Dermal absorption of neat liquid solvents on brief exposures in volunteers

The dermal absorption of liquid 1,1,1-trichloroethane (111TRI), trichloroethene (TRI), tetrachloroethene (TETRA), toluene (TOL), and m-xylene (XYL) was studied in volunteers. The solvents were applied for 3 min on the volar forearm over an area of 27 cm2. An inhalation exposure with a known input rate served as a reference exposure. Using the linear system dynamics method, permeation rates were calculated from exhaled air concentration courses measured after both inhalation and dermal exposure. The permeation time courses of the solvents showed two different patterns. TRI, TOL, and 111TRI in three subjects showed fast increase in permeation, reaching maximal permeation rates a few minutes after initiation of exposure. Slower permeation was seen in the other three subjects exposed to 111TRI and in all subjects exposed to TETRA and XYL with the time of maximal permeation rates of 15-25 min. These differences in the permeation may partly be explained by the irritation of the skin observed in all subjects showing fast permeation kinetics. The flux into the skin averaged over the exposure period amounted to 56, 430, 69, 223, and 46 nmol/cm2/min for 111TRI, TRI, TETRA, TOL, and XYL, respectively. Comparing the dermal uptake with the respiratory uptake at the TLV, all solvents showed substantial skin absorption, although at present only TOL has a skin indication in the American Conference of Governmental Industrial Hygienists threshold limit value list.