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Mutagenesis Advance Access published online on September 23, 2008
Mutagenesis, doi:10.1093/mutage/gen053
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© The Author 2008. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.

Genetic damage in wood dust-exposed workers

P. V. Rekhadevi, M. Mahboob, M. F. Rahman and Paramjit Grover*

Toxicology Unit, Biology Division, Indian Institute of Chemical Technology, Hyderabad 500 607, Andhra Pradesh, India

Exposure to wood dust is common in carpentry workshops. Wood dust is known to be a human carcinogen, with a very high relative risk of adenocarcinoma of the nasal cavities and paranasal sinuses. The goal of this investigation was to conduct genotoxicity monitoring of carpenters involved in wooden furniture industry in order to test possible wood dust-induced genotoxic effects due to occupational exposure. The level of genetic damage was determined by comet, micronucleus and chromosomal aberration (CA) assays in peripheral blood lymphocytes (PBL) of 60 carpentry workers. In addition, the micronucleus test in buccal epithelial cells was carried out in the same subjects. Total antioxidant enzyme activities were measured by the indices: superoxide dismutase, glutathione peroxidase and catalase. A group of 60 non-exposed subjects matched by age, smoking and alcohol consumption habits were chosen as controls. The effect of age, smoking, alcohol consumption and duration of exposure was also analysed in the subjects of the present study. The results showed a statistically significant increase in mean DNA damage by comet assay, micronuclei frequency in buccal cells as well as PBL and frequency of CA in the exposed workers when compared to controls (P < 0.05). Analysis of the data showed that all the confounding factors had a significant effect on DNA damage and micronucleus frequency in buccal epithelial cells and PBL. Smoking and alcohol consumption did not have any significant effect by chromosomal aberration test. Antioxidant enzyme levels significantly decreased in the exposed subjects. Our findings indicate enhanced levels of genotoxicity in carpenters. Hence, these workers may have an increased cancer risk.


   Introduction
Top
 Introduction
Materials and methods
 Results
 Discussion
 Funding
 References
 
Wood work in carpentry shops for manufacture of furniture has been a major industry since several decades throughout the world. Every year ~1700 million m3 of wood is being harvested for industrial purposes (1Go). About 3.5 million workers were occupied in furniture industry in the year 2000 (2Go). Processing of wood for a variety of uses generates wood dust, a complex mixture of cellulose, polyoses, lignin and a variable number of polar, non-polar and water-soluble compounds (1Go). Wood dust becomes a potential health problem when wood particles from processes such as sanding, cutting, drilling, chipping, sawing or turning to shape wood become air borne. These particles cause mucosal, allergic and non-allergic respiratory symptoms and cancer when they get deposited in nose, throat and other airways. Review of literature reveals that occupational exposure to wood dust may result in cancer and other health hazards (3Go–7Go). Induction of colorectal cancer (8Go), cancer of lung, pharynx and stomach (9Go) and adenocarcinoma of nasal cavity (10Go) has been confirmed from several studies on human populations exposed to wood dust.

Genetic effects have important health implications for the induction of cancer. Hence, the undesirable health effects caused by wood dust exposure in humans are of special concern. Genetic biomonitoring of populations exposed to potential carcinogens is an early warning system for genetic diseases or cancer. It also allows identification of risk factors at a time when control measures could still be implemented (11Go). In order to ascertain occupational exposure to wood dust, measurement of biomarkers such as comet assay, micronucleus test (MNT), chromosomal aberrations (CA) and sister chromatid exchanges (SCEs) can be considered suitable in molecular epidemiological studies.

