A study was conducted in subjects admitted to hospital for chronic obstructive bronchopulmonary disease (COPD) in the city of Parma (Italy). The aim was to evaluate changes in patients' percent vital capacity (VC), forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), as a function of changing degrees of atmospheric pollution as measured by PM10, NO2 and O3 concentrations in the outside air. Study results revealed an association between PM10 concentrations and hospital admissions for COPD. Statistically significant differences were found between PM10 concentrations measured three-four days before admission and in days not followed by admission to hospital. Regression analysis between PM10 concentrations at 24, 48, 72, and 96 hours before admission and respiratory function showed a significant association between FVC% and FEV1% and PM10 concentrations at 96 hours. The relative risk was calculated to be 1.016 (95% confidence intervals: 1.001-1.032), which corresponds to a 1.6% increased risk of admission to hospital for COPD for each unit increase in PM10 concentration in the outside air.