Predicting dermal absorption from contact with chemically contaminated soils

Dermal absorption from contaminated soils is poorly understood and more experimental study is needed. To guide selection of experimental Variables for testing and to facilitate interpretation of resulting data, we have developed mathematical models describing dermal absorption of organic chemicals (1.59 less than or equal to log(10)K(a/w) less than or equal to 5.53 and MW less than or equal to 700) from contaminated soils (with about 0.2% or more organic carbon and with clay fractions which are less than 60 times the weight fraction of organic carbon). Assumptions about the kinetics of soil desorption relative to dermal absorption must be included in these models, although little quantitative information is presently available. Consequently, the models presented here represent two extreme situations in which either the dermal barrier, or the soil controls the rate of dermal absorption. For estimating the relative effect of changing exposure conditions (e.g., changes in soil loading, contamination levels, chemical, etc.), the predictions from both models are generally consistent with experimental results. However, the models assuming fast soil release kinetics predict more absorption than was observed experimentally for lindane and 2,4-D. This suggests that soil release kinetics may limit the amount of dermal absorption in at least some situations.