Evaluation of the effects of repeated disinfection on medical exam gloves: Part 1. Changes in physical integrity.

COVID-19 has created shortages of personal protective equipment. In resource-constrained situations, limited cycles of disinfection and extended use of gloves is recommended by the U.S. Centers for Disease Control and Prevention to conserve supplies. However, these guidelines are based on limited evidence. In this study, serial cycles of hand hygiene were performed on gloved hands using an ethanol-based hand rub (six and 10 cycles), 0.1% sodium hypochlorite (bleach) solution (10 cycles), or soap and water (10 cycles) on latex and nitrile medical exam gloves from the United States and India. A modified water-leak test evaluated glove integrity after repeated applications of these disinfecting agents. When aggregated, dilute bleach demonstrated the lowest difference between treatment and control arms: -2.5 percentage points (95% CI: -5.3 to 0.3) for nitrile, 0.6 percentage points (95% CI: -2.6 to 3.8) for non-powdered latex. For U.S.-purchased gloves tested with six and 10 applications of ethanol-based hand rub, the mean difference in failure risk between treatment and control gloves was within the prespecified non-inferiority margin of five percentage points or less, though some findings were inconclusive since outside the margin. The aggregated difference in failure risk between treatment and control was 3.5 percentage points (0.6 to 6.4) for soap and water, and 2.3 percentage points (-0.5 to 5.0) and 5.0 percentage points (1.8 to 8.2) for 10 and 6 applications of ethanol-based hand rub, respectively. Most leaks occurred in the interdigital webs (35%) and on the fingers (34%). This indicates that some combinations of glove types and disinfection methods may allow for extended use. Ten applications of dilute bleach solution had the least impact on glove integrity. However, the majority of glove and exposure combinations were inconclusive. Additional testing of specific glove and disinfectant combinations may inform future strategies to guide extended use during glove shortages. Additional considerations, not evaluated here, include duration of use, disinfectant chemical permeation, and the effects of hand temperature, movement, and manipulation of instruments on glove integrity.

Evaluation of the effects of repeated disinfection on medical exam gloves: Part 2. Changes in mechanical properties.

Many healthcare professionals have been forced, under acute shortages, to extend medical exam gloves beyond their intended single use. Despite limited available literature, the CDC proposed a set of guidelines for repeated exam gloves use, indicating a maximum number of treatments for three widely available disinfectants. This study examines how these treatments affect the mechanical properties of latex and nitrile gloves. Furthermore, an acceptability threshold is proposed for changes in tensile property, specifically elastic modulus, as an indication of degradation. This proposed criterion was also applied to similar studies available in the literature to determine applicability and aid in recommendation development. Three different latex glove brands and three nitrile brands were exposed to repeated treatments of an alcohol-based hand rub, diluted bleach, or soap and water. Tensile tests of samples cut from untreated and treated gloves were performed to assess the change in elastic modulus induced by each treatment. The findings suggest that latex gloves performed well within the CDC recommended guidelines of six repeated treatments for an ethanol-based hand rub and 10 repeated treatments of either dilute bleach or soap and water. Nitrile exam gloves, on the other hand, showed significant changes in elastic modulus, with more inconclusive results among brands. This was especially true for treatment with dilute bleach and soap and water. Further research is needed to investigate the effects of disinfection products on the mechanical integrity of nitrile exam gloves. The results support the use of five repeated treatments of ethanol-based hand rub for nitrile exam gloves, a lower threshold than currently recommended by the CDC. This research also supports that the CDC recommendation of 10 repeated treatment with soap and water is appropriate for latex exam gloves, but not for nitrile exam gloves. Occupational safety and health professionals involved in the selection of disposable exam gloves for infection control should consider the compatibility of the glove polymer type with available disinfectants, especially if extended use with repeated disinfection becomes necessary.

Chemical permeation of similar disposable nitrile gloves exposed to volatile organic compounds with different polarities: Part 1: Product variation.

