Organic Wood Dust Exposure as a Risk Factor for Lung Function Disorders in Workers : Systematic Review

Wood dust is wood particles that result from wood processing and handling. The level of fine dust in the work environment can expose to workers breathing and cause lung function disorders. Obstructive lung function disorders, namely blockages that make it difficult for air to escape from the lungs, resulting in a decrease in airflow velocity. The purpose of this systematic review was to determine wood dust exposure and risk factors for impaired lung function for workers. Article searches carried out through the Portal Garuda Indonesia, PubMed, Scopus, ProQuest, and Google Scholar. There are 9 articles reviewed. Exposure to wood dust was assessed as a significant risk factor for impaired lung function in workers as seen from the statistical analysis results in each study showing that the p-value < 0.05. The risk factors that were stated to have a significant relationship were the concentration of wood dust, gender, work location, use of personal protective equipment (mask), length of work, and smoking habits. Exposure to wood dust increases the risk of impaired lung function in workers, with dust levels ranging from 1.15 mg/m 3 – 24 mg/m 3 .


Introduction
The problem of air pollution has become a cause of health problems, especially in industrialized countries that have many factories and motorized vehicles (Summa'mur, 2014). Air pollution has also become a common phenomenon in several countries, especially in developing countries. This is because the existing industry still pays less attention to air pollution control. Air pollution produced from industrial premises is generally in the form of dust from industrial activities. Dust is a solid chemical substance, caused by natural or mechanical forces such as processing, crushing, softening, rapid packing, and blasting of objects, both organic and inorganic (Summa'mur, 2014). Generally, particles that can enter the respiratory tract are particles smaller than 10 µm whereas particles of that size are also called PM10 (Sumantri, 2010).
One of the industries that causes air pollution is the wood industry. Pollutants produced by the wood industry are wood dust particles. Processing in the wood industry includes cutting, stripping, sawing, shaping, sanding, and finishing processes. This mechanical process tends to produce pollutants such as wood dust particles. This is because about 10 to 13% of the sawn wood will be in the form of wood dust, which will fly in the air (Asrini, 2013). Dust from wood processing in the work environment will cause workers to be exposed to wood dust in different concentrations and sizes (Very, 2010).

Methods
This research is a systematic review. Research using the systematic review method is research to identify, evaluate, and interpret all relevant research results related to certain research questions, certain topics, or phenomena of concern (Siswanto, 2010).
The source of this research data comes from national and international journals obtained via the internet in the form of scientific research results from several sources. Data retrieval is carried out through internet searching related to international journal searches carried out through databases; PubMed, Scopus, ProQuest, and Google Scholar, as well as searches for national journals are carried out through the Portal Garuda Indonesia with keywords entered, namely 'paparan debu kayu dan gangguan fungsi paru' and 'faktor risiko gangguan fungsi paru pada pekerja' for Indonesian language journals, while for English-language journals, the keyword 'exposure to wood dust and impaired lung function in workers' is used.
Sorting articles begin by skimming the title, then reviewing the abstracts that are relevant to the research topic. From a total of 196 articles, 16 articles were found to matched. Next, a full-text review was conducted where articles were sorted based on inclusion and exclusion criteria. The inclusion criteria in this study were: 1) Articles published in 2011-2021 2) Articles with this type of observational research 3) The dependent variable in the research article is impaired lung function in workers 4) The independent variable in the research article is exposure to wood industry dust Exclusion criteria were articles that did not clearly describe the method of measuring wood dust exposure and did not impair lung function. After conducting a full-text review, 9 articles that met the criteria were found. The flow chart for sorting articles can be seen in Figure 1. The next step is to conduct a critical study to assess the quality and relevance of the literature found. The guidelines used are Critical Appraisal Tools from the Joanna Briggs Institute (JBI) (Joanna Briggs Institute, 2017). The data/information obtained from the article will be recapitulated and presented in the form of a synthetic matrix table. The analysis is presented in a narrative form.

