The Relationship between Occupational Exposure to Cement Dust and Prevalence of Respiratory Symptoms and Disorders

Introduction: 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 association between exposures to cement dust and either respiratory symptoms or functional impairment has not been conclusive. This study was, therefore, undertaken to examine, more thoroughly, the effects of occupational exposure to cement dust on the respiratory system.

Materials and Methods: The present study was a historical cohort investigation. The study population, as evaluated by statistical procedures, consisting 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 reference group. Both groups had identical socioeconomic, demographic status and length of employment. Subjects were interviewed, and respiratory symptom questionnaires were administrated to them. They also underwent chest X-ray and lung function tests. Additionally, using gravimetric method with a filter holder containing a membrane filter connected to a cyclone, personal dust monitoring for airborne inhaling and respiring 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, on a fee for service basis.

Results: Levels of exposures to inhaling and respiring cement dust were estimated to be 53.4±42.6 and 26±14.2 mg/m³ respectively (Mean ±SD).  These values exceeded current TLV of 5 mg/m³ for such particles. Statistical analysis (T-test and Chi-square) 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. 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 as diagnosed by the specialist. Furthermore, no significant differences were noted between the two groups as far as the number of smokers and the length of smoking were concerned.  

Conclusions: Given the fact that both groups had identical socioeconomic and demographic status and were similar as far as important confounding variables such as cigarette smoking was concerned, it is very likely that the significant reductions in the parameters of pulmonary function, as well as a significantly increased prevalence of respiratory symptoms among exposed workers, could be attributed to their exposure to cement dust. Therefore, our data provides further evidence to support the proposition that exposure to cement dust is associated with respiratory symptoms, radiographic changes in the lungs and functional impairments.