Accepted Manuscript Occupational Tasks Influencing Lung Function and Respiratory Symptoms among Charcoal- Production Workers: a Time-Series Study Walaiporn Pramchoo, Alan F. Geater, Ph.D, Silom Jamulitrat, Sarayut L. Geater, Boonsin Tangtrakulwanich PII:
S2093-7911(16)30322-5
DOI:
10.1016/j.shaw.2016.11.006
Reference:
SHAW 209
To appear in:
Safety and Health at Work
Received Date: 6 March 2015 Revised Date:
7 November 2016
Accepted Date: 20 November 2016
Please cite this article as: Pramchoo W, Geater AF, Jamulitrat S, Geater SL, Tangtrakulwanich B, Occupational Tasks Influencing Lung Function and Respiratory Symptoms among Charcoal- Production Workers: a Time-Series Study, Safety and Health at Work (2017), doi: 10.1016/j.shaw.2016.11.006. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Occupational Tasks Influencing Lung Function and Respiratory Symptoms among Charcoal-
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Production Workers: a Time-Series Study
Walaiporn PRAMCHOO, Epidemiology Unit, Faculty of Medicine, Prince of Songkla University. Alan F. GEATER, Epidemiology Unit, Faculty of Medicine, Prince of Songkla University.
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Silom JAMULITRAT, Department of Community Medicine, Faculty of Medicine, Prince of Songkla University.
University.
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Sarayut L. GEATER, Department of Internal Medicine, Faculty of Medicine, Prince of Songkla
Boonsin TANGTRAKULWANICH, Department of Orthopedic Surgery and Physical Medicine, Faculty
Corresponding author:
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of Medicine, Prince of Songkla University.
Alan F. GEATER, Ph.D., Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Hatyai,
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Songkhla 90110, Thailand.
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Tel: 66-74-451165; Fax: 66-74-429754; email:
[email protected]
Running title:
Charcoal-production tasks and respiratory function
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Abstract Background: The tasks involved in traditional charcoal-production variously expose workers to charcoal
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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 non-work days followed by 11 workdays. Peak expiratory flow rate (PEFR) was measured 4 times/day. Results: PEFR was reduced and the prevalence
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of respiratory symptoms increased over the first 6-7 workdays. PEFR increased up to evening on nonwork days but not on work-days. Loading the kiln and collecting charcoal from within the kiln markedly
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reduced the PEFR and increased the odds of respiratory symptoms. Conclusion: Tasks involving entry into the kiln were strongly associated with short-term drop in PEFR and the occurrence of respiratory symptoms, suggesting a need for the use of protective equipment and/or the operation of an effective kiln
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ventilation system.
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Keywords: Charcoal-production worker; Peak expiratory flow rate; Respiratory symptoms; Wood smoke
ACCEPTED MANUSCRIPT Introduction
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Charcoal is an important fuel in many countries.
A large amount of charcoal is consumed in
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developing countries, mostly in urban areas, such as Zambia, northeastern Brazil and Kenya. In Kenya
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the charcoal industry employs over 700,000 people providing domestic energy for 82% of urban and
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34% of rural households[1-3]. Charcoal is a wood fuel made from burning wood in a low-oxygen
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environment [4,5]. In the traditional setting charcoal production results in the emission into the
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ambient atmosphere of smoke and dust from the burning of wood and husk. Wood smoke contains
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particulate matter and other toxic compounds such as carbon monoxide, carbon dioxide and nitrogen
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oxides [6,7]. Humans exposed to wood smoke, whether in domestic setting or occupationally, have
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been reported to have decreased lung function, and increased risk for respiratory symptoms, asthma
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and chronic obstructive pulmonary disease [7-13]. Thus, women who use wood as fuel for cooking
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have more cough, dyspnea and asthma than women who use gas for cooking [14]. Workers exposed
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occupationally to smoke, such as firefighters, brick-kiln workers and charcoal-production workers, also
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have been shown to have lower values of spirometry parameters and increased prevalence of
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respiratory symptoms during and/or after exposure than before [8-10, 15,16]. Charcoal workers were
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found to have significantly more respiratory symptoms and poorer lung function parameters than
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workers in non-exposed occupations in Crete [9] and in Thailand [10], and these effects were more
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pronounced among charcoal workers who were smokers than those who were non-smokers [17].
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In the traditional setting in Thailand a charcoal-production plant consists of a number of kilns which
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are operated asynchronously and each worker may perform a number of different tasks, the major tasks
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being carrying wood from the wood stack to place it beside the kiln, loading wood into the kiln, firing
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the kiln to start the pyrolysis process and, after charcoal in the kiln has cooled down, collecting the
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charcoal and putting it into sacks or baskets. For any one worker, tasks performed may differ from day
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to day and several different tasks may be performed on the same day. Thus, the intensity of exposure
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to smoke and dust may be quite varied. Personal protective equipment is not used.
