Epidemiol Health ; e Published online: Jul 4, Functional disorders of the lung and symptoms of respiratory disease associated with occupational inhalation exposure to wood dust in Iran. It is used in many processing industries, such as chipboard manufacturing, woodworking, furniture making, or on a smaller scale in enterprises such as carpentry [ 2 ].
Wood dust is one of the most common sources of occupational dust exposure [ 3 ]. It is estimated that 1, million m 3 of forests are harvested for industrial purposes annually, and at least 2 million people per day are exposed to wood dust [ 1 ]. Wood dust is a complex mixture generated when wood is cut and shaped through processes such as grinding, sawing, turning, drilling, and grinding [ 1 ]. Studies have shown that wood dust mainly includes particles larger than 10 microns [ 5 ]. Respiratory diseases are the most common occupational diseases. Pulmonary function tests PFTs , including spirometry, play an essential role in diagnosing pulmonary diseases [ 6 ].
Wood dust is heavily contaminated with fungi and Gram-negative bacteria, especially in hot and humid areas.
Occupational inhalation exposure to wood dust and its associated bioaerosols has been associated with adverse respiratory effects [ 7 - 11 ]. Exposure to these agents can result in organic dust toxic syndrome, upper respiratory tract infections, and extrinsic allergic alveolitis [ 7 , 12 , 13 ]. Some studies have shown that inhalation of wood dust can lead to occupational asthma [ 11 , 14 , 15 ], irritation of the eyes or nose [ 15 - 17 ], dermatitis [ 18 , 19 ], nasal cancer [ 20 - 22 ], and respiratory tract cancers [ 23 , 24 ].
Previous studies have shown a significant association between inhalation of wood dust and an increased prevalence of respiratory symptoms [ 2 , 17 , 25 - 27 ] and decreased lung functional capacity, as manifested by reduced peak expiratory flow PEF , forced vital capacity FVC , and FEV1 stands for forced expiratory volume in the first second [ 2 , 7 , 17 , 25 - 29 ].
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The results of Mandryk et al. Comparison of these 2 groups revealed a higher exposure-related prevalence of regular cough, nasal congestion, sneeze, sinus problems, flu-like symptoms, and eye and throat irritation. Conversely, some other studies have not shown any significant association between occupational exposure to wood dust and pulmonary function parameters [ 30 - 32 ]. For example, in a study by Liou et al. Additionally, the prevalence of respiratory symptoms in the exposed group, including smokers and non-smokers, was not significantly higher than in the reference group.
In light of the above findings, controversy exists regarding the potential of wood dust to produce respiratory symptoms or functional abnormalities in the lungs. Additionally, despite the fact that exposure to wood dust, due to its wide applications in different industries, is pervasive, there is a paucity of studies in which the respiratory effects of this organic dust have been evaluated at the national or regional level. Finally, to the best of our knowledge, bioaerosols contaminating wood dust have not previously been characterized and quantified in Iran.
This study was undertaken to more thoroughly investigate and address these issues. The exposed group was comparable to the reference group in terms of sample size, age, sex, smoking habits, and other variables such as marital status, income, and education. Additionally, they had no history of occupational and non-occupational exposure to dust or other chemicals with known pulmonotoxic properties, and were free from pre-existing medical conditions such as asthma and chronic respiratory diseases or a history of thoracic surgery.
The subjects in the exposed group were more or less similar in terms of their exposure to wood dust and bioaerosols, and they worked 8-hour daily shifts 8 a. Each participant completed a questionnaire to ensure that they met the inclusion criteria. Pretest measurements showed that the appropriate flow rate and sampling time to avoid filter overloading were 2 liters per minute and 60 minutes, respectively. Bioaerosol sampling Using NIOSH method [ 34 ], bacteria and fungi were sampled by an Andersen single-stage sampler with a flow rate of The culture media was malt extract agar for airborne fungi and trypticase soy agar for bacteria.
The sampling time was 10 minutes. Finally, microbiological and mycological tests were performed on the plates. None of the sawmills were equipped with local exhaust ventilation systems and none of the exposed workers wore any respiratory protective equipment. Standard respiratory symptom questionnaire A valid and reliable European Community Respiratory Health Survey questionnaire [ 35 ] was used to investigate the prevalence of respiratory symptoms in the exposed and reference groups.
The Cronbach alpha of this questionnaire was calculated to be 0. This questionnaire included questions about respiratory symptoms cough, phlegm, wheezing, dyspnea, etc. The test was carried out twice in the workers exposed at their workplace: 1 Prior to the shift, on the first work day of the week after an exposure-free period of at least 48 hours; 2 Immediately after the end of the daily work shift on the first work day of the week. First, the workers were provided with the necessary training for performing spirometry. They were then asked to sit in a chair for 5 minutes to rest, and then the maneuver was conducted at least 3 times for each subject.
The workers were asked to refrain from smoking and bathing at least 2 hours before spirometry [ 36 ]. The Student t -test, paired t -test, chi-square test, or the Fisher exact test was used for statistical comparisons, as appropriate. Linear and logistic regression analyses backward elimination method were used to investigate the associations of exposure to airborne contaminants with changes in pulmonary function parameters and the prevalence of respiratory symptoms, while potential confounders were controlled in the model.
To differentiate between the chronic and acute respiratory effects of wood dust, pulmonary function parameters were measured prior to the shift following a hour exposure-free period and at the end of the shift. Before-shift parameters that were significantly lower in exposed workers than the corresponding baseline values for their non-exposed counterparts were considered to indicate a chronic irreversible effect.
