Annals of Occupational Hygiene Advance Access originally published online on March 4, 2004
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Ann. occup. Hyg., Vol. 48, No. 3, pp. 267-275, 2004
© 2004 British Occupational Hygiene Society
Published by Oxford University Press
Dermal Exposure to Terpenic Resin Acids in Swedish Carpentry Workshops and Sawmills
1 Department of Occupational and Environmental Medicine, University Hospital of Northern Sweden, SE-901 85 Umeå; 2 National Institute for Working Life, SE-907 13 Umeå, Sweden 3 Present address: Alcontrol Laboratories, PO Box 6519, 906 12 Umeå, Sweden
Received 28 April 2003; in final form 30 July 2003; published online on 4 March 2004
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Objectives: The aim of this study was to evaluate dermal exposure to the resin acids abietic acid, dehydroabietic acid and 7-oxodehydroabietic acid during collecting in sawmills and during sawing in carpentry workshops, respectively. Methods: Sampling was performed by fastening patches at 12 different areas on a sampling overall, one patch on the front of a cap, one patch on the chest inside the clothing and one patch on the inner lower right leg. Exposure of the hands was assessed by fastening patches on cotton gloves representing the dorsal sides and the palms of the left and right hands. Sampling was performed on 30 different occasions in the sawmills and in the carpentry workshops with mean sampling times of 120 and 59 min, respectively. The acids were solvent desorbed from the patches. Identification and quantification of the resin acids was performed by gas chromatography–mass spectrometry. Results: The geometric means (GMs) of the potential body exposures to abietic acid, dehydroabietic acid and 7-oxodehydroabietic acid during sawing and collecting of wood from pine and spruce were 3346 and 17 247 µg/h, respectively. The GM of the potential exposure on the hands was 3020 µg/h in the carpentry workshops and 4365 µg/h in the sawmills. Resin acids were detected on the inner chest and inner lower front right leg, respectively. Conclusions: There is a potential dermal exposure to terpenic resin acids in carpentry workshops as well as in sawmills. The hands have the highest exposure during sawing as well as during collecting. There is a spatial distribution of contaminants, with the outer chest, arms and legs showing the highest exposures. Resin acids also contaminated the inner chest and inner lower leg. It is necessary to take action to reduce dermal exposure to these allergenic substances.
Keywords: dermal exposure; patch sampling; terpenic resin acids
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Wood processing is one of the main industries in Sweden with
20 000 employees. Swedish sawmill workers and employees within carpentry workshops and joinery shops treat pine (Pinus sylvestris) and spruce (Picea abies) during the production of boards and wooden products, respectively. Mechanical treatments, such as sawing, boring and drilling of trees and boards, releases volatile monoterpenes and wood dust into the indoor air of the premises (Eriksson et al., 1996, 1997; Rosenberg et al., 1999). Other substances present in the trees are monocarboxylic diterpene resin acids, which are the main constituents of the oleoresin of these coniferous species. The acids are mainly of abietic and pimaric type, with abietic acid and dehydroabietic acid as the dominant substances. Abietic acid and dehydroabietic acid are oxidized by air and one of the oxidation products has been identified by Karlberg et al. (1988) as 7-oxodehydroabietic acid. The acids and especially the oxidized acids have shown dermal allergenic activity in animal studies (Hausen and Mohnert, 1989; Hausen and Mohnert et al., 1989, 1990; Hausen and Hessling, 1990; Färm, 1997). Individuals occupied in different forms of woodwork are exposed to resin acids in sawdust from pine and spruce and may develop hand dermatitis as well as dermatitis due to airborne allergen exposure (Krutmann et al., 1989; Cook and Freeman, 1997; Färm, 1997; Watsky, 1997). Demers et al. (2000) have recently shown that workers in a Canadian sawmill are exposed to abietic acid and pimaric acid by inhalation during sawing of wood from pine, spruce and fir. Following emission into the indoor air of the premises, wood dust and resin acids may deposit onto the workers outer clothing, hands, face and head, respectively. The substances are likely to settle onto machinery, tools, boards, planks and wood pieces and may contaminate the worker following contact with the technical equipment and other contaminated surfaces. In addition, direct contact with the wood product by the hands is likely to contribute to dermal exposure. To our knowledge, no studies have been performed to study skin complaints or to estimate the potential dermal exposure to resin acids in the wood treatment industries. We performed assessments during collecting in sawmills and during sawing in carpentry workshops as these tasks were considered to give relatively high dermal exposures to these substances. |
MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Sawmills
Swedish sawmills usually consist of a sawing shed, a kiln and a grading house. In the sawing shed the barked trees are sawn into centre boards and edge boards and unsightly edges are sawn away. The worker performing these tasks sits in a well-ventilated cabin. The finished boards and planks are then sorted according to size and quality before being transported to the kiln. A worker who often sits or stands relatively close to the moving belt performs the collection (Fig. 1). The sorted boards are then transported to the kiln where they are kept at a temperature of
25–45°C for 24–48 h to reduce the water content of the planks. After the drying procedure is completed, the boards are transported to the grading house where they are quality rated by specially trained personnel who sit in a ventilated cabin. The ventilation system at the premises included general ventilation with no local extractor at the conveyor where collection of boards was carried out.
