A cross-sectional study was conducted in a randomly selected factory producing Portland cement in eastern. Saudi Arabia to determine· the prevalence. of ...
Pulmonary Effects of Occupational to Portland Cement:
Exposure
A Study from Eastern Saudi Arabia SEIFEDDIN G. BALLAL, FFOM, HAFIZ O. AHMED, PHD, BASIL A. ALI, PHD, ADNAN A. ALBAR, FFCM (KFU), ABDULLAH Y. ALHASAN, FRCR
A cross-sectional study was conducted in a randomly selected factory producing Portland cement in eastern Saudi Arabia to determine· the prevalence. of respiratory symptoms and diseases and chest x-ray changes consistent with pneumoconiosis in the employees. A sample of 150 exposed and 355 unexposed employees was selected. A questionnaire about respiratory symptoms was completed during an interview. Chest x-rays were read according to the ILO criteria for pneumoconiosis. Dust level was determined by the gravimetric method. Concentrations of personal respirable· dust ranged from 2.13 mg/m3 in the kilns to 59.52 mg/m3 in the quarry· area. Cough and phlegm were found to be related to cigarette smoking, while wheezing, shortness of breath, and bronchial asthma were related to \ dust levels. It is recommended that engineering measures be adopted to reduce the dust level in this company, together with health monitoring of exposed employees. Key words: Portland cement; respiratory symptoms; Saudi Arabia; silicosis. INT j OCCUP
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HEALTH 2004;10:272-277
of occupational diseases and levels of pollutants' in excess of the threshold limit values (TLVs), respectively. Exposure to cement dust at the .workplace is known to cause chronic respiratory ailments in the form of cough, dyspnea, or chronic bronchitis: 1-5 Reports about occupational hazards in Saudi industry are very few, and to our knowledge there is virtually no published report from this country addressing specifically the adverse health effects of Portland cement on exposed workers. There are now ten companies producing Portland cement in the KSA. Three of these are in the eastern province, and one of them was randomly selected for this study The objectives of this cross-sectional study were to determine the prevalence of respiratory symptoms and diseases and chest x-ray changes consistent with pneumoconiosis in the lungs of workers exposed to Portland cement dust in a cement-producing factory in eastern Saudi Arabia and the relations of these to the level of respirable dust particles in the work environment.
SUBJECTSAND METHODS
T.
he utilization of natural gas and other natural resources has diversified both basic and supporting industries in the Kingdom of Saudi Arabia (KSA), which requires the hiring of more workers. Consequently, more individuals are exposed to occupational hazards, and their protection is a moral obligation on the part of the employer. Built-in preventive measures (i.e., safety measures built into the process) coupled with education in occupational health and safety are the ideal means of preventing accidents and diseases. Health and work environment monitoring can detect early symptoms/signs
Received from the Department of Family and Community Medicine (SBC, HOA, AAA), the Department of Physiology (BAA), and the Department of Radiology (AYA), College of Medicine, King Faisal University, Dammam, Kingdom of Saudi Arabia. Supported by grant AR-10-024 from King Abdul-Aziz City for Science and Technology, Riyadh, Kingdom of Saudi Arabia. Address correspondence and reprint requests to: Professor S.C. Ballal, MD, P.O. Box 2114, Dammam 31451, Kingdom of Saudi Arabia; e-mail: .
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Study Samples The studied sample of 150 male workers exposed to Portland cement was selected by systematicsampling (one-infive) using the company's payroll. A control group of 355 males was similarly selected from unexposed industrial employees (clerical staff) from a number of companies. Females in KSAdo not work in factories.
Respiratory Symptoms' Questionnaire The British Medical Research Council's Questionnaire on Respiratory Symptoms (MRC) 6 was used in our study, with additional questions relevant to the objectives of the study. The companies' physicians were briefed on the contents of the questionnaire and the instructions and on how to ask the questions and what pitfalls to look for. During the interview the objectives of the study were explained to the participants and verbal consent was obtained from each before the questionnaire was completed.