Studies on genotoxicity of wood dust have been conducted in several short-term tests using a variety of end points. A study on human epithelial cell line A549 incubated with extracts of wood dust showed detectable DNA damage (2Go). Beech wood extract was found to be mutagenic when tested on Salmonella typhimurium by Ames assay (12Go). Genotoxicity of wood dust when analysed by MNT showed significant induction of micronuclei (MN) in mice treated with birchen wood dust (13Go), bass wood (14Go) and rats dosed with beech wood dust (15Go). Genotoxicity assessment in carpenters using comet assay (1Go,16Go,17Go), MNT in buccal cells (18Go), MNT in peripheral blood lymphocytes (PBL) (13Go,14Go,19Go), CA (20Go) and SCEs (19Go) revealed a significant genetic effect from occupational exposure to wood dust. The generation of oxygen-free radicals, lipid peroxidation and activity of superoxide dismutase (SOD) were determined in a study to analyse dose–effect relationship of wood dust and genotoxicity. The activity of SOD was significantly lowered and lipid peroxidation was found to be higher in exposed subjects in comparison to controls (14Go). Altered enzyme activities were reported for house painters (21Go).

So far, there is limited data available on the genotoxicity and biochemical alterations induced by occupational exposure to wood dust from India. Hence, in the present study, the genotoxicity related to wood dust exposure has been evaluated using comet assay, MNT in buccal cells/PBL and CA. The comet assay has become an important tool in the area of human biomonitoring studies to assess genetic damage in exposed populations (11Go). The buccal cell MNT, first proposed by Stich et al. (22Go), is useful as a biomarker of genetic damage caused by lifestyle habits, exposures to environmental pollutants and medical procedures. In human population studies, the frequency of MN is also determined in cultured PBL and the most frequently applied methodology uses the cytokinesis-block micronucleus technique in which scoring is limited to cells that have divided once since mitogen stimulation (23Go). The CA analysis is a traditional method used to assess exposure to genotoxins that is internationally recognized. The influence of confounding factors like age, smoking, alcohol consumption and duration of exposure on the differences in genotoxicity was also analysed. Biochemical estimation of altered enzyme activities gives information on oxidative stress (OS) that may be a potential indicator of DNA damage and carcinogenic mechanism (24Go). Reduced antioxidant enzyme levels reflect a state of some sub-clinical disorders. The radical-scavenging enzymes SOD, glutathione peroxidase (GPx) and catalase (CAT) were analysed in the exposed workers and compared to controls. Documentation of wood dust concentrations in and around the working area in carpentry workshops gives an estimate of respirable levels of wood dust. Exposure limit as recommended by National Institute for Occupational Safety and Health (NIOSH) (25Go) is 1 mg/m3. Data on concentration of wood dust in workshops has been reported (18Go,19Go). Measurement of amount of wood dust deposited on the surface, in the workplace on a single working day was also carried out in the present study.


   Materials and methods
Top
 Introduction
 Materials and methods
Results
 Discussion
 Funding
 References
 
Study population
The study was carried out on 60 male furniture workers. All of them were working in various poorly ventilated carpentry units in Hyderabad, India. The workers were mainly exposed to a mixture of dust from soft and hard wood occupationally, but were also sometimes exposed to chemicals that were used in polishing and as adhesives during furniture manufacture. The control group consisted of 60 healthy men who had no history of exposure to wood dust. It includes subjects who were employees in government organizations and mostly worked indoors for long hours. Samples from these subjects were collected at their work places within the office premises. Sampling for a fixed number (n = 6) of exposed and control subjects was done on the same day. All the coded samples were transported together on ice to the laboratory for analysis. The selection criteria of study persons were based on a questionnaire. All subjects were asked to complete a face-to-face questionnaire, which included standard demographic data (age, gender, etc.) as well as medical (exposure to X-rays, vaccinations, medication, etc.), lifestyle (smoking, coffee, alcohol, diet, etc.) and occupational questions (working hours/day, years of exposure, use of protective measures, etc.). Details on individual work place exposure (type of wood processed, chemicals used, precautionary measures taken, etc.) were also recorded. Only those subjects who had worked for at least 5 years in the carpentry workshops were considered eligible. It was assured that the exposed workers and the controls did not statistically differ from each other except for occupational exposure. It was also ensured that the exposed and the control subjects had not been taking any medicines, nor had they been exposed to any kind of radiation for 12 months before sample collection. The subjects who smoked more than five cigarettes and who took at least five glasses of an alcoholic drink per day at least for 1 year were considered as smokers and alcohol drinkers, both in study and control groups. Table I shows the main characteristics of both groups. The local ethical committee approved the study. Informed consent was obtained from each individual prior to the beginning of the study. All subjects involved in the study received detailed information concerning the aims of the research study. Blood and buccal smear samples were collected from all the exposed personnel on the last day of their 6-day work shift in the morning hours before the beginning of their work shift which consisted of 8–10 h/day. The information from the carpenters in the present study revealed the use of hard wood species like teak wood (Tectona grandis), ash wood (Fraxinus excelsior), mango (Mangifera indica), neem (Azadirachta indica), tamarind (Tamarindus indica), sandal wood (Pterocarpus santalinum), rose wood (Dalbergia latifolia) and satin wood (Zanthoxylum rhetsa). Soft wood from timber-yielding plants like guava (Psidium species), Pinus and Picea species and deodar (Cedar deodara) was also used. Both hard wood and soft wood were known to be routinely used in combinations. Six control and six exposed samples were taken every 7 days. Sampling was carried out over a period of 3 months. Samples were coded to avoid possible bias.


