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To evaluate the extent of genetic damage caused by the wood dust exposure in carpentry workers of Bhopal-Mad-hya Pradesh, blood samples from 25 carpentry workers and 25 controls were collected after written informed consent and analyzed for chromosome aberrations. Genotoxicity was studied by chromosomal aberration assay in cultured peripheral blood...
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... to determine genotoxicity in wood dust exposed workers of Bhopal-Madhya Pradesh by performing chromosomal aberration assay in their peripheral blood lymphocytes. The study group included twenty five healthy workers of the carpentry shops in Bhopal, India. It was made sure that all the workers are non-smokers and not exposed to any kind of radia- tion or other hazardous chemicals. All the workers were included after their informed consent as per the guidelines of Institu- tional Ethics Committee. Twenty five volunteers were included in the study as the controls, following the same criteria. All the wood workers and the controls were males and belonged to the age group of 25-45. A 2ml of peripheral blood sample was collected from each per- son of the exposed and the control group once with the help of vacutainers and all the samples were immediately transported to the laboratory for culturing. Lymphocyte cultures were set according to the standard proto- col given by Moorhead et al 12 . Peripheral venous blood samples of wood dust workers were aseptically transferred into sterile culture bottles with 5-8ml of RPMI-1640 medium (Sigma,USA), supplemented with L- glutamine, 10% fetal bovine serum (Himedia Labs, India), Penicillin - streptomycin solution (Invitrogen, USA) and phytohaemagglutinin (Himedia Labs, India). The cultures were incubated in a CO 2 incubator for 72 hours. 50μl col- chicine was added to each tube at the completion of 70 hours to arrest the cells at metaphase. After 72 hours of incubation, the cell suspensions were centrifuged for 10 minutes at 1000 rpm. The supernatant was discarded and the pellets were treated with hypotonic solution (0.075M KCl) by gentle flushing and cy- clomixed. The centrifuge tubes were incubated again at 37°C for 45 minutes. The tubes were again centrifuged carefully at 1000 rpm for 15 minutes. The supernatant was removed and 5-8 ml of freshly prepared pre-chilled Cornoy’s fixative was added to the pellets while mixing on cyclomixer. The tubes were allowed to stand overnight and washed with freshly prepared pre-chilled Cornoy’s fixative repeatedly for 3-4 times. The slides were pre- pared by air drop method and stained with 1% Giemsa stain 13 . Chromosomal aberrations were recorded on well spread metaphases and at least thirty metaphases were screened per sample. Student’s T test was performed on the means of chromosomal aberrations in the control and the exposed group with the help of PRISM version 4 software on PC. Chromosomal aberrations were found to be higher in the wood dust exposed persons than the controls. The mean percentage of total aberrant metaphases in the exposed group was found to be 24.05 ± 2.25 which was statistically higher (P<0.01) than mean percentage of the total aberrant metaphases in the control group (8.46 ± 1.05). The chromosomal aberrations observed in the exposed group included chromosome-type and chromatid-type aberrations. The chromosome-type aberrations comprised of dicentric chromosomes and acentric fragments (Figure 1). The chromatid-type of aberrations included terminal deletions and chromatid breaks (Figure 2). All these types of aberrations were found to be statistically higher in the exposed group than that in controls. The in- cidences of these chromosomal aberrations are given in Table 1. *Significantly increases when compared to the control group (P value <0.001) The mean percentage of total aberrant metaphases in the exposed group was found to be statistically higher than that of control group. This is an evidence of genotoxicity in the workers exposed to wood dust. Genotoxicity of wood dust has been studied in several short-term tests using a variety of end points. A study on human epithelial cell line A549 incubated with different wood dust extracts showed detectable DNA damage 2 . Besides, beech wood extract was found to be mutagenic when test- ed on Salmonella typhimurium by Ames assay 14 Genotoxicity of wood dust, when analysed by micronucleus test (MNT) showed significant induction of micronuclei in mice treated with birchen wood dust 15 , bass wood 16 