Many glove manufacturers of chemical protective clothing produce chemical resistance guides to aid in selection of an appropriate product. Some manufacturers provide permeation data, but others provide a general rating system without reporting testing their own products. A critical issue is that considerable variation in chemical resistance, both with breakthrough times and steady-state permeation rates, have been observed with disposable nitrile gloves. The main purpose of this study was to determine whether significant variation in chemical resistance was present between products from a single brand that provided a generalized chemical resistant guide. The objective was to determine if the ratings noted on the chemical resistance guide were sufficient for protection against chemical permeation. The chemical permeation of ten disposable nitrile gloves against three organic solvents of varying polarity (cyclohexane, tert-butanol, and cyclohexanol) was performed in triplicate. Despite the similar chemical resistant ratings for the products, significant variation in both breakthrough times and steady-state permeation rates were observed among the ten nitrile gloves. The largest variation in breakthrough time was about 8-fold. The largest variation in steady-state permeation rate was about 177-fold. A proposed chemical resistance rating system was used to further evaluate the variation in performance, as it would relate to similar rating systems used by glove manufacturers or brands. Polarity played a role in the observed performance, with the nitrile gloves providing increased protection with an increase in solvent polarity, more notably with the dielectric constant. Using a proposed rating system, the percentages of products rating as excellent to good were 20% (cyclohexane), 60% (tert-butanol), and 90% (cyclohexanol). Ultimately, the ratings noted on the general chemical resistance guide were not sufficient for worker protection against chemical permeation. It is not valid to assume that little variation should exist among the different glove products under a same brand or based on the use of generic chemical resistant data. When critical, occupational health and safety professionals should base glove selection on product-specific chemical permeation data.

Chemical permeation of similar disposable nitrile gloves exposed to volatile organic compounds with different polarities Part 2. Predictive polymer properties.

A follow-up study evaluated the chemical and physical parameters of 10 disposable nitrile glove products in association with the observed variability in chemical permeation performance. The aim was to determine which polymer properties explained or were predictive of the observed wide variation in breakthrough time and steady state permeation rate. The physical and mechanical properties evaluated were thickness, area density, volume fraction and modulus 50-100%. The chemical composition properties evaluated were relative acrylonitrile content, relative carboxylation content, oily plasticizers, inorganic fillers and organic polymer content. A combination of correlation and multiple regression analyses were performed to evaluate the predictive nature of these parameters. For the regression analyses, stepwise, forward selection and backward elimination methods were used to determine an optimal regression fit. Both thickness and area density were strongly correlated with the breakthrough time. With the addition of volume fraction, these factors accounted for about 88-89% of the variation in breakthrough times. The correlation results for the steady-state permeation rate were largely inconclusive and only a moderate correlation with thickness was observed with one solvent. However, regression analyses revealed a moderate to strong association (R2 = 0.742; p < 0.001) between the permeation rate and thickness and volume fraction. With the inclusion of volume fraction in all regression models, the microstructure of the polymer played a critical role in chemical permeation, which requires further investigation. Based on these results, selection based on the availability of chemical permeation data for the product should always be preferred, especially when skin protection is critical. When chemical resistance ratings are based on general performance data, additional factors such as thickness and area density should be taken into consideration. In general, increases in thickness and area density are associated with increases in breakthrough time and decreases in the steady-state permeation rate. However, evidence in the literature and this study support the need for inclusion of additional factors associated with the microstructure of the polymer.

Evaluating polymer degradation with complex mixtures using a simplified surface area method.

