Ann. occup. Hyg., Vol. 47, No. 3, pp. 219-226, 2003
© 2003 British Occupational Hygiene Society
Published by Oxford University Press
Exposure Assessment to 
- and ß-Pinene, 
3-Carene and Wood Dust in Industrial Production of Wood Pellets
1 Department of Occupational and Environmental Medicine, Örebro University Hospital, SE-701 85 Örebro, Sweden; 2 Department of Occupational and Environmental Medicine, University Hospital of Umeå, SE-901 85 Umeå, Sweden; 3 Department of Business Administration, Computer Science, Economics and Statistics, Örebro University, SE-701 82 Örebro, Sweden
Received 15 July 2002; in final form 7 October 2002
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
The main aim of the study was to measure the exposure to monoterpenes (
- and ß-pinene and 
3-carene) and wood dust during industrial production of wood pellets and briquettes. Additional aims were to compare the results from wood dust sampled on a filter with real time measurements using a direct reading instrument and to identify peak exposures to dust. Twenty-four men working at six companies involved in industrial production of wood pellets and briquettes participated in the study. Monoterpenes were measured by diffusive sampling and wood dust was measured as total dust. A data logger (DataRAM) was used for continuous monitoring of dust concentration for 18 of the participants. The sampling time was 
8 h. The personal exposure to monoterpenes ranged from 0.64 to 28 mg/m3 and a statistically significant (Kruskal–Wallis test, P = 0.0002) difference in levels of monoterpenes for workers at different companies was seen. In the companies the personal exposure to wood dust varied between 0.16 and 19 mg/m3 and for 10 participants the levels exceeded the present Swedish occupational exposure limit (OEL) of 2 mg/m3. The levels of wood dust during the morning shift were significantly (Mann–Whitney test, P = 0.04) higher compared with the afternoon shift. Continuous registration of dust concentration showed peak values for several working operations, especially cleaning of truck engines with compressed air. For 24 workers in six companies involved in industrial production of wood pellets the personal exposure to monoterpenes was low and to wood dust high compared with the present Swedish OEL and previous studies in Swedish wood industries. Since the DataRAM can identify critical working tasks with high wood dust exposure a reduction in exposure levels could probably be achieved by changes in working routines and by the use of protective equipment.
Keywords: DataRAM; monoterpenes; total dust; wood dust; wood pellets
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
The environmental and energy policy in Sweden aims at replacing fossil energy with renewable sources such as biofuels, of which wood pellets and wood briquettes are examples. The production of wood pellets in Sweden has increased by 50% during the last 5 years and around 700 000 tons were produced in 2000. Wood pellets and briquettes are produced from compressed wood shavings and sawdust from pine (Pinus sylvestris) and spruce (Picea abies). Pine and spruce contain monoterpenes, with
-pinene, ß-pinene and 3-carene as the main constituents (Fengel and Wegener, 1983). These substances are released not only during mechanical treatment of the wood but also during storage of sawdust and shavings. Monoterpenes are irritating to the skin, eyes and mucous membranes and can cause both non-allergic and allergic contact dermatitis (Eriksson and Levin, 1990; Falk-Filipsson, 1995). Monoterpenes can also easily penetrate the different barriers of the body and uptake of pinenes can occur through the lungs, the gastrointestinal tract and intact skin (Cavender, 1994). The occupational exposure limit (OEL) in Sweden is 150 mg/m3 for either individual monoterpenes or their sum (Arberskyddsstyrelsen, 2000). Air levels between 10 and 550 mg/m3 have been measured in previous studies in sawmills and joinery shops in Sweden (Hedenstierna et al., 1983; Eriksson and Levin, 1990; Eriksson et al., 1996, 1997). In a study previously done in sawmills in Finland a geometric mean (GM) between 2.0 and 138 mg/m3 was reported (Rosenberg et al., 2002). In Canada Demers et al. (2000) have shown a GM for monoterpenes of 0.5 mg/m3 within a large lumber mill handling pine, spruce and fir.
