pneumoconiosis. A total of 583 male workers from 50 iron foundries in central Taiwan were investigated. First, workers' respiratory symptoms were categorized ...
Occup. Mod. Vol. 49, No. 8, pp. 499-505, 1999 Copyright O 1999 Uppincott Williams & WllWns for SOW Printed In Great Britain. All rights reserved
0962-7480/99
Respiratory abnormalities among male foundry workers in central Taiwan H.-W. Kuo,* C.-L. Chang,* W.-M. Liang* and B.-C. Chung* *Institute of Environmental Health, China Medical College, Taichung, Taiwan; *Provincial Feng-Yuan Hospital, Taiwan Provincial Health Department, Taiwan
Key words: Foundry workers; lung function; male; pneumoconiosis; respiratory symptoms. Occup. Med. Vol. 49, 499-505, 1999 Received 8 February 1999; accepted in final form 15 June 1999 This itudy was supported by a grant from the Institute of Occupational Safety and Health, Council of Labor Attain, Executive Yuan, ROC, IOSH 83-H2203.
INTRODUCTION Foundry processes produce many hazardous chemicals that are released into the workplace and may have damaging effects on the health of the workers, such as respiratory abnormalities, including silicosis that results from extended exposure. These hazardous chemicals include diphenyl methane diisocyanate, phenol formaldeCorrespondence to: H.-W. Kuo, Institute of Environmental Health, China Medical College, No. 91, Hsueh-Shln Road, Taichung, Taiwan, ROC. Tel: (+886) 4-205^076 ext. 22; Fax: (+886) 4-2019901; email: wukuoOmail.cmc.edu.tw.
hyde and their decomposition products as well as silicacontaining particulates. l~3 Basic foundry operations include the creation of a sand-based mould, metal melting and pouring, cast shakeout and finishing and sand reclamation. Because workers in different areas are exposed to different particle sizes and concentrations, some foundry jobs are more hazardous than others. Such minute particles are formed by melted metals which coagulate in the air due to the temperature gradient outside the furnace. Without proper personal protective equipment, these particles can be easily inhaled and have damaging effects on respiratory function.
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The objectives of this study were to determine the relationship between exposure levels and respiratory abnormalities, to measure FVC and FEV1, changes per year based on work duties and to Investigate the prevalence of and factors related to pneumoconiosis. A total of 583 male workers from 50 iron foundries in central Taiwan were investigated. First, workers' respiratory symptoms were categorized using a modified American Thoracic Society (ATS) questionnaire and then were verified by physician's examination. Next, pulmonary function tests were performed including: forced vital capacity (FVC), forced expiratory volume in one second (FEV^ and forced expiratory flow rate. A chest radiograph was used to diagnose pneumoconiosis according to ILO criteria. Furnace workers were found to have the highest prevalence of chronic phlegm, thoracic disorders and chronic bronchitis. In general, smokers had a higher prevalence of respiratory symptoms as compared with non-smokers. Pulmonary function abnormalities and pneumoconiosis were closely linked to smoking and work duration. After adjusting for age, height and smoking there was a significant decrease based on work duration in FVC and FEV, for furnace and moulding workers compared with after-processing and administrative workers. The overall prevalence of pneumoconiosis was 8.8%, highest among furnace (16.3%) and after-processing workers (11.4%) and lowest among administrative workers (2.5%). Using multiple logistic regression, the risk of developing pneumoconiosis (as compared with the administrative workers) for furnace workers was highest (8.98 times greater risk), followed by after-processing workers (6.77 times greater risk) and moulding workers (5.41 times greater risk). Prolonged exposure to free silica, and smoking habits, can result in respiratory abnormalities among foundry workers.
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Malmberg4 reported a poor correlation between lung function and radiographic changes indicating silicosis. Confounding factors (such as age, smoking, worker turnover and job transfers within the foundry) make it difficult to find a clear relationship between the health effect on exposed workers and airborne dust concentrations. Koskela5 conducted a retrospective cohort study of foundry workers, metal product workers and electrical workers. Koskela reported that foundry workers had a higher rate of chronic bronchitis than the corresponding groups of metal product and electrical workers. The prevalences of all diagnosed lung diseases were the highest (42%) at the high exposure level, the second highest (36%) at the medium exposure level and the lowest (32%) at the light exposure levels. Ostiguy6 conducted a cross-sectional and longitudinal survey of 494 workers in a copper refinery. Ostiguy found that the prevalence of chronic obstructive pulmonary diseases (COPD) was 5%, small airway dysfunction (SAD) was 7%, but these did not differ from the control populations. The data show that low-level, long-term exposure to metal dusts, gases and foundry fumes does not necessarily cause respiratory dysfunction.
