Lung function and surface electromyography of intercostal muscles in cement mill workers

Impairment of pulmonary function in cement mill workers has been previously reported without considering a variety of parameters that can help evaluate more thoroughly the effect of cement dust on the respiratory system. In addition, an integrated approach has not been considered to assert the involvement of respiratory muscles. Therefore, in the present study spirometry and surface electromyography (SEMG) of intercostal muscles were used for indicating pulmonary impairment. In this study, a group of 50, apparently healthy volunteers, male cement mill workers aged 20-60 years with exposure of 13 years on average, were randomly selected. They were matched with another group of 50 control healthy male subjects in terms of age, height, weight and socioeconomic status. Both groups met the standard exclusion criteria. Spirometry was performed on an electronic spirometer, while SEMG of intercostal muscles was performed by using a chart recorder. The results demonstrated statistically significant reduction in lung function parameters i.e., force vital capacity (FVC) (p < 0.0005); force expiratory volume in first second (FEV1) (p < 0.0005); peak expiratory flow (PEF) (p < 0.005); and maximum voluntary ventilation (MVV) (p < 0.0005) in cement mill workers, when compared with controls. However, the FEV1/FVC ratio was significantly higher (p < 0.025) in cement mill workers. Similarly, the parameters obtained from SEMG of intercostal muscles, i.e. number of peaks (NOP) (p < 0.0005); maximum peak amplitude (MPA) (p < 0.0005); peak to peak amplitude (PPA) (p < 0.0005); duration of response (DOR) (p < 0.0005) and maximum peak duration (MPD) (p < 0.0005), were significantly lower in cement mill workers than in controls. It is concluded that exposure to cement dust not only impairs lung function but also affects costal muscle performance, thus possibly indicating the decreased lung and thoracic compliance.     

Dust exposure and respiratory symptoms among cement factory workers in the United Arab Emirates

This study was conducted in a cement factory in the United Arab Emirates to assess cement dust exposure and its relationship to respiratory symptoms among workers. A total of 149 exposed and 78 unexposed workers participated in this cross-sectional study. Information on demographic and respiratory symptoms was collected by questionnaire. Personal total dust levels were determined by the gravimetric method. Concentration of the total dust ranged between 4.20 mg/m(3) in the crushers and 15.20 mg/m(3) in the packaging areas, and exceeded the exposure limit in the packaging and raw mill areas. The prevalence of respiratory symptoms was higher among the exposed workers, but the difference from that of unexposed workers was statistically significant only for cough (19.5%; OR=4.5; 95%CI=1.5-13.2), and phlegm (14.8%; OR=13.3; 95%CI=1.8-100.9). Cough and phlegm were found to be related to exposure to dust, cumulative dust and smoking habit, while chronic bronchitis was related to smoking habit. The few factory workers (19.5%) who used masks all the time had a lower prevalence rate of respiratory symptoms than those not using them. High dust level was the only variable that influenced the workers to use the mask all the time. It is recommended that control measures be adopted to reduce the dust and workers should be encouraged to use respiratory protection devices during their working time.     

Dust exposure and respiratory health effects in cement production

Dust can be produced by almost all production processes in Portland cement factory. Dust exposure potentially can affect respiratory function. But evidence for respiratory effect of cement dust exposure has not been conclusive. In this study we assessed effect of cement dust exposure on respiratory function in a cement production factory. A respiratory symptoms questionnaire was completed and pulmonary function tests were carried out on 94 exposed and 54 non exposed workers at a cement factory in the east of Iran. Additionally, respirable dust level was determined by the gravimetric method. X-ray fluorescence (XRF) technique was performed to determine the silica phases and the SiO(2) contents of the bulk samples. The arithmetic means (AM) of personal respirable dust were 30.18 mg/m(3) in the crushing, 27 mg/m(3) in the packing, 5.4 mg/m(3) in the cement mill, 5.9 mg/m(3) in the kiln and 5.48 mg/m(3) in the maintenance that were higher than threshold limit value (TLV) of the American Conference of Governmental Industrial Hygienists (ACGIH) which is 5 mg/m(3). This value in the unexposed group was 0.93 mg/m(3). In this study cough, sputum, wheezing and dyspnea were more prevalent among exposed subjects. Exposed workers compared to the unexposed group showed significant reduction in Forced Expiratory Volume in one second (FEV(1)), Forced Vital Capacity (FVC), and Forced Expiratory Flow between 25% and 75% of the FVC (FEF(25-75%)) (P<0.05). It can be concluded that in our study there was close and direct association between cement dust exposure and functional impairment among the cement factory workers.     

