BPA levels in humans dramatically underestimated, study finds
Date:December 5, 2019
Source: Washington State University
Researchers have developed a more accurate method of measuring bisphenol A (BPA) levels in humans and found that exposure to the endocrine-disrupting chemical is far higher than previously assumed. The study provides the first evidence that the measurements relied upon by regulatory agencies, including the US Food and Drug Administration, are flawed, underestimating exposure levels by as much as 44 times.
Researchers have developed a more accurate method of measuring bisphenol A (BPA) levels in humans and found that exposure to the endocrine-disrupting chemical is far higher than previously assumed.
The study, published in the journal The Lancet Diabetes & Endocrinology on Dec. 5, provides the first evidence that the measurements relied upon by regulatory agencies, including the U.S. Food and Drug Administration, are flawed, underestimating exposure levels by as much as 44 times.
“This study raises serious concerns about whether we’ve been careful enough about the safety of this chemical,” said Patricia Hunt, Washington State University professor and corresponding author on the paper. “What it comes down to is that the conclusions federal agencies have come to about how to regulate BPA may have been based on inaccurate measurements.”
BPA can be found in a wide range of plastics, including food and drink containers, and animal studies have shown that it can interfere with the body’s hormones. In particular, fetal exposure to BPA has been linked to problems with growth, metabolism, behavior, fertility and even greater cancer risk.
Despite this experimental evidence, the FDA has evaluated data from studies measuring BPA in human urine and determined that human exposure to the chemical is at very low, and therefore, safe levels. This paper challenges that assumption and raises questions about other chemicals, including BPA replacements, that are also assessed using indirect methods.
Hunt’s colleague, Roy Gerona, assistant professor at University of California, San Francisco, developed a direct way of measuring BPA that more accurately accounts for BPA metabolites, the compounds that are created as the chemical passes through the human body.
Previously, most studies had to rely on an indirect process to measure BPA metabolites, using an enzyme solution made from a snail to transform the metabolites back into whole BPA, which could then be measured.
Gerona’s new method is able to directly measure the BPA metabolites themselves without using the enzyme solution.
In this study, a research team comprised of Gerona, Hunt and Fredrick vom Saal of University of Missouri compared the two methods, first with synthetic urine spiked with BPA and then with 39 human samples. They found much higher levels of BPA using the direct method, as much as 44 times the mean reported by the National Health and Nutrition Examination Survey (NHANES). The disparity between the two methods increased with more BPA exposure: the greater the exposure the more the previous method missed.
Gerona, the first author on the paper, said more replication is needed.
“I hope this study will bring attention to the methodology used to measure BPA, and that other experts and labs will take a closer look at and assess independently what is happening,” he said.
The research team is conducting further experiments into BPA measurement as well as other chemicals that may also have been measured in this manner, a category that includes environmental phenols such as parabens, benzophenone, triclosan found in some cosmetics and soaps, and phthalates found in many consumer products including toys, food packaging and personal care products.
“BPA is still being measured indirectly through NHANES, and it’s not the only endocrine-disrupting chemical being measured this way,” Gerona said. “Our hypothesis now is that if this is true for BPA, it could be true for all the other chemicals that are measured indirectly.”
This study was supported by grants from the National Institutes of Health.
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Materials provided by Washington State University. Original written by Sara Zaske. Note: Content may be edited for style and length.
- Roy Gerona, Frederick S vom Saal, Patricia A Hunt. BPA: have flawed analytical techniques compromised risk assessments?The Lancet Diabetes & Endocrinology, 2019; DOI: 1016/S2213-8587(19)30381-X
Dr Piergiorgio Gentile, lead author and a Biomedical Engineer at Newcastle University, explains:
“Mesh is implanted inside the body to provide stability while the internal tissues heal but, unfortunately, it also provides the perfect surface for bacteria to grow on. Once the bacteria form a biofilm on the surface, it’s very difficult to treat the infection. By sandwiching the honey in a multilayer coating on the mesh surface and slowly releasing it, the aim is to inhibit the growth of the bacteria and stop the infection before it even starts.
“These results are really very exciting. Honey has been used to treat infected wounds for thousands of years but this is the first time it has been shown to be effective at fighting infection in cells from inside the body.”
Dr Mancuso, a lecturer within the Nanotechnology and Integrated Bioengineering Centre (NIBEC) at Ulster University, adds:
“Although numerous antibiotic-based coatings, constructed through layered approaches, and intended for the development of antibacterial implants, have been investigated so far, it has been found that the effect of antibiotics may decrease with time, since antibiotic resistant bacteria may potentially develop.”
Honey has been used to treat infected wounds since ancient times, and thousands of years before the discovery of bacteria.
Most honey is believed to have some bacteria killing properties because it contains chemicals that produce hydrogen peroxide.
However, in 1991 a New Zealand study showed that when you remove the hydrogen peroxide from a range of honeys, Manuka — made from nectar collected by bees that forage on the wild Manuka tree — was the only type that kept its ability to kill bacteria. This is due to the presence of a unique ingredient, now identified as methylglyoxal, which has specific antimicrobial properties.
Using medical-grade Manuka honey, the team used the Layer-by-Layer assembly technology to create alternating layers of negatively-charged honey and positively-charged conventional biocompatible polymer to modify the surface of electrospun membrane, each layer just 10-20 nanometers thick.
Tested in-vitro on different soft tissue cell lines to test their biocompatibility, the functionalised meshes were exposed to a range of common bacterial infections such as MRSA, Staphylococcus and E coli.
“Too little honey and it won’t be enough to fight the infection but too much honey can kill the cells,” explains Dr Gentile. “By creating this 16-layerd ‘charged sandwich’ we were able to make sure the honey was released in a controlled way over two to three weeks which should give the wound time to heal free of infection.”
Dr Mancuso adds:
“With our study we have demonstrated the promising combination of a naturally-derived antibacterial agent with a nanotechnology approach, which may be translated to the design and development of novel medical devices with advanced functionality.”
Materials provided by Newcastle University. Note: Content may be edited for style and length.
- Elena Mancuso, Chiara Tonda-Turo, Chiara Ceresa, Virginia Pensabene, Simon D. Connell, Letizia Fracchia, Piergiorgio Gentile. Potential of Manuka Honey as a Natural Polyelectrolyte to Develop Biomimetic Nanostructured Meshes With Antimicrobial Properties. Frontiers in Bioengineering and Biotechnology, 2019; 7 DOI: 3389/fbioe.2019.00344