SKIN ABSORPTION OF THE INDUSTRIAL CATALYST DIMETHYLETHYLAMINE IN-VITRO IN GUINEA-PIG AND HUMAN SKIN, AND OF GASEOUS DIMETHYLETHYLAMINE IN HUMAN VOLUNTEERS

Objectives: The aims of the study were threefold: to assess the skin u ptake of the industrial catalyst dimethylethylamine (DMEA) (a) in vitr o from water solutions by fresh guinea-pig and human skin specimens, ( b) in gaseous form in vivo in human volunteers, and (c) to estimate th e relevance of the uptake as an occupational hazard. Methods: Specimen s from the in vitro and in vivo experiments were analysed by gas chrom atography using a nitrogen-sensitive detector. Design: DMEA, diluted w ith water or isotonic saline solution was applied to fresh human or gu inea-pig skin, mounted in Teflon flow-through cells with a perfusion f luid flow rate of 1.5 ml/h, samples being collected at 2-h intervals f or 48 h. Three healthy male volunteers each had their right forearm ex posed (in a Plexiglass chamber) for 4 h to DMEA at each of three diffe rent levels (250, 500 and 1000 mg/m(3) air). Urine was collected up to 24 h after the start of each experiment. Results: DMEA penetrated bot h guinea-pig and human skin. The median steady-state flux and permeabi lity coefficient (K-p) values, were 0.009 mg/cm(2) x h and 0.001cm/h, respectively for guinea-pig skin, and 0.017 mg/cm(2) x h and 0.003 cm/ h, respectively, for human skin. The median uptake in the three volunt eers at the different DMEA exposure levels (250, 500 or 1000 mg/m(3)) was 44, 64 and 88 mu g, respectively. The median K, for all experiment s was 0.037 cm/h. Conclusion: Uptake of DMEA through the skin is of fa r less importance than simultaneous uptake via the airways. Thus, the amount of DMEA excreted in urine is a variable of limited use for the purposes of biological monitoring. Although a wide range of K, values was obtained in the in vitro experiments, both for guinea-pig and huma n skin, there was no marked difference in median K, values between the two types of skin. The K, values were lower than those obtained for h uman forearm skin in vivo. However, future studies of other tertiary a liphatic amines may show the in vitro method to yield values predictiv e of those obtained in in vivo studies.