Dose responses of years of exposure on lung functions in flour mill workers

Flour dust is a heterogeneous substance with respiratory sensitizing properties; its long-term exposure may cause acute or chronic respiratory diseases. Therefore, the aim was to investigate the dose response effects of flour dust on lung function. An additional objective was to minimize the potential health risks in flour mill workers by providing them with information about the hazards of flour dust. Pulmonary function was studied in forty-six male flour mill workers who worked without the benefit of flour dust control ventilation or respiratory protective devices and a similar number of male control subjects. All participants were non-smokers and were matched for age, height, weight and socio-economic status. Pulmonary function tests were performed by using an electronic Spirometer and results were compared by a paired t-test. The present study results showed a significant decrease in the mean values of FVC, FEV(1), PEF and MVV and this impairment was increased with duration of exposure in the flour mills. This group of flour mill workers had occupationally related pulmonary function impairment and stratification of results showed a dose response of years of exposure in flour mills on lung function.     

Exposure to cement dust at a Portland cement factory and the risk of cancer.

The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 14 cases of respiratory cancer were observed (observed/expected (O/E) 1.52, 95% confidence interval (95% CI) 0.90-2.57) when compared with all Danish men. Men with 1-20 years exposure had O/E 1.14 (95% CI 0.59-2.19) based on nine cases of cancer. After excluding all men with documented exposure to asbestos during employment in an asbestos cement factory no increased risk of overall cancer or respiratory cancer was found among cement workers compared with white collar workers from the local reference population, using a Cox regression model controlling for age and smoking habits. Relative risks were 0.5 (95% CI 0.1-1.5) and 1.0 (95% CI 0.4-2.6) for men with 1-20 and more than 20 years of exposure to cement dust respectively compared with white collar workers.     

Exposure to cement dust at a Portland cement factory and the risk of cancer.

The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 14 cases of respiratory cancer were observed (observed/expected (O/E) 1.52, 95% confidence interval (95% CI) 0.90-2.57) when compared with all Danish men. Men with 1-20 years exposure had O/E 1.14 (95% CI 0.59-2.19) based on nine cases of cancer. After excluding all men with documented exposure to asbestos during employment in an asbestos cement factory no increased risk of overall cancer or respiratory cancer was found among cement workers compared with white collar workers from the local reference population, using a Cox regression model controlling for age and smoking habits. Relative risks were 0.5 (95% CI 0.1-1.5) and 1.0 (95% CI 0.4-2.6) for men with 1-20 and more than 20 years of exposure to cement dust respectively compared with white collar workers.     

Work-related respiratory symptoms and ventilatory disorders among employees of a cement industry in Shiraz, Iran

Although the main hazard in cement processing is dust and respiratory tract disorders are the most important group of occupational diseases in this industry, evidence for associations between exposure to cement dust and either respiratory symptoms or functional impairment has not been conclusive. This study was, therefore, undertaken to more thoroughly examine the effects of occupational exposure to cement dust on the respiratory system. The study population consisted of a group of 88, randomly selected, male workers with current exposure to cement dust and 80 healthy male office workers without present or past history of exposure to dust that served as the referent group. Subjects were interviewed and were given respiratory symptom questionnaires to answer. They also underwent chest X-ray and lung function tests. Additionally, personal dust monitoring for airborne inhalable and respirable dust was carried out at nine different worksites. Moreover, X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were performed to determine the silica phases and the SiO2 contents of the dust samples. Levels of exposures to inhalable and respirable cement dust were estimated to be 53.4+/-42.6 and 26+/-14.2 mg/m3, respectively (Mean+/-SD). Statistical analysis of the data revealed that symptoms like regular cough, phlegm, wheezing and shortness of breath were significantly (p<0.05) more prevalent among exposed workers. Similarly, chest radiographs of exposed workers showed various degrees of abnormalities including emphysematous changes, old calcified granulomas, emphysematous changes associated with inflammatory processes, evidence of chronic inflammatory processes, focusal calcification of the lungs and infiltrative changes. However, no significant changes were noted in the radiographs of the referent group. Furthermore, exposed workers compared to their referent counterparts showed significant reductions in the parameters of lung function. In conclusions, our data provide corroborative evidence further substantiating the contention that exposure to cement dust is associated with respiratory symptoms and functional impairments.     