TABLE 1. Distribution by Area of the Personal Respirable
Area
No. of Samples
Range of Dust (mg/m3)
29
13.3-59.5 4.3-47.6 4.8-25.8 2.1-22.2 7.1- 6.7
Quarry Raw mills
25
Cement packaging Kilns Cement mills
20 15 8
the ACGIH Limit* No. (°/0) of Samples Above the ACGIH Limit*
29 24 19 12 8
(100) (96) (95) (80) (l00)
92 (94.9)
97
TOTAL *5 mg/m3 of
Dust Samples That Exceeded
air.
Dyspnea -was graded, according to the MRC questionnaire, into five levels of severity: I, normal (no dyspnea); II, dyspnea on effort (hurrying on level ground or walking up a slight hill); III, unable to keep pace with people of own age and body build; IV, unable to walk at own pace without the need to stop to regain breath; V, dyspnea at rest or while dressing. The latter grade was not included in the questionnaire since it was assumed that no subject who_was gainfully employed would have this degree of dyspnea. Current smokers were those who had smoked at least one cigarette a day for as long as a year and had been smokers up to one month or less from the date of the interview. Ex-smokers were those who had been regular smokers up to more than one month prior to the study.
comparisons within factory areas as well as with the standard limits. The exposed workers were divided into exposure groups based on: 1) the predominant types of the dust in the work areas (to reflect qualitative differences in the types of dust present in the plant); and 2) the sections in which the' workers were performing their jobs. Eight air samples from the bulk materials used in cement production in addition to samples of cement itself and air samples from the other areas of the factory were analyzed for free silica content by the x-ray diffraction method. The Saudi Arabian American Oil Company Laboratories (Dhahran, Saudi Arabia) performed the analysis. Ninety-seven personal· respirable dust samples were collected and analyzed.
Statistical Analysis Chest X-ray A qualified radiologist read the films according to the ILO 1980 International Classification of Pneumoconiosis.7 Profusion categories of' 011 and 110 were considered to represent suspected pneumoconiosis.
A database file was created in a personal c.omputer and statistical analysis was done by means of the Statistical Package for Social Sciences (SPSS). A p-value of < 0.05 was taken as the level of significance.
RESULTS Respirable Dust Sampling and Analysis Respirable Dust The gravimetric method was used to determine the concentration of respirable dust by drawing a known volume of air through a filter of known weight under controlled conditions (flow rate of pump, time of sampling). Reweighing of the filter gives a direct measurement of the dust weight. The sampling strategy adopted fulfilled the following requirements8: the samples represented workers' exposures, in that they were collected over a period of time that reflects work. schedule cycles. This strategy was achieved during the study through, the following: The exposed workers in the factory were divided into exposure zones (which are hypothetical zones in which workers perform similar tasks}. The number of samples obtained from each exposure zone was determined in proportion to the number of workers in the area. The geometric mean for each area in the factory was assigned for each worker in that area, and was used for
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The concentrations of personal respirable dust ranged from 2.13 mg/m3 in the kilns to 59.52 mg/m3 in the quarry area (Table 1). The concentrations in 92 (94.9%) of the 97 samples exceeded the recommended threshold limit value (TLV) adopted by the American Conference of Governmental Industrial Hygienists (ACGIH) for nuisance respirable particulates, which is 5 mgl m3 of air.9 The geometric mean of respirable dust was twice or more than the ACGIH recommended upper limit in three areas in the company (quarry, raw mills, and cement packaging) (Table, 2).
Free Silica Content The percentages of quartz ranged from zero in the bauxite and clinker to 3.9 % in the clay. The concentrations of quartz in air (mg/m3) ranged from 0.16
Pulmonary Effects of Portland Cement
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TABLE2. Geometric Means of Respirable Oust in the Factory Sections Geometric Mean (± SO) (mg/m3 of Air)
Area Quarry Raw mills Cement packaging Kilns Cement mills
95
20,3 (1.3) 15,2(1.7) 14,8 (1,5) 7,1 (1,8) 10.6 (1.4)
mg/m3 in the quarry crusher area to 34.1 mg/m3in quarry drilling area.