Chemical-resistant gloves, designed to protect workers from chemical hazards, are made from a variety of polymer materials such as plastic, rubber, and synthetic rubber. One material does not provide protection against all chemicals, thus proper polymer selection is critical. Standardized testing, such as chemical degradation tests, are used to aid in the selection process. The current methods of degradation ratings based on changes in weight or tensile properties can be expensive and data often do not exist for complex chemical mixtures. There are hundreds of thousands of chemical products on the market that do not have chemical resistance data for polymer selection. The method described in this study provides an inexpensive alternative to gravimetric analysis. This method uses surface area change to evaluate degradation of a polymer material. Degradation tests for 5 polymer types against 50 complex mixtures were conducted using both gravimetric and surface area methods. The percent change data were compared between the two methods. The resulting regression line was y = 0.48x + 0.019, in units of percent, and the Pearson correlation coefficient was r = 0.9537 (p ≤ 0.05), which indicated a strong correlation between percent weight change and percent surface area change. On average, the percent change for surface area was about half that of the weight change. Using this information, an equivalent rating system was developed for determining the chemical degradation of polymer gloves using surface area.

Changes in chemical permeation of disposable latex, nitrile, and vinyl gloves exposed to simulated movement.

Glove movement can affect chemical permeation of organic compounds through polymer glove products. However, conflicting reports make it difficult to compare the effects of movement on chemical permeation through commonly available glove types. The aim of this study was to evaluate the effect of movement on chemical permeation of an organic solvent through disposable latex, nitrile, and vinyl gloves. Simulated whole-glove permeation testing was conducted using ethyl alcohol and a previously designed permeation test system. With exposure to movement, a significant decrease (p ≤ 0.001) in breakthrough time (BT) was observed for the latex (-23%) and nitrile gloves (-31%). With exposure to movement, only the nitrile glove exhibited a significant increase (p ≤ 0.001) in steady-state permeation rate (+47%) and cumulative permeation at 30 min (+111%). Even though the nitrile glove provided optimum chemical resistance against ethyl alcohol, it was most affected by movement. With exposure to movement, the latex glove was an equivalent option for overall worker protection, because it was less affected by movement and the permeation rate was lower than that of the nitrile glove. In contrast, the vinyl glove was the least affected by movement, but did not provide adequate chemical resistance to ethyl alcohol in comparison with the nitrile and latex gloves. Glove selection should take movement and polymer type into account. Some glove polymer types are less affected by movement, most notably the latex glove in this test. With nitrile gloves, at least a factor of three should be used when attempting to assign a protection factor when repetitive hand motions are anticipated. Ultimately, the latex gloves outperformed nitrile and vinyl in these tests, which evaluated the effect of movement on chemical permeation. Future research should aim to resolve some of the observed discrepancies in test results with latex and vinyl gloves.

Tensile properties and integrity of clean room and low-modulus disposable nitrile gloves: a comparison of two dissimilar glove types.

BACKGROUND: The selection of disposable nitrile exam gloves is complicated by (i) the availability of several types or formulations, (ii) product variability, and (iii) an inability of common quality control tests to detect small holes in the fingers. Differences in polymer formulation (e.g. filler and plasticizer/oil content) and tensile properties are expected to account for much of the observed variability in performance. OBJECTIVES: This study evaluated the tensile properties and integrity (leak failure rates) of two glove choices assumed to contain different amounts of plasticizers/oils. The primary aims were to determine if the tensile properties and integrity differed and if associations existed among these factors. Additional physical and chemical properties were evaluated. METHODS: Six clean room and five low-modulus products were evaluated using the American Society for Testing and Materials Method D412 and a modified water-leak test to detect holes capable of passing a virus or chemical agent. RESULTS: Significant differences in the leak failure rates and tensile properties existed between the two glove types (P ≤ 0.05). The clean room gloves were about three times more likely to have leak failures (chi-square; P = 0.001). No correlation was observed between leak failures and tensile properties. Solvent extract, an indication of added plasticizer/oil, was not associated with leak failures. However, gloves with a maximum modulus <4 MPa or area density (AD) <11 g cm(-2) were about four times less likely to leak. CONCLUSIONS: On average, the low-modulus gloves were a better choice for protection against aqueous chemical or biological penetration. The observed variability between glove products indicated that glove selection cannot rely solely on glove type or manufacturer labeling. Measures of modulus and AD may aid in the selection process, in contrast with common measures of tensile strength and elongation at break.

