Wood-dust exposure and respiratory health among particleboard workers in Ethiopia
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Background Work in the wood industry is often associated with exposure to wood dust, endotoxins and formaldehyde, which may cause respiratory health problems. Particleboard is a type of wood product manufactured primarily from wood chips, glued with urea formaldehyde resin and bonded under heat and pressure. In Ethiopia the manufacturing sector, like the wood industry, is growing. However, there is a scarcity of Knowledge, Attitude and Practice (KAP) concerning chemical health hazards and personal protective equipment (PPE) among particleboard workers. On top of this, workers’ exposure to inhalable wood dust, endotoxins and formaldehyde and their effect on respiratory health has been insufficiently studied.
Objectives The aim of this thesis was to assess exposure to wood dust, endotoxins and formaldehyde, respiratory health and KAP regarding chemical hazards and use of PPE among Ethiopian particleboard workers.
Method and materials The thesis consist of three papers conducted in three phases from 2016 to 2017 at the two largest particleboard factories in Ethiopia. In Phase One a cross-sectional study design was used for collection of data on KAP concerning chemical health hazards and PPE in production and administrative workers (n=172), and the study used both closed-ended and open-ended questions. Both permanent and temporary employees were included in the study. In Phase Two an exposure study was performed. A total of 152 dust and endotoxin samples were collected using a conductive plastic inhalable conical sampler (CIS) in the two largest particleboard factories. One field blank sample was taken per day (n=18). In addition, 45 stationary formaldehyde samples were taken using Dräger tubes. Inhalable dust was analysed using the gravimetric method in a room with controlled climatic conditions using an analytical balance with 0.1 μg readability, and the concentration was estimated in mg/m3. Endotoxins were analysed using the Kinetic Amoebocyte Lysate test, and the concentration was estimated in EU/m3. In Phase Three a cross-sectional study involving 74 workers from two particleboard factories and 73 controls from two water-bottling factories was performed. Respiratory symptoms were collected using the American Thoracic Society’s (ATS) standard questionnaire. A lung-function test was performed using spirometry following ATS guidelines. Data was analysed using descriptive statistics, content analysis, the Chi-square test or Fisher’s exact test, the t-test, Pearson’s correlation analysis, regression analysis and mixed-effects models.
Results For Paper I the mean age of the respondents was 28, and the average years of service was 3.7. The permanent workers were older than the temporary workers (29 vs 26 years, p= 0.001), and a very high proportion of the permanent workers had completed vocational education (90%), compared with the temporary workers (11%). The permanent production workers had significantly more knowledge of topics related to chemical hazards than did temporary workers, as well as more positive responses than temporary workers to questions about attitudes related to reduction of chemical hazards and the general work environment. Educational status was significantly associated with a total knowledge score. PPE was provided for permanent workers, but few temporary workers reported PPE provision from the factory. Neither permanent nor temporary workers were using a full set of PPE. The frequency of medical check-up at the health institution was reported as being 25% for temporary and 37% for permanent workers. The administrative personnel are aware of the chemical hazards in their factory. However, the majority of them believe all PPE offers the same level of protection, and they purchase PPE without any safety and quality specification. There was no regular training on occupational safety and health in the factory.
In Paper II the overall geometric mean (GM) of 142 personal inhalable dust and endotoxin exposure were 4.66 mg/m3 (range 0.47 to 184) and 62.2 EU/m3 (range 0.9 to 9202) respectively. The highest exposure to inhalable dust was found among workers performing sizing, forming, flaking and chipping. The highest endotoxin exposure was found in chipping and flaking workstation workers. Of the 142 samples, 93% exceeded 1 mg/m3, the TLV set by ACGIH for inhalable dust, and 41% samples exceeded 90 EU/m3, the occupational exposure limit for endotoxins set by the Netherlands. The correlation between dust and endotoxin level was relatively high (r= 0.68). Factories and downtime explained 27% of the total variability in inhalable dust level, while workstations explained 34% of the total variability in endotoxin level. The highest median concentration of formaldehyde was recorded at blending workstations (3.5 ppm). Formaldehyde was detected at all the selected workstations except the first and last, i.e. chipping and sizing. Of the 45 samples, 13% exceeded the Norwegian peak exposure limit of 1 ppm.
In Paper III particleboard workers were older than the controls (28 vs 25 years; p= 0.006). The exposed workers had also more years of service than the controls (4 vs 2 years; p< 0.001). The prevalence of all recorded respiratory symptoms, wheezing, cough, cough with sputum production, phlegm and shortness of breath was significantly higher in particleboard workers (range of prevalence: 24% to 45%) than in controls (2.7% to 15%). Lung-function status was not statistically different when comparing the exposed persons and the controls, and did not appear to be associated with inhalable dust, endotoxins or formaldehyde exposure. </p>
Conclusions The study revealed that permanent production workers had significantly more knowledge of topics related to chemical hazards, and more a positive response to attitudes related to reduction of chemical hazards and the general working environment than temporary workers. Practice in use of PPE depended on the access to PPE. The geometric mean exposure levels to inhalable dust exposure in the particleboard factories were above the Threshold Limit Value (TLV) of 1 mg/m3 set by the American Conference of Governmental Industrial Hygienists (ACGIH). The geometric mean endotoxin level was lower than the recommended Dutch occupational exposure limit (OEL) of 90 EU/m3. However, the endotoxin levels exceeded this limit at chipping and flaking workstations. The highest median formaldehyde concentration was found in blending workstations (3.5 ppm) – a level above the peak exposure limit value of 1 ppm set by Norway. There was a higher prevalence of respiratory symptom in particleboard workers than in water-bottling workers. However, lung function status was similar in both groups. The symptoms might be related to the high dust-exposure levels found in the factories, but the results must be interpreted with caution because of the cross-sectional study design.