Jul 28 2016
Monday we wrote a blog about a study that linked the chemical Bisphenol A (BPA) found in plastic water bottles to ADHD in boys. We talked to lead author of the study, Shruti Tewar, clinical assistant professor at the Stead Family Department of Pediatrics at University of Iowa Children’s Hospital, to clarify a few things.
The data came from the National Health and Nutrition Examination Survey (NHANES) taken in the 2003 to 2004 cycle, Tewar said. The urine was collected at the time of the NHANES visit. The urine was analyzed then, including looking for BPA. The parents or guardians of the children were contacted within two weeks of the urine collection for a phone diagnostic interview to determine if the child had ADHD. The children were ages 8 to 15 during the time of study data collection.
Multivariate regression analysis was used to determine the connection between ADHD (yes or no) and BPA in the urine, Tewar said. The analysis accounted for several other factors that could have an influence towards an ADHD diagnosis. These confounding factors included age, sex, income, and lead levels.
Questions about synthetic estrogens began in the 1960s. Seven women were diagnosed with a rare cancer. They tried to determine the cause. They determined it was diethylstilbestrol (DES), a synthetic estrogen given to pregnant women to prevent miscarriages. The FDA said to stop giving DES to pregnant women because of it’s cancer causing properties in the early 70s.
This work spurred work looking into another endocrine disruptor: BPA. Animal studies were first. Oral BPA exposure was also found in a study of rats to be linked to mammary cancer. Scientists started to talk about the growing body of evidence pointing to the chemical causing cancer in animals. A 2012 study linked BPA to human breast cancer cell growth.
In addition, the chemical has been linked to changes in the hippocampus, the brain’s memory center, and the prefrontal cortex, which may have clinical applications that resemble Alzheimer’s disease, according to a study. The toxin is known to have estrogenic properties.
A study from China found a link between the chemical and brain cancer. People with higher levels of BPA in their urine were 1.6 times more likely to have a type of brain tumor called meningioma. The link was observed even accounting for other factors that may cause meningioma. This analysis is similar to that of the ADHD and BPA study. They followed 247 brain cancer patients and 258 with no history of cancer who were getting exams. Then urine samples were collected. Surveys were used to determine the other factors such as gender, age, and hormone therapy.
A New York Times article referenced a study that found a link between the toxin and high blood pressure. This was a one-time exposure that showed immediate health effects. Participants drank soy milk from a can. Their BPA levels in their urine raised significantly along with their blood pressure in the following hours. On days when they drank the soy milk from glass bottles, which don’t contain BPA, their BPA levels and blood pressure did not rise. The study suggests that people who drink from several cans or plastic bottles per day could be more likely to have hypertension.
BPA presents many risks to your health. If you are concerned about BPA exposure, try to eat fresh foods not in containers and avoid drinking from plastic bottles or cans. It’s better to opt for glass bottles.
A causal link between BPA and cancer in humans has not yet been confirmed. “Definitive proof of the role of BPA in human cancer induction is likely to remain limited, not least by ethical limits to human experiments,” the World Health Organization wrote in a 2014 report. To expose a human to BPA on purpose is unethical, so the ability to prove the causal link is limited.
However, the findings in animals are very telling. We have to extrapolate those findings to humans, said Dr. Ana Soto, a biologist at Tufts. “If we take the results in animal models together, I think we have enough evidence to conclude that BPA increases the risk for breast and prostate cancer in humans,” she said.