Annals of Occupational Hygiene Advance Access originally published online on May 17, 2005
Annals of Occupational Hygiene 2005 49(6):535-541; doi:10.1093/annhyg/mei015
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Original Article |
Internal Contamination of Gloves: Routes and Consequences
1 The Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK; 2 The Health and Safety Executive, Magdalen House, Bootle L20 3QZ, UK
* Author to whom correspondence should be addressed. Tel: +44 1298 218429; fax: +44 1298 218172; e-mail: john.cocker{at}hsl.gov.uk
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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The effect of internal glove contamination was investigated using N-methyl pyrrolidone (NMP) as a biological marker to assess systemic absorption when wearing internally contaminated gloves, and when not wearing gloves but subjected to the same challenge contaminant. The routes by which the insides of gloves become contaminated were also investigated. The area of dermal contamination was quantified using a fluorescent tracer dye and a surface monitoring fluorimeter. The main routes of internal glove contamination were found to be self-contamination, cuff entry and failed gloves. Wearing internally contaminated gloves led to higher systemic absorption than was gained from the equivalent skin contamination when not wearing gloves. Repeat wetting of fingers with aqueous NMP, when gloves were not worn, gave higher systemic absorption than the equivalent continuous exposure, probably due to the low volatility of NMP leading to increased concentration and longer residence time on the skin.
Keywords: biological monitoring • dermal contact • gloves • hygiene
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Personal protective equipment (PPE) is intended to reduce the risks arising from hazardous processes and exposure to hazardous substances at work. Chemical protective gloves are one of the most widely used forms of PPE intended to prevent skin exposure to hazardous substances. Exposure of the hands can be an important contributor to total exposure to the skin and has been shown to account for between 50 and 90% of the total body exposure (Abbot et al., 1987
; Karr et al., 1992; Archibald et al., 1995). Some substances can cause damage to the skin on contact (Dooms-Goossens et al., 1991, 1995), while for those substances which can be absorbed through the skin, contact can lead to systemic effects. In the UK there are estimated to be 39 000 people who at some time in any 12-month period believe that they have a skin disease due to work (Jones et al., 2003). In practice, PPE is often not as effective as it should be as a risk reduction measure (Fenske et al., 1990; Cattani et al., 2001) and can, in some cases, actually increase the risk. Published breakthrough times for glove materials are often underestimates of the ‘true’ breakthrough times, because the experimental measurements do not take into account increased temperature and flexing of the material during use (Perkins and Rainey, 1997; HSE, 2001), which is not accounted for in experiments to determine breakthrough times. Substances could penetrate around the edges of gloves or through seams. Contamination could also be transferred into the gloves from contaminated hands (Garrod et al., 2001). Contamination of the inside of gloves is common (Creely and Cherrie, 2001; Garrod et al., 2001; Machera et al., 2003) and brings the hazardous material into intimate contact with the skin. Occlusion by gloves raises skin temperature and hydration leading to a reduction in its natural barrier properties (Graves et al., 1995). Some substances can pass through the skin (Bress and Bidanset, 1991; Zorin et al., 1999), often without causing visible damage to the skin itself. If the substance is harmful then systemic toxicity can occur (Williams et al., 1985; Fiorito et al., 1997) when the substance enters the body's circulatory system, and this can lead to damage to internal organs. When substances can be absorbed through the skin and there are concerns that dermal absorption will lead to systemic toxicity, they are given an ‘Sk’ notation in UK occupational exposure limits (HSE, 2002): gloves often form part of the control strategy. Damaged skin, including dermatitis, can also lead to inefficient skin barrier properties which, in turn, can lead to an increased permeation of chemicals through the skin (Bronaugh and Stewart, 1985). The mechanism of contamination and the consequences for health are not well understood or investigated. Knowledge of the route(s) of contamination is important if this form of PPE is to be made more effective and control procedures are to be improved. Knowledge of the extent of enhancement of dermal absorption under PPE could help inform the risk assessment process for both regulatory bodies, like the Health and Safety Executive, and industry. The aim of this study was to determine quantitatively, first, the routes and sites of any internal contamination in gloves and, second, the extent of any enhanced absorption (consequences) through the skin when wearing gloves with internal contamination.
