Annals of Occupational Hygiene Advance Access originally published online on March 2, 2004
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Ann. occup. Hyg., Vol. 48, No. 3, pp. 219-227, 2004
© 2004 British Occupational Hygiene Society
Published by Oxford University Press
Dermal Exposure During Filling, Loading and Brushing with Products Containing 2-(2-Butoxyethoxy)ethanol
TNO Chemistry, Department of Chemical Exposure Assessment, PO Box 360, 3700 AJ Zeist, The Netherlands
Received 20 May 2003; in final form 26 August 2003; published online on 2 March 2004
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSION AND CONCLUSIONSREFERENCES |
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Introduction: Limited quantitative information is available on dermal exposure to chemicals during various industrial activities. Therefore, within the scope of the EU-funded RISKOFDERM project, potential dermal exposure was measured during three different tasks: filling, loading and brushing. DEGBE (2-(2-butoxyethoxy)ethanol) was used as a ‘marker’ substance to determine dermal exposure to the products that workers were handling. Methods: Potential whole body exposure was measured using self-constructed cotton sampling pads on 11 body locations. Cotton gloves were used to determine the contamination of both hands. Bulk samples were collected to determine the concentration of DEGBE so as to be able to calculate exposure to the handled product. Results: A total of 94 task-based measurements were performed, 30 on filling, 28 on loading and 36 on brushing, which resulted in potential dermal hand exposure to the handled product of 4.1–18 269 mg [geometric mean (GM) 555.4, n = 30], 0.3–27745 mg (GM 217.0, n = 28) and 11.3–733.3 mg (GM 98.4, n = 24) for each of the scenarios, respectively. Potential whole body exposure to the product during filling and loading ranged from 1.67 to 155.0 (GM 15.2, n = 9) and <LOD to 176.2 (GM 0.30, n = 10). Because of sampling and analytical problems, whole body exposure during brushing could not be determined. Conclusion: Dermal exposure during filling and loading were of the same order of magnitude, while brushing resulted in much lower exposure levels, probably due to differences in work activities and work precision. For each of the scenarios, contamination was mainly found on the hands, representing up to 96% of the total exposure for filling. For filling and loading the most important source of variability in exposure was due to between-company variability rather than to either between-worker or within-worker variability. The pooled between-worker variability was the most important source of variability in dermal exposure levels for the brushing scenario.
Keywords: brushing; dermal exposure; DEGBE; filling; glycolether; loading; variance components
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSION AND CONCLUSIONSREFERENCES |
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Standardized exposure assessment strategies comprising both a well-designed sampling strategy and appropriate sampling techniques are currently lacking for dermal exposure (Vermeulen et al., 2000). At present, very limited information is available on either qualitative or quantitative dermal exposure for various scenarios across different industries. Consequently, dermal exposure models are either simplifications or specific to certain occupational settings. The aim of the EU-funded RISKOFDERM project (Project QLK4-CT-1999-01107) is to improve the current paucity of good quality dermal exposure information and to develop validated predictive models for estimating and managing dermal exposure.
The RISKOFDERM project contains four work parts. In work part 2, quantitative dermal exposure data on various predefined scenarios are generated in a large-scale measurement programme in several EU member states. The collection of quantitative dermal exposure data serves as a basis for subsequent modelling activities as defined in other work parts of RISKOFDERM (2001, 2002). The present study was conducted in the context of work part 2 and measurements on three of the predefined scenarios were performed: (i) filling of smaller packages from a large package or reactor of a product (typically at the end of a production process); (ii) loading of a product into a production process (typically handled products will be pure substances); (iii) brush application of paint.
