Press "Enter" to skip to content

Endocrine Disruptors: Evidence Still Damning

Last December, MedPage Today covered a studyr that linked early-life exposure to some endocrine-disrupting chemicals (EDCs) to early puberty, particularly among young girls. These EDCs are found in many everyday household items, such as furniture and cosmetics. In this follow-up feature, we review research developments in environmental health and EDCs since that story appeared.

New Reports of Harmful BPA Links

In a game-changing study published in December 2019, a group of researchers revealed how exposure to the EDC bisphenol A — commonly known as BPA — may be wildly underestimated. Specifically, indirect techniques utilized by the the U.S. Food and Drug Administration (FDA) to estimate BPA exposure via urine may yield such low estimates.

To assess this, Roy Gerona, PhD, MS, of the University of California San Francisco, and colleagues monitored the disappearance of BPA glucuronide in human urine. Although 50 ng/mL of the conjugate was released into the urine, the indirect method of BPA analysis used by the FDA picked up only 8.3% of the deconjugation. However, methods utilized by the U.S. Centers for Disease Control and Prevention (CDC) were able to pick up the complete and accurate estimation of BPA in the urine, the researchers reported in The Lancet Diabetes & Endocrinology.

“Using the direct method, we obtained a geometric mean for these urine samples of 51.99 ng/mL total BPA, 44-times higher than the latest geometric mean for adults in the USA reported by the National Health and Nutrition Examination Survey (NHANES),” Gerona’s group wrote. “By contrast, the indirect method yielded a geometric mean for total BPA of 2.77 ng/mL, nearly 19 times lower than the direct method but in good agreement with NHANES data.”

“Importantly, disparity between indirect and direct results increased substantially as exposure increased,” the team continued.

The researchers also pointed out that the “bulk” of data on human BPA exposure has utilized indirect analysis techniques, which may be leading to a grave underestimation of the public’s exposure to these potentially harmful chemicals.

These findings made waves throughout the research community, as well. Commenting on this study on Twitter, Leonardo Trasande, MD, MPP, of NYU Langone Health in New York City, who was not involved with the research, wrote: “This [study] further exposes the profound scientific flaws in [the FDA’s] approach to bisphenols and other contaminants in food.”

“This finding does not mean that existing epidemiological studies of BPA are flawed. On the contrary: in many cases exposure imprecision biases against finding effects at all,” Trasande pointed out in another tweet.

Another recent report, in Environmental Health Perspectives, found that newborns may be at particularly high exposure to chemicals in neonatal intensive care units (NICUs). These chemicals range from a variety of EDCs, including BPA and parabens such as methylparaben, ethylparaben, propylparaben, and butylparaben.

In particular, Nicolás Olea, MD, PhD, of the Instituto de Investigación Biosanitaria in Granada, Spain, and colleagues found that NICU products including small dummy nipples, three-way stopcocks, and patterned transparent film dressing yielded the highest estrogenic activity and androgenic activity.

“Our findings suggest that NICU newborns may be exposed to BPA and [parabens] via inhalation, oral, dermal, and IV/parenteral routes, with the possibility that other hospitalized infants may be similarly exposed,” the researchers warned.

Beyond BPA: More Risky Chemical Associations

A study published in December found a link between breast cancer risk and hair dye and chemical relaxers and straighteners. Carolyn Eberle, MPH, of the University of North Carolina at Chapel Hill, and colleagues found that use of permanent hair dye was tied to a 45% higher risk for breast cancer in black women (HR 1.45, 95% CI 1.10-1.90), but in white women, the risk was only 7% higher (HR 1.07, 95% CI 0.99-1.16).

“The strength of association observed for permanent dye use among black women is consistent with toxicological assessments that report higher concentrations of estrogens and endocrine-disrupting compounds in hair products marketed to black women,” the team wrote in the International Journal of Cancer.

However, both black and white women saw an elevated risk for breast cancer with the use of nonprofessional semi-permanent hair dye, as well as chemical straighteners — with this risk increasing with frequency of use.

The researchers pointed out that hair products can contain thousands of chemicals, many of which are hormonally active. Some of the chemicals commonly found in hair products include aromatic amines, 2,3-diaminoanisole sulfate, paraphenylenediamine, 4-aminobiphenyl, and formaldehyde.

“These results support the hypothesis that hair dye and straightener use, which are highly prevalent exposures, could play a role in breast carcinogenesis,” Eberle’s group concluded.

Another study that made headlines reported an association between the antibacterial chemical triclosan and an increased risk for osteoporosis in women.

Led by Yingjun Li, PhD, of Hangzhou Medical College School of Public Health in China, the group found that adult woman who were exposed to greater amounts of the EDC triclosan had a nearly 2.5-fold increased chance of developing intertrochanteric osteoporosis (odds ratio 2.46, 95% CI 1.19-5.11). The study in the Journal of Clinical Endocrinology & Metabolism found that higher amounts of exposure to this chemical were also tied to lower levels of bone mineral densities in several parts of the body.

Although the FDA banned triclosan in over-the-counter soaps in 2016, and then subsequently banned its use in hand sanitizers this past April, triclosan can still be found in several everyday items, like athletic wear and contaminated water.

In another incriminating study of EDCs, Eva Tanner, PhD, MPH, of the Icahn School of Medicine at Mount Sinai in New York, and colleagues linked exposure to various chemicals with reduced intellectual ability in kids.

The Swedish study, published in Environment International in October, found that boys who had higher-than-average exposure to a mixture of 26 different EDCs during the first trimester in utero had an average 1.9-point drop in IQ by the age of 7. Top chemicals of concern included phenoxybenzoic acid — a short-lived pesticide — as well as 3,5,6-trichloro-2-pyridinol, 5-ethyl-2-methylpyridine, perfluorooctanoic acid, perfluorooctanesulfonic acid, triclosan, BPA, perfluorohexanesulfonic acid, methylenedioxybenzyl, and 2-4-methyl-7-oxyooctyl-oxycarbonyl-cyclohexane carboxylic acid.

However, this IQ drop was most strongly associated with exposure to bisphenol F — commonly used in food packaging, adhesives, and plastics — and diphenylphosphate, an organophosphate flame retardant.

“Many of the chemicals we identified as potentially harmful only stay in the body a short amount of time,” Tanner previously told MedPage Today. “This means that if someone takes steps to lower exposure now, the levels detected in their body will quickly decline. However, it can be difficult to know what chemicals are contained in many consumer products since they are not typically labeled.”

“When regulators set safety guidelines, they only look at one chemical at a time. However, our results indicate that mixtures of chemicals can be harmful, even when individual chemical levels are low,” Tanner concluded.

2019-12-28T12:00:00-0500

Source: MedicalNewsToday.com