
Ho and her colleagues analyzed urine samples from 60 men, 27 of whom had prostate cancer and 33 who did not. Men with prostate cancer had levels of urinary BPA about four times higher than those who did not have prostate cancer.
The apparent effect of high BPA levels was even greater in men under 65. Younger men with prostate cancer had urinary BPA levels that were eight times higher than men without prostate cancer. This may be because BPA has only been commercially used for the last 50 years, so younger men may have had more exposure to BPA early in life compared to older men, according to Ho.
Bottles and cans with recycling codes 1, 2, 3, 4, 5, and 6 are unlikely to contain BPA.
BPA disrupts centrosomes, structures within cells that are necessary for normal cell division. Centrosome abnormalities have been observed in different types of cancer cells. When the investigators exposed prostate cancer cells and non-cancerous prostate epithelial cells to five different doses of BPA, they found that BPA exposure increased the percentage of cells with centrosome abnormalities by anywhere from two- to eight-fold.
The group hopes to conduct more studies to understand better the relationship between BPA and cancer. The findings do not show that BPA causes cancer; but the strong relationship between higher levels of BPA and the occurrence of prostate cancer suggests that the chemical somehow sets the stage for cancer.
BPA has been in the news lately, none of it good. One study found that people who handled thermal receipts without gloves had far higher urinary levels of BPA than those who used gloves. Another report noted that chemicals, including BPA, found in processed food packaging can be absorbed into the food.
There is no way to know the consequences of low levels of long-term exposure to these chemicals, and except for people whose jobs put them in daily contact with the chemicals (such as handling thermal receipts), it can be difficult to estimate a person's exposure since the chemicals are used in so many items.
Children are believed to be especially vulnerable because their bodies are developing. That is one reason why BPA is no longer found in baby bottles. It may be that some people are genetically more susceptible to endocrine-disrupting compounds.
The apparent effect of BPA levels was even greater in men under 65. Younger men with prostate cancer had urinary BPA levels that were eight times higher than men without prostate cancer.
Larger studies with more participants, different populations, and multiple measurements of urinary BPA levels will be needed going forward. For example, if one reduces exposure to BPA as measured by urinary BPA, would it reduce the risk of prostate cancer or slow the progression of the disease?
Ho, director of the Cincinnati Cancer Center and Chair of Environmental Health at the University of Cincinnati College of Medicine, says prevention or intervention studies are the ultimate goal.
The study is published in PLOS ONE and is freely available to the public.