The main objective of the study was to collect quantitative data on potential dermal exposure in the above described situations and to obtain information on the determinants of exposure. Moreover, this paper describes dimensions of dermal exposure variability observed in the three scenarios. Dermal exposures are likely to vary widely between persons and over time and exposure assessment and management strategies should be based on a thorough analysis of these exposure profiles (Fenske, 1993; van Hemmen and Brouwer, 1995; Kromhout and Vermeulen, 2001). Total dermal exposure variability is evaluated and separated into personal and temporal variability.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSION AND CONCLUSIONSREFERENCES |
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Measurement strategy
Task-specific potential dermal exposure during filling, loading and brushing was assessed for 2-(2-butoxyethoxy)ethanol (DEGBE) (CAS no. 112-34-5) as a marker substance. DEGBE is a liquid belonging to the group glycol ethers. The substance is widely used as a (co)solvent in paints, dyes, inks, detergents and cleaners. DEGBE has the potential to penetrate the skin, causing systemic exposure and may also cause local skin effects, such as irritation and contact dermatitis. Long-term exposure effects include defatting of the skin (World Health Organization, 1993; Schliemann-Willers et al., 2000). DEGBE has a low vapour pressure of 2.7 Pa at 20°C and can be analytically extracted from (dried) paint and other products for analysis, which makes it a suitable marker substance. With the known (measured) concentration of DEGBE in the product of interest, the potential dermal exposure to the total product was calculated.
Companies were randomly selected from lists obtained from trade organizations and workers voluntarily participated in the study. In total, over 60 companies were contacted, of which 16 agreed to participate. Other companies did not participate because the specific scenarios were not present, no DEGBE-containing products were handled or they did not wish to cooperate.
Measurements were performed under normal working conditions and working procedures. During their activities the workers wore personal protection as prescribed by the employer’s safety and health protocols (‘as is’). If the test subject usually wore protective gloves, a new pair of protective nitrile rubber gloves was provided prior to the sampling period to replace these. It was intended to perform repeated measurements for the same workers on separate days. In some cases this was not feasible and therefore repeated measurements were conducted among workers performing the same task on the same day and on separate days.
A total of 94 measurements were conducted in 16 different companies (some were visited for both the filling and the loading scenarios). During the study some analytical problems with background DEGBE in the materials used were encountered that resulted in 63 of the whole body results being discarded; the hand data of these measurements was not discarded. It appeared that a subsection of the sampling pads were constructed using PVC-backed foils, which leached DEGBE into the sampling cotton. This created a large background concentration in both the quality control samples and the exposure samples, which triggered an investigation of the problem. PE-backed foils, not containing DEGBE, were used for the rest of the study. Therefore, only 9 of 30 measurements carried out for filling resulted in both hand and body data while 21 measurements resulted in only hand data; for brushing 12 of 36 measurements resulted in both hand and body data (24 only hand data) and for loading 10 of 28 measurements resulted in both hand and body data (18 only hand data). Because of a background concentration of DEGBE of unknown origin in some workplaces, some of the brushing data could only be interpreted in terms of analyte exposure and could not be extrapolated to product exposure. Contamination of the sampling pads and gloves was excluded and it was suspected that sanding operations nearby created DEGBE-containing dust that settled on both the quality control and exposure samples.
Description of workplaces and tasks
Measurements were performed in companies of various sizes, although the focus was on small and medium-sized enterprises. The companies were selected from among producers of paints or cleaning agents (filling and loading scenarios) and professional painters (brushing scenario). Tasks during filling mainly comprised handling of empty packages, filling packages and closing of packages. The level of process automation varied from manual to semi-automated to automated filling. Occasionally some minor machine problems, such as accumulation of empty cans in the machine, were solved during the sampling period. However, this was observed to take a relatively short time and was judged to modify the exposure pattern only marginally. Loading typically involved handling of packages containing pure DEGBE and adding them to a production process. This was performed manually and sometimes included tapping of a certain amount of DEGBE from larger packages, such as drums, into cans before adding the substance to the process. Brushing was always carried out indoors and mostly on construction sites. The painted objects were mainly doors and window frames. Mixing and preparing of paints was excluded; only brushing activities were included in the sampling period.