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METHODS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Routes protocol
All volunteers were given an information sheet detailing the study and what was required of them and asked to sign a consent form for their participation. Each volunteer chose the size of glove that they preferred at the start and used the same size throughout all tests. The types of glove chosen were considered representative of those most commonly used in cleaning tasks in hospitals and laboratories. Volunteers (n = 10) wearing gloves (London Rubber Company, Marigold Tripletec PlusTM) performed a task using a solution containing UVITEX.MST, a fluorescent marker compound. The task involved wiping the inside of a fume cupboard, for 15 min, using a cloth dipped into a bowl of the solution (2 l) as required. The volunteer then removed the gloves and photographs were taken of the hands under UV light to show any contamination. The gloves were then put back on and the task repeated. The task was carried out three times to show the effects of reusing the gloves. In the initial set of experiments the volunteers were asked to put the gloves on and take them off ‘naturally’—without instruction (naïve). In a second set of experiments, the whole process was repeated, this time with the volunteers given instruction on how to use the gloves correctly (instructed). The instruction consisted of an explanation and practical demonstration for donning and removing gloves. A third set of experiments used disposable gloves (Ansell Touch N TuffTM) that were replaced after each use (disposable), and again instruction on glove use was given.
Consequences protocol
The hands of volunteers (n = 5) were ‘dosed’ on four separate occasions (leaving at least one week between each dosing), twice wearing gloves and twice without gloves. Gloves worn were disposable nitrile gloves (Ansell Touch N TuffTM). The same fluorescent marker compound was used as above, but this time with the addition of 15% N-methyl pyrrolidone (NMP) as a biological marker to facilitate measurement of systemic absorption. For the first exposure scenario (A) volunteers wore gloves for 30 min before dosing (to get skin warm and hydrated), then 1 ml of solution was introduced between the skin and each glove (2 ml in total) and left for 15 min before glove removal. The second scenario (B) was the same as the first but with gloves left on for 30 min after dosing. In the third exposure scenario (C), no gloves were worn and the solution was applied directly to the hands (1 ml per hand, 2 ml total, as before) and allowed to dry. In each scenario (A–C), the solution was placed as evenly as possible across the palm and fingers of each hand. The final scenario (D) was also with no gloves but with hands kept moist by repeat dipping into the solution for 15 min. The fingers were dipped up to the third knuckle and allowed to drip dry; when the fingers looked dry they were dipped again and this continued for 15 min. For all exposures, volunteers supplied a pre-exposure urine sample and collected all urine for 48 h post exposure.
Temperature
During the consequences part of the study, skin temperature while wearing gloves and while not wearing gloves, was recorded using a squirrel data logger and a thermocouple taped to the volunteers' finger.
Fluorescence analysis
Analysis of the fluorescent marker is achieved using a surface monitoring fluorimeter (SMF3), which allows visualization and quantification of dermal exposure (Roff, 1994, 1997; Cherrie et al., 2000). The system allows photographs to be taken under UV light after skin has been exposed to a fluorescent tracer dye (Fig. 1). The fluorescent marker used throughout the study was 8 g of UVITEX.MST liquid in 10 l of distilled water. Calibration was performed by applying concentrations of fluorescent dye, to known areas of skin, to produce a standard curve. The constants produced were used in the SMF3 quantification software when analysing the photographs. The SMF3 system was used for quantifying the amounts of dye and for measuring the areas of exposure found on volunteers' skin. Background photographs are also taken and analysed at the start of each test to allow for variations in natural fluorescence to be taken into account.
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Video
Video recordings were taken at various stages of the experiments, particularly when volunteers were removing and reusing gloves. When the video and SMF3 photographs are used together they give a good indication of how and where the contamination has occurred (Fig. 2).
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Urine analysis
Urine samples were analysed for the metabolite 5-hydroxy-N-methyl pyrrolidone (5-HNMP) (Akrill et al., 2002
). Briefly, 5-HNMP was extracted from the urine using an automated solid-phase extraction procedure with C8 extraction cartridges. This was followed by derivatization with bis(trimethylsilyl)trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TMCS), and analysis by GC–MS (gas chromatography with mass spectrometry). An internal standard (d4-5-HNMP) was added at the start to account for any differences in extraction and derivatization efficiency between samples. The study was approved by HSE's Research Ethics Committee (ETH/COM/REG/01/02).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Routes
The results from SMF3 were quantified using the associated software to give the amount of contamination. The level of dye, given in nanograms, was used to calculate the equivalent volume of total solution present on the hand. This was done for each photograph of the front and back of both hands at each stage of the experiment, and for all three experiments. The results for the front and back of each hand were combined to give a total result for that hand. Each hand was then given a rating to show the level of contamination present: none = 0–3.2 µl; low = 3.2–8.5 µl; medium = 8.5–30.0 µl; high = 30.0+ µl. The choice of these rating boundaries was arbitrary, based on a subjective impression of the appearance of the hands, but the ratings were assigned from the SMF3 results. A high result does not necessarily have to have a large surface area coverage. Examples of the various levels are shown in Fig. 1.
