EFFECT OF WATER TEMPERATURE ON DERMAL EXPOSURE TO CHLOROFORM

We have developed and applied a new measurement methodology to investi gate dermal absorption of chloroform while bathing. Ten subjects bathe d in chlorinated water while breathing pure air through a face mask. T heir exhaled breath was delivered to a glow discharge source/ion trap mass spectrometer for continuous real-time measurement of chloroform i n the breath. This new method provides abundant data compared to previ ous discrete time-integrated breath sampling methods. The method is pa rticularly well suited to studying dermal exposure because the full fa ce mask eliminates exposure to contaminated air. Seven of the 10 subje cts bathed in water at two or three different temperatures between 30 degrees C and 40 degrees C. Subjects at the highest temperatures exhal ed about 30 times more chloroform than the same subjects at the lowest temperatures. This probably results from a decline in blood Bow to th e skin at the lower temperatures as the body seeks to conserve heat fo rcing the chloroform to diffuse over a much greater path length before encountering the blood. These results suggest that pharmacokinetic mo dels need to employ temperature-dependent parameters. Two existing mod els predict quite different times of about 12 min and 29 min for chlor oform flux through the stratum corneum to reach equilibrium. At 40 deg rees C, the time for the flux to reach a near steady-state value is 6- 9 min. Although uptake and decay processes involve several body compar tments, the complicating effect of the stratum corneum lag time made i t difficult to fit multiexponential curves to the data; however, a sin gle-compartment model gave a satisfactory fit.