Sampling
Dermal exposure of the hands and the whole body was measured using cotton gloves, without gauntlets, and cotton pads (both 100% 200 g/m2 cotton), respectively. Prior to use, the cotton was washed to remove any contaminants, according to internal protocols. The pads were constructed by cutting the cotton into appropriate pieces (5 x 5 cm for the head pad and 10 x 10 cm for other body part pads) and stapling it to a polyethylene (PE) plastic-backed cover of the same size. Medical tape was used to attach the pads on top of the workers clothing; the head pad was attached to a cotton headband which was worn by the worker. Eleven pads were placed at representative places on each of the body parts (head, chest, back, upper left and right arm, lower left and right arm, upper left and right leg and lower left and right leg) according to the OECD sampling protocol (OECD, 1997). Furthermore, the workers were asked to put on cotton sampling gloves. If the test subject usually wore protective gloves, sampling gloves were worn over new protective gloves.
At the end of a task, the field investigator removed the pads and gloves, separated the PE plastic backing of the cotton sampling pad and put the cotton pads and gloves in labelled jars containing methanol. The field investigators were wearing latex gloves to prevent cross-contamination. Pads from corresponding body locations (left and right) were pooled and analysed as one sample. The pooled gloves and pads were put in jars containing 300 ml and 80 ml methanol, respectively. The chest, back and head pads were not pooled and were put in separate jars containing 40 ml (chest and back pads) or 10 ml (head pads) methanol.
Samples of the substance that was handled during the filling, loading or brushing were collected for analysis of the DEGBE content of the product.
A set of quality control samples was collected each measurement day, which consisted of two fortified samples (field spikes, 25 µg pure DEGBE on one pad and 2 mg pure DEGBE on one glove) and one blank control sample (pad).
All samples were transported to the research facility and stored at room temperature until analysis.
Chemical analysis
In the laboratory all samples (gloves, pads, product samples, spikes and blanks) were analysed for DEGBE content. The DEGBE on the pads and gloves was extracted in methanol and analysed with an autosampler and gas chromatograph (HRGC 5300) (Zebron ZB-Wax column 60 m long x 0.32 mm i.d. x 0.5 µm df). DEGBE was detected using flame ionization detection and was identified based on the retention time. Turbochrom® was used for data analysis. 2-Ethylnaphtalene was added to the samples as an internal standard. If necessary, for low concentrations the extract (with the added internal standard) was concentrated under nitrogen. For further details on the chemical analysis, a standard operation procedure is available to those interested.
For the product samples, 50–100 mg was extracted in 50 ml of methanol, diluted to a concentration within the range of calibration and analysed similarly to the exposure matrices. Standard curves for 2-(2-butoxyethoxy)ethanol in methanol were linear up to at least 40 mg/l. For 2-(2-butoxyethoxy)ethanol in methanol after a concentration step, linear curves to 2.38 mg/l were found. Extracted 2-(2-butoxyethoxy)ethanol concentrations between 1.5 and 40 mg/l were measured directly; extracts with higher concentrations were diluted to a concentration within 1.5–40 mg/l. Extracts with a concentration <1.5 mg/l were concentrated under nitrogen.
The LOD was determined on the basis of five blank samples as the average blank signal plus 3 x SD. The LOQ was determined as the average blank signal plus 10 x SD. The limit of detection (LOD) of the analysis was 0.98 µg for one pad and 2.6 µg for the pooled gloves. The limit of quantification (LOQ) was 2.5 µg for one pad and 6.6 µg for the pooled gloves.
The recovery of DEGBE from two test paints (Acrylaat Dispersie Verf PSB 990164 and Sigma S2U Nova Satin) was determined after a period of drying of the paint on the cotton matrix. Three concentration levels of paint, representing a range of 0.04–9.4 mg DEGBE/glove, were tested with three different drying times (0, 120 and 240 min). For all concentrations of paint, after a drying period of 120 and 240 min average recoveries of 91 and 85%, respectively, were found. No correction of the analysis results was made for recovery. DEGBE on gloves and pads in methanol stored at ambient temperature was stable for a period of at least 5 weeks.
Calculations and statistics
Chemical analysis provided data on contamination of individual body pads and gloves by the marker substance DEGBE and provided the DEGBE concentration in each of the products used during the scenarios. Using the concentration of DEGBE in the product, exposure to the product on the individual pads and gloves could be extrapolated.
