Reply to Mathews: Misplaced focus on experimental detail

Leranth, Csaba; Hajszán, Tibor; MacLusky, Neil J.; Saal, Frederick vom

doi:10.1073/pnas.0810299105

Cited by 1 publication

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“…Free BPA is generally regarded as the most toxic form of BPA and was reported to comprise less than 1% of total BPA in blood following oral exposure. , As a result, arguments have been made that the adverse effects observed in animal models following subcutaneous dosage are questionable, because efficient first-pass metabolism following an oral exposure in humans would effectively decrease or eliminate free BPA in systemic circulation. − Although data are limited in our study (2 samples from the same person), a high percentage of free BPA- d 16 (greater than 50%) was observed in the two sera collected at 22 and 51 h postdermal exposure (Table ), suggesting a lower biotransformation efficiency of BPA following dermal exposures. Low biotransformation efficiency of BPA was also observed by Marquet et al in an vitro study, in which unconjugated BPA accounted for >97% of the total BPA in the receptor fluid after 24 h exposure in human skin .…”

Section: Discussionmentioning

confidence: 70%

Prolonged Exposure to Bisphenol A from Single Dermal Contact Events

Liu

Martin

2017

Environ. Sci. Technol.

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Bisphenol A (BPA) is an endocrine disruptor frequently detected in human biofluids. Dermal absorption of BPA from thermal paper receipts occurs but BPA pharmacokinetics following dermal exposure is not understood. To compare the pharmacokinetics of dermal and dietary BPA exposure, six male participants handled simulated receipts containing relevant levels of BPA (isotope-labeled BPA-d) for 5 min, followed by hand-washing 2 h later. Urine (0-48 h) and serum (0-7.5 h) were monitored for free and total BPA-d. One week later, participants returned for a dietary administration with monitoring as above. One participant repeated the dermal administration with extended monitoring of urine (9 days) and serum (2 days). After dietary exposure, urine total BPA-d peaked within 5 h and quickly cleared within 24 h. After dermal exposure, cumulative excretion increased linearly for 2 days, and half the participants still had detectable urinary total BPA-d after 1 week. The participant repeating the dermal exposure had detectable BPA-d in urine for 9 days, showed linear cumulative excretion over 5 days, and had detectable free BPA-d in serum. Proportions of free BPA-d in urine following dermal exposure (0.71%-8.3% of total BPA-d) were generally higher than following the dietary exposure (0.29%-1.4%). Compared to dietary BPA exposure, dermal absorption of BPA leads to prolonged exposure and may lead to higher proportions of unconjugated BPA in systemic circulation.

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