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OCR for page 221
Appendix D
Evaluating Skin
Decontamination Techniques
Howard I. Maibach and Hongbo Zhai
1
Both in vitro and in viva techniques have been developed to determine
skin decontamination. A brief introduction to the models and a summary
of the relative data from recent studies follows. The models described
below have been developed with nonvesicant agents that are available for
occupational and home use.
IN VIVO DECONTAMINATION MODEL
Wester et al. (1991) tested the extent and rate of decontamination on
rhesus monkeys. A water-soluble chemical, glyphosate, was completely
removed from rhesus monkey skin with three successive soap and water
or water only washes. Approximately 90-percent of the glyphosate was
removed in the first wash. There was no difference between washing with
soap and water and washing with water only. Alachlor, a lipid-soluble
chemical, was also removed by washing with soap and water and water
only. In contrast to glyphosate, however, more alachlor was removed
with soap and water than with water alone. Although the first alachlor
washing removed most of the chemical, successive washings contributed
to overall decontamination.
Methylene bisphenyl isocyanate, an industrial chemical, is a potent
1The following material was prepared for the use of the principal investigators of this
study. The opinions and conclusions herein are the authors' and not necessarily those of the
National Research Council.
221
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222
STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
contact sensitizer. Decontamination potential was determined in viva in
rhesus monkeys. A grid of 1-cm areas was drawn on the abdomen of the
monkey (the same can be done with humans) and the same amount of
chemical applied to all areas. At set times, individual grid areas were
washed/decontaminated by water-only, 5-percent soap, 50-percent soap,
polypropylene glycol, polypropylene glycol cleaner, and corn oil. After
each washing procedure, skin tape stripping was used to quantify re-
sidual contamination. Water-only and soap-and-water washing were
minimally effective. Polypropylene glycol, polypropylene glycol cleaner,
and corn oil were more effective. The chemical that was not removed by
the washing procedures was recovered in the tape stripping (Wester and
Maibach, 1999a). Two factors affect in vivo skin decontamination: (1) the
"rubbing effect" that removes loose surface stratum corneum from natu-
ral skin desquamation, and (2) the "solvent effect," which is related to
chemical lipophilicity and may influence the washing effects (Wester et
al., 1991~.
van Hooidonk et al. (1983) evaluated a wide variety of common
materials as skin decontaminants against chemical agents. Flour followed
by wet tissue paper removed 93 percent of VX and 98 percent of mus-
tard. This treatment also reduced the penetration of mustard (measured
by radiolabel) and VX (measured by anti-acetylcholinesterase activity).
In vivo tests confirmed a significant reduction in mortality with flour/
wet tissue paper after VX and soman exposures. The authors found that
washing alone (with no flour pretreatment), either with water or soap
and water, was highly effective against nerve agents, but resulted in
much larger areas of skin damage for mustard. Therefore, the authors
concluded that the best decontaminant for mustard, VX, and soman
was decontamination with flour followed by an after-treatment with wet
tissue.
IN VITRO DECONTAMINATION MODEL
In vitro skin mounted in diffusion cells can be decontaminated with
solvents. The mounted skin is fragile, however, and cannot be rubbed as
vigorously as in vivo skin. Another in vitro technique is mixing powdered
human stratum corneum with radiolabeled formulations (Wester et al.,
1987~. For example, a water-only wash (and subsequent centrifugation)
removed only 4.6 + 1.3 percent of the "bound" alachlor. However, when
the bound alachlor- powdered human stratum corneum was washed with
10-percent soap and water, 77.2 + 5.7 percent was removed; with 50-
percent soap and water, 90.0 + 0.5 percent was removed. This model
would predict that alachlor cannot be removed from the skin by washing
with water alone but that soap will decontaminate the skin. The reason
OCR for page 223
APPENDIX D
223
may be that the "lipid" constituents of soap offer a more favorable parti-
tioning environment for the alachlor (Wester and Maibach, l999b). These
results were confirmed in in viva studies. Large-scale in vitro decontami-
nation screening can be done with the powdered human stratum cor-
neum model.
In vitro studies conducted by decontaminating pig skin exposed to
radiolabeled DFP (an organophosphorus compound, cholinesterase in-
hibitor) and radiolabeled n-butyl 2-choloroethylsulfide (a vesicant) com-
pared the decontamination efficiency of a water shower (tap water), the
M-258 kit, and a pad impregnated with a reactive resin mixture. Decon-
tamination efficiencies were found to be similar for all three methods
(Reifenrath, 1990~. Shower decontamination with an aqueous surfactant
solution did not increase the skin penetration of topically applied soman
or thickened soman (Reifenrath et al., 1984~.
References
Reinfenrath, W.G. 1990. In vitro determination of skin decontamination efficacy using a
water shower. Toxicologist 10: 615.
Reifenrath, W.G., M.M. Mershon, F.B. Brinkley, G.A. Miura, C.A. Broomfield, and H.B.
Cranford. 1984. Evaluation of diethyl malonate as a simulant for 1,2,2-trimethylpropyl
methylphosphonofluoridate (soman) in shower decontamination of the skin. Journal
of Pharmaceutical Science 73: 1388-1392.
van Hooidonk, C., B.I. Ceulen, J. Bock, and J. van Genderen. 1983. CW Agents and the Skin:
Penetration and Decontamination. Pp. 153-160 in Proceedings of the International
Symposium on Protection against Chemical Warfare Agents. Umea, Sweden: National
Defence Research Institute.
Wester, R.C., M. Mobagen, and H.I. Maibach 1987. In vivo and in vitro absorption and
binding to powered stratum corneum as methods to evaluate skin absorption of envi-
ronmental chemical contaminants from ground and surface water. Journal of Toxicol-
ogy and Environmental Health 21~3~: 367-374.
Wester, R.C., J. Melendres, R. Sarason, J. McMaster, and H.I. Maibach. 1991. Glyphosate
skin binding, absorption, residual tissue distribution, and skin decontamination. Fun-
damentals of Applied Toxicology 16: 725-732.
Wester, R.C., and H.I. Maibach. 1999a. In Vivo Methods for Percutaneous Absorption Mea-
surements. Pp. 215-227 in Percutaneous Absorption, 3rd ea., R.L. Bronaugh and H.I.
Maibach, eds. New York: Marcel Dekker, Inc.
Wester, R.C., and H.I. Maibach. l999b. Dermal Decontamination and Percutaneous Absorp-
tion. Pp. 241-254 in Percutaneous Absorption, 3rd ea., R.L. Bronaugh and H.I. Maibach,
eds. New York: Marcel Dekker, Inc.
Representative terms from entire chapter:
polypropylene glycol
