PERCUTANEOUS PENETRATION OF DIMETHYLNITROSAMINE THROUGH HUMAN SKIN IN-VITRO - APPLICATION FROM COSMETIC VEHICLES

Human skin penetration of N-dimethylnitrosamine (DMN) from three vehic les has been determined in vitro. When applied as an infinite dose in isopropyl myristate (IPM, 1 mu g/mu l) the average total absorption ov er 48 hr was 2.6 +/- 1.2% of the applied dose (all data presented are expressed as means +/- standard errors). When applied as a finite dose in a representative oil-in-water emulsion vehicle the average total a bsorption over 48 hr was 4.0 +/- 0.3% of the applied dose. When applie d as a finite dose in a representative shampoo vehicle for 10 min foll owed by rinsing (i.e. to represent in-use exposure conditions) the ave rage total absorption over 48 hr was 1.1 +/- 0.1% of the applied dose. Approximately 72% of the DMN in the applied shampoo vehicle was remov ed by rinsing. There was considerable evaporative loss of DMN from the IPM and oil-in-water emulsion vehicles, such that absorption was comp lete within 3 hr of application. The overall data indicate that DMN ca n penetrate the skin rapidly but that in practice the amount actually available for penetration is significantly reduced by high permeant vo latility. In contrast, application of N-nitrosodiethanolamine (NDELA) at a concentration of 1 mu g/mu l as an infinite dose generated an ave rage total absorption over 48 hr of 23.6 +/- 6.4%, representing a tota l flux of 103.9 +/- 28.4 mu g/cm(2). In the case of NDELA, no evaporat ive loss was evident.