CHAPTER XVIII
OINTMENT PROTECTION AGAINST MUSTARD GAS a
Dichlorethylsulphide was so extensively used on the Western Front and caused so large a number of casualties in consequence of its skin irritating properties that great effort was made to protect against skin burns due to this gas. The majority of burns were apparently due to vapor, although many, constituting a small percentage, were due to the liquid. Statistics on the relative number of liquid and vapor burns in the field are not available.
In the protection of the skin against dichlorethylsulphide burns two propositions were involved: (1) The protection of the skin against burning by droplets of the liquid, and (2) protection against vapors of dichlorethylsulphide.
Again, in protection against dichlorethylsulphide, there was to be considered the protection of men in factories in which the gas was being produced and in the filling stations, and the protection of soldiers in the field against dichlorethylsulphide used by the enemy. It soon developed in the course of the investigations that it was impossible to protect the skin by means of any ointment or skin dressing against burning by droplets of the liquid. Moreover, it also developed early that the only protection which should be offered to men in factories and filling stations was in the nature of protective clothing and gloves. A large amount of work was done on this subject at the American University, University of Wisconsin, and elsewhere, but this discussion is confined to the consideration of protection by ointments.
The first efforts were directed toward the development of an impervious paint, which soon proved to be entirely impracticable since it was uncomfortable, cracked, and interfered with the normal functioning of the skin. A number of investigators then sought to find an ointment which, when placed on the skin, would offer partial or complete protection against burns by vapor of dichlorethylsulphide.
Among the protective varnishes studied were the following: Shellac, aluminum paint, asphalt ether, and collodion. These substances either offered no protection at all or actually increased the irritation produced by the dichlorethylsulphide.
The following protective films were then studied: Raw linseed oil, boiled linseed oil, olive oil, castor oil, cocoanut oil, linoleic acid, oleic acid, paraffin, cod-liver oil, petrolatum, soy-bean oil, peanut oil, lanolin, liquid petrolatum, turpentine.
Since none of these protective films were sufficiently serviceable, it was sought to increase their protective power by incorporating other material. In most instances, no chemical reaction was possible between dichlorethylsulphide and the substances incorporated, and these are named first: Cocoanut charcoal, fuller's earth, talcum, magnesium oxide, zinc oxide, zinc stearate, zinc oleate, calcium carbonate, silver abietate, calcium hydroxide, manganese resinate, soap and calcium sulphide, soap and agar agar, soap and gum tragacanth, green soap, egg albumin, gelatin, flaxa liquid soap, reduced iron, soap, tannic acid, powdered zinc, collargol, glycerin (50 percent), glucose, soap and albumin, soap and gum acacia, soap and glycerin, carnauba wax, litharge.
a These investigations were conducted by the section of pharmacology and toxicology, Research Division, Chemical Warfare Service
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The following substances, which would presumably react with dichlorethylsulphide and destroy it, were used: Hexamethylene tetramine, bleaching powder (calcium hypochlorite), chloramine-T, dichloramine-T, tincture of iodine, potassium permanganate.
METHOD OF TESTING THE VALUE OF PROTECTIVE OINTMENT
The method which was used in studying the value of protective ointments improved as the work progressed. Wilson and Fuller, who did the largest volume of work on the subject, described the following method of testing in their later work: 1 An area of 1 by 3 inches was marked off on the skin of the forearm. This area was treated with 0.1 c. c. of the ointment. Except for a short time immediately after the application of the ointment, no effort was made to prevent rubbing of the treated area by the clothing. A test tube 41 by ½ inch was inclosed in a second larger test tube to obtain an air space around the inner tube. A tightly packed piece of glass wool was introduced into the inner tube about 2 inches from the open end. About 1 c. c. of pure dichlorethylsulphide was dropped onto this wool. In making this exposure, the stopper was removed from the inner tube so that the area to be tested was only in contact with the open end of the inner test tube. Exposures were made for a definite length of time, using a stop watch. The period of time elapsing between the application of the ointment and exposure to the vapor varied in these experiments. The area exposed to the dichlorethylsulphide was circular and measured one-half inch in diameter. Other much more accurate methods of studying the effect of vapors of skin irritants were devised in connection with other work, 2 but they were not used in connection with protective ointment.
The individual was given a similar burn on an unprotected portion of the skin, and an attempt was made to estimate the degree of protection offered by the ointment by comparing the burn produced through the ointment with that produced on the bare skin. The ointment on the bare skin was given a value of 100, and then the degree of burning through the ointment was estimated on this basis. A 100 percent burn would mean that the ointment offered no protection; a 50 percent burn would mean that the burn was only one-half as severe. Using this method, Wilson and Fuller developed ointment No. 146 as the best protection. This substance has the following composition:
Parts by weight
Zinc oxide (100 mesh, U. S. P.)..................45
Benzoated lard...........................................10
Refined raw linseed oil................................30
Hydrous lanolin (adeps lane, U. S. P.).........15
Coloring matter to give flesh color.
The method of manufacture was briefly as follows: The zinc oxide was thoroughly mixed with the linseed oil, and benzoated lard containing sufficient coloring matter was then added to the mixture of zinc oxide and linseed oil. Finally the lanolin was added and the whole thoroughly mixed.
It was directed that the soldier should apply the ointment twice a day when exposure to vapor of dichlorethylsulphide was anticipated, but not to the entire body. He was directed merely to apply it to the crotch, the armpits, hands and feet, and exposed portions of the face.
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The theory of the protective action of ointments of the class represented by ointment No. 146 is as follows: The dichlorethylsulphide, being soluble in fats, would pass into the ointment and remain there as long as the exposure to dichlorethylsulphide continued. On removal from the vapor the dichlor- ethylsulphide would supposedly evaporate again into the air and protection would thus be afforded. It was found that all those substances which reacted with dichlorethylsulphide and destroyed it were too irritating to apply to the skin. The method of testing used in the work was not satisfactory because of the small area of skin exposed to the gas. It is obvious that a small area of skin deleteriously affected by exposure to an irritant but surrounded by healthy skin would show less effect than a similar area of skin surrounded by tissue similarly affected. Thus, a small area might not show a blister on exposure to a given concentration, whereas a larger area might readily blister. The only satisfactory method of determining the protective value of an ointment is by sending an individual into a chamber containing a definite and known concentration of the vapor and exposing a sufficiently large surface of his skin to the action of gas. By a sufficiently large area is meant one-half or one-fourth of a forearm. The rest of the body could be protected by means of special protective clothing and a mask. When this test was applied to ointment No. 146, it was found to be extremely doubtful whether it offered any protection at all against such concentrations of dichlorethylsulphide as would probably be encountered in the field, and it was the conviction of those who examined these burns that the ointment was of little or no value. It may be stated, therefore, that no satisfactory ointment for protection against burns by vapors of dichlorethylsulphide was found.
REFERENCES
(1) Wilson and Fuller: General Report on Protective Ointments Against G-34. Defense Chemical Research Section, Research Division, Chemical Warfare Service, American University Experiment Station, Washington, D. C., September 14, 1918, 0473.9-D, p. 55.
(2) Eyster, J. A. E., and Maver, Mary E.: An Apparatus for the Exposure of Skin or Mucous Membrane to the Vapor of Toxic Substances, with Observations on Dichlorethylsulphide. Journal of Pharmacology and Experimental Therapeutics, Baltimore, Md., 1920-21, xv, No. 2, 95.