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  		Table I. Demographic characteristics of controls and exposed wood workers

 
Measurement of wood dust levels
The amount of wood dust accumulated on the surface of work area on a workday gives us a relative estimate of exposure. Measurements were performed on the day of sampling at the end of work.

Collection of blood samples
A 3 ml of venous blood was collected once from all the exposed and control subjects using heparinized syringes. The samples were transported on ice to the laboratory and were processed within 2 h.

DNA damage analysis using the comet assay
Forty microlitres of blood was taken from the collected samples for the comet assay, which was carried out according to Singh et al. (26Go) with slight modifications as described earlier (27Go). Cell viability determined by the trypan blue exclusion technique ranged from 94 to 96% (data not shown). Slides were prepared in duplicate per subject. Analysis was performed using a x400 objective with Olympus BX 51 fluorescent microscope equipped with an excitation filter of 515–560 nm and a barrier filter of 590 nm. Slides were randomized and coded to blind the scorer. All slides were scored by one person, to avoid inter scorer variability. A total of 100 individual cells were screened per subject (50 cells from each slide). Undamaged cells resemble an intact nucleus without a tail and damaged cell has the appearance of a comet. The length of the DNA migrated in the comet tail, which is an estimate of DNA damage was measured using an ocular meter and calculated as comet tail length (µm) = (maximum total length) – (head diameter).

Micronucleus assay (buccal epithelial cells)
The MNT was carried out on the buccal epithelial cells of 60 exposed and 60 control subjects. Buccal cell samples were obtained by rubbing the inside of the cheeks of study subjects with a toothbrush. The cells were collected in sample bottles containing 20 ml of buffer solution (0.1 M ethylenediaminetetraacetic acid, 0.01 Tris–HCl and 0.02 M NaCl, pH 7) and transported to our institute for processing. After three washes in the buffer solution by centrifugation at 400 g for 10 min, 50 µl of cell suspension was dropped onto pre-heated (55°C) slides and allowed to air dry for 15 min on a slide warmer. The slides were made in triplicates for each subject. The slides were fixed in 80% cold methanol for 30 min, air-dried overnight at room temperature and stored at –20°C until use. The slides were stained with a DNA-specific dye, 4', 6-di-amidino-2-phenylindole dihydrochloride (1 µg/ml). A total of 5000 buccal epithelial cells were screened per subject and the frequency of MN per 1000 cells was calculated (28Go). Scoring was done with Olympus BX 51 fluorescent microscope.

Micronucleus assay (PBL)
The MNT was conducted according to the method of Fenech and Morley (23Go). Briefly, 0.5 ml of whole blood was mixed with 4.5 ml of RPMI-1640 medium supplemented with 20% fetal calf serum, 100 U/ml penicillin and 100 µg/ml streptomycin. A 0.2 mg/ml phytohaemagglutinin-M (PHA) was added to stimulate the culture. Cultures were incubated in duplicates at 37°C for 72 h. Cytochalasin-B was added at the 44th h of culture growth at a final concentration of 5 µg/ml to arrest the cells at cytokinesis. The cultures were harvested by centrifugation after 72 h. The lymphocytes were subjected to mild hypotonic treatment with 0.075M KCl for 5 min and then fixed in fresh fixative solution (3:1, methanol:acetic acid). This fixation was repeated twice. Few drops of cell suspension was smeared on pre-cooled microscopic slides and air-dried. The slides were stained using 10% Giemsa of pH 6.8 for 10 min. Two thousand binucleated lymphocytes (500 cells per culture) were scored at x400 magnification. Frequency per 1000 cells is calculated.

