Changes in hematologic indices and inflammatory markers in a double-blind real world traffic exposure study

Traffic-related air pollution is associated with inflammation and cardiovascular disease. Commute exposures are a significant source of exposure to traffic-derived pollutants. We studied whether exposure to roadway-derived exhaust in a typical commute causes effects in human subjects. 16 healthy adults had 2-hr highway commutes on 3 separate days in a double-blind, crossover trial randomized to order. On two days, on-road air was entrained into the cabin through the vehicle’s regular vents with sham filtration. On a third day, the vehicle was equipped with effective filtration. In-vehicle pollutants were measured continuously. Blood was collected before the drive (baseline), and 5-hrs and 22 hrs after. Outcomes were complete blood count with differential, cortisol, C-reactive protein, and IL-6. Within-person filtration effect on each outcome was estimated using a mixed-effects model. Filtration reduced in-vehicle particle count by 85% and gases by 20%. Compared to filtered drives, exposure to traffic pollution was associated with significant decrease in total circulating leukocytes and non-granulocyte populations: (WBCs [-360/ul (95% CI:-680 to -30)], monocytes [-70/ul (95% CI:-130 to -10)], and lymphocytes [-290/ul (95% CI:-460 to -120)] at five hours post exposure. A decrease in lymphocyte count persisted for 22 hours post exposure [-220/ul (95% CI:-400 to -40)]. There were no significant changes in cortisol, IL-6, or C-reactive protein. Short-term exposure to on-road air pollutants results in small but significant reductions in circulating mononuclear and lymphocyte cell populations, which can be prevented with effective particle filtration.