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Carpentries
Prior to the manufacturing process, the water content of the boards is reduced to 8–10% (w/w) in a kiln, commonly located in the vicinity of the joinery shop. Following the drying procedure the planks are used in the production process, which comprises the following steps. The deals are transported to the planer on a conveyor, onto which they are put automatically or manually. After planing, the planks are manually removed from a belt leading from the planer and put onto a materials handling trolley. When fully loaded, the trolley is delivered to the sawyers, who cut the wood. The cut pieces are then milled, drilled and sanded. All of the wood treatment machinery is often located in the same room, except for the plane, which is situated in a separate room. The workers are usually trained to perform all these different tasks, but they mostly specialize in a particular job. We studied dermal exposure during one of these tasks, sawing (Fig. 2). This task included manually carrying board or wood pieces from the materials handling trolley to the saw, sawing wood pieces of different size and removing the object from the tool to put it onto another materials handling trolley. The machinery was equipped with local extractors in addition to the general ventilation of the premises.
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Sampling
Patches (5 x 5) cm were cut out from a cotton/charcoal cloth (Blücher GmbH, Erkrath, Germany). The cloth consists of two layers of cotton fabric with activated charcoal woven in between the two fabric layers. Patches made of other materials, such as surgical gauze and filter paper, were also considered for use, but the charcoal/cotton cloth was the only material with no background levels of resin acids. Patches covered with aluminium foil on the back were fastened at 12 different spots, each spot representing a body area, on the outside of a sampling overall. Exposure of the head and face was determined by fastening a patch on the front of a cap. Exposure of the hands was estimated by fastening one patch on each side of two cotton gloves representing the palm and the dorsal side, respectively. The patches were fastened with staples onto the overall, the cap and the cotton gloves in the laboratory. Exposure of the inner chest and inner lower front right leg was estimated by fastening patches to the skin with surgical tape. The workers wore long trousers and a short- or long-sleeved shirt between the sampling overall and the patches on the bare skin. The individuals wore the cotton gloves during the sampling period, as they were unwilling to wear cotton gloves with patches underneath their protective gloves. Table 1 shows the sampling spots and their corresponding surface areas (OECD, 1997). To minimize the amount of substances possibly interfering during analysis the patches were preheated in an oven at 80°C overnight before use. During transportation from the laboratory to the premises, the overalls were kept in a tightly sealed box. Patches on the inner chest and inner lower right leg were fastened by the worker him/herself. The workers were told to wash their hands before fastening the patches to the skin. The worker then dressed in the overall, the cap and gloves in a clean area within the premises a few minutes before the onset of assessment. If repeated sampling was performed on the same day the worker dressed in another overall, a new cap and new gloves with patches already attached. These items were kept in the box until used. The unexposed patches fastened to the inner chest and inner lower right leg were kept in a tightly sealed glass jar in the box until used. Directly after the end of sampling the exposed patch was put into a 10 ml glass bottle. The vial was sealed with a screw cork and transported to the laboratory in the box. On each sampling day two patches was spiked with 20–40 µg of a mixture of the three resin acids and the internal standard in dichloromethane by means of a syringe. One unexposed patch for each sampling day was used as a field blank. The spiked patch and the field blank samples were handled in the same way as the exposed patches. The overall onto which the patches were fastened was used repeatedly on different days. The overalls were given an airing for at least one night before re-use. To evaluate whether the remaining resin acids contaminated unused patches, one patch was fastened to the chest area on the outside of an overall overnight and analysed for its content of resin acids. In the sawmills (n = 3) assessment of dermal exposure was carried out for 4 days on 20 individuals performing collection of boards. Repeated sampling (n = 2) was carried out on 10 individuals and one sampling was performed on 10 individuals, resulting in 30 measurements. The sampling time was 120 min at each occasion and
80 m3 wood was sorted during this time. In the carpentry workshops (n = 3) measurements were performed on 10 sawyers over 5 days. Sampling was carried out one to four times on the same individual and altogether 30 measurements were carried out. The sampling time was 55–120 min (mean 95 min) and during this time 1–2 m3 of wood was mechanically treated.