Respiratory symptoms and ventilatory function in workers exposed to portland cement dust

The healthy worker effect and incomplete exposure information have been problems in former studies regarding the association between exposure to Portland cement dust and respiratory effects. We included former workers and made an individual estimation of particle exposure to reduce the selection bias in this controlled cross-sectional study on the effects of cement dust exposure on respiratory symptoms and ventilatory function in long-term exposed Norwegian cement plant workers. A total of 119 workers from the largest cement plant in Norway and 50 workers from a nearby control plant, born 1918 to 1938, performed spirometry and gave information on respiratory symptoms in 1998 and 1999. The prevalence of symptoms and mean pulmonary function indices were similar for exposed workers and controls. There was no dose-response-related increase in symptoms or decrease in lung function indices. The estimated power to detect a true difference between forced expiratory volume in one second (FEV1) in the two groups of 0.3l was 0.90, assuming 95% significance level. The prevalence of chronic obstructive pulmonary disease was 14.3% in the exposed group and 14.0% among the controls. These findings do not support the hypothesis that cement dust exposure has a negative impact on lung function or gives an increase in respiratory symptoms.     

Mortality in a cohort of cement workers in a plant of Central Italy

Purpose  

Workers of cement production are exposed to alkaline dust with irritant effects on the respiratory system. Most previous studies have examined workers in cement/asbestos factories, but there is limited information of the effects of exposures to Portland cement alone. The present study examines the effects of cement dust in a cohort of Portland cement workers through the analyses of their mortality records.     

Acute respiratory health effects among cement factory workers in Tanzania: an evaluation of a simple health surveillance tool

Objectives: The effects of cement dust exposure on acute respiratory health were assessed among 51 high exposed and 33 low exposed male cement workers. The ability of the questionnaire to diagnose acute decrease in ventilatory function was also assessed. Methods: Acute respiratory symptoms were recorded by interview using a structured optimal symptom score questionnaire. Peak expiratory flow (PEF) was measured preshift and postshift for each worker with a Mini-Wright PEF meter. Personal respirable dust (n=30) and total dust (n=15) were measured with 37-mm Cyclone and 37-mm closed-faced Millipore cassette. Twenty-nine workers had concurrent respirable dust, PEF and questionnaire on the same day. Results: The geometric means of personal respirable dust and total dust among high exposed were 4.0 and 13.2 mg/m³, respectively, and 0.7 and 1.0 mg/m³ among low exposed. High exposed workers had more acute cough, shortness of breath and stuffy nose than the low exposed. Mean percentage cross-shift decrease in PEF was significantly more pronounced among high exposed workers than low exposed (95% CI 1.1, 6.1%). For workers with concurrent respirable dust, PEF and questionnaire assessment, an exposure–response relationship was found between log-transformed respirable dust and percentage cross-shift decrease in PEF (4.5% per unit of log-respirable dust in mg/m³ ; 95% CI 3.3, 5.6%). Respirable dust exposure ≥2.0 mg/m³ versus <2.0 mg/m³ was associated with increased prevalence ratio for cough (7.9) and shortness of breath (4.2). Shortness of breath was associated with the highest sensitivity (0.87) and specificity (0.83) for diagnosing a percentage cross-shift decrease in PEF of ≥10%. Conclusion: The observed acute respiratory health effects among the workers are most likely due to exposure to high concentrations of irritant cement dust. The results also highlight the usefulness of the questionnaire for health surveillance of the acute respiratory health effect.     