Chemical resistance of disposable nitrile gloves exposed to simulated movement.

Large discrepancies between laboratory permeation testing and field exposures have been reported, with indications that hand movement could account for a portion of these differences. This study evaluated the influence of simulated movement on chemical permeation of 30 different disposable nitrile glove products. Products were investigated out-of-box and with exposure to simulated whole-glove movement. Permeation testing was conducted using ethanol as a surrogate test chemical. A previously designed pneumatic system was used to simulate hand movement. No movement and movement tests were matched-paired to control for environmental conditions, as were statistical analyses. Permeation data were collected for a 30-min exposure period or until a breakthrough time (BT) and steady-state permeation rate (SSPR) could be determined. A third parameter, area under the curve at 30 min (AUC-30), was used to estimate potential worker exposure. With movement, a significant decrease in BT (p ≤ 0.05), ranging from 6-33%, was observed for 28 products. The average decrease in BT was 18% (p ≤ 0.001). With movement, a significant increase in SSPR (p ≤ 0.05), ranging from 1-78%, was observed with 25 products. The average increase in SSPR was 18% (p ≤ 0.001). Significant increases in AUC-30 (p ≤ 0.05), ranging from 23-277%, were also observed for all products where it could be calculated. On average, there was a 58% increase (p ≤ 0.001). The overall effect of movement on permeation through disposable nitrile gloves was significant. Simulated movement significantly shortened the BT, increased the SSPR, and increased the cumulative 30-min exposure up to three times. Product variability also accounted for large differences, up to 40 times, in permeation and cumulative exposure. Glove selection must take these factors into account. It cannot be assumed that all products will perform in a similar manner.

Evaluation of coarse and fine particulate sources using a portable aerosol monitor in a desert community.

The purpose of this study was to use a portable aerosol monitor as a preliminary screening tool to identify local sources of coarse (PM(10-2.5)) and fine (PM(2.5)) particulate matter within the Coachella Valley, a low-elevation desert community. The portable aerosol monitor proved to be useful in identifying particle sources unique to the region, namely, sand dunes with sparse ground cover (vegetation), a river wash, and diesel truck and freight train traffic. The general limitations relate to discrepancies in the fraction of PM(10-2.5) when compared to regional air quality data and a lack of accurate mass-based data.

Integrity of disposable nitrile exam gloves exposed to simulated movement.

Every year, millions of health care, first responder, and industry workers are exposed to chemical and biological hazards. Disposable nitrile gloves are a common choice as both a chemical and physical barrier to these hazards, especially as an alternative to natural latex gloves. However, glove selection is complicated by the availability of several types or formulations of nitrile gloves, such as low-modulus, medical grade, low filler, and cleanroom products. This study evaluated the influence of simulated movement on the physical integrity (i.e., holes) of different nitrile exam glove brands and types. Thirty glove products were evaluated out-of-box and after exposure to simulated whole-glove movement for 2 hr. In lieu of the traditional 1 L water-leak test, a modified water-leak test, standardized to detect a 0.15 ± 0.05 mm hole in different regions of the glove, was developed. A specialized air inflation method simulated bidirectional stretching and whole-glove movement. A worst-case scenario with maximum stretching was evaluated. On average, movement did not have a significant effect on glove integrity (chi-square; p=0.068). The average effect was less than 1% between no movement (1.5%) and movement (2.1%) exposures. However, there was significant variability in glove integrity between different glove types (p≤0.05). Cleanroom gloves, on average, had the highest percentage of leaks, and 50% failed the water-leak test. Low-modulus and medical grade gloves had the lowest percentages of leaks, and no products failed the water-leak test. Variability in polymer formulation was suspected to account for the observed discrepancies, as well as the inability of the traditional 1 L water-leak test to detect holes in finger/thumb regions. Unexpectedly, greater than 80% of the glove defects were observed in the finger and thumb regions. It is recommended that existing water-leak tests be re-evaluated and standardized to account for product variability.