Oxidative biomarkers of exhaled breath condensate in adults exposed to traffic-related air pollution: a case-control study

Traffic-related air pollution exposure (TRAP) is a major public health problem. The effects of TRAP exposure on the oxidative biomarkers of exhaled breath condensate (EBC) of adults are seldom studied. We compared the oxidative EBC biomarkers in a group of individuals exposed to TRAP with those of individuals unexposed to TRAP. We conducted a case-control study in Bhopal City (Madhya Pradesh, India). Adults with a history of exposure to TRAP were enrolled as cases and adults with less exposure to TRAP were used as a control. Based on respiratory symptoms and smoking habits, study subjects were stratified into six subgroups. EBC was collected by TURBO14 (Medivac SRL, Italy) at -5 °C. The EBC pH was measured after gas standardization with argon. EBC hydrogen peroxide (H2O2), cystenine leukotrienes (Cys-LTs), 8-isoprostane were measured by commercial ELISA kit. A total of 250 consecutive adult (male: 194) subjects were recruited. Among them, 133 were TRAP-exposed (male: 128) and 117 were non-TRAP-exposed (male: 66). The respiratory symptoms between TRAP-exposed and non-TRAP-exposed subjects were not different. The post-gas standardized EBC pH (median: 7.72; interquartile range (IQR): 7.15-7.94 vs. median: 7.60, IQR: 6.72-7.87;p= 0.09) and EBC H2O2(median: 2.20µmol l-1; IQR: 1.46-3.51 vs. median: 1.99, IQR: 1.41-3.10;p= 0.29) in TRAP-exposed subjects were statistically not different from the non-TRAP-exposed subjects. The EBC Cys-LTs (median: 69.81; IQR: 57.0-83.38 vs. median: 47.21 pg ml-1; IQR: 39.90-54.87,p< 0.001) and EBC 8-isoprostane (median: 12.55 pg ml-1; IQR: 5.51-18.09 vs. median: 7.12; IQR: 4.60-16.04,p= 0.026) in TRAP-exposed subjects were higher compared to those in non-TRAP-exposed subjects. The subgroup analysis showed that TRAP-exposed subjects, irrespective of their smoking habits and respiratory symptoms, had higher EBC Cys-LTs compared to the non-TRAP-exposed subjects. TRAP exposure increases oxidative biomarkers of the EBC in adults.