The contamination on each of the pads was assumed to represent the contamination on a certain body area. Dermal whole body contamination (excluding the hands) was calculated by multiplying the contamination on individual pad samplers by the anatomical dimensions in the OECD guidelines (OECD, 1997). Whole body exposure presented a surface area of 18 720 cm2. The surface area of both hands was assumed to be 820 cm2. Extrapolation was not needed to determine the total contamination on the hands, because of the use of sampling gloves covering the hands as a whole.
Values below the limit of detection (<LOD) were assumed to be 0. In situations where values were above the limit of detection and below the limit of quantification (>LOD and <LOQ), LOQ was substituted for these values. For calculation of the mass per surface area per time unit, the duration of the measurements (min) was used.
The SAS system for Windows (version 8.2) was used to calculate descriptive statistics, correlation coefficients and within- and between-worker variation components. The exposure distributions were tested using Proc Univariate. A nested two-way random effects analysis of variance (ANOVA) model was used to evaluate the contribution of between-company, between-worker and within-worker factors to the total exposure variance. In this model, worker is supposed to be nested in company and day in both worker and company. The ANOVA method was only used to calculate components of variance for hand exposure, since very few repeated measurements were available for the whole body. The ANOVA table produced by this analysis was used to estimate three variance components, i.e. the between-company variance (Sbc2), the pooled between-worker variance (Sbw) and the pooled within-worker variance (Sww). This model has also been described previously for inhalation and dermal exposure (Kromhout et al., 1996; Kromhout and Vermeulen, 2001).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSION AND CONCLUSIONSREFERENCES |
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Dermal exposure during filling
A total of 30 measurements during various filling scenarios were performed of which only 21 resulted in hand exposure data. In total 23 workers in 10 different companies participated; four workers (from three companies) were measured twice on the same day and the measurements for three workers (from two companies) were repeated on separate days. It was not possible to do the remaining measurements in duplicate because the batches of product containing DEGBE were not produced on a regular basis or different workers were involved. The ranges of the important parameters in the filling measurements are given in Table 1. When smaller amounts of product were handled, tasks mainly involved filling buckets (e.g. paint). Larger amounts were mainly transferred to containers or drums (e.g. cleaning agents for industry). In most cases general ventilation was present in the workplace (n = 29) and additional local exhaust ventilation (LEV) was present in 11 cases. Figure 1 shows an example of the filling scenarios.
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Table 2 shows the exposure results in mg and µg/cm2/min. The dermal exposure ranges found during filling activities were very wide and exposure distributions were characterized by very large geometric standard deviations (GSDs). The percentages of measurements above the limit of quantification were 100 and 41% for hand and individual pad samples, respectively. Taking into account the nine measurements for which both hand and whole body data were present, calculations showed that exposure of the worker was mainly due to exposure of the hands (95.5%). The remaining contamination was on the chest (1.7%), lower arms (1.1%), upper arms (0.73%) and lower legs (0.64%).
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Dermal exposure during loading
Measurements during loading were performed in eight different companies producing paints, cleaning agents or base chemicals. Loading of DEGBE typically involved addition of the pure substance to the production process or a mixer. DEGBE was usually packaged in cargo containers or drums and was transferred to the process or mixer using a bucket or a pump. As an example of the loading scenario, Fig. 2 shows the addition of DEGBE from a drum with an inner bag, which is squeezed out. In general, there was no LEV present during the addition of DEGBE to the process or mixer, but general ventilation was present in all cases. The ranges of important parameters of the filling measurements are given in Table 1.
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A total of 28 measurements were performed, of which 18 only resulted in hand exposure data. In total 15 workers participated in the loading measurements. Most workers were measured only once or twice on different days, one worker was measured four times on the same day, one worker was measured twice on the same day and one worker was measured eight times on three different days. Potential dermal exposure during loading activities is presented in Table 2. Exposure levels varied extremely in this scenario and GSDs were also very large (14.7–19.9). Exposure was mainly due to contamination of the hands (all samples were quantifiable), whereas most of the individual body pads were non-detectable (59%) or non-quantifiable (33%). Of the 10 measurements (containing seven pad samples per measurement) where whole body exposure was determined, only six individual samples were above the limit of quantification.
