RESUMO
Air pollution encountered in many towns and cities throughout the world is associated with high levels of fuel vapors and motor vehicle-generated exhaust. A consistent association was reported between the levels of particulate matter and semi-volatile organic compounds in the ambient air with increasing mortality and morbidity. Although the epidemiological evidence is strong, there are yet neither established biological mechanisms to explain the toxicity in humans nor biologically established biomarkers for both exposure and severity of disease. This study was done to determine the impact of vehicle exhaust on the human airways among extensively exposed workers in few gas stations. The extent of exposure to polycyclic aromatic hydrocarbons [PAHs] is measured by estimating the level of 1-hydroxypyrene [1-OHP], a pyrene metabolite. Respiratory inflammation is clinically assessed and evaluated using pulmonary function tests. The impact of respired vehicle exhaust on the immunobiology of the respiratory system is evaluated by estimating the level of the cytokine interleukin-8 [IL-8] in serum, being used as an indication for respiratory inflammation and tissue damage. The study population consisted of 34 highway gas-station workers exposed to vehicle exhaust and 30 matched non-exposed office workers. The exposed population was further subdivided into a fueling group [n=22] working in petrol filling of cars and a car washing group [n=12] working in car cleaning. The study population was subjected to thorough clinical examination, pulmonary function testing and laboratory investigations. Measurement of the urinary 1-OHP level was done using the high performance liquid chromatography [HPLC] with electrochemical water detectors. As for the cytokine IL-8, estimation was done using quantitative sandwich enzyme-linked immunosorbent assay [ELISA]. Medical history and clinical examination revealed significantly higher frequency of repeated chest infections among the exposed group [41%] than among the control subjects [6.6%]. As for chronic bronchitis, asthmatic attacks and dyspnea, the results were higher among the exposed groups but with no statistically significant difference. Ventilation function tests revealed the presence of an obstructive affection among exposed workers correlating strongly with age and smoking habits but not with the duration of exposure. The level of FEV[1] /FVC ratio correlated with the level of 1-OHP that is the PAHs biomarker of exposure [r=-0.313; P<0.01]. The urinary 1-OHP was found to be significantly higher among the exposed population, but still no significant correlation was obtained with exposure duration. The serum IL-8 level was markedly elevated among the exposed workers and significantly correlated with FEF[25%-75%] [r = -0.263; P<0.05] revealing the presence of a high risk of chronic inflammation and lung cancer. Occupational exposure of workers in the gas stations to vehicle exhaust carries an increased risk for respiratory diseases such as repeated chest infections, chronic bronchitis and asthmatic attacks as proved by the presence of dyspnea and the decrement in pulmonary functions. Alteration of the immunological responses of the respiratory epithelium should be considered bearing a risk factor for lung cancer development later on in life. Using the urinary 1-OHP level as a biomarker for exposure and the serum IL-8 level for chronic inflammation and respiratory disease severity and progression should be further evaluated. Long-term impact on the environment needs to be properly investigated in addition to the implementation of protective measures aiming at reducing the occupational exposure to diesel-related polycyclic aromatic hydrocarbons