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Analysis
Standard preparation
Standard solutions were prepared by dissolving known amounts of abietic acid (95%) (Helix Biotech), dehydroabietic acid (99%) (Helix Biotech) and 7-oxodehydroabetic acid (99%) (Helix Biotech) in 10 ml of dichloromethane. To 400 µl of a standard solution was added 200 µg of heptadecanoic acid used as internal standard and 200 µl of N,N-dimethylformamide dimethyl acetal and the substances were derivatized for 30 min at 60°C. Following derivatization the solution was evaporated to near dryness under nitrogen, reconstituted in 1000 µl of dichloromethane and 1 µl was injected onto a gas chromatographic mass spectrometric system.
Sample preparation
At the laboratory 200 µg of heptadecanoic acid was added to the exposed patches, the blank sample by means of a syringe. An aliquot of 5 ml of dichloromethane was added to the glass bottle containing the patch. The acids were desorbed from the patch by ultrasonification for 30 min and following desorption the patch was removed from the bottle with a pair of tweezers. The organic solvent underwent evaporation to near dryness under nitrogen. After evaporation the resin acids and the internal standard were derivatized to their methyl ester, by adding 200 µl of N,N-dimethylformamide dimethyl acetal to the glass bottle followed by 400 µl of dichloromethane. The solution was transferred to a microvial and the sample was heated to 60°C in a water bath for 30 min, evaporated to near dryness under nitrogen and reconstituted in 1000 µl of dichloromethane. An aliquot of 1 µl was injected onto a gas chromatograph–mass spectrometer by means of an automatic injector (model 7630; Hewlett Packard, The Netherlands). Samples were prepared on the evening of the sampling day 8 h after the end of sampling
Gas chromatography–mass spectrometry
The gas chromatographic–mass spectrometric method has been published elsewhere (Demers et al., 2000). The samples were analysed using a Hewlett-Packard model 5890 gas chromatograph equipped with a mass selective detector (HP 5973) and a 50 m x 0.25 mm i.d. Ultra 2 (Hewlett Packard) capillary column with a film thickness (5% crosslinked phenyl methyl siloxane) of 0.33 µm. Helium was used as carrier gas with an inlet pressure of 46 p.s.i. at an average velocity of 32 cm/s. The injector was set at 250°C and the gas chromatograph temperature was programmed as follows: initial temperature 140°C for 1 min, a temperature rise at 40°C/min to 200°C followed by 5°C/min to 300°C, with a hold at 300°C for 1 min. The retention time for the methyl esters of dehydroabietic acid, abietic acid and 7-oxodehydroabietic acid were 18.6, 19.4 and 22.4 min, respectively. The methyl ester of heptadecanoic acid had a retention time of 12.8 min. The mass selective detector was used in the EI mode. The transfer line temperature was set at 280°C. The mass spectrometer manifold was set at manifold temperature of 220°C. The limits of detection (LOD) were 0.27, 0.79 and 1.23 µg for abietic acid, dehydroabietic acid and 7-oxodehydroabietic acid, respectively, expressed as 3 SD of the background noise of a blank sample. The limits of quantification, determined as 10 SD of the background noise of a blank sample, were estimated to be 0.90, 2.62 and 4.10 µg, respectively. The limit of quantification (LOQ) for the 5 x 5 cm patch was determined to be 2.0 µg, expressed as the sum of the three acids. The amounts of acids on the patches fastened on an overall overnight were all less than the LOD.
Recovery of the field-spiked samples was 81–96% with a relative standard deviation (RSD) of 3.9–9.1%.
Statistics
Pearson correlation coefficients were used to investigate the relation between dermal exposure of individual body regions and between the left and right sides of the same body part, as well as between the palm and the dorsal side of the hands. The effect of clothing has been evaluated using the paired t-test. The calculations were performed with SPSS package version 11.0 and log10 of the exposure values were used.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Potential exposure of individual body parts
The exposure was calculated by using the sum of the three resin acids. Dehydroabietic acid was the dominant resin acid during both sawing and collecting, with a mean of 85–86% (Tables 2 and 3). The mean amount of abietic acid was 8–9% and the mean amount of 7-oxodehydroabietic acid was 6% of the total mass of resin acids. Dehydroabietic acid was the only acid detected on the inner chest of the sawyers as well as collectors. The collectors showed traces of abietic acid (0.5%) and 7-oxodehydroabietic acid (0.5%) on the inner lower right leg, with dehydroabietic acid as the dominant acid (99%). Dehydroabietic acid was the only acid identified on the inner chest and inner lower right leg of sawyers.
