Skin absorption as a source of error in biological monitoring

Concentrations of toluene, tetrachloroethylene, and 1,1,1-trichloroethane were determined in blood collected from both forearms of subjects after one of their hands was soaked for 5 min in the corresponding solvent or in a thinner containing toluene, as a simulation of the washing of hands with solvent after work. The concentrations of toluene, tetrachloroethylene, and 1,1,1-trichloroethane on the soaked side were high, maximally 5.4, 9.0, and 4.0 mumol/l, respectively, and 20-, 130-, and 35-fold, respectively, compared to the contralateral side. Intraindividual differences were very marked, and dramatic changes were detected within a short period of time. It was not until after 3 h with toluene and 5 h with the chlorinated solvents that the difference between the two arms vanished. It is concluded that analyses of solvents in blood specimens drawn during or immediately after the workday may lead to markedly erroneous estimations of exposure.