Abstract

This is the first study that reports on the dose-response relationships between occupational exposure to charcoal dust, respiratory symptoms and lung function among charcoal-processing workers in Namibia. Methods: A cross-sectional study was conducted among 307 workers from charcoal factories in Namibia. All respondents completed interviewer-administered questionnaires. Spirometry was performed on a subset of the sample and ambient and resipirable dust levels were assessed in different work sections. Results: Exposure to respirable dust levels across most of the job categories was above occupational exposure limits, with packing and weighing having the highest dust exposure levels (median 27.7 mg/m3, range: 0.2–33.0 for the 8 hour time weighted average). A high prevalence of respiratory symptoms was observed among males and females respectively: for cough (39% and 22%), cough for more than 3 months (19.4% and 13%), breathlessness (21% and 35.5%), wheezing (29% and 26%) and phlegm (30.3% and 33%). Higher cumulative dust exposure (CDE) was associated with chronic cough, phlegm for most days, and doctor-diagnosed diseases. Ex-smokers had elevated odds ratio for phlegm for most days (OR: 1.2, 95% CI: 0.4–3.7), shortness of breath (OR: 1.3, 95% CI: 0.4-.4.1), and wheezy chest (OR: 1.6, CI: 0.5–4.9). Among those having lung function tests (n = 291), a lower mean predicted% FEV1 was observed (98.1% for male and 95.5% for female) among the higher exposed workers as compared to the low dust exposure category (FEV1%: 101.1% (males) and 104.1% (females). Conclusions: Charcoal dust levels exceeded the US OSHA recommended limit of 3.5 mg/m3 for carbon black containing material. Participants presented with exposure related adverse respiratory outcomes in a dose-response manner. Our findings suggest that stronger enforcement of regulations within the industry is required.