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ACCEPTED MANUSCRIPT The aim of this study, therefore, was to identify the acute respiratory effects of the different tasks. A
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new analysis of time-series data (secondary data) previously collected to compare pulmonary function
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and respiratory symptoms of charcoal workers and rubber tappers [10] was undertaken. Identification
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of the specific occupational tasks that most influence lung function in the short term, as reflected by a
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reduction in peak respiratory flow rate (PEFR) and occurrence of respiratory symptoms, could be
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useful for the rational planning and implementation of protective measures for these charcoal-
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production workers.
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ACCEPTED MANUSCRIPT Materials and methods
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Fifty charcoal-production workers (28 males and 22 females) who were willing to join the study were
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recruited from nine charcoal-production plants (3-7 workers per plant) in Ta Khun district, Surat Thani
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province, southern Thailand. Each charcoal plant included between 5 and 20 separate kilns and the
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cycles of kiln loading, kiln firing and charcoal collection were generally asynchronous among the
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kilns. All workers who had been employed in their current charcoal-production plant for at least 1 year
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were requested to join the study. Subjects who had hypertension, hypotension, ischemic heart disease,
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aneurysm in thorax or brain, cataract lasik eye surgery or respiratory infection or who were pregnant at
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the time of the study were excluded. The study was approved by the Ethics Committee of the Faculty
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of Medicine, Prince of Songkla University. An explanation of the study was given to all participants
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and formal signed consent was obtained before any data were collected.
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Data collection included interviews using a questionnaire, direct observation, and measurement of
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height, weight, blood pressure using an automatic blood pressure monitor, and PEFR using a portable
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peak flow meter with a range of 60-900 dm3min-1 (Micro Peak; Kent, UK). A record form was used to
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record data, covering PEFR, daily tasks undertaken, respiratory symptoms, and starting and stopping
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times of working each day. The questionnaire was adapted from the American Thoracic Society and
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Division of Lung Diseases of the National Heart and Lung Institute questionnaire (ATS-DLD-78-
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adult) [18] and pilot-tested with thirty subjects in a different district of Surat Thani province, and
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revised before using it to collect data in this study. In both the pilot and the actual study, the
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questionnaire data were collected by the investigator, who face-to-face interviewed individual subjects.
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PEFR measurements were made on 14 consecutive days, the first 3 days being non-work days and the
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subsequent 11 days being workdays. Each subject was measured four times in each day, namely in the
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morning before starting work, at midday, in the evening after finishing work, and before going to bed.
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Three measurements were made and recorded in units of dm3/min at each time. Measurements were
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made by the researcher at morning, midday and after work but by the participant him/herself before
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ACCEPTED MANUSCRIPT going to bed. The tasks performed each day and any respiratory symptoms (cough, sputum production,
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dyspnea, wheezing, nasal irritation, nasal congestion) that were experienced during the day were
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recorded on a checklist after PEFR measurement after work by the researcher and before bed by the
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participant. On each day, each symptom was coded as 1 if experienced and 0 otherwise.
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Workers were instructed on how to make the PEFR measurements. They were instructed to ensure the
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PEFR meter was set to zero before making a measurement, to hold the meter by its handle, stand up
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straight, inhale rapidly but not forcefully, insert the mouthpiece, seal the lips and exhale with
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maximum force as soon as the lips had sealed around the mouthpiece. The meter was then to be
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removed from the mouth and the reading recorded. The procedure was to be repeated twice. Finally the
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mouthpiece was to be removed and discarded and the meter wiped with alcohol.
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Statistical analysis
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Descriptive statistics were used to summarize the general characteristics of the subjects. The maximum
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of the three PEFR readings at each measurement session was used for analysis [19]. Mean daily PEFR
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over the 3 non-work days, over all 11 workdays and on each successive workday following the non-
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work period were calculated. Mean PEFR at each time of day was also calculated for non-work days
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and according to tasks performed on workdays.
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Mixed-effects multiple linear regression modeling was used to estimate the independent effects of
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worker characteristics, cumulative day of work following the non-work period, and the interaction of
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time of day and tasks performed during the day on PEFR; and mixed-effects logistic regression
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modeling was used to identify worker characteristics, cumulative day of work following the non-work
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period and tasks influencing the occurrence of respiratory symptoms (cough, cough with phlegm,
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phlegm, dyspnea, wheeze and sneeze). In these mixed-effect models, worker was considered to be the
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random element and other variables to have fixed effects. For each of the multiple regression models,
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variables which showed some evidence of a relationship with outcome (P