Table 1 summarizes all the results and shows the number of volunteers receiving different levels of contamination for the three glove uses: natural/naïve removal, instructed removal, disposable gloves. For volunteers with no training on how to remove and put on gloves correctly (naive), 9 out of 10 had some level of contamination on their hands. The amount of contamination was evenly spread from low level to high level. After training was given on how to use the gloves correctly only 1 volunteer out of 10 had contamination on their hands and that was at a low level. The majority of trained volunteers (9 out of 10) successfully used their gloves repeatedly with no contamination to the hands. In the case where disposable gloves were used, training in how to use the gloves was again given, and 7 out of 10 volunteers successfully used gloves without receiving any contamination to their hands. Of the three volunteers who did have contamination two had leaking/faulty gloves, and one was likely to have been due to entry at the cuff.
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The information can also be used to identify at what stage the contamination occurred, i.e. whether contamination occurred during the first use of gloves, or the second or third use (when they were reused). The results in Table 2, for naïve glove use, show that for 7 out of 9 volunteers, first contamination occurred at the second use of the gloves, i.e. at the first reuse. The one instructed volunteer, who was contaminated, also received their contamination when reusing gloves. This shows that reusing gloves that are already contaminated on the outside can easily cause the contamination to be transferred to the inside of the glove.
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From the SMF3 photographs, the fluorescent marker shows which parts of the hands became contaminated. The photographs can be used to identify possible routes of entry of the solution to the inside of the gloves. Used in conjunction with the video recordings of the volunteers removing gloves and carrying out tasks, the causes of some of the contamination can be identified. The three main routes of internal contamination of gloves were identified to be: self-contamination (caused by the volunteer handling the outside of contaminated gloves, both at removal and reuse); cuff entry (contamination due to the solution entering at the cuff); failed glove (fault in the glove which allowed contamination to enter e.g. hole). In addition to receiving contamination to the hands, many volunteers received contamination to the arms. Some examples of using video recordings and SMF3 photographs together to identify routes of entry are given in Fig. 2.
Consequences
The experiments consisted of four scenarios: A, With gloves, 2 ml total dose (1 ml per hand), wearing the gloves for 15 min; B, With gloves, 2 ml total dose, 30 min; C, Without gloves, 2 ml total dose, left to dry (
15 min); D, Without gloves, repeat dipping, 15 min.
There was an average temperature difference of 11°C between the skin of volunteers when wearing gloves (scenario B), and when not wearing gloves (scenario D). The temperatures recorded were: scenario B, wearing gloves, average temperature 32°C, range 22.4–35.9°C; scenario D, no gloves, average temperature 21°C, range 18.1–23.2°C.
Urinary 5-hydroxy-N-methyl pyrrolidone (5-HNMP) results are a measure of systemic absorption of NMP into the body (Åkesson and Jönsson, 2000). These results are presented in Fig. 3, which compares 5-HNMP results for all the scenarios and clearly shows which gave the least and which gave the greatest systemic absorption. Lowest systemic absorption was scenario C (without gloves, 2 ml dose), next was scenario A (with gloves, 2 ml dose, 15 min), followed by scenario B (with gloves, 2 ml dose, 30 min) and finally highest systemic absorption was for scenario D (without gloves, repeat dipping). The statistical significance of these results was checked by performing paired t-tests between the datasets. Significance between scenarios was found to be at least 99.4% in all cases. The repeat dipping scenario gave the highest systemic absorption. To understand this better, the results were compared with those from a previous study (Akrill et al., 2002) where volunteers were exposed to a 15% NMP solution for 15 min by continuous immersion. In that study, the average result for continuous immersion was 284 µmol 5-HNMP, compared to 420 µmol 5-HNMP for repeat dipping in this study. It is likely that this surprisingly high result is due to the low volatility of the NMP, leading to the water evaporating first and leaving more concentrated NMP in contact with the skin. Vapour pressure of NMP is 0.345 mm Hg compared to a vapour pressure of 23.8 mm Hg for water (both values are at 25°C, from Daubert and Danner 1989).
