In Vitro Model for Decontamination of Human Skin

By: Hongbo Zhai, MD, University of California; and Howard I. Maibach, MD, University of California School of Medicine

Posted: April 1, 2009, from the April 2009 issue of Cosmetics & Toiletries.

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Background
Chemical injuries are commonly encountered following exposure to acids and alkali, including hydrofluoric acid, formic acid, anhydrous ammonia, cement and phenol. The concentration of corrosive agents, and potency and duration of their contact primarily determine the degree of skin destruction. Tregear¹ initiated this field in the 1940s, but practical interventions have since remained limited.

Immediately following exposure to such chemicals, washing with water, or soap and water, is the traditional measure to reduce damage and minimize percutaneous penetration. Wester et al.² reported that the removal of alachlor with water alone was less effective than doing so with soap and water. A traditional soap and water wash and the emergency water shower are relatively ineffective at removing methylene bisphenyl isocyanate, a potent contact sensitizer, from skin.³ Thus, water or soap and water may not be the most effective means of skin decontamination, particularly for lipophilic materials. In some cases, the amount of chemical that remains on the skin after traditional washing procedures can have toxic consequences.⁴ The need for further development of robust decontamination agents thus becomes apparent.

Formaldehyde, used widely by various industries, is a common allergen and irritant5 and was thus selected as a model compound. This study compared the capacity of decontamination solutions utilizing an in vitro model system on human skin.

Materials and Methods
Contaminant: An aqueous solution of radio-labeled [14C]-formaldehydea (0.1 mCi/mL; specific activity: 51.9 mCi/m mol) was used for this study.

Model decontamination solutions: Isotonic salineb (0.9%; pH = 5.94) and hypertonic salineb (1.8%; pH = 5.71) also were obtained for the present study. The tap water used (pH = 8.09) was taken from the faucet, the source of which was the Hetch Hetchy reservoir, located in California’s Sierra Nevada Mountains.