Traffic-related pollutants and their impact on allergic respiratory diseases

There is good evidence that urban air pollutants, and particularly diesel exhaust particles (DP), contribute to the increasing prevalence of asthma and allergic rhinitis. Diesel exhaust particles act as adjuvants in the immune response and may aggravate allergic inflammation. This was first suggested by epidemiological studies and has now been largely confirmed by numerous experimental studies in animals and humans. We review the different underlying mechanisms, including effects on cytokine and chemokine production and immune cell activation. We also discuss the metabolic and cellular activation pathways followed by polycyclic aroma tic hydrocarbons and allergens, and their interaction with diesel particles, which act in synergy in this immune response, resulting in IgE production and triggering allergic inflammation.