昌吉州某水泥生产线职业病危害因素检测与评价

目的了解昌吉州水泥生产行业职业病危害因素现状,以采取有效的控制措施,减少职业病的发生。方法对昌吉州某水泥生产厂进行现场职业卫生学调查、职业病危害因素检测,对检测结果进行分析与评价。结果原料系统、烧成系统、制成系统、包装粉尘检测浓度超过国家职业接触限值的岗位是石灰石破碎、煤破碎、石膏破碎、打包装车,噪声强度超过国家职业接触限值的岗位是石灰石库底巡检、生料磨、煤磨,其他检测点粉尘、噪声、高温检测结果均符合国家标准。结论该水泥厂关键职业病危害因素控制点在原辅料的破碎作业岗位产生的粉尘,磨机作业岗位产生的噪声,应在控制点加强除尘、降噪等卫生防护措施,保护作业人员的职业健康。     

Variability in dust exposure in a cement factory in Tanzania

Dust exposure levels were studied in a cement factory in Dar es Salaam, Tanzania, as part of an epidemiological study assessing chronic respiratory health effects. One hundred and twenty personal 'total' dust samples were collected from 80 randomly selected workers from eight a priori occupational groups (OGs) based on work areas using a 37 mm Millipore sampler. The between-group, within-group and within-worker variances were determined to assess the contrast in exposure level between the OGs and to estimate the attenuation and standard error of the theoretical exposure-response slope. Using mixed-effect model estimates, the probability of overexposure relative to the occupational exposure limit (OEL) was assessed for each OG. The geometric means of total dust exposure were higher in the cranes (38.64 mg m(-3)), packing (21.30 mg m(-3)) and crusher (13.48 mg m(-3)) than in the cement mill (3.23 mg m(-3)), kiln (2.87 mg m(-3)), raw mill (1.85 mg m(-3)), maintenance (1.16 mg m(-3)) and administration (0.29 mg m(-3)). The a priori grouping scheme seems to be an efficient scheme because of the high contrast in exposure level between the OGs (0.78) and minimal attenuation of the theoretical exposure-response slope (1.0%). When using the reduced mixed-effect model, the probabilities of overexposure () relative to the OEL of 10 mg m(-3) for total cement dust were higher in the crane (96%), packing (88%) and crusher (73%) than in the cement mill (16%), kiln (14%), raw mill (5%), maintenance (2%) and administration (0.01%).     

Respiratory symptoms and chronic obstructive pulmonary disease among cement factory workers

OBJECTIVES: This study assessed chronic respiratory symptoms and chronic obstructive pulmonary disease (COPD) among workers exposed to cement dust at a Tanzanian cement factory. METHODS: A total of 120 exposed workers and 107 controls participated in this cross-sectional investigation. Information on demographics, occupational history, chronic respiratory symptoms, smoking habits, and use of respiratory protection equipment was collected by questionnaire. Ventilatory function testing and measurement of personal total dust exposure were also carried out. COPD was diagnosed for workers with chronic bronchitis who also had spirometric airflow obstruction. Chronic respiratory symptoms and COPD were correlated with cumulative total dust exposure and adjusted for age, pack-years, and education. RESULTS: The exposed workers had more chronic cough [odds ratio (OR) 4.5, 95% confidence interval (95% CI) 1.9-10.4], chronic sputum production (OR 10.8, 95% CI 4.4-26.4.), dyspnea (OR 5.3, 95% CI 1.9-15.2), work-related shortness of breath (OR 4.8, 95% CI 1.6-14.2), and chronic bronchitis (OR 5.5, 95% CI 2.0-15.3) than the controls. Chronic cough, chronic sputum production, dyspnea, work-related shortness of breath, and chronic bronchitis were significantly related to cumulative dust exposure of 20.0-99.9 and > or = 100.0 versus <20.0 mg/m3-years. The prevalence of COPD was higher for the exposed group (18.8%) than for the controls (4.8%). The odds ratio for COPD was significantly increased for cumulative dust exposure, > or = 100.0 versus <20.0 mg/m3-years (OR 11.2, 95% CI 2.2-56.0). CONCLUSIONS: Cement workers seem to be at high risk of developing chronic respiratory symptoms and COPD, probably caused by cumulative total dust exposure independent of smoking habits.     