Result and Discussion
The research locations of all the articles studied are in several countries. Three studies were conducted in Indonesia, two studies in Nigeria and Iran, and one study was conducted in Thailand, Nepal, and Malaysia. The type of research in the article being studied is observational and the design used is cross-sectional. Based on a review of 9 selected articles, the number of samples in the study varied from 30 to 697. All the research subjects worked in the wood industry and the majority of research subjects were workers in the wood processing division (not offices).
The measuring instrument or instrument used in research related to wood dust exposure with impaired lung function in all articles is a questionnaire. The determination of lung function disorders is based on the level of inhaled dust that exceeds the NAV. Measurement of wood dust exposure using a questionnaire that was assessed based on several variables and measurements of inhaled dust mostly used portable spirometry, but there was one article using a PVC filter, and one article using a personal dust sampler.
Based on the results of a review of 9 selected articles, all articles stated that exposure to wood dust was significantly associated with impaired wood function in workers, as seen from the results of statistical analysis in each study, which showed that the p-value < 0.05, or the OR value and limit below or above the 95% CI value is more than 1. Exposure to wood dust was assessed as a significant risk factor for impaired lung function in workers. The magnitude of the risk of impaired lung function in workers due to exposure to wood dust is indicated by the OR value. The OR values in each of the articles studied varied ( Table 1). The variables that were stated to have a significant (significant) relationship were the concentration of wood dust (Thepaksorn et al., 2017;Thetkathuek et al., 2010;Hosseini et al., 2020;Yusof et al., 2019;Neghab et al., 2018;Rachma et al., 2018;Okta et al., 2017;Kartika et al., 2017;Nafisa et (Hosseini et al., 2020;Nafisa et al., 2016) and smoking habit (Hosseini et al., 2020;Neghab et al., 2018).  there was a low percentage predicted forced expiratory volume at one minute (PPFEV1) and percentage predicted ratio of FEV1 and FVC  A negative correlation was observed between the degree of exposure to the hazards and lung function of the workers (r = -0.655, P-Value = 0.0001)  A statistically significant association existed between exposure to wood dust and lung function respiratory symptoms. 3 Work location Sawmill workers have a higher risk of lung function disorders such as chest tightness and shortness of breath than office workers in these industries. This is because the dust content in wood processing is higher than the dust content in the office/finishing section. Smoking habits Woodworkers belonging to smokers have significantly impaired lung function than workers who do not smoke Hosseini et al., 2020;Neghab et al., 2018 The wood industry always produces sawdust particles every processing around the work area, which has the potential to be inhaled by workers. Basically, it is more effective to measure dust than inhalation so that it shows more specific results. The level of wood dust in the workplace, also called total wood dust or wood dust inhaled, affects the performance of lung function. The very small size of dust particles from wood will be very dangerous for individual lung function, because the smaller it is, the easier it is to enter the respiratory tract and end up in the lungs. Wood dust particles measuring 0.1-10 microns are very harmful to exposed individuals (Februar et al., 2016) The results of the research summary show that more than 50% of workers in the wood industry are affected by the lung function system, while the total amount of wood dust and wood dust inhaled is above the NAV. In this study, the value of dust exposure was significantly associated with the occurrence of pulmonary function disorders. So it can be said that the increased exposure to wood dust levels is proportional to the worker's risk of developing lung function disorders (Thepaksorn et al., 2017;Nafisa et al., 2020;Hosseini et al., 2020;Yusof et al., 2019;Neghab et al., 2018;Rachma et al., 2018;Okta et al., 2017;Kartika et al., 2017;Omole et al., 2018). The relationship between dust exposure and lung function capacity is that exposure that is inhaled into the respiratory tract will cause non-specific defense mechanisms, namely sneezing or coughing, and for a long period of time will cause impaired lung function (Amerta, 2020). Asri's study (2020) found a significant correlation with FEV1/FVC, which may suggest that constant exposure to high levels of wood dust can lead to decreased lung function (p= 0.018). Moreover, this study is in agreement with previous studies conducted on decreased lung function parameters among common workers in the lumber industry (Jacobsen et al., 2013;Redlich et al., 2015).
Most of the workers working in the wood industry are males. This is because, men have greater energy than women when placed in work that is classified as heavy. The results of research by Thepaksorn (2017) and Yusof (2019) explain that male workers have a higher risk of developing lung function disorders due to the workload of male workers in areas with high dust potential. This is in line with Agita's research (2016) where workers in wood processing facilities have abnormal lung function capacity, which is more common in male workers, namely 42.1% with significant results (p = 0.007). Furthermore, volume capacity The lungs also have an effect where men have a larger volume of air so that more dust deposits are inhaled in the lungs (Umakaapa et al., 2013).
