Percutaneous absorption and exposure risk assessment of organophosphate esters in children's toys.

The percutaneous penetration and exposure risk of organophosphate esters (OPEs) from children's toys remains largely unknown. Percutaneous penetration of OPEs was evaluated by EPISkin™ model. Chlorinated OPEs (Cl-OPEs) and alkyl OPEs, except tris(2-ethylhexyl) phosphate, exhibited a fast absorption rate and good dermal penetration ability with cumulative absorptions of 57.6-127 % of dosed OPEs. Cumulative absorptions of OPEs through skin cells were inversely associated with their molecular weight and log octanol-water partition coefficient. Additionally, a quantitative structure-activity relationship model indicated that topological charge and steric features of OPEs were closely related to the transdermal permeability of these chemicals. With the clarification of the factors affecting the transdermal penetration of OPEs, the level and exposure risk of OPEs in actual toys were studied. The summation of 18 OPE concentrations in 199 toy samples collected from China ranged from 6.82 to 228,254 ng/g, of which Cl-OPEs presented the highest concentration. Concentrations of OPEs in toys exhibited clear type differences. Daily exposure to OPEs via dermal, hand-to-mouth contact, and mouthing was evaluated, and dermal contact was a significant route for children's exposure to OPEs. Hazard quotients for noncarcinogenic risk assessment were below 1, indicating that the health risk of OPEs via toys was relatively low.

Effects of polyethylene microplastics on cell membranes: A combined study of experiments and molecular dynamics simulations.

Microplastics (MPs), widely distributed within the environment, can be ingested by humans easily and cause various biological reactions such as oxidative stress, immune response and membrane damage, ultimately representing a threat to health. Cell membranes work as first barrier for MPs entering the cell and playing biological effects. For now, the researches on interactions of MPs on cell membranes lack an in-depth and effective theoretical model to understand molecular details and physicochemical behaviors. In present study, observations of calcein leakage established polyethylene plastic nanoparticles (PE PNPs), especially of high concentrations, harming cell membrane integrity. SYTOX green and lactate dehydrogenase (LDH) assays supported the evidence that the exposure of cells to PE PNPs caused significant cell membrane damage in dose-response. Molecular dynamics (MD) simulations were further applied to determine the effects of PE on the properties of dipalmitoyl phosphatidylcholine (DPPC) bilayer. PE permeated into lipid membranes easily resulting in significant variations in DPPC bilayer with lower density, fluidity changes and membrane thickening. Besides, PE aggregates bound were more likely to cause pore formation and serious damage to the DPPC bilayer. The interaction mechanisms between MPS and cell membrane were explored which provided valuable insights into membrane effect of MPs.