Triphenyl phosphate (a phosphorus acid ester known as TPP or TPHP) has shown to be absorbed into the body via skin or nails when present in nail polishes. The substance is also used as a flame retardant. Concentrations of up to 1.7% by weight of TPP were found in 8 out of 10 nail polishes purchased from supermarkets and pharmacies in the USA.
Volunteers painting nail polish containing around 1% TPP by weight onto their nails showed significant increases in TPP metabolites in urine, with much lower levels when the volunteers painted the product onto the outside of gloves (which were then worn or kept near hands for 1 hour). The authors conclude that TPP is absorbed into the body from nail polish principally via the dermal route (rather than inhalation) and that nail polish can be a significant exposure route for users.
“Nail polish as a source of exposure to triphenyl phosphate”, E. Mendelsohn et al., Duke University, Durham, USA, Environment International 86 (2016), pages 45–51 http://dx.doi.org/10.1016/j.envint.2015.10.005