In contrast, pulmonary function parameters that were significantly lower at the end of the shift than before the shift were considered to indicate an acute cross-shift decrement. RESULTS As shown in Table 1 , there were no statistically significant differences between the exposed and reference groups in age, height, weight, marital status, work history, mean duration of smoking, or the number of cigarettes smoked per day. The proportion of smokers in the exposed and reference groups was However, the proportion of educated individuals in the unexposed group was significantly higher than in their exposed counterparts.
PUBLICATION TOPICS: Asthma & Pulmonary Function
The concentrations of inhalable and respirable dust were found to be 2. The bacterial and fungal concentrations were measured to be The predominant bacteria found in the present study were Gram-negative. Klebsiella pneumonia , Rhinoscleromatis spp. Similarly, for fungi, zygomycetes Rhizopus , Mucor , and Syncephalastrum and Aspergillus spp. The prevalence of respiratory symptoms in the 2 groups is presented in Table 2. As can be seen, the prevalence of all symptoms in the exposed group was higher than in the non-exposed group.
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Participants in the exposed group were 4. The prevalence of respiratory symptoms among smokers was higher than among non-smokers. Moreover, all respiratory symptoms except dyspnea showed statistically significant differences between smokers and non-smokers.
Furthermore, the prevalence of respiratory symptoms among exposed cigarette smokers was higher than among non-exposed cigarette smokers. Table 3 shows the results of PFT. Comparing the mean values of lung function parameters before and after exposure showed that exposure to wood dust during a work shift significantly reduced pulmonary function parameters such as VC, FVC, and FEV1. Additionally, the mean values of lung function parameters were compared in exposed and non-exposed cigarette smokers. Exposed subjects with a normal spirogram or with obstructive, restrictive, or mixed lung disease were examined before and after the work shift.
Of the exposed subjects, 49 had a normal spirogram after the shift, while 26, 20, and 5 exposed subjects had obstructive, restrictive, or mixed lung disease, respectively. Table 4 compares the pulmonary function parameters between smokers in both groups. As shown, most pulmonary function parameter values were significantly lower in the exposed group than in the control subjects. To control for the effects of confounding variables, such as cigarette smoking and other tobacco product use, age, weight, height, and work experience, the results of the study were further analyzed using logistic and multiple linear regression.
Table 5 shows the associations between exposure to airborne contaminants and the prevalence of respiratory symptoms based on logistic regression analysis. Table 6 shows the associations between exposure to airborne contaminants and changes in lung function parameters. The average concentration of inhalable dust in the present study was 2. These values exceeded the existing TLV for this organic dust [ 6 ].
Similarly, the average concentration of dust reported by other researchers, such as Magagnotti et al.
This can be explained, at least in part, due to the fact that in the present study, the cleaning procedures involved using an air jet and dry sweeping. Additionally, the studied plants lacked any artificial ventilation system, and most of the managers and workers were illiterate and therefore were not aware of the potential health effects of wood dust. The predominant bacteria in the present study were Gram-negative. The average concentrations of bacteria and fungi were The predominant fungi, Grampositive bacteria, and Gram-negative bacteria reported by Oppliger et al.
The dominant fungi found by Badirdast et al. Although the health effects of bioaerosol exposure have been identified, TLVs have not been established for them [ 12 ]. This can be explained by the diversity of bioaerosols and their different pathogenic potential. After controlling for confounding variables age, height, weight, work experience, smoking, etc. These results are in line with those of a previous study conducted by authors on respiratory effects of exposure to bioaerosols [ 42 ]. In some studies of wood workers, the prevalence of respiratory symptoms in the exposed group was higher than that of the reference group [ 2 , 17 , 25 - 27 ].
The results of those studies are consistent with the present study. In the study conducted by Bislimovska et al. Moreover, according to Shamssain [ 28 ] the prevalence of all respiratory symptoms, including cough In contrast, the results of some other studies are not consistent with the present study, as they did not report any association between exposure to airborne contaminants and the prevalence of respiratory symptoms. Similarly, those studies indicated no significant difference in the prevalence of respiratory symptoms between the exposed and non-exposed groups [ 30 , 31 , 43 ].
For instance, Borm et al. In the present study, in order to differentiate between the acute and chronic effects of exposure to airborne contaminants in sawmills, lung function parameters were measured before and after the work shift and compared with each other and with the reference group.
These findings indicate that exposure to wood dust during a work shift acutely reduces some parameters of pulmonary function.
In addition, the differences in VC, FVC, FEV1, and PEF between the exposed group were statistically significant before exposure on the first work day of a week after a 2-day exposure-free period and the reference group. The fact that PET values in the exposed workers, even after cessation of exposure and a hour exposure-free period, were still significantly lower than those of the control group indicates that the exposed subjects suffered from irreversible chronic respiratory disorders. Moreover, because additional, statistically significant cross-shift decrements were noted in the PFT results, it is concluded that the exposed workers also experienced acute, partially reversible pulmonary effects.
These results are consistent with the studies of other researchers [ 2 , 11 , 17 , 27 , 29 , 44 ]. Mandryk et al. Additionally, significant cross-shift decrements in these parameters were observed. Furthermore, Mandryk et al. Conversely, the results of some studies are not consistent with the present study. These studies showed that pulmonary function of exposed workers was normal [ 31 , 32 , 46 ].
For instance, Bohadana et al.