Across-shift lung function variation in cottonseed oil workers

BACKGROUND: The effects of cotton dust on pulmonary function among workers employed in cotton-spinning mills are well known. However, little data exist on the prevalence of this disorder in 'non-textile' cotton industries, including cottonseed oil mills, where high levels of exposure to dust have been demonstrated. AIMS: This study was performed in order to determine the across-shift and across-week decline of FEV(1) and respiratory symptoms among workers in a cottonseed oil mill. METHODS: Sixty-six exposed and 48 unexposed workers of a cottonseed oil mill in Turkey were investigated by questionnaire and lung function test (LFT). LFTs were performed before and after shift on all the working days of the week. Acute airway response was defined as an across-shift decline in FEV(1) of 5% or more on the first working day. RESULTS: Smoking was the only risk factor for having respiratory symptoms. Acute airway response was more frequently observed in the exposed group as compared to the unexposed group (OR = 6.2, 95% CI = 2.3-16.7). The median across-shift decline in FEV(1) on the first day (120 ml) significantly improved on the following days (10, 50, 60 and -30 ml). CONCLUSION: Smoking appears to be the main risk factor for having respiratory symptoms. Cottonseed dust may cause an acute pulmonary function decline on the first working day, but not on the following days of the week. This decline is associated with respiratory symptoms in exposed workers.     

回转窑与立窑水泥生产粉尘危害的对比研究

目的探讨水泥生产中采用的回转窑法和立窑法的粉尘控制效果及其对作业人员健康的危害情况,为今后水泥生产的粉尘控制提供科学依据。方法根据我国《建设项目职业病危害控制效果评价技术导则》等要求,对尘源及其浓度进行调查、检测,根据《职业健康监护技术规范》对接尘工人进行职业健康检查。本次检测是在生产线所有设备运转正常、满负荷生产中进行。选择有代表性的地点、工种进行检测,连续检测3个工作日,每个工作日分上、下午各1次。结果回转窑生产方法对粉尘危害的控制效果显著好于立窑生产方法,两种水泥生产方法主要接尘工种的粉尘合格率分别为86.57%和32.11%;主要尘源点粉尘合格率分别为83.94%和15.62%,两者差异均有统计学意义(χ2=198.2,P<0.05)。回转窑水泥厂体检了4 210名粉尘作业工人,检出尘肺观察对象以上者29人,检出率为0.67%;立窑水泥厂体检了1 300名粉尘作业工人,检出尘肺观察对象以上者65人,检出率为4.23%。两种窑尘肺检出率差异有统计学意义(χ2=8 291.1,P<0.05)。结论回转窑在生产过程中对粉尘的控制效果明显好于立窑,其粉尘对作业人员的危害相对于小立窑,改革水泥生产工艺、提高水泥生产自动化、机械化是降低水泥生产过程粉尘危害的关键。     

常州市5家水泥生产线的粉尘危害现状

目的了解常州市某区水泥生产行业粉尘危害现状,以采取有效的控制措施,减少尘肺的发生。方法对5家相同类型的水泥生产线,采用现场职业卫生学调查、职业病危害因素检测、职业健康监护等方法。结果该行业职业卫生管理不到位,工作场所中水泥粉尘检测样品合格率为66.7%,磨机、散装水泥操作处为Ⅰ级(轻度危害作业),包装岗位为Ⅱ级(中度危害作业),97名接尘工人高仟伏X线摄片检查,均在正常范围内。结论该区5家水泥厂,作业场所中水泥粉尘浓度高,职业危害严重。须对生产设备、工艺、防护设施进行整改,切实保护工人的身体健康。     

Respiratory illnesses and ventilatory function among workers at a cement factory in a rapidly developing country