CA analysis (PBL)
The CA analysis was conducted following a standard protocol with slight modifications (29Go). A total of 0.8 ml aliquot of whole blood was cultured in F-10 medium supplemented with 20% fetal bovine serum, 0.5 ml PHA, 5000 IU/ml penicillin and 1000 IU/ml streptomycin. Each culture was incubated in 5% CO2 and 95% air incubator at 37°C for 48 h. Metaphases were obtained by adding 0.2 µg/ml colchicine to the cultures 3 h before harvesting. The cells were collected by centrifugation, re-suspended in a pre-warmed hypotonic solution (0.075 M KCI) for 15 min at 37°C and fixed in acetic acid:methanol (1:3, v/v). Chromosome preparations were stained with 3.3% Giemsa. The slides were analysed at x1000 magnification using a light microscope and 200 metaphase cells were screened per each individual. Cells with 46 chromosomes were scored for CA. The analysis of CA included chromatid and chromosome breaks, chromatid deletions, chromatid rings, dicentrics, quadriradial figures and acentric fragments.

Antioxidant enzyme assays
A total of 1.5 ml of the total blood collected was processed to obtain serum for biochemical analysis. Protein determination was also done in all the samples according to Lowry et al. (30Go).

SOD: The activity of SOD was measured spectrophotometrically as described by Sun et al. (31Go). Briefly, xanthine–xanthine oxidase was utilized to generate a superoxide flux. Reduction of nitrobluetetrazolium (NBT) by superoxide anion to blue formazon was determined at 560 nm. One unit of enzyme activity was defined as the amount of protein causing 50% inhibition in NBT reduction by superoxide.

GPx: The activity of GPx in serum was measured spectrophotometrically as described by Paglia and Valentine (32Go). The enzyme reaction was initiated by the addition of H2O2 to the reaction medium and the rate of NADPH oxidation was followed at 340 nm. The amount of enzyme that oxidizes 1 µmol NADPH per minute was considered to be one unit.

CAT: The activity of CAT was determined according to the method described by Aebi (33Go). The decomposition of the substrate, H2O2, was monitored spectrophotometrically at 240 nm. One unit of enzyme was defined as 1 µmol H2O2 utilized per minute.

Statistical analysis
The samples were coded at the time of preparation and scoring. They were decoded before statistical analysis for comparison. Mean and standard deviation (SD) was calculated for each biomarker. As the distribution of DNA mean tail length and MN in PBL did not significantly differ from the normal distribution, untransformed data were used. Since the frequency of MN in buccal epithelial cells and CA when analysed by Levene's test for equality of variances was found to be significantly different between controls and exposed subjects, a non-parametric test (Mann–Whitney's U-test) was done. The significance of the differences between control and exposed subjects’ end point means were analysed using independent samples t-test (mean DNA tail length and MN in PBL and antioxidant enzyme levels). All calculations were performed using Graph Pad Prism 4 Software package for windows. Mean values and SDs were computed for the scores and the statistical significance (P < 0.05) of effects (age, smoking, alcohol consumption and exposure) was determined. Analysis of co-variance (ANCOVA) was performed to assess the association between end points and the independent variables with smoking and alcohol consumption as covariates.


   Results
Top
 Introduction
 Materials and methods
 Results
Discussion
 Funding
 References
 
The genotoxic effect of occupational exposure to wood dust in carpenters, working in wood industries in Hyderabad, was evaluated along with control subjects. They were assessed by the comet assay, MNT in buccal cells and PBL and CA. The antioxidant enzyme levels were also determined. Table I represents the distribution of subjects with respect to age, smoking, alcohol consumption, years of exposure and duration of work per day. The two groups studied had similar demographic characteristics. The mean age of the control and exposed group was 38 years ranging from 19 to 60 and 28 to 57 years, respectively.