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As the area of contact with a contaminant can affect the level of absorption, results were compared taking into account the area of contact (see Table 3). Comparing scenarios A and C (with and without gloves for 15 min), the 5-HNMP per area results are the same. There is an increased contact area with the contaminant when wearing gloves compared with when not wearing gloves, and the increased absorption could simply be due to the increased contact area. Comparing scenarios A and B (wearing gloves for 15 and 30 min) there is an increase in absorption with time. This increase would be expected to be linear i.e. doubling the time would double the absorption (Akrill et al., 2002
), but in this case it is a more than 3-fold increase. It could be argued that, over time, the contact area (inside gloves) increases, thereby increasing absorption. However, in this case the area of contact was actually smaller for the 30-min exposure, and therefore the increased systemic dose must be due to some other, complex relationship with time or increased humidity and/or temperature.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Routes
The combination of SMF3 photographs and video footage was very effective at identifying the sites of contamination. The results showed that internal contamination of gloves does occur, and that training in glove use was found to be an excellent way of reducing the levels of contamination contacting the hands. This was particularly true where gloves were reused. The majority of volunteers received contamination to the arms. Some of this was due to the liquid contaminant dribbling down the glove and accumulating at the cuff. Performing the task also caused some arm contamination. Two out of 30 pairs of disposable gloves were faulty and leaked causing contamination. Care must be taken with this type of glove to detect leaks. Disposable gloves also had a high incidence of wrist contamination, which partly came from the gloves being too short for the task and not providing protection for the wrist or lower arm, and partly from incorrect glove removal (even after training). Disposable gloves are often tighter and therefore more difficult to remove than other gloves, requiring more care to avoid contamination. Decontamination of gloves before removal could be advantageous and is the subject of a further study.
Consequences
The highest systemic dose occurred for the repeat dipping of the hands into solution. This exposure was even higher than an equivalent continuous contact exposure, seen in the Akrill study (Akrill et al., 2002). We hypothesize that due to the low volatility of the NMP solution used, the water evaporates first leaving a more concentrated NMP solution in contact with the skin. With repeat exposure the NMP becomes ever more concentrated and, as a consequence, absorption is increased. This has an important occupational hygiene message for dermal contact with solutions where the carrier may evaporate and leave the material in contact with the skin, such as pesticides. Wearing gloves, which will keep any internal contamination in contact with the skin, can lead to a higher systemic dose than the equivalent contamination when not wearing gloves. This is, in part, due to increased contact area and, in part, due to increased humidity, and therefore decreased barrier function of skin, or a combination of these. The barrier properties of skin are linked to the hydration of the skin. The more hydrated skin becomes, the less efficient the barrier. Comparison between this study and the Akrill study shows that the hydration under gloves is less than the hydration during total immersion, and consequently systemic absorption is lower. However, duration of exposure is important because hydration increases with time and, therefore, absorption increases. Several occupational hygiene messages can be learnt from this, the most important being that repeat contact with a chemical could lead to much higher exposures than expected, higher even than total immersion. Glove use can also lead to higher than expected exposures if the inside of the gloves is contaminated, and can cause exposures to be higher than if no gloves were worn.
Glove choice is an important element of ensuring proper control of exposure but there is widespread recognition that published protection factors may not be achieved in practice (Perkins and Rainey, 1997; HSE, 2001) and there is no consensus on how workplace effectiveness might be assessed. Cherrie et al. (2004) proposed a workplace protection factor based on the ratio of the estimated uptake of chemicals through the hands without gloves to the uptake through the hands while wearing gloves and suggested biological monitoring as a means of evaluating it. The workplace study of Chang et al. (2004) used biological monitoring to assess exposure to 2-methoxyethanol and the effectiveness of gloves. The results clearly show reductions in absorption when using gloves but it also shows the difficulties in assessing protection factors in field studies due to varying exposure levels, alternative routes of exposure and small numbers of different workers in each group. A more controlled experimental study proposed by Cherrie et al. (2004) may be a better approach to assessing workplace protection factors. The work reported here shows that this is feasible but it also shows that care should be taken with assumptions about absorption rates through the skin with and without gloves.
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CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Without training 9 out of 10 volunteers had internal contamination of their gloves when they reused them but if they were trained this reduced to 1 out of 10. Although single use gloves may reduce the potential for internal contamination, in this study 3 out of 10 volunteers were contaminated due to leaking or faulty gloves.
Wearing gloves which are internally contaminated can lead to increased systemic absorption due to increased area of contact and reduced skin barrier properties, and repeated skin contact with low-volatility chemicals can give higher than expected exposure if evaporation of the carrier occurs and the concentration in contact with the skin increases.
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ACKNOWLEDGEMENTS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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The authors would like to thank Martin Roff, Ian Dick, Jennifer Grimley and Joanne Walker of HSL for their help with various aspects of the study. Thanks also to all the volunteers who willingly took part in the study. This human volunteer study was approved by the Health and Safety Executive (HSE) Research Ethics Committee and was funded by CSD3 of the HSE.
Received December 1, 2004; in final form March 9, 2005
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