In addition to monoterpenes, the employees are exposed to wood dust. Wood dust from pine and spruce has been reported to cause irritation in the eyes and upper airways at air levels between 0.1 and 6.3 mg/m3. There are also indications that wood dust levels around 1 mg/m3 may cause reduced lung function (Eriksson and Liljelind, 2000). Moreover, exposure to wood dust from these species can cause eczema (Färm, 1997). Air levels between 0.1 and 7.3 mg/m3 have been measured in the Swedish woodwork industry (Hedenstierna et al., 1983; Eriksson et al., 1996, 1997; Eriksson and Liljelind, 2000). Many measurements of wood dust from soft woods (pine and spruce) have been performed in sawmills in Finland, Germany, Denmark and Canada and in carpentries in Finland, Denmark, Germany, the UK, USA and Canada. The mean air levels in sawmills were between 0.1 and 7.8 mg/m3 and in the carpentries between 0.8 and 18 mg/m3 (IARC, 1995).
The present Swedish OEL for wood dust measured as total dust is 2 mg/m3, but the Swedish Labour Protectorate recommends an exposure <1 mg/m3 when new enterprises are established or old factories are rebuilt (Arberskyddsstyrelsen, 2000). The American Conference of Governmental Industrial Hygienists (ACGIH) recommended OEL for softwoods is 5 mg/m3 measured as inhalable dust, but with a notice of intended change to 2 mg/m3 for ‘nonallergenic and noncarcinogenic’ wood dusts and to 1 mg/m3 for ‘other respiratory allergic wood dusts’ (ACGIH, 2002). Inhalable dust is defined as the total amount of airborne particles that can be inhaled through the mouth and nose (Eriksson and Liljelind, 2000; ACGIH, 2002). Total dust is defined as dust measured on a filter in an open-faced cassette with a diameter of 37 or 25 mm.
In general, exposure to wood dust is expressed as the average air level during the sampling time. This sampling technique gives limited information about the variations of exposure over time. Instruments that provide real time data are therefore useful to identify emission sources and work tasks which may cause high short-term exposures. As the production of wood pellets and briquettes is increasing, it is important to study the occupational exposure in order to prevent health effects in the future.
The main aim of this study was to measure the exposure to monoterpenes (- and ß-pinene and 3-carene) and wood dust during industrial production of wood pellets and briquettes. Additional aims were to compare the results from wood dust sampled on a filter with real time measurements using a direct reading instrument and to identify peak exposures to dust.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
Company data
Six companies located in central Sweden participated in the study. The companies were located near our research group and were chosen on the basis of location. They all produced wood pellets and two of the companies also manufactured briquettes. The production of wood pellets at each company ranged from 12 000 to 40 000 tons/yr. In the production process of wood pellets, sawdust is always dried before grinding, while shavings can be ground at once. After grinding, the material is pressed in the presses at 100°C (Fig. 1). The wood pellets are then transported through a cooling tower to bagging or storage or for transportation via trucks. The production of briquettes uses a simpler technique, where sawdust and shavings are mechanically forced together. The participants worked morning, afternoon or day shifts on the day of measurement. However, not all companies used a day shift (Table 1). All companies had general ventilation and some companies had local exhaust ventilation situated at specific worksites, for example at bagging and briquette production.
|
|
Study population
Thirty-nine workers were employed in the industrial production of wood pellets in the six companies. The 24 men who were present at work on the day of measurement were asked to participate and all accepted. Working operations for morning and afternoon workers are, among others: loading of raw material, monitoring from the control room, maintenance work, repairs, sweeping and cleaning of truck engines with compressed air. Day shift workers mainly drove trucks and worked on bagging. The protective equipment was hearing protectors and respirators. The respirators were seldom used during the measurements.
Sampling strategy
In all companies measurements were made during an afternoon shift (14.00–22.00) and during the following morning shift (6.00–14.00). In three of the six companies measurements were also carried out during the day shift (7.00–16.00) on the same day as the measurements for the morning shift. The sampling time was 8 h.
Monoterpenes
Air sampling of monoterpenes was done by diffusive sampling using a Perkin Elmer tube with Chromosorb 106 (Markes International) as adsorbent (Sunesson et al., 1999). The sampler was attached to the lapel of the workers overalls, i.e. in the breathing zone. Static samples were taken at three to five different positions in each company (Table 1). The samplers were positioned at strategic points where high wood dust and/or monoterpene exposure was expected and the participants worked, such as the sawdust and shaving store, or where the workers spent a lot of time, for example the control room.