%
CI
Relation to the ACGIH Limit of 5 mg/m3 of Air
pValu~
3 x limit 2 x limit 2 x limit Exceeded Exceeded
< 0.005 < 0,005 < 0,005 < 0,05 < 0.005
18,6-22.1 12,7-18,3 12,8-17,1
5,4- 9,3 8,3-13,4
the
Cigarette Smoking The differences in the numbers of cigarettes smoked (pack-years) by the ~xposed compared with the unexposed workers in each smoking category in the company were not large enough to attain significance (Table 3).
exposed showed consistently higher mean values for the former group, but statistical levels of significance were reached only for wheezing (p 0.0268) and shortness of breath (p 0.037) (Table 5). The cumulative exposure levels for those with respiratory diseases were again higher than those of workers free from these diseases, sometimes more than twice as high. Statistical significance was attained for the diagnosis of bronchial asthma (p 0.037).
LOGISTIC REGRESSION MODELS Respiratory Symptoms and Chest Conditions A fifth of the exposed workers had grade II or more severe forms of dyspnea, compared with 13.3 % of the controls. However, this difference was not statistically significant (RR, 95% CI: 1.51,0.99-2.28). Only two of the exposed workers (1.3 %) had grade IV dyspnea, as opposed to 3.1 % of the unexposed workers. More than a third (35.3%) of the exposed workers claimed to have had episodes of acute bronchitis, and a further 10.7% reported histories of asthmatic attacks. These rates were much higher than those reported by the unexposed workers (RR and 95% CI 2.67; 1.893.76, and 3.16; 1.53-6.51, respectively). Similarly, those who admitted to have had acute attacks of both conditions .combined were significantly more among the exposed (RR, 95% CI: 5.41; 2.27-12.88) (Table 4). Of the exposed workers who gave histories of previous episodes of acute bronchitis (53) or asthma (16), 9.4% and 56.3%, respectively, were found to satisfy the definitions of these respiratory conditions. Comparison of the cumulative cement dust levels to which the symptomatic and asymptomatic groups were
Since cigarette smoking is a major confounder for respiratory symptoms, particularly cough and phlegm, a logistic regression analysis was undertaken for each of the respiratory symptoms, in addition to bronchial asthma and chronic bronchitis as outcome variables. The predictors (independent variables) were cigarette smoking (yes = 1, no = 0), age (for dyspnea only), tenure, and dust concentration. Table 6 depicts only the predictors that had significant relationships with the outcome variables. Cough and phlegm had positive correlations with both cigarette smoking and tenure. The lower limit of the confidence interval for the latter variable was rounded down to one. Wheezing, with or without shortness of breath, was significantly related to dust concentration (OR, 1.20, 95% C I, 1.04-1.39; and OR, 1.23, 95% C I, 1.07-1.42, respectively) . Of the respiratory diseases investigated, only bronchial asthma but not chronic bronchitis was found to be significantly related to dust .concentration (OR, 1.2~, 95 % CI, 1.07-1.42). Since all those who admitted
TABLE3. Pack-years of Current Smokers and Ex-smokers of the Studied Groups Unexposed, No. (%) Pack-years 1-10 11-20 ~ 21 TOTAL
E>,cposed,No. (%)
Current Smokers
Ex-smokers
Current Smokers
Ex-smokers.
61 (54,5) 28 (25,0) 23 (20,5)
46 (66,7) 11 (15,9) 12 (17.4)
28(57,1) 9 (18,4) 12 (24,5)
13 (56,5) 6 (25,1) 4 (17,4)
112
69
49
23
NS*
NS*
P-Value *Not statistically significant.
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TABLE4. Histories of Attacks of Asthma and/or Bronchitis and Questionnaire-based Diagnoses of Chronic Bronchitis and/or Asthma among the Exposed Workers with the Significant Relative Risks (RR) and 95% Confidence Intervals (CI) Indicated Medical
Condition
History of acute bronchitis RR (95