and rats dosed with beech wood dust 17 . Genotoxicity assessment in carpenters using comet assay 1,18,19 , MNT in buccal cells 20 , MNT in peripheral blood lymphocytes 15,16,21 , chromosomal aberrations 22 and sister chromatid ex- changes 21 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 signifi- cantly lowered and lipid peroxidation was found to be higher in exposed subjects in comparison to controls 16 . Chromosomal aberrations were found to be statistically higher in the exposed group than the control group. The role of some chemicals in inducing DNA double-strand breaks that, if not re- paired, result into structural chromosomal aberrations during cell division has been established 23 . Besides, measuring the frequency of chromosomal damage in humans exposed to environmental clastogens has been a priority in public health studies for decades and an increased level of chromosomal aberrations in population groups is currently interpreted as an evidence of genotoxic exposure and early biologic effects on DNA 24 . Significantly higher percentage of chromosomal aberrations in the exposed individuals of the present study can be therefore attributed to their exposure to the toxic chemicals released with the wood dust. As the lesions induced by chemicals are mostly S phase dependent for expression in the subsequent divisional cycle, the damaged T lymphocytes may remain circulating for long periods and these aberrations can be observed only if the cells are stim- ulated to divide in vitro 25 . In general, the types and frequencies of induced chromosomal aberrations depend on the type of mu- tagen exposure and the cell cycle stage at the time of exposure. Therefore, the increased structural chromosomal aberrations in the carpentry workers of the present study can be attributed to their routine exposure to the different chemicals that are liber- ated from different woods. Our findings are supported well by the results of the studies car- ried out by Rekhadevi et al. (2009) 26 . They observed a statistically significant increase in mean DNA damage by comet assay, micronuclei frequency in buccal cells as well as peripheral blood lymphocytes and frequency of chromosomal aberrations in the exposed workers when compared to controls. Chromosome-type aberrations are formed in the G 0 stage by a mechanism where apurinic or apyrimidinic sites are converted into strand breaks and misrepaired 27 . Dicentric chromosomes are produced by the interchange between two separate chromosomes when breaks occur in each one early in interphase and sticky ends are formed. The presence of dicentric chromosomes only in the exposed individuals is indicative of severe clastogen- ic effect of the wood dust exposure. Incidence of acentric fragments was also found to be higher in the exposed group than the controls. As these fragments do not have centromeres, they are consequently lost in the subsequent cell divisions. The frequency of chromatid-type aberrations in the exposed group was observed to be higher than the control group. This could be due to the reason that genotoxic chemicals induce a wide variety of lesions in the DNA of lymphocytes in different proportions. Most of the chemically induced aberrations are formed only during the DNA synthesis phase, probably due to replication errors. Exposure to chemical mutagens induces lesions in the DNA of lymphocytes, most of which are removed by cellular repair processes. The non-repaired fraction of lesions gives rise to chromatid-type aberrations during S phase, when the lymphocytes are treated with mitogen in vitro 27,25 . The findings of the present study suggest that wood dust is an effective clastogen and the workers of carpentry shops are therefore at an elevated risk of diseases that can be caused by the chromosomal ...
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Citations
... 1,2 Handling of wood generates wood dust, a complex mixture of cellulose, lignin and polar, non-polar and water-soluble compounds. 3,4 Some of the dustiest jobs are manual sanding in furniture making, cutting and drilling. However, the dust is often decreased by the addition of filters or local aeration on the machines. ...
... They grow when favorable temperature, relative humidity and product moisture are present. 4,8,9 Aspergillus produces four major aflatoxins B1, B2, G1, and G2 (AFB1, AFB2, AFG1, and AFG2), that are identified to be toxic to humans and animals. 10,11 Aflatoxin exposure may lead to aflatoxicosis, aflatoxin-related immune suppression, liver cirrhosis and cancer. ...
