Epidemiologic studies have shown an increased prevalence of allergic asthma in children living in a German smelter area (Hettstedt) compared with a cohort who live in a nonindustrialized area (Zerbst). However, it is not known whether ambient particles (particulate matter_2.5 [PM_2.5]) from these areas induce distinct lung inflammation, which might be an explanation for this difference. Therefore, 100 μg of PM_2.5 suspensions, collected simultaneously in the two areas, were instilled through a bronchoscope into contralateral lung segments of 12 healthy volunteers. PM_2.5 from both Hettstedt and Zerbst increased the number of leukocytes in the bronchoalveolar lavage performed 24 hours later. PM_2.5 from Hettstedt, but not Zerbst, induced a significant influx of monocytes (Hettstedt: 7.0% vs. Zerbst: 4.3%) without influencing the expression of surface activation markers on monocytes and alveolar macrophages. Oxidant radical generation of bronchoalveolar lavage cells and cytokine concentration (interleukin-6 and tumor necrosis factor-α) in bronchoalveolar lavage fluid was significantly increased after instillation of Hettstedt PM_2.5. We conclude that environmentally relevant concentrations of PM_2.5 from the smelter area induced distinct airway inflammation in healthy subjects with a selective influx of monocytes and increased generation of oxidant radicals. The higher concentration of transition metals in PM_2.5 from Hettstedt might be responsible for this increased inflammation.