Percutaneous Absorption of Two Bisphenol A Analogues, BPAF and TGSA: Novel In Vitro Data from Human Skin

Bisphenol AF (BPAF) and 4,4'-Sulfonylbis[2-(prop-2-en-1-yl)phenol] (TGSA) are analogues of Bisphenol A (BPA). BPAF is commonly used in polymer synthesis, whereas TGSA finds application in thermal papers. BPAF is classified as toxic to reproduction 1B and TGSA as a skin sensitizing category 1 chemical by the EU. However, the other potential health effects of TGSA are not fully understood. Contamination by BPAF has been reported among workers in electronic waste dismantling, while TGSA exposure has been documented in various professions. Despite skin contact being a significant route of exposure, data on skin permeation rates for TGSA and BPAF are limited.<br/>
In this study, we aimed to generate percutaneous absorption data for these substances following OECD guidelines. [14C]-labeled BPAF or [14C]-labeled TGSA was dissolved in water and applied in vitro to freshly obtained human skin samples using static Franz diffusion cells for exposure periods of 20 and 40 hours, respectively. Key parameters such as steady-state flux (Jss), lag time (Tlag), and skin permeability coefficient (Kp) were meticulously calculated. Furthermore, the distribution of the dose across different compartments, particularly within the skin, was evaluated at the conclusion of the experiment. Sequential strippings and epidermis-dermis separation were conducted for BPAF to predict the potential absorption of the remaining dose present within the skin.<br/>
The permeability coefficients for BPAF and TGSA were found to be 1.9 E-03 and 1.6 E-03 cm/h, with 22% and 23% of the applied doses absorbed, respectively. Based on their Kp values, both BPAF and TGSA would fall under the classification of "fast" penetrants.<br/>
Taken together, these results indicate that both BPAF and TGSA are absorbed through the skin, suggesting that workers may be exposed to these chemicals through dermal contact. These newly obtained percutaneous absorption data will undoubtedly contribute to a more comprehensive assessment of occupational risks associated with these chemicals.