The goal of the present study is to estimate the oxidative effects of AFB1 induced hepatotoxicity in furniture wood dust exposed workers. A cross-sectional comparative study was designed for comparing AFB1/albumin (AFB1/alb) levels and liver functions [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP)], malondialdehyde (MDA), glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) in 88 furniture workers and 78 controls not occupationally exposed to wood dust. The AFB1/Alb, AST, ALT, MDA, and GPx were significantly higher; while, CAT significantly reduced in workers compared with controls. There was a significant correlation between AFB1/Alb and MDA level with the liver enzymes among both groups. CAT was inversely correlated with AFB1/Alb and the liver enzymes, and GPx was inversely correlated with AST in the workers. It was concluded that wood dust exposure is associated with raised serum levels of AFB1 and oxidative stress.
Wood is the raw material of the wood industry, which is used in the form of solid wood or in the processed form. Occupational exposure to wood dusts occur during processing and woodworking. The highest levels of wood dust concentrations in the work environment were recorded in the furniture and carpentry industries. The number of workers exposed to wood dust in Poland estimated during WOODEX project (2000-2003) amounted to 310 000, of which 79 000 workers were exposed to wood dust at concentrations < 0.5 mg/m3, 52 000 workers at concentrations: 0.5 ÷ 1 mg/m3, 63 000 workers at concentrations: 1 ÷ 2 mg/m3, 72 000 workers at concentrations: 2 ÷ 5 mg/m3 and 44 000 workers at concentrations > 5 mg/m3. According to data from selected sectors of the economy in Poland in the years 2001-2005, developed in collaboration with the Chief Sanitary Inspectorate at the Institute of Occupational Medicine in Łódź, the arithmetic mean value of inhaled wood dust concentrations in the wood and wood products sector (excluding furniture) was 2,08 mg/m3. This concentration was calculated on the basis of 8 602 measurements. In the case of hardwood dust, exceeded values of NDS at worksites were reported in more than 20% of the measurements, whereas in case of softwood – in less than 10% of measurements. Exposure to hardwood dust (mainly oak and beech wood) or in mixture with conifer species (softwood) is correlated with nasopharyngeal adenocarcinomas, whereas non-neoplastic respiratory symptoms, excluding asthma, are not correlated with the specific type of wood. Occupational asthma is most often the result of action of the biologically active compounds present in some wood species (both hardwood and softwood). One of the better-known species of wood and source of knowledge about occupational asthma is the dust of red cedar wood. Both dust hardwood and softwood may impair clear airway, resulting in chronic lung disease. The health effects of exposure to wood dust concern the upper or lower respiratory tract depending on the size of the wood particles. Occupational exposure to wood dust causes: chronic bronchitis, rhinitis and conjunctivitis and skin irritation, also allergic skin reactions. Spirometry has shown the reduction of the lung function index as a result of mechanical or chemical irritation of the lung tissue. It should be noted that changes in pulmonary function and the occurrence of occupational asthma was found in the woodworking industry workers, mainly employed in furniture industry (with no history of atopy) at concentrations below 1 mg / m3 of wood dust. A review of the studies in humans and in experimental animals show that wood dusts exhibit mutagenic and genotoxic effects. Analysis of DNA taken from people with cancer of the paranasal sinuses, employed in exposure to wood dusts showed mutations, mainly in the gene k-ras, which is one of the most frequently activated oncogenes in human cancers. Furthermore, h-ras mutations in adenocarcinoma patients, chromosomal aberrations in carpenter peripheral blood lymphocytes, damage to DNA strands in rats' hepatocytes, increase in micronuclear frequency in cells of mouse intestine and rats' nasal epithelium have been found. Based on results of epidemiological studies, including case-control studies showed the relationship between the incidence of the nose and paranasal sinuses cancer and the exposure to the wood dust. The risk of adenocarcinoma was a significantly higher compared to the risk of squamous cell carcinoma. The International Agency for Research on Cancer concluded that there was sufficient evidence