Background
It is well established that common solvents can enhance the permeation of chemicals through gloves. This carrier or vehicle effect of solvents has been demonstrated to be the determining influence of chemical breakthrough times (BTT) in agricultural operations. (Schwope, et al., 1992). It is therefore important to select gloves based on permeation testing with the actual “in use” product formulation rather than individual component data.

This same vehicle effect of solvents can also enhance dermal absorption of toxic chemicals when solvents are used to clean the skin. It is well established convention to discourage the use of solvents to wash workers’ hands as this can actually enhance systemic exposure.

Defining the problem
It is rather common workplace practice to use solvents to clean chemical contamination from gloves and other protective clothing. This is particularly true in hand lay-up operations involving resins and adhesives in production of composite materials. Workers periodically wash excess resins from their gloves in a bucket of solvent (acetone, MEK, etc).

This practice is effective in reducing secondary contamination of tools and workplace surfaces. It also enhances worker productivity by removing excess resin build up. The alternative to washing with the bucket of solvent method is to dispose of gloves and PPC as they become contaminated. However, frequent glove change is expensive and increases waste disposal costs.

A recently published study (Garrod, et al., 2001) demonstrated that re-use of contaminated gloves can significantly increase worker exposure to under glove hand contamination. Contamination from pesticides was found inside the gloves of 38% of workers wearing disposable latex gloves compared to 90-100% of more costly chemical protective gloves made of polymers that were being re-used. The authors concluded that “human factors” contributed and that workers donning contaminated gloves would inevitably contaminate their hands in the process. Disposal is costly but re-use can be worse.

A third alternative is to effectively decontaminate the outside of gloves before removal. The potential benefit in reducing “human factor” exposures is obvious. In addition, frequent decontamination of gloves reduces contamination of workplace surfaces and may increase the useful life of the glove by reducing chemical permeation.

High molecular weight solvent for glove decontamination
D-TAM® Skin Cleansers are unique high molecular weight (HMW) formulations that have limited theoretical skin permeability. The use of these HMW solvents has been demonstrated to be superior to soap and water for skin decontamination of isocyanate exposure. (Landry, et al., 1998; Wester, et al., 1999) For chemicals with limited water solubility, i.e., lipophilic compounds, the use of soap and water to decontaminate the skin can actually enhance systemic absorption (Moody et al., 1995; Loke et al., 1999).

The USEPA (1992) has adopted a model for estimating the dermal absorption potential (est. Kp) of chemicals. This equation is dependant on two variables, molecular size and polarity.

log Kp = 2.72 + 0.71 log Ko/w – 0.0061 MW

Thus as the molecular weight of a chemical increases, its ability to permeate the skin decreases due to the effect of stearic hindrance. Theoretically, HMW solvents will permeate CPC at a slower rate than low molecular weight solvents. This study was designed to determine if the use of HMW solvents to clean gloves has a potential to reduce permeation of chemicals through CPC.

Study design
The combination of aniline and industrial latex gloves (Pioneer 18 mil Tri Fab) was chosen as a challenge test because of current published relatively rapid breakthrough time data. CLI’s colorimetric Permea-Tec® sensor detection system for aromatic amines was used to determine breakthrough time and relative permeation rates. A modified ASTM procedure was used for the glove challenge testing.

A 10% solution of aniline in four different decontamination solutions was used for the glove challenge with 100% aniline included as a control.

Decontamination solutions:
     10% Ivory® Soap and water (S/W)
     D-TAM® polyglycol skin cleanser (D-PG)
     D-TAM® oil based skin cleanser (D-OIL)
     Fast Orange® natural citrus hand cleaner (CIT)

Observations
The octanol water partition coefficient (log Ko/w) of aniline is 0.9, and that will theoretically demonstrate maximum solubility in the D-PG. Aniline has a 4% saturation solubility in water and at the 10% concentration was immiscible with the S/W solution. 10% aniline was observed to be soluble in the D-OIL and CIT solutions.

The colorimetric sensors were visually examined to detect breakthrough at 30 minutes and every 15 minutes thereafter.

Results
Breakthrough of aniline was detected after 30 minutes for all challenge solutions except D-PG. The colorimetric indicator's detection limit is 5-10 ug aniline. Permeation dose was qualitatively determined by observing the color intensity on the indicator.

Permeation dose at 30 minutes: CIT > neat aniline > D-OIL > S/W.

Breakthrough was detected at 90 minutes for the D-PG at a level similar to the other challenge solutions.

Discussion
There are several limitations to this initial study that caution against immediate extrapolation of the results to other combinations of chemicals and glove polymers.

• The modified ASTM procedure employed a continuous exposure to the 10% aniline, where in practice, use of a decontamination solution would be intermittent and wiped or rinsed from the glove.
•The choice of the glove polymer was based on a relatively short breakthrough time. This is in contradiction to normal workplace practice.
•Compatibility of the latex polymer with the various decontamination solutions was not evaluated.

Despite these limitations, several observations warrant further study. In principle to be effective, a decontaminant should demonstrate a high solubility for the chemical to be removed. Like dissolves like. Soap and water are compatible with latex, yet the low water solubility of aniline resulted in a similar BTT as neat aniline.

Latex is incompatible with lipophilic solvents and some swelling was observed with the oil based (D-OIL) and citrus based (CIT) cleansers. Of greater concern was the rapid and high level of breakthrough with the CIT. Limonene is the active ingredient in citrus oil and is a powerful solvent with a low molecular weight (106). The apparently increased permeation in CIT compared to neat aniline is noteworthy and suggests this cleanser should be avoided for this purpose.

Conclusions
The high solubility of aniline in the D-TAM® polyglycol and the apparent low permeability of the HMW formulation resulted in an increase in the observed breakthrough time. The data indicated that the potential for the solvent to carry chemical through the glove was decreased and even reversed, apparently, for one solvent more than the others. The use of compatible HMW solvents may offer a safer approach to decontaminate gloves and CPC than the use of common solvents and has the potential to significantly extend the useful life of CPC in industry at a minimal cost.

References
Garrod, A.N.I., et al. (2001) Potential Exposure of Hands Inside Protective Gloves—a Summary of Data from Non-Agricultural Pesticide Surveys, Annals of Occupational Hygiene, Volume 45(1): 55-60.

Landry, T.D., et al. (1998) In Vivo Evaluation of MDI Skin Decontamination Procedures, Presented September 1998, Polyurethane Expo, Sponsored by the International Isocyanate Institute.

Loke, W.-K., et al. (1999) Wet Decontamination-induced Stratum Corneum Hydration — Effects on the Skin Barrier Function to Diethylmalonate, J. Appl. Toxicol. 19: 285-290.

Moody, R.P., et al. (1995) In Vitro Dermal Absorption of N,N-Diethyl-m-toluamide (DEET) in Rat, Guinea Pig, and Human Skin, In Vitro Toxicology, Vol. 8(3): 263 - 275.

Schwope, A.D., et al. (1992) Permeation Resistance of Glove Materials to Agricultural Pesticides, Am. Ind. Hyg. Assoc. J., 53(6): 352–361.

USEPA (1992) Dermal Exposure Assessment: Principles and Applications, EPA 600/8-91/011B, Office of Health and Environmental Assessment, Interim Report.

Wester, R.C., et al. (1999) In Vivo Evaluation of MDI Skin Decontamination Procedures, Toxicol Sci 48:1-4.