Exposure assessment
Total wood dust concentrations in the carpentry workshops where the current study group were employed ranged from 7.40 to 25.80 mg/m3. The estimates were all based on the surface samples. Higher wood dust levels indicate an increased risk of genetic damage. These levels exceeded the limit of 1 mg/m3 recommended by the NIOSH.

Comet assay
The extent of DNA damage evaluated by comet assay in leucocytes of all study subjects as measured by comet tail length is presented in Table II. The comet tail length significantly increased in wood dust-exposed workers (14.35 versus 7.08 µm; P < 0.05). A statistically significant difference in DNA damage was observed with age, smoking and alcohol consumption in exposed and control subjects. No significant effect on mean DNA tail length was observed with years of exposure to wood dust (P > 0.05). Duration of exposure to wood dust for ≥5 h/day had a significant effect on DNA damage as seen in Table III. Subjects who smoked and consumed alcohol showed greater DNA damage than those in controls (P < 0.05). The results of ANCOVA when smoking and alcohol consumption were included as co-variates are summarized in Table IV. The effect of age and exposure on DNA damage was significant (P < 0.05).


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  		TABLE II. Inter-group comparison of mean DNA damage (comet tail length in µm), MN and CA frequency in controls and exposed wood workers

 


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  		Table III. DNA mean tail length (µm) by age, smoking, alcohol and exposure in controls and exposed wood workers

 
MN frequency in buccal cells
The frequency of MN in wood dust exposed workers was statistically significant when compared to controls (2.83 versus 0.40; P < 0.05) as seen in Table II. Age, smoking, alcohol consumption and exposure to wood dust revealed a statistically significant induction of MN in exposed subjects when compared to controls. A significant increase in MN frequency was found in the control subjects with respect to smoking and alcohol consumption as seen in Table V. Smokers and alcohol consumers in exposed group showed higher MN frequency than those in controls (P < 0.05). The results of ANCOVA showed a significant effect of exposure on MN frequency in buccal cells as seen in Table IV.


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  		Table IV. ANCOVA in exposed wood workers

 


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  		Table V. MN frequency ({per thousand}) in buccal epithelial cells with respect to age, smoking, alcohol and exposure in controls and exposed wood workers

 
MN frequency in lymphocytes
The results of MN frequency in PBL of wood dust-exposed workers increased significantly, as compared with controls (5.08 versus 3.95; P < 0.05) as seen in Table II. All the confounding factors had a significant effect on MN frequency in exposed subjects except daily exposure (Table VI). Similar effect was observed in controls. Smoking and alcohol consumption had significant effect on MN frequency in PBL of exposed subjects in comparison to controls. ANCOVA revealed a significant effect of age and exposure to wood dust with MN frequency in lymphocytes (Table IV).


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  		Table VI. MN frequency ({per thousand}) in lymphocytes with respect to age, smoking, alcohol and exposure in controls and exposed wood workers

 
CA frequency in lymphocytes
The mean CA frequency in the exposed workers and control subjects are summarized in Table II. In the exposed workers, a significant increase in CA indicating chromosomal damage was observed when compared with controls (7.98 versus 3.15; P < 0.05). Age and exposure to wood dust had a statistically significant effect on CA frequency in exposed workers. No significant effect of the confounding factors was observed in control subjects as seen in Table VII. Smokers and alcohol consumers in exposed subjects revealed a higher CA frequency when compared to the controls. All types of CA showed a statistically significant increase in the exposed group with respect to controls (P < 0.05). The exposed group had significantly greater mean for chromatid breaks (4.41 ± 0.76 versus 1.75 ± 0.60), chromosome breaks (3.71 ± 0.58 versus 1.45 ± 0.59), chromatid rings (3.20 ± 0.63 versus 1.15 ± 0.40), dicentrics (2.76 ± 0.49 versus 0.96 ± 0.36) and acentric fragments (1.86 ± 0.67 versus 0.98 ± 0.34) in comparison with the controls. Exposure to wood dust had a significant effect on CA frequency as analysed by ANCOVA as shown in Table IV.