of carcinogenicity of wood dust in humans and assigned them to Group 1 - a substances with proven carcinogenic effects in humans. The Commission of the European Union has included works related to exposure to hard and mixed wood dusts to technological processes classified as carcinogenic to humans (Directive 2004/37 / EC) and has established a BOELV value for the inhalable wood dust fraction on a level of 5 mg/m3 indicating that if there is a mixture of hardwood dust with other wood dusts then NDS refers to the total wood dust present in the mixture. SCOEL Scientific Committee resigned from the division into hard and soft wood and proposed the exposure limit value for wood dust, taking into account not only its irritating effects on upper and lower respiratory tract but also carcinogenicity (inhalable fraction: 1 mg/m3, total dust 0.5 mg/m3). The health effects of exposure to wood dust and the socio-economic conditions have alsobeen considered by the Committee on Safety and Health at Work (ACSHW), which has proposed a BOELV value for hard wood dusts of 3 mg/m3, taking into account that the lower value would result in the closure of many companies, mostly small, employing 1 to 9 employees. Establishment of the hygienic standards of wood dust is complicated by the fact that we never expose to the wood dust itself. At the same time, we are exposed to naturally occurring chemicals in wood (most of them are irritating and sensitizing). In addition, the biological fraction (bacteria, mold) found in wood dust, mainly fresh, as well as wood preservatives such as organic solvents or formaldehyde, increase the health risk. Another variable considered when assessing risk associated with exposure to wood dust is the particle size emitted during wood processing, which varies according to the type of wood and its treatment. Aerodynamic diameter of the particles is generally in the range of 10 to 30 m, which classifies them into an extra thoracic fraction (penetrating head area) or thoracic fraction (penetrating the trachea bronchial area). Percentage of respirable fraction is usually 15 ÷ 20%. When setting the NDS value for wood dusts, data from a cross-sectional survey of 161 people employed in wood dust exposure in 54 furniture companies were used. Nasal patency was examined after exposure to mixed wood dust at a low concentration (0.17 ÷ 0.74 mg/m3), mean (0.74 ÷ 1.42 mg/m3) and high (1.42 mg/m3). With regard to nasal patency before commencement of the work, exposure to medium and high concentration of wood dust significantly increased nasal congestion, reduced nasal cavity capacity and reduced nasal cross-sectional area as a result of 4-7 hours exposure. There was a statistically significant relationship between the concentration of wood dust and the nasal obstruction grade determined by the method of acoustic rhinometry and the subjective assessment. These symptoms also occurred when the dust concentrations were small, but these symptoms were not statistically significant. Furthermore, patients in the control group had significant differences in nasal passivity before commencement of work compared to the post-work period, thus undermining the observed changes at low concentrations (0.17 ÷ 0.74 mg/m3) of wood dust. Taking into account the above data as well as socioeconomic factors discussed with wood industry representatives in Poland, the Interdepartmental Commission on NDS and NDN at its 84th meeting on 4 November 2016 adopted a concentration of 3 mg/m3 for the maximum permissible concentration (NDS) for the inhalable fraction of all wood dust. Socioeconomic considerations were also taken into account in determining the BOELV value for the inhalable wood dust fraction (3 mg/m3) in the European Union. The adoption of this value without distinction for hard and soft wood is a compromise between current NDS values for wood dust with the exception of dust oak and beech (4 mg/m3) and beech and oak dust (2 mg/m3). The proposed value of NDS is at the level proposed by the European Commission for BOELV for the hard wood dust inhalable fraction (3 mg/m3), which takes into account socio-economic conditions of enterprises. Due to the fact that wood dusts have been shown to be carcinogenic, mutagenic and cause pneumoconiosis, the determination of NDSCh values is unjustified. It is proposed to mark the wood dust notation: "Carc. – category 1 carcinogen, according to the classification of the International Agency for Research on Cancer and, by reason of possible sensitization, the letter "A ".
