Occupational Tasks Influencing Lung Function and Respiratory Symptoms Among Charcoal-Production Workers: A Time-Series Study

Abstract

Background: Tasks involved in traditional charcoal production expose workers to various levels of charcoal dust and wood smoke. This study aimed to identify specific tasks influencing lung function and respiratory symptoms.

Methods: Interviews, direct observation, and task/symptom checklists were used to collect data from 50 charcoal-production workers on 3 nonwork days followed by 11 workdays. The peak expiratory flow rate (PEFR) was measured four times per day.

Results: The PEFR was reduced and the prevalence of respiratory symptoms increased over the first 6-7 workdays. The PEFR increased until evening on nonwork days but not on workdays. Loading the kiln and collecting charcoal from within the kiln markedly reduced the PEFR and increased the odds of respiratory symptoms.

Conclusion: Tasks involving entry into the kiln were strongly associated with a short-term drop in the PEFR and the occurrence of respiratory symptoms, suggesting a need for the use of protective equipment and/or the operation of an effective kiln ventilation system.

Keywords: charcoal-production worker; peak expiratory flow rate; respiratory symptoms; wood smoke.

Fig. 1

Distribution of model-derived daily average PEFR (dm³/min) of charcoal workers on nonwork days (Day 0) and consecutive workdays (Days 1–11). The filled circles and vertical lines represent means and 95% confidence intervals for all workers. Values of PEFR for each day not having a lowercase letter in common differ significantly (p < 0.05, mixed-effects linear regression model in which the worker is the random element). PEFR, peak expiratory flow rate.

Fig. 2

Distribution of daily prevalence of charcoal workers experiencing respiratory symptoms on nonwork days (Day 0) and consecutive workdays (Days 1–11). Values of prevalence within each symptom not having a lowercase letter in common differ significantly (p < 0.05, Poisson regression model clustered on workers).

Fig. 3

Distribution of model-derived PEFR (dm³/min) of charcoal workers by task and time of day. The times of day 1–4 refer to morning, midday, evening, and before bed, respectively. The filled circles and vertical lines represent means and 95% confidence intervals for all workers. Values of PEFR within each task for each time not having a lowercase letter in common differ significantly (p < 0.05, mixed-effects linear regression models in which the worker is the random element). PEFR, peak expiratory flow rate.