Chronic exposure to Portland cement dust has been reported to lead to a greater prevalence of chronic respiratory symptoms and a reduction of ventilatory capacity. The seriousness of pulmonary function impairment and respiratory disease has not been consistently associated with the degree of exposure. Regular use of appropriate personal protective equipment, if available at the worksite, could protect cement workers from adverse respiratory health effects. For a variety of reasons, industrial workers in rapidly developing countries do not adequately protect themselves through personal protective equipment. This study explores the prevalence of chronic respiratory symptoms and ventilatory function among cement workers and the practice of use of personal protective equipment at work. An interviewer-administered questionnaire was used to collect information on sociodemographic characteristics, smoking profile and history of respiratory health among workers at a Portland cement plant (exposed) and workers occupationally unexposed to dust, fumes and gases (unexposed). Pulmonary function was assessed and pulmonary function impairment was calculated for the exposed and the unexposed workers. A higher percentage of the exposed workers reported recurrent and prolonged cough (30%), phlegm (25%), wheeze (8%), dyspnoea (21%), bronchitis (13%), sinusitis (27%), shortness of breath (8%) and bronchial asthma (6%). Among the unexposed, prevalences of these symptoms were 10, 5, 3, 5, 4, 11, 4 and 3%, respectively. Ventilatory function (VC, FVC, FEV(1), FEV(1)/VC, FEV(1)/FVC and PEF) was significantly lower in the exposed workers compared with unexposed workers. These differences could not be explained by age, body mass index (BMI) or pack-years smoked. Ventilatory function impairment, as measured by FEV(1)/FVC, showed that 36% of the exposed workers had some ventilatory function impairment compared with 10% of those unexposed. Certain jobs with greater exposure to cement dust had lower ventilatory function compared with others among the exposed workers. It was concluded that adverse respiratory health effects (increased frequency of respiratory symptoms and decreased ventilatory function) observed among cement workers could not be explained by age, BMI and smoking, and were probably caused by exposure to cement dust.     

Knowledge and practices related to occupational hazards among cement workers in United arab emirates

Background: In United Arab Emirates (UAE), the rate of industrialization has increased significantly over the past decades. However, few studies have been conducted to investigate the occupational hazards and the knowledge & practice of the working population relevant to these hazards. Objectives: To assess the knowledge and practice of workers in cement factory in Ras Al-Khaimah, UAE on the occupational hazards of their work. Material and Methods: A cross-sectional study involving 153 cement factory workers. A semi- structured interview questionnaire was used to assess the knowledge and practice of workers towards occupational hazards in general and dust in particular. Results: The majority 114 (74.5 %) of the workers knew that exposure to the dust was a serious hazard to their health, but only 52.9 % of the workers knew the hazards other than the dust that were associated with their work. All the workers mentioned that they had been provided with masks to protect them from dust, however, only 28.8 % of them claimed that they used the masks all the time during working hours. The variables: years of education, being informed about the hazards associated with the worker's job, and attending a training course about occupational health and safety were found to have a significant influence on the workers' knowledge about the occupational hazards and on their use of the personal protective equipment at work. Conclusion and Recommendations: Despite the relatively high knowledge of the cement factory workers about the adverse health effects of exposure to dust, the use of respiratory protective equipment was poor. A program to promote safety education and the use of personal protective equipment among cement factory workers is recommended.     

Long-term exposure to cement dust and later hospitalization due to respiratory disease

Summary The relationship between exposure to cement dust in a Portland cement factory and later hospitalization due to respiratory disease and in particular chronic obstructive lung disease (COLD) was examined in a cohort initially examined in 1974. A total of 546 men with different lengths of employment in the cement factory were compared with 857 randomly sampled men of the same age from the same geographical area. Information on hospitalization was obtained from a nationwide register administered by the Danish National Board of Health. During a 9-year, 8-month period, 7.8% of the total population studied had been admitted to hospital at least once because of respiratory disease and 4.3% had been admitted because of COLD. Cement workers had no increased rates of hospitalization when compared with other blue collar workers from the random sample or the whole random sample. A vague tendency towards increasing rates of hospitalization due to COLD with increasing duration of exposure to cement dust up to 30 years was found. Given at least one hospitalization, exposure to cement dust was not related to the accumulated number of days in hospital in the observation period. We conclude that long-term exposure to cement dust does not lead to higher morbidity of severe respiratory disease than other types of blue collar work.This study was supported by grants from The Danish Medical Research Council (12-5877) and the Knud Højgaard Foundation (7818)     

Symptoms, ventilatory function, and environmental exposures in Portland cement workers

Data on respiratory symptoms and pulmonary function were obtained for 2736 Portland cement plant workers and 755 controls. Personal dust samples contained a geometric mean concentration of 0.57 mg/m3 for respirable dust and 2.90 mg/m3 for total dust. Cement workers and controls had similar prevalences of symptoms, except that 5.4% of the cement workers had dyspnoea compared with 2.7% of the controls. The mean pulmonary function indices were similar for the two groups. Among cement plant workers, the prevalence of chronic phlegm increased with tenure whereas the prevalence of wheezing increased with both tenure and current dust level. Other symptoms and pulmonary function indices were not significantly related to exposure.