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August 2010  |  Return to issue home

How Readily Are Household Chemicals Absorbed Through Skin?

By Alexander Domesle, Department of Environmental and Occupational Health Sciences

Alexander Domesle
Alexander Domesle

Every day, we are exposed to a host of pesticides, phthalates, and other semi-volatile organic compounds (SVOCs) that are ubiquitous in the food we eat and in the air and dust that surround us. Many of these compounds are known to have neurological or carcinogenic effects.

Several studies have detected measurable amounts of SVOCs and their urinary metabolites in the general population. What remains unclear is the relative importance of various exposure routes (such as ingestion, inhalation, and dermal (skin) exposure) in accounting for the total amount of a given chemical found in the body. Data indicate that conventional exposure models may underestimate the contribution of dermal absorption, compared with ingestion and inhalation, by extrapolating from earlier dermal studies in which very high chemical loads were applied to skin. We believe that these high-load experiments do not realistically model the very low, but chronic, exposure we encounter in ambient, residential settings. It may be that if less chemical is applied to skin, a greater fraction of the chemical will actually be absorbed. Therefore, the rather low absorption efficiency measured in past high-load experiments cannot be considered accurate for scenarios where very small amounts of chemicals land on skin continuously.

My M.S. research, under the direction of Dr. John Kissel, seeks to measure how efficiently low loads of SVOCs are absorbed through the skin, particularly under conditions similar to those encountered during ambient, residential exposure. To this end, I have constructed a novel experimental chamber for in vitro application and detection of around one nanogram of the target chemical per square centimeter of human cadaver skin. After application of the chemical, the skin was washed and dissolved in a basic solution. The amount of chemical remaining in the solubilized skin was considered absorbed. Results for the wood preservative pentachlorophenol and the insecticide chlorpyrifos indicate that dermal absorption is considerably higher at these low chemical loads than previously assumed.

If future research continues to indicate that a greater proportion of chemicals detected in humans can be attributed to the dermal route, my new findings for SVOCs will help create more robust chemical exposure models and will support the notion that the existing exposure paradigm underestimates the effects of dermal exposure. This will, in turn, help prioritize efforts to reduce inadvertent harmful exposures and may provide insight into exposure routes for other classes of organic compounds.

August 2010  |  Return to issue home

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