Analysis of monoterpenes
Desorption of monoterpenes was performed with an automatic thermal desorber (Perkin Elmer 400) connected to a gas chromatograph (GC) (Hewlett Packard 6890) with a mass selective detector (Hewlett Packard 5972). The samples were desorbed at 200°C for 5 min at a desorption flow of 70 ml/min helium (He) without an inlet split and collected on a Tenax TA filled trap at –30°C. The analytes were desorbed from the trap at 200°C for 10 min with an outlet split flow of 50 ml/min. The column used was a 50 m x 0.32 mm capillary with a film thickness of 1.05 µm of crosslinked methylsiloxane (HP-1). The temperature of the GC was programmed as follows: initial 50°C hold for 1 min, 5°C/min to 120°C, 35°C/min to 290°C and hold for 10 min. For identification of the monoterpenes the mass selective detector was run in the full scan mode (29–550 a.m.u.) after a solvent delay of 8 min. The monoterpenes were identified against a NIST/EPA/NIH mass spectral database (HP G1033A revision C.00.00 1992). The total ion chromatogram signal of the monoterpenes was used for quantification. The monoterpenes were quantified against calibration graphs ranging from 50 ng to 2 µg/sample. The calibration points were prepared by injection of 3 µl of a standard solution of monoterpenes in methanol onto a Tenax TA tube under a flow of 100 ml/min He over 1 min and analysed in the same way as the field samples. The limit of detection (LOD) was estimated to be 7 ng and was calculated as 3 SD of the signal at the lowest calibrated concentration. The coefficient of variation was 5% at the 50 ng/sample level (n = 12). The highest concentration on the calibration curve was 2 µg/sample for the different monoterpenes, but previous experience suggests that the curve is linear at higher concentrations, therefore extrapolation was done for higher concentrations (K. Eriksson, University Hospital of Umeå).
Wood dust
Pumped sampling of wood dust was done using a 25 mm cellulose acetate filter placed in an open-faced, antistatic cassette with an air flow of 2 l/min. The filter cassette was placed in the breathing zone by attaching it to the collar of the workers shirt or overalls. The filters were conditioned for 48 h at 20 ± 1°C and at a relative humidity of 50 ± 3% before and after the sampling. The filters were gravimetrically determined using a scale with a lowest detection level of 0.001 mg. Static sampling was performed at the same sample sites as for the monoterpenes.
Real time data for wood dust
Continuous monitoring of dust concentration was done using a personal data logging, real time aerosol monitor (DataRAM; MIE, Bedford USA) in parallel with collecting wood dust on a filter for 18 of the participants. The DataRAM is a photometric monitor and measures particles with a diameter between 0.1 and 10 µm in the range 0.001–400 mg/m3. The DataRAM relies on the diffusion of ambient air into a sensing chamber and the optimal sensitivity is, according to the manufacturer, for the respirable fraction of dust (<5 µm). The DataRAM was calibrated against SAE Fine (ISO Fine; Powder Technology), a test dust, by the manufacturer. The DataRAM was placed on the belt of the worker and the intake of air was from below. Registration of the dust concentrations was done every 20 s and stored in a data logger in the instrument and then transferred to a PC. A peak was defined as successive registrations over a threshold value of 0.4 mg/m3. During the DataRAM measurements the participants were asked to keep a work diary and to register time as well as duration of different working tasks.
Statistical analysis
The descriptive measures calculated for concentrations of wood dust and monoterpenes are the GM and arithmetic mean (AM), along with the range. For analysis of correlations between wood dust and monoterpenes, as well as between wood dust on filters and wood dust analysed with a DataRAM, the Spearman correlation was used. Differences in personal exposure between companies were tested with the Kruskal–Wallis non-parametric test with a Monte Carlo estimate of the exact P-value, since the number of observations was low and the distribution of the variable was skewed. For the same reason, the differences in exposure between morning and afternoon shifts were analysed with the Mann–Whitney test with an exact P-value. Measurements under the LOD were recorded as LOD/
2 (Hornung and Reed, 1990). If at least half of the values in one group were under the detection limit there was no calculation done for GM and AM.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
Air concentration of monoterpenes
In total, 24 exposure measurements of monoterpenes were performed and the GM of the personal exposure to monoterpenes for each of the six companies varied from 1.8 to 17 mg/m3 (Table 2). All the full-shift measurements ranged from 0.64 to 28 mg/m3. High levels of monoterpenes were noticed at company number 4 compared with the other companies and a statistically significant (P = 0.0002) difference in monoterpene levels for workers at different companies was seen. No significant (P = 0.99) difference in levels of monoterpenes was seen between workers on the morning shift compared with the afternoon shift. The air levels obtained by static sampling ranged from <0.84 to 74 mg/m3 (Table 3). Low levels of monoterpenes were measured at the grinder (GM 1.2 mg/m3) and high levels in the sawdust and shaving store (GM 12 mg/m3).