Wood processing workers have different levels of exposure to wood dust particles depending on the process of their work. The process of sanding and sawing wood produces a lot of wood dust (IARC. 2012). This is in accordance with the research by Thepaksorn (2017), which shows that sawmills have the highest concentration of respirable wood dust exposure, while office workers have a low average exposure to respirable wood dust (Thepaksorn, 2017). Hosseini's research, 2020 also supports the above statement by showing the prevalence of cough symptoms, coughing with phlegm. , chest tightness, and wheezing were significantly higher in workers who processed wood compared to office workers. (Hosseini et al., 2020). This is in line with Dahlqvist's research where the lung response to dust in the sawmill shows a greater positive response than office workers (29%) (Dahlqvist et al., 1992). In addition, it is also in line with the research by Thetkathuek, 2010 which states that the highest levels of exposure to wood dust to the lowest levels are sanding, transfer of raw materials, assembly, drilling, and cutting (Thetkathuek, 2010). This is supported by the Malmberg study in which the novel response to lung function testing in sawmill workers was more exposed than workers outside the sawmill (Malmberg et al., 1996). Douwes' research also shows that wood processing workers have 3 times higher dust concentrations compared to workers who only penetrate wood in furniture. In addition, the furniture section also shows 5.4 times higher exposure using circular saws. This is because in the process of using a chainsaw, a lot of fine dust particles are produced, so that it can be easily inhaled by humans (Douwes, 2017).
Masks are one type PPE that can be used when working by workers in the wood processing industry. Masks are able to protect lung health optimally when used in accordance with the type of dust and mask material. Dust has different sizes, so it must match the type of mask used. There are two studies related to the use of PPE on lung function, namely in the study of Thepaksorn, 2017 andKartika, 2017 where workers who do not comply with the use of PPE have a higher risk of being exposed to wood dust than workers who use PPE when working (Thepaksorn et al., 2017;and Kartika et al., 2017). This study is also in line with the Nafisa research which states that workers who use protective masks at work have a low risk of impaired lung function compared to workers who do not use protective masks (p= 0,049) (Nafisa et al., 2016). Raynel's research shows that the use of PPE (masks) in workers affects lung function disorders, with the results of the analysis showing p = 0.002. This happens because the habit of using PPE in the industrial environment is not continuous (Raynel et al., 2014). According to the theory put forward by Moray and Nadel in Khumaidah (2009) the use of masks by industrial workers whose air contains a lot of dust is an effort to reduce the entry of dust particles into the respiratory tract. By using masks, it is hoped that workers will be protected from the possibility of respiratory problems due to exposure to air with high levels of dust. The habit of wearing masks is a "safe" way for workers who are in a dusty work environment to protect their health (Khumaidah, 2009). Masks are able to prevent the number of contacts because, in principle, masks do not eliminate the danger but can only reduce it (Kurniawati, 2019). Wood industry workers are at risk for occupational diseases due to wood dust allergens. This action can be carried out by using a mask appropriately according to its function, so that it can explain the exposure of wood dust to the wood industry while working in the workplace (Laili, 2018).
The working period determines the length of a person's exposure to dust that can cause lung function disorders. The longer the exposure (working period), the more likely a person is to get the risk, so one of the potential variables that can cause lung function impairment is the length of time a person is exposed to dust (Umakaapa et al., 2013). In Hosseini's study, 2020 workers who were exposed for 15 years longer experienced a decline in lung function (Hosseini et al., 2002). In the Omole study, sawmill workers with an exposure duration of more than 10 years were more likely to have a significant FEV1 (p= 0.001) (Omole et al., 2018). This is in line with Nafisa's research, 2016 where wood processing workers who have worked for 15 years or more have a lower mean parameter value than those who have a service period of fewer than 15 years (Nafisa et al., 2016). Increased values of FEV1 and FVC were detected in woodworkers with a working period of more than 10 years and in wood dust with concentrations above 4 mg/m 3 (Osman et al., 2009). Several studies have shown that the longer a sawmill worker is exposed to sawdust, the greater the concentration level that will be absorbed through the lungs (Meo, 2006;Okwari et al., 2005;and Ennin et al., 2015). According to theory, the time it takes for a person exposed to dust to develop lung function impairment is approximately 10 years (Morgan and McGincley, 2018). A person's smoking habit affects their lung capacity. Almost all smokers who were observed showed a decrease in their lung function. Smoking habits will not only affect the level of oxygen exchange in the blood, but will also be a potential factor for several lung diseases, including lung cancer. Theoretically, smoking is four times more likely than a non-smoker to alter the structural and functional characteristics of the respiratory system and lung tissue. Therefore, smoking habits can affect lung function disorders (Umakaapa et al., 2013). This is in line with research by Hosseini, 2020 andNeghab, 2018 where non-smoking woodworkers have lower lung function disorders than the control group, namely smokers (Hosseini et al., 2020;Okta et al., 2017). In the osman Study, there was a decrease in FEV1, FVC, and FEF for workers compared to non-smokers (p<0.0001) (Osman et al., 2009). In Raynel's research, furniture workers have a smoking habit, that is, out of 50 respondents, 37 respondents (74%) have a smoking habit with impaired lung function capacity, and 13 respondents (26%) smoke with normal lung function capacity (Raynel et al., 2014). This is in line with the research of Triatmo, which also stated that there is a relationship between smoking habits and decreased lunf function (Triatmo et al., 2007). Then, Suryani's research, stated that there is a relationship between smoking habit and impaired lung function with p = 0.021 (Suryani, 2005).

Conclusions
Exposure to wood dust can affect the incidence of pulmonary function disorders in workers. Other risk factors that affect workers affected by pulmonary function disorders are dust levels, the male gender of workers, work locations in departments that produce a lot of sawdust, inconsistent use of PPE (masks), working periods of more than 10 years, and smoking activity. Policies or strategies to reduce the risk of wood dust exposure to workers where there are still many industries that do not prioritize the health of their workers, such as installing larger ventilation so that dust does not accumulate in the workspace, providing PPE according to standards, and measuring the health of workers regularly.