Dermal exposure during brushing of paint
The measurements for brushing were carried out among professional painters involved in the development of new buildings and building/renovation activities. Paint was applied using a brush for frames and in some cases a roller was used to spread the paint on larger areas (e.g. doors). Brushing activities always took place indoors. The workers involved in the study worked for five different companies, which were generally small sized. The measurements were performed at nine different locations. Two painters were measured only once and one painter was measured four times in two days. All other painters were measured twice on the same day, performing similar tasks, but always painting different window frames or doors. A total of 36 measurements, of which 24 resulted in data only on hand exposure, were performed. For 12 of the measurements exposure to the product could not be calculated, because of contamination of the samples by other sources of DEGBE than the painting activities at three of the work sites. These measurements may only be interpreted as analyte exposure.
Parameters regarding the brushing scenario are given in Table 1. The duration of the brushing measurements was up to 139 min, while in general the painters were painting during most of their working day. Measurements were stopped when coffee or lunch breaks occurred, which resulted in limited measurement duration. No LEV was present during brushing activities, but in most cases (n = 20) natural ventilation was present in the form of open doors and windows. Figure 3 shows an example of the brushing scenario.
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The results of the dermal exposure measurements during brushing are presented in Table 2. Compared with the filling and loading scenarios, exposure variability during brushing was smaller, with GSDs ranging from 3.0 to 4.0. Based on the analyte exposures of 12 measurements, for which both hand and whole body results were available, exposure during brushing was calculated to be mainly to the hands (almost 95% of total exposure). All 36 hand samplers contained a quantifiable amount of DEGBE. There was minor exposure to the upper and lower legs (together 3.5%) and to the forearms (1%). Of the 12 whole body measurements (containing seven pad samples per measurement) all pads contained detectable but small amounts of DEGBE, while the contamination of four pads was below the calibration curve and could not be quantified.
Components of variance in dermal exposure
The results of the ANOVA model for hand exposure are shown in Table 3. The ANOVA models provided relatively similar results for hand exposure expressed as µg/cm2/min and mg. Results of only the latter measure of exposure are presented in Table 3. ANOVA models were not used to assess components of variance for whole body exposure, since only a few repeated measurements were available. The results indicate that the most important source of variability in exposure during filling and loading was due to between-company variability rather than to either within-worker or between-worker variability. Thus, heterogeneity in exposure between companies is for these scenarios far more important than exposure differences between workers within a company or between measurements within the same worker. It appears that specific characteristics of the companies (e.g. process features and equipment) that make up the work environment were possibly the major source of exposure variability rather than individual work practices or temporal variation. For filling and loading the second most important source of variability was within-worker variability.
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The brushing scenario shows a different exposure profile, with the pooled between-worker component as the most important source of variability. Thus, differences in work practices or the work environments of individual workers appear to be the most important source of exposure variation for this scenario. The second most important source of exposure variation was within-worker variability (for product) and between-company variability (for DEGBE). The company itself does not seem to play a role; on average, dermal exposure seems to be similar across companies.
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DISCUSSION AND CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSION AND CONCLUSIONSREFERENCES |
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The present study describes dermal exposure levels observed during the predefined scenarios: filling, loading and brushing. Tasks were kept as pure as possible, meaning that measurements were stopped if the workers performed different tasks than those intended. In a few cases some minor deviations, such as solving of minor machine problems (during filling) and occasional use of a roller (during brushing) were accepted during the measurements, as in practice these often coincide.
The results clearly show that potential dermal exposure during filling and loading is found at significant levels on the hands. Body exposure during these tasks contributes little to the total individual exposure. For filling and loading 22 and 59%, respectively, of the individual body pads were below the LOD and, additionally, 37 and 33% were below the LOQ. This high number of values below the LOD or LOQ may be explained by the fact that potentially contaminated objects are handled and no aerosol generation takes place. A structured description of different transport mechanisms of contaminant mass from the source of the substance to the surface of the skin has recently been outlined in a conceptual model (Schneider et al., 1999). This conceptual model was used to observe the exposure processes resulting in contamination. Contamination of the body was observed to take place mainly due to spills and splashes, incidental contact with contaminated surfaces and relocation of hand contamination when the worker touches his clothes or forehead with his hands.