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  		Table VII. CA frequency (%) with respect to age, smoking, alcohol and exposure in controls and exposed wood workers

 
Antioxidant enzyme levels
Serum protein levels did not show any significant difference between carpenters and control subjects. Activities of antioxidant enzymes, SOD and GPx were significantly decreased in exposed subjects when compared to controls. SOD levels were found to be lower in exposed subjects when compared to controls (27.55 versus 40.67; P < 0.05). Similar result was seen with GPx (7.86 versus 25.33; P < 0.05). CAT did not show any statistically significant difference between exposed and control subjects (35.19 versus 34.43; P > 0.05) as seen in (Table VIII). The effect of smoking and alcohol consumption on antioxidant enzyme levels revealed that the exposed subjects who were smokers and alcohol consumers showed significantly reduced levels of SOD and GPx in comparison to their control counter parts. CAT levels did not seem to be effected by smoking or alcohol consumption.


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  		Table VIII. Inter-group comparison of antioxidant enzyme levels (mean ± SD, U/mg protein) in controls and exposed wood workers

 

   Discussion
Top
 Introduction
 Materials and methods
 Results
 Discussion
Funding
 References
 
Wood dust is known to be a human carcinogen with several health hazards associated with its exposure. It is a complex of physical, chemical and biological agents which make it difficult to detect a specific allergen or irritant (34Go). In this study, we assessed the genotoxic effects in carpenters exposed to wood dust and other substances generated in the course of manufacturing wooden furniture. The investigation was conducted by utilizing the comet assay, MNT and CA. The level of DNA damage was determined as the percentage of cells with comets. In the present study, significant increase in comet tail length was observed in carpenters when compared to the controls using the comet assay. The results indicate sufficiently high level of exposure at work place and also the sensitivity of the assay used. Studies reporting DNA damage in carpenters are limited. Wood workers in a furniture plant using comet assay showed increased levels of DNA damage in the exposed group (1Go). Statistically significant increase in DNA single-strand breaks (SSBs) was detected in PBL of exposed workers from Poland (16Go). A study on DNA SSB as determined by the microfiltration assay and liquid scintillation method in PBL of carpenters indicated higher DNA damage in wood workers (17Go). These studies support the results of the present investigation.

Researchers have been using MNT for assessing chromosome damage as it enables both chromosome loss and chromosome breakage to be measured reliably. The method is now applied to various cell types for monitoring populations for genotoxicity. In the current study, the MNT in buccal epithelial cells and PBL was conducted in carpenters. The results suggest that exposure to wood dust has significant genotoxic effect in buccal cells when analyzed by MNT. Similarly, significant induction of MN in PBL was found in wood dust-exposed workers of the present study. A study conducted by Celik and Kanik (18Go) showed a higher frequency of MN in buccal epithelial cells in carpenters than in controls. Few investigations on wood workers utilizing MNT in PBL have shown positive results (14Go,19Go). These results are in accordance with the present study. However, no statistically significant difference in frequency of MN was observed in PBL of workers exposed to birchen wood dust (13Go).

In our investigation, CA analysis was also utilized to evaluate the extent of genome damage in carpenters. CA are particularly dangerous to the cell because the physical discontinuity of the chromosome may cause loss of genetic information and even cell death if a housekeeping gene is involved (35Go). The present investigation revealed higher frequencies of CA in exposed subjects when compared to controls. Likewise, a study of workers employed in plywood industry showed a statistically significant elevation in frequency of CA in PBL (20Go). However, contradictory to our results, the frequencies of SCEs in PBL of 30 non-smoking workers exposed to wood dust were higher than in the controls, but the difference was not statistically significant (19Go).

