Assessments of drinking water safety rely on the assumption that ingestion represents the principal route of exposure. A review of the experimental literature revealed that skin penetration rates for solvents are remarkably high, and that the stratum corneum is a less effective barrier to penetration than traditionally assumed. Based on published skin absorption rates, we used Fick's law (Jos = Kop delta Cos) to determine permeability constants for selected compounds. We then calculated dose per kilogram for nine different exposure situations and compared this to the oral dose per kilogram. We found that skin absorption contributed from 29-91 per cent of the total dose, averaging 64 per cent. Dose per kilogram body weight ranged from .0002 mg/kg-.18 mg/kg, with an average of .03 mg/kg. In weak aqueous solutions, flux of the solute is directly proportional to concentration. Laboratory approaches differ markedly from environmental exposures and can underestimate absorption. We conclude that skin absorption of contaminants in drinking water has been underestimated and that ingestion may not constitute the sole or even primary route of exposure.