MATERIALS AND METHODS Most of the factories investigated in this study were relatively small-scale and employed fewer than 30 workers. In comparison with current international standards, working conditions including cleanliness and quality of equipment and facilities were generally poor. The
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In a 1985 study of 78 foundry workers, Johnson7 reported the prevalence of pneumoconiosis to be 4.8%. In 1987, Myers et al.3 found that 10.3% tested positive for pneumoconiosis among South African foundry workers. For those with 15 or more years of foundry work experience, the prevalence increased to 38%. Three major studies have been conducted in Taiwan evaluating health effects on foundry workers. The first, in 1985, by Mao et al.8 focused on 179 workers from one foundry and reported their respiratory dust concentrations varied significantly (0.3-112 mg/m3) depending on workplace location. About 20% of the workers were found to have lung function abnormalities. A second study in 1990 by Lin9 investigated 291 workers from 16 foundries and found that 12.7% of workers had lung function abnormalities and 6.9% had silicosis. Respiratory dust concentrations ranged from none detected (ND) to 71.5 mg/m3, with a geometric mean of 0.76 mg/m3. The third study was conducted by Tainan Hospital10 on 327 workers from 10 foundries, and found that 9.73% had lung function abnormalities and 2.7% had silicosis. However, these studies lack data pertaining to respiratory symptoms, and the foundries investigated are not representative of foundries throughout Taiwan. The current study was performed to determine the relationship between exposure levels and respiratory abnormalities, to measure FVC and FEV1 changes per year based on work duties, and to investigate the prevalence of and factors related to pneumoconiosis.
foundry workers studied were predominantly male, had an average age of 40 years and had completed a low level of education. Since duties performed by furnace and moulding workers require a high level of skill, work durations tended to be long and often occupied much of their adult lives. A total of 583 male workers from 50 government-licensed foundries in central Taiwan were included in this study. One hundred and twenty-five female workers were excluded from the study since about 90% were involved in administration and this would affect comparison of the other groups. Workers were classified into four groups based on exposure to airborne dust concentrations: moulding (high-exposure group), furnace (medium-exposure group), after-processing (low-exposure) and administrative (control group). Due to the uneven gender distribution between the groups, women were excluded from the study. In order to avoid the 'healthy worker effect', information was taken regarding their individual working histories. Environmental sampling was conducted in 35 foundries (15 foundries were unwilling to co-operate). Area sampling was performed to measure total airborne dust concentrations, of which the moulding area tested highest (5.96 mg/m3), followed by the furnace area (3.74 mg/m3), and after-processing (1.61 mg/m3). Concentrations were consistent based on personal sampling, moulding workers tested highest (5.55 mg/m3), followed by furnace (2.89 mg/m3), and after-processing workers (0.77 mg/m3). Total airborne dust concentrations in the administrative area were comparably low (< 0.2 mg/m3) for both area and personal sampling. Average respirable dust concentration" was 1.89 mg/m3 for the moulding group, 2.76 mg/m3 for the furnace group and 2.07 mg/ m3 for the after-processing group. A modified version of an American Thoracic Society (ATS) questionnaire was used to interview subjects.12 Questions involved employment history, respiratory symptoms (as defined by the ATS) (Table 2), health status and use of personal protective equipment. After completing the questionnaire, all workers were examined by a qualified occupational physician to verify any reported respiratory symptoms. Dummy variables regarding circulatory system and digestive system symptoms were included to improve the reliability of the questionnaire. The ATS criterion classifies respiratory symptoms in terms grades: grade 0 is normal and grades 1 and above are abnormal. Since there were very few subjects in grades 3 and 4, only grades 1 and 2 were included; these were combined so that the study comprised just two groups, abnormal and normal. Lung function tests were performed using a Fukada HI-296 Spirometer. Variables included vital capacity and forced expiratory flow rate at 25%, 50% and 75% of the FVC curve. According to the ratio between FEVj and FVC, subjects were classified as normal, obstructed, restricted or mixed. Subjects were instructed to refrain from smoking, excessive eating and use of vasodilators or bronchodilators on the day of testing. Standard procedures for operating the spirometer were given and a demonstration was performed. Prior to testing, a 1-litre
H.-W. Kuo ef a/.: Respiratory abnormaStles of fowidry workers
models. Lastly, factors influencing lung function abnormalities and pneumoconiosis were analyzed using the Mantel-Haenszel test for trend and logistic regression models. RESULTS Personal characteristics for workers in the four groups are shown in Table 1. Age was the only significant variable between the groups. The furnace and after-processing groups had the highest percentage of workers over 50 years of age: 32.8% and 33%, respectively. Other variables including work duration, smoking and pack-year were not significant. Furnace and moulding workers had the highest percentage of smokers (both over 60%) and the highest pack-year values (> 26), 25.7% and 30.2%, respectively. Respiratory symptoms for the four groups revealed significant differences between smokers and non-smokers (Table 2). The prevalence of respiratory problems was higher for smokers. Among smokers, the only significant symptom was thoracic disorder (subject diagnosed by a physician as having had a chest illness or chest tightness within the past three years and has been absent from work for at least one day as a result). Furnace and moulding workers were highest overall, 12.5% and 8.4%, respectively. Chronic phlegm and chronic cough were the most common symptoms found in all groups, with the furnace group the highest (32.5% and 27.5%, respectively). Bronchitis was most commonly found among moulding workers: 9.4% (smokers) and 9.5% (non-smokers). Overall, the prevalence of COPD was the lowest among all the disorders. Results from pulmonary function tests for the four groups were compared (Table 3). Overall, non-smokers had better test results than smokers. Among smokers, the furnace workers had significantly poorest results for
Table 1. Foundry worker's personal characteristics based on job description Variable
Administrative (n--= 112) n
Age (yrs) 50 Work duration (yrs) 16 Smoking No Yes Ex-smoker Pack-years 0 1-7 8-25 >26
(%)
After processing = 112) n