|
|
Wood dust on filter
For all companies the personal exposure to wood dust varied between 0.16 and 19 mg/m3, with a GM for each company between 0.63 and 19 mg/m3 (Table 2). One of the measurements (3.7 mg/m3) was underestimated since the filter was overloaded and therefore it was excluded from all statistical analyses, tables and figures. For 10 of the participants the wood dust exposure exceeded the present Swedish OEL of 2 mg/m3 (Fig. 2). No statistically significant (P = 0.11) difference in levels of wood dust was seen between the different companies. However, higher levels were often measured during the morning shift compared with the afternoon shift and this difference was statistically significant (P = 0.04). The correlation between exposure to wood dust and monoterpenes was moderate (r = 0.44). For static sampling of wood dust the air levels ranged from <0.10 to 34 mg/m3 (Table 3). Low levels were measured in the control room (<0.10–0.18 mg/m3) and high levels in the sawdust and shaving store (GM 7.3 mg/m3).
|
Measurements with the DataRAM
Measurements of dust with a DataRAM showed large variations in peak exposures between workers, within as well as between companies. The number of peaks (>0.4 mg/m3) recorded for each worker varied between 4 and 49 over an 8 h working day. Peak values were observed at several working operations, for example management of machines, bagging of product, loading of raw material, sweeping and cleaning of truck engines with compressed air (Fig. 3).
|
A high correlation (r = 0.89) was seen between the parallel measurements of wood dust on a filter and dust with a DataRAM. Levels measured with the DataRAM were systematically lower than the levels measured on the filter. At high levels of wood dust on the filter (> 2 mg/m3) the DataRAM measurements were in general 1/10 of the measurements of wood dust on the filter (Fig. 4). However, at lower levels of wood dust (<2 mg/m3) the levels measured with the DataRAM varied from 0.008 to 0.8 of the levels of wood dust on the filter.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
The personal exposures to monoterpenes were relatively low while the levels of wood dust were high compared with the present OEL and previous studies in the Swedish woodwork industry (Hedenstierna et al., 1983; Eriksson and Levin, 1990; Eriksson et al., 1996, 1997; Eriksson and Liljelind, 2000). The differences in levels of monoterpenes compared with sawmills and joinery shops can probably be explained by differences in the production processes. In sawmills and joinery shops wood is split, which leads to breaking of cells and a higher release of monoterpenes. No splitting is done in the production of pellets and the mechanical impact on the wood is less. Compared with the other test sites, high levels of monoterpenes were measured at the briquette machine (42 mg/m3) in one of the companies. The production of wood briquettes is a more mechanical process and the impact on the wood is higher. The higher levels of wood dust might be due to the handling of shavings and sawdust in the production of wood pellets, which does not occur to the same extent in other woodwork industries.
Since the upper respiratory system is the target site for wood dust, measurements of inhalable dust would have been preferable. This was not done since the OEL for wood dust in Sweden refers to total dust. In comparisons between total dust and inhalable dust it has been shown that the level of inhalable dust is on average 2–4 times higher than total dust (Davies et al., 1999; Lidén et al., 2000).
The difference in monoterpene concentrations between the companies could be due to the fact that the release of monoterpenes depends on how dry and new the raw material is (Eriksson et al., 1997). This can probably explain the higher exposure to monoterpenes that was noticed at company number 4. In this company the raw material was transported via on-line pipes from a nearby planing mill into the production area. This difference could also depend on differences in proportions of pine and spruce in the raw material, since pine releases more monoterpenes than spruce, which, for example, has been seen during sawing of pine and spruce (Welling et al., 2001; Rosenberg et al., 2002). However, the companies did not report any differences in the proportions of pine and spruce in their production and the supplier did not have exact information of the composition. Different species of pine and spruce in the raw material could probably also explain the low levels that were measured in a Canadian study compared with Swedish studies (Demers et al., 2000).
The personal wood dust measurements showed considerable variation within and between workers. This could probably be explained by differences in working tasks and/or differences in working routines, which might also explain the higher level of wood dust that was noticed during the morning shift compared with the afternoon shift. From the working diary no systematic differences were seen between working tasks for the morning and afternoon shifts. No association between working tasks and levels of wood dust exposure could be noticed either. Differences in working tasks for morning and afternoon workers in different companies were noticed: at companies numbers 1 and 4 monitoring from the control room dominated (34–71% of the working day), while in the other companies maintenance work and repairs (39–60%) and driving of trucks (44–76%) were the most common working tasks.