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The amounts of resin acids on the individual patches have been scaled up assuming uniform exposure on each individual body part and using the surface area for the corresponding body parts as shown in Table 1.
Sawing
Exposure of the outer chest was 896 µg/h [geometric mean (GM)], as shown in Table 2. The upper and lower left and right legs had a GM of 169–312 µg/h and the left and right upper arms and left and right forearms had a GM of 81.8–131 µg/h. The GM for exposure of the outer back, back of the neck, front of the neck and head and face was estimated to be 9.73–108 µg/h. The inner chest showed a GM for exposure of 56.0 µg/h and the lower inner right leg 98.6 µg/h. The GMs for exposure of the dorsal sides of the hands were 103 and 112 µg/h and for the palms were 652 and 725 µg/h.
Collecting
The GM for exposure of outer chest was 2198 µg/h (Table 3). The upper and lower left and right legs had a GM of 1543–2802 µg/h and the left and right upper arms and left and right forearms had a GM of 271–419 µg/h. The GM for exposure of the outer back, back of the neck, front of the neck and head and face was 24.1–387 µg/h. The GMs for exposure of the dorsal side of the hands and the palms were estimated to be 170, 201, 1551 and 1629 µg/h, respectively. The GM for exposure of the inner chest was 331 µg/h and of the lower inner right leg 699 µg/h.
Potential body and hand exposure
Sawing
The GMs for potential exposure on the body and the hands were estimated to be 3346 and 3020 µg/h, respectively (Table 2).
Collecting
The potential exposure (GM) of the body and the hands were estimated as 17 247 and 4365 µg/h, respectively (Table 3).
Statistics
Effects of clothing
The paired t-test (Table 4) showed that exposure of the inner chest and inner lower right leg were significantly lower compared with exposure of the outer chest and outer lower right leg during sawing and collecting.
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Correlation between individual body parts, dorsal sides and palms of the left and right hands.
Sawing. Correlations between contaminant mass at individual sites were in general relatively low, as shown in Table 5, except between the left and right upper legs (0.75, P < 0.01), left and right lower legs (0.86, P < 0.01) and outer chest and right forearm (0.69, P < 0.01). The correlation between the dorsal sides of the left and right hands was 0.82 (P < 0.01) and the palms of the left and right hands was 0.88 (P < 0.01).
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Collecting. Correlations between exposure to terpenic acids were in general low (Table 5), except between the left upper arm and left forearm (0.71, P < 0.01), right upper arm and right forearm (0.75, P < 0.01), outer back and back of neck (0.72, P < 0.01) and back of neck and front of neck (0.79, P < 0.01). The correlations between the dorsal sides of the left and right hands and the palms of the left and right hands were relatively low, with correlation coefficients of 0.27 and 0.41 (P < 0.01), respectively.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The results of patch sample analysis indicate that dermal exposure to abietic, dehydroabietic acid and 7-oxodehydroabietic acid took place during sawing of coniferous wood in carpentry workshops and collection of pine and spruce boards in sawmills. Workers in sawmills seems to have a higher potential dermal exposure compared with sawyers in carpentry workshops. For both sawyers and collectors the hands, and especially the palms of the hands, have the highest potential exposure. The sawyers as well as the collectors frequently touch the pieces of wood and the boards with their hands during work. In the sawmill fresh wood is treated, while the boards in the carpentry workshops have been dried on at least two different occasions. Fresh wood is often contaminated with oleoresin, which contains resin acids, on the surface of the planks and boards. During the drying procedure in the kiln the oleoresin on the surface dries and will almost certainly have fallen off due to contact with conveyors or other equipment during grading and transportation. This probably accounts to some degree for the higher exposure to resin acids of the hands of the collectors compared with the sawyer’s. The higher exposure of the palms compared with the dorsal sides of the hands is understandable as the palm is in direct contact with the workpiece more often than the dorsal side. The sawyers usually use protective gloves made of leather during work to protect the hands and fingers from being hurt by the saw or splints. We observed that the workers used the gloves until completely worn out, i.e. with holes on the fingers and the palm of the glove, indicating a potential risk of dermal exposure. Protective gloves made of leather are supplied by the employer but the collectors frequently do not use them, indicating that they may have a higher risk of contamination of the skin of the hands compared with sawyers.