Age, smoking, alcohol consumption and duration of exposure per day had a significant effect on DNA damage in the current study. The effect of smoking on comet assay results of this study is in accordance with other investigations. In a study, DNA SSB in smoking wood workers was significantly higher than their non-smoking counter parts (17Go). A 2-fold increase in DNA damage was observed in lymphocytes of smoking wood workers exposed to wood dust (16Go). Similarly, the confounding factors significantly effected the MN induction in buccal epithelial cells of the exposed subjects of our study. Significant effect of smoking and exposure was observed in a study on MNT in buccal cells (18Go). Effect of confounding factors was also seen with MNT in PBL. Likewise, significant effect of exposure on MN frequency in PBL has been demonstrated in a study by Elavarasi et al. (19Go). Our results of ANCOVA indicated that continued exposure to wood dust on a regular basis was a factor affecting the increase in DNA damage. Age-dependent DNA damage was also seen in the current study. Duration of exposure to wood dust in carpentry workshops induced MN and CA. Per day exposure to wood dust enhanced the genetic damage in the subjects of present study.

In view of our findings, we can only suggest that occupational exposure to wood dust may be the main factor that produced the genetic damage in the workers. However, the chemicals used to confer resistance and durability to wooden furniture may also be a cause for the genetic effect. The mechanism behind the DNA-damaging effect of wood dust may possibly be the production of reactive oxygen species (ROS) as detected by Long et al. (36Go). To substantiate our results and to provide a biochemical biomarker for the present study, total antioxidant enzyme profile in the serum of exposed workers was analysed and the results were compared to controls. In the present study, serum SOD and GPx were significantly lowered in exposed but contrary to this, the CAT levels did not show any significant difference. Decreased SOD levels were seen in wood workers exposed to bass wood dust (14Go). Literature on biochemical studies in wood dust-exposed workers are scarce but similar studies in other group of workers revealed decreased levels of antioxidant enzyme levels in exposed workers in comparison to controls (21Go,37Go–39Go). Under normal metabolic conditions, the continuous formation of ROS and other free radicals is important for normal physiological functions and cellular redox reactions. Endogenous biological and exogenous environmental factors may cause an increase in free radical generation. In spite of numerous biodefense systems, excessive production of these free radicals overwhelms the cells intrinsic antioxidant defenses that lead to OS. This occurs due to an imbalance in body's defense mechanisms and free radical generation and promotes cellular injury and tissue damage. Under conditions of OS, cells display various dysfunctions due to lesions caused by ROS to proteins, lipids and DNA. Consequently, it is assumed that wood dust induced OS in cells can be partially responsible for its genotoxic effects. These results strongly support our findings that reflect the state of antioxidant stress due to depletion of substrate molecules and an increase in ROS.

The health concerns raised by the carpenters were skin and eye infections, nose and throat irritations, cough, asthma and nausea. None of the exposed personnel used facemasks or gloves. The positive genotoxicity in the present study may be due to lack of protective measures. Using more or less safety measures is also a factor that may explain the positive findings of this study and so there is a need to educate the carpenters about the potential hazard of occupational exposure and the importance of using protective measures. Since DNA damage is an important step in events leading from carcinogen exposure to cancer, our study represents an important contribution to the correct evaluation of the potential health risk associated with wood dust exposure. Nevertheless, controversial results from various studies are always difficult to interpret since each study population has a different lifestyle, nutritional habit, lives and works in different areas under different climatic conditions. It is suggested that the biomonitoring of the genotoxic effects in wood industry with furthermore comprehensive controlled studies are needed to support our observations.


   Funding
Top
 Introduction
 Materials and methods
 Results
 Discussion
 Funding
References
 
Sidhu Singh Foundation, USA.


   Acknowledgments
 
The authors express their sincere thanks to Dr J. S. Yadav, Director, Indian Institute of Chemical Technology, Hyderabad, for providing facilities and his encouragement during the study. Senior Research Fellowship through Council of Scientific and Industrial Research, New Delhi (to P.V.R) is gratefully acknowledged. We are grateful to Dr.V.Bhaskar for his help in analyzing the data by ANCOVA.

Conflict of Interest Statement: None declared.


   Notes
 
* To whom correspondence should be addressed. Tel: +91 40 27193135; Fax: +91 40 27193227; Email: param_g{at}yahoo.com


   References
Top
 Introduction
 Materials and methods
 Results
 Discussion
 Funding
 References
 

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Received on May 14, 2008; revised on July 1, 2008; accepted on August 26, 2008.


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