A high correlation between the levels of dust measured with a DataRAM and wood dust measured on a filter was seen, but the levels measured with the DataRAM were systematically lower than measurements on the filter. Wood dust on the filter is a total dust measurement while the DataRAM mainly measures the respirable fraction, which could explain the difference between the two methods. In a study comparing levels measured with a DataRAM with respirable dust on the filter, a regression slope of ~1 was seen (Thorpe and Walsh, 2002). Since measurements of dust with the DataRAM showed lower levels than wood dust on a filter, the DataRAM values cannot be compared with the OEL.
However, the DataRAM is a good instrument for showing changes in exposure over time and can therefore identify critical working tasks. Cleaning of truck engines with compressed air is a very critical working task with respect to wood dust exposure. Since high exposure to wood dust can be linked to specific working operations, a reduction in exposure levels could probably be achieved by changes in working routines and by use of protective equipment.
Other exposures in the production of wood pellets could be oxidized monoterpenes. Monoterpenes are easily oxidized by oxygen and ozone (Calogirou et al., 1999; Falk-Filipsson, 1995), with the main oxidation products being pinon aldehyde, pina ketone and 3-caron aldehyde, from -pinene, ß-pinene and 3-carene, respectively. Pinon aldehyde and 3-caron aldehyde are both more reactive than the original monoterpene, while pina ketone is more stable (Calogirou et al., 1999). The health effects are supposed to be similar to the effects of the original monoterpenes.
A known problem in storage of sawdust is allergic alveolitis, which is due to mould in damp sawdust. No problems with mould have been reported by the companies. Since the turnover is very rapid and the sawdust used is quite dry, mould should not be a problem. Another potential exposure is engine exhaust from the trucks used. In studies on storage of wood pellets, hexanal, acetone, carbon monoxide and methanol have been identified. The level of hexanal was 28 mg/m3 and measurements of hexanal are of interest since aldehydes in general are irritating to the eyes, skin and airways (Svedberg and Galle, 2001).
Hydroperoxides of monoterpenes, especially 3-carene, are known to be allergic agents. However, no report on the occurrence of monoterpene hydroperoxides in the air in wood industries has, to our knowledge, been published. The resin in pine and spruce contains other derivatives of terpenes, namely resin acids. The major components are abietic and dehydroabietic acid, which are readily oxidized by air. The acids and especially the oxidized forms are suspected to cause contact allergy, occupational asthma and urticaria (Färm, 1997). Abietic acid, at a level between <0.05 and 370 µg/m3, has been identified in sawmills and lumber mills handling pine and spruce (Demers et al., 2000; Teschke et al., 1999). Future studies within this kind of industry should focus on these substances.
|
CONCLUSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
For 24 workers involved in the industrial production of wood pellets, personal exposure to monoterpenes was low and to wood dust high, compared with the present Swedish OEL and previous studies in Swedish woodwork industries. Since the DataRAM can identify critical working tasks with high wood dust exposures, a reduction in exposure levels could probably be achieved by changes in working routines and by the use of protective equipment.
Acknowledgments—Financial grants from the Department of Occupational and Environmental Medicine, Örebro University Hospital, Örebro, Sweden, and the Swedish Energy Agency, Eskilstuna, Sweden, are gratefully acknowledged. We would also like to thank Lennart Andersson, Krister Berg, Britt-Marie Isaksson, Birgitta Linder and Håkan Westberg for their help in the field, laboratory and with the article. Last, but not least, we would like to thank all the companies for participating in the study.
|
FOOTNOTES |
|---|
* Author to whom correspondence should be addressed. E-mail: katja.edman{at}orebroll.se
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES |
|---|
ACGIH. (2002) 2002: Threshold limit values and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
Arberskyddsstyrelsen. (2000) Occupational exposure limits and measures against air contaminants (in Swedish). Solna: Arbetarskyddsstyrelsen.
Calogirou A, Larsen BR, Kotzias D. (1999) Gas-phase terpene oxidation products: a review. Atmos Environ; 33: 1423–39.[CrossRef]
Cavender F. (1994) Alicyclic hydrocarbons. In: Clayton GD and Clayton FE, eds. Patty’s industrial hygiene and toxicology, Vol II, Part B. New York: John Wiley & Sons. pp. 1267–300.
Davies HW, Teschke K, Demers PA. (1999) A field comparison of inhalable and thoracic size selective sampling techniques. Ann Occup Hyg; 43: 381–92.
