For the first time, researchers have confirmed an association between bisphenol-A (BPA) — a common chemical used to make plastics — and the development of autism spectrum disorder (ASD) in children.
The study, by researchers at Rowan University School of Osteopathic Medicine (RowanSOM) and Rutgers New Jersey Medical School (NJMS), shows that BPA is not metabolized well in children with ASD, suggesting they may be vulnerable to building up high levels of the potentially toxic chemical.
The researchers published their findings in the peer-reviewed journal Autism Research.
“It has been suspected for a lot of years that BPA is involved in autism, but there was no direct evidence,” said Dr. Peter Stein, of RowanSOM and the study’s lead author. “We’ve shown there is a link. The metabolism of BPA is different in some children with autism than it is in otherwise healthy children.”
Widespread exposure to BPA is a ‘significant public health concern’
BPA is an extremely common chemical used in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics are often used in containers that store food and beverages, such as water bottles, as well as a variety of other consumer goods. Epoxy resins are used to coat the inside of metal products, such as food cans, bottle tops and water supply lines. Some dental sealants and composites also may contain BPA.
The primary source of exposure to BPA for most people is through the diet. While air, dust, and water are other possible sources of exposure, BPA in food and beverages accounts for the majority of daily human exposure. The Centers for Disease Control and Prevention (CDC) reports that detectable levels of BPA are present in 95 percent of adult human urine samples and 93 percent of samples in children.
BPA is known as an endocrine disruptor — a substance which interferes with the production, secretion, transport, action, function and elimination of natural hormones. BPA can imitate our body’s own hormones in a way that could be hazardous for health. Babies and young children are thought to be especially sensitive to the effects of BPA.
In 2008, the possible health risks of the Bisphenol A (BPA) — a common chemical in plastic — made headlines. Parents were alarmed, pediatricians inundated with questions, and stores sold-out of BPA-free bottles and sippy cups.
Although public authorities set BPA safety levels, many experts believe these levels should be reviewed after a number of recent studies suggested the chemical may be more harmful than previously thought. In 2009, the Endocrine Society released a scientific statement that expressed concern over current human exposure to BPA, calling it a “significant public health concern” and urging regulatory bodies to restrict its use.
While past studies have indicated a link between BPA exposure and health problems such as hormonal and reproductive disorders, cancer, heart disease and diabetes, increasing evidence suggests that BPA may also be a culprit in abnormal brain development and resulting neurobehavioral disorders.
‘There might be a benefit to reducing BPA exposure’
In this latest study, Dr. Stein’s team examined urine specimens from 46 children with ASD and 52 healthy control children for both free BPA and total BPA concentrations. Like many chemicals, BPA becomes water soluble when it is bound to glucose in the liver — a process called glucuronidation. Conversion to a glucuronide and then excretion of the glucuronide in the urine is a major pathway for removing toxins from the body.
The researchers also conducted a metabolomic analysis — a study of the chemical processes involving metabolites — to screen for all the chemicals found in the children’s urine. The metabolomics analyses showed the mean number of statistically significant correlations between metabolites detected and total BPA excreted to be approximately three times greater with the ASD group than the controls, and the number of statistical significant correlations with fraction of BPA bound was approximately 15 times higher in the children with ASD.
In other words, in two different types of analyses, the metabolism of BPA was found to be altered in kids with autism, which could make them susceptible to accumulating toxic levels of the chemicals.
“Other studies involving rodent data have shown that BPA functions as an endocrine disruptor, but ours is the first to show this in humans and the first to associate it to autism,” said Dr. Stein. “The observations show that for some children there was a relationship between intermediary metabolism, the ability to conjugate BPA and symptoms of autism.”
Although the study involves a relatively small number of subjects, Stein said, “The key point is that the study seems to link BPA to autism and creates an open area for further research. One implication of our study is that there might be a benefit to reducing BPA exposure for pregnant women and for children with autism.”
Environmental exposures linked to autism
An estimated 1 in 68 children in the U.S. is diagnosed with an autism spectrum disorder, a group of disorders characterized by problems with brain development. Individuals with autism tend to have difficulties with social interaction, adopt repetitive behaviors and have problems with verbal and nonverbal communication.
While the causes of autism are not fully understood, a growing body of evidence points to environmental exposures as a likely risk factor. For instance, one recent study found that women who live in close proximity to pesticide sites during pregnancy are two thirds more likely to have children with autism or other developmental delays than women who live far away from such sites.
Other recent research has found that children with autism are more likely to have been exposed to air pollutants in early life and during fetal development than those without the condition. Children living in polluted urban areas have also been found to be at increased risk for brain inflammation and other neurodegenerative changes, including Alzheimer’s and Parkinson’s disease.