The tasks during filling and loading are rather similar, indicating a similar potential for dermal exposure. This is also indicated by exposure results that show that hand and body exposure to the product are of the same order of magnitude for filling and loading activities; however, the range of dermal exposure during loading appears to be wider. Regarding the exposure to DEGBE, these tasks result in different exposure levels and also different levels of variability because of differences in DEGBE concentration in the products. During loading mainly pure DEGBE was handled and during filling mainly products containing lower concentrations of DEGBE (mean 32%) were used. The exposure rate is lower for the filling than for the loading scenario. The loading scenario typically lasted only a few minutes (average 6 min), while the duration of filling activities was generally longer (average 65 min) and showed a wider range.
Brushing resulted in rather different exposure levels compared with filling and loading. Unfortunately exposure of the body could only be interpreted in terms of exposure to DEGBE and not exposure to the product. This was due to the fact that on three construction sites where painting activities took place DEGBE contamination was found on the quality control samples (both on spikes and blanks) and the exposure samples that was unlikely to be caused by the brushing activities. The cause was probably an unknown source of DEGBE present in the workplace that was not related to the measured task, such as sanding of painted surfaces. It was decided that the exposure present on body pads and gloves could only be interpreted as exposure to DEGBE, because calculation of exposure to the product using the concentration of DEGBE in the paint would result in very unreliable exposure results. The quality control samples (blanks, spikes and calibration samples) proved to be of vital importance to identify problems in the field and in the chemical analyses.
Hand exposure during brushing was observed to take place mainly by touching contaminated work tools, such as the brush or the can of paint. Hand exposure to the product was considerably lower during brushing than during filling or loading. The exposure rate was also lower than during filling or loading. The difference in tasks performed and the fact that painters handle the brush with precision and care may explain the lower exposure. This is in contrast to the much less careful way that some workers handled potentially contaminated work equipment and tools during filling and loading. In addition, activities during loading and filling had more potential for spills and splashes than during brushing. The ranges of exposure levels for brushing were less wide than for loading and filling. This may be explained by the different tasks performed and the techniques used. Brushing was always performed using similar tools (a brush and occasionally a roller), while during filling in particular, the techniques used varied from manual to automated.
The method of determining whole body dermal exposure using exposure pads assumes a uniform distribution of exposure over the body part in question (Fenske, 1993; Tannahill et al., 1996; OECD, 1997). This assumption was used in the calculations of whole body exposure, since contaminant levels on each pad sampler were extrapolated to a larger anatomical region represented by that sampler. Whether this criterion of uniform distribution within the discreet anatomical region was met could not be tested. Yet, this is probably not the case, since observations indicated that the main route of body contamination was from spills and splashes, incidental contact with contaminated surfaces and relocation of contamination, mainly from the hands to other parts of the body. This implies a chance factor of a drop or spot coming into contact with the sampling pad, which may explain in part the fact that contamination on pads was in many cases non-detectable. Alternatively, the sampling gloves covered the whole of both hands and therefore represent the true exposure of the hands. Because of the observed exposure routes, in future research the whole body method, where the sampler covers the whole body area, would be preferred to the pad method for these specific scenarios.
Pad sampling was the chosen method within the RISKOFDERM project. This sampling technique depends heavily on the assumption that pads accurately represent a skin region with a certain surface area. However, all methods used to assess dermal exposure (such as skin washing or wiping, skin stripping, fluorescent tracer techniques, pads or the whole body method) have advantages and disadvantages and each exposure situation places different demands on the sampling method (Brouwer et al., 2000; Cherrie et al., 2000; Soutar et al., 2000). In practice there is a need to develop standardized protocols or guidelines for dermal exposure studies.