Following the hands, the chest, the legs, the arms and outer back had the highest exposures. The face and head and back and front of neck showed the lowest exposures. The sawyers and the collectors stand rather close to the emission source (Figs 1 and 2). Sawing of wood emitted a relatively high amount of dust, but a local extractor on the equipment probably significantly reduced the amount of dust entering the workroom air compartment. The boards are not sawn or in any other way mechanically treated during collection and therefore no local extractors have been installed. The planks are, however, rotated on the conveyor for quality inspection reasons and dust present on the boards as well as on the moving belt is whirled up into the air. The chest and the arms were level with the saw and moving belt, respectively, and deposition of airborne particles is likely to be higher on these body parts compared with the head and back and front of the neck, respectively. The relatively high exposure of the legs could be explained by deposition of dust emitted from the saw and the moving belt, respectively, but in addition also as a result of dust whirled up from the floor. Exposure of the outer back indicates additional exposure from colleagues performing similar or other work tasks, such as cleaning of equipment using compressed air. Air movement in the area surrounding the sawyers and collectors was determined by smoke generated from a smoke tube. For the sawyers the airflow was mainly away from the worker while for the collectors the airflow was mainly towards the worker. The direction of airflow with its ‘content’ of wood dust, resin acids and other particles towards the collector, probably as an effect of the absence of an extractor, may in some part explain the higher exposure among collectors compared with sawyers.
Usually, workers in the carpentry workshops and sawmills wear protective shoes with socks and trousers. Workers in the carpentry workshops wear a long-sleeved shirt while collectors are usually dressed in a T-shirt. Short-sleeved T-shirts do not cover the lower arms and parts of the upper arms as well as the front and back of the neck. Resin acids are thus likely to contaminate the unprotected skin of these body compartments. In addition, the skin of the face is also exposed to these allergenic substances. The workers use these clothes for at least 1 week before changing to a clean shirt and newly washed trousers. We have shown that there is substantial deposition of resin acids on the outer chest, outer back and arms and legs. Identification of resin acids on the inner chest and inner front lower right leg indicates that the substances are likely to penetrate or permeate through the clothing and contaminate the skin of the worker. However, clothing effectively reduces the amounts of resin acids reaching the skin of the worker. The workers taking part in this survey anecdotally said that they experienced air movements along their legs underneath the trousers, a possible additional means of exposure to resin acids of the skin of the legs.
Interestingly, the oxidized allergen 7-oxodehydroabietic acid was identified on several of the body parts, which indicates a risk of an allergenic response or effect on the skin of the individuals following short- or long-term exposure. We used dichloromethane as the solvent extraction for the patches. The acids may be present as ‘free’ particles and/or be adsorbed onto the surface of wood dust or other dusts present on the patch. We cannot distinguish between ‘free’ acids and particle-bound acids with the extraction method used. If the ‘free’ acids are those responsible for the biological response the exposure may have been overestimated.
There were high statistically significant correlation coefficients between exposure of the upper left and right legs, between the lower left and right legs and between the palms and the dorsal sides of the hands, respectively, during sawing. During collection a highly statistically significant correlation was determined between the left upper and right forearms, between the left and right upper arms, between the outer back and back of the neck and between back of the neck and front of the neck, respectively. These findings indicate the existence of uniform exposure of some body areas. The number of sampling spots may thus be reduced and this probably would not result in a different exposure classification than that based on exposure utilizing all 17 patches used in this study.
In conclusion, sawing in carpentry workshops and collecting in sawmills of pine and spruce caused a considerable potential dermal exposure to resin acids. The hands seem to have the highest exposure levels, more than 10-fold higher than other body parts. Direct contact with the wood and/or contact with contaminated surfaces are the most important sources of dermal exposure in this study. There is a spatial distribution of contaminants over the body, with the outer chest, arms, legs and outer back showing the highest exposures. The results show that acids are reaching and probably contaminating the dermal layer of the workers. It is necessary to take action to reduce dermal exposure to these substances. Gloves should be used and changed before becoming worn out. Ventilation should be improved, possibly with more effective local extractors on the saws and the conveyor in the collecting department of the sawmills. The workers can probably further reduce dermal exposure by using long-sleeved shirts and changing their working clothes as often as possible.
Acknowledgements—Professor Jan-Olof Levin at the National Institute for Working Life is greatly acknowledged for providing us with the analytical equipment and other laboratory resources. This study was performed within a European project RISKOFDERM (Project QLK4-CT-1999-01107) with financial support from the EU. The National Institute for Working Life, Umeå, Sweden, and the Department of Occupational and Environmental Medicine, University Hospital of Northern Sweden, Umeå, Sweden, also financially supported the project, which is gratefully acknowledged.
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FOOTNOTES |
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* Author to whom correspondence should be addressed. Fax: +46-9078-52456; e-mail: kare.eriksson{at}vll.se
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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