To estimate the proportion of TPHP from a nail polish application that is absorbed and metabolized to DPHP by the user, we took the ratio of moles of urinary DPHP (molecular weight = 2.50 × 10 5 mg/mol) excreted by each participant during the nail phase (with the number of moles from each participant's control phase subtracted to account for background DPHP) to the moles of TPHP we estimated to be in a nail polish application.