Demers PA, Teschke K, Davies HW, Kennedy SM, Leung V. (2000) Exposure to dust, resin acids, and monoterpenes in softwood lumber mills. Am Ind Hyg Assoc J; 61: 521–8.
Eriksson K, Levin JO. (1990) Identification of cis- and trans-verbenol in human urine after occupational exposure to terpenes. Int Arch Occup Environ Health; 62: 379–83.[CrossRef][Medline]
Eriksson K, Liljelind I. (2000) Consensus report for wood dust. In: Scentific basis for Swedish occupational standards XXI, Arbete och Hälsa 2000:22. Stockholm: National Institute of Working Life. pp. 51–71.
Eriksson KA, Stjernberg NL, Levin JO, Hammarström U, Ledin MC. (1996) Terpene exposure and respiratory effects among sawmill workers. Scand J Work Environ Health; 22: 182–90.[Web of Science][Medline]
Eriksson KA, Levin JO, Sandström T, Lindström-Espeling K, Lindén G, Stjernberg NL. (1997) Terpene exposure and respiratory effects among workers in Swedish joinery shops. Scand J Work Environ Health; 23: 114–20.[Web of Science][Medline]
Falk-Filipsson A. (1995) Toxicokinetics and acute effects of inhalation exposure to monoterpenes in man. Arbete och Hälsa 1995: 3. Solna: National Institute of Working Life.
Färm G. (1997) Contact allergy to colophony: clinical and experimental studies with emphasis on clinical relevance, PhD thesis, Karolinska Institut, Stockholm.
Fengel D, Wegener G. (1983) Wood: chemistry, ultrastructure, reactions. Berlin: Walter de Gruyter & Co. p. 186.
Hedenstierna G, Alexandersson R, Wimander K, Rosén G. (1983) Exposure to terpenes: effects on pulmonary function. Int Arch Occup Environ Health; 51: 191–8.[CrossRef][Web of Science][Medline]
Hornung RW, Reed LD. (1990) Estimation of average concentration in the presence of nondetectable values. Appl Occup Environ Hyg; 5: 46–51.
IARC. (1995) IARC monographs on the evaluation of carcinogenic risk to humans number. 62: Wood dust and formaldehyde. Lyon: International Agency for Research on Cancer.
Lidén G, Melin B, Lindblom A, Lindberg K, Norén JO. (2000) Personal sampling in parallel with open-face filter cassettes and IOM samplers for inhalable dust – implications for occupational exposure limits. Appl Occup Environ Hyg; 15: 263–76.[CrossRef][Medline]
Rosenberg C, Liukkonen T, Kallas-Tarpila T et al. (2002) Monoterpene and wood dust exposures; work-related symptoms among Finnish sawmill workers. Am J Ind Med; 41: 38–53.[Medline]
Sunesson AL, Sundgren M, Levin JO, Eriksson K, Carlson R. (1999) Evaluation of two absorbents for diffusive sampling and thermal desorption-gas chromatographic analysis on monoterpenes in air. J Environ Monit; 1: 45–50.[CrossRef][Medline]
Svedberg U, Galle B. (2001) The use of FTIR technique for determination of gas phase emissions from wood pellet manufacturing (in Swedish). Stockholm: Värmeforsk Service AB.
Teschke K, Demers PA, Davies HW, Kennedy SM, Marion SA, Leung V. (1999) Determination of exposure to inhalable particulate, wood dust, resin acids, and monoterpenes in a lumber mill environment. Ann Occup Hyg; 43: 247–55.
Thorpe A, Walsh PT. (2002) Performance testing of three portable, direct-reading dust monitors. Ann Occup Hyg; 46: 197–207.
Welling I, Mielo T, Räisänen J et al. (2001) Characterization and control of terpene emissions in Finnish sawmills. Am Ind Hyg Assoc J; 62: 172–5.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  K. Hagstrom, C. Lundholm, K. Eriksson, and I. Liljelind Variability and Determinants of Wood Dust and Resin Acid Exposure during Wood Pellet Production: Measurement Strategies and Bias in Assessing Exposure-Response Relationships Ann. Hyg., November 1, 2008; 52(8): 685 - 694. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Meijster, E. Tielemans, J. Schinkel, and D. Heederik Evaluation of Peak Exposures in the Dutch Flour Processing Industry: Implications for Intervention Strategies Ann. Hyg., October 1, 2008; 52(7): 587 - 596. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||