Validation results showed that DEGBE could be efficiently recovered from dried paint. All tests with different types of paint, representing three different concentrations (0.04–9.4 mg DEGBE/glove) and different drying times under ambient conditions gave recoveries that were well over 80%, indicating that no correction for recovery was needed. The recovery of the experimental glove samples may in practice have been lower, because despite the low vapour pressure, DEGBE may evaporate faster from the sampler due to body heat and movement of the test person. This effect probably causes a slight underestimation of hand exposure. Whole body exposure was probably less affected as the pads were placed on top of clothes where the effect of body heat and movement is less. Furthermore, recovery efficiency was not tested for the high exposure levels found on gloves (up to 28.3 g DEGBE on two gloves during loading), which may also have affected the recovery efficiency. This indicates that the high exposure levels that were found for the loading and filling scenarios may in fact be even higher. However, for these high exposure samples there is also an effect leading to overestimation of exposure, which is due to the fact that the cotton sampling glove can retain more material than skin, especially when handling liquids and direct contact with the contaminant source is an important exposure route. These effects, together with the potential extrapolation errors in calculations of whole body exposures, are to be borne in mind when evaluating absolute exposure levels.
The measured exposure values cannot be interpreted directly as the amount of substance available for dermal uptake. This is inherent in the method used, as it only determines potential exposure, by placing sampling pads on top of work clothes. If the values are to be used to estimate the actual exposure on the skin, the use of personal protective equipment, such as gloves, should be considered as a factor reducing exposure. Hence, actual dermal exposure can be estimated by multiplying potential exposure by assumed particular protection factors for hands and other body parts. Some algorithms for the transformation of potential exposure to actual exposure have recently been described (van Wendel de Joode et al., 2003).
Only very limited information is available on personal and temporal variations in dermal exposure levels. An effort to fill this knowledge gap was undertaken by Kromhout and Vermeulen (2001), who created a first database of approximately 6400 dermal exposure measurements (DERMDAT). Our ANOVA results are based on only a limited measurement series. Yet, given the paucity of information on components of dermal exposure variation across exposure situations and industries, our results add to the existing knowledge base with respect to dermal exposure variation. One should take into account several discrepancies between our study and DERMDAT when interpreting the results. First, this paper describes task-based rather than shift-based exposure measurements. Thus, the influence of time–activity patterns on exposure profiles is not incorporated in the presented components of variance. Second, in the current survey only a very limited number of repeated measurements were conducted on different days for the same individuals. This is a major limitation when using the data for evaluation of personal and temporal variation. As a matter of fact, day-to-day variation and within-day variation could not be disentangled. The within-worker component of variance represents both day-to-day and within-day variation and may therefore be an underestimation of the true variation over a longer period.
Gaining insight into components of variance may have important implications for future modelling exercises and development of measurement strategies as well as dermal exposure control strategies. For example, the predominant between-company factor found for filling and loading suggests that measurement strategies should aim at covering a broad range of different companies to provide an adequate picture of differences in exposure levels. In applying these components of variance to exposure control the following approach would be reasonable. For scenarios where between-worker variation is the greatest contributor to the total exposure variability, control measures should begin by determining between-worker factors such as differences in individual work practices or differences in specific work environments. For example, one worker’s behaviour may cause more spills and splashes than another. Conversely, when the between-company factor is the major source of exposure variation, the first control objective should be to identify and correct company-related situations resulting in high exposure, e.g. differences in the particular production process in the various companies that impact on a workers’ exposure.
Acknowledgements—This study was financially supported by the DG Science of the EU (QLK4-CT-1999-01107) and the Dutch Ministry of Social Affairs and Employment. Ms H. van Drooge, Mr M. Lurvink, Mr M. Kerkman, Mrs M.J. van Leeuwen, Mr L. Ravensberg and Mr R. Engel are each greatly acknowledged for their contribution to the project, during study design, field measurements and analysis.
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FOOTNOTES |
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* Author to whom correspondence should be addressed. Tel: +31-30-6944093; fax: +31-30-6944926; e-mail: gijsbers{at}chemie.tno.nl
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