English sparrows (Passer domesticus) were studied to assess the usefulness of this species as a relatively stationary air sampler and biological indicator of atmospheric pollutants significant to man. Histopathology of bird necropsy tissue revealed numerous granule-laden macrophages in the pulmonary stroma of birds taken from polluted atmospheres (inland sample) but not from unpolluted atmospheres (coastal sample). Electron microscopy demonstrated several different types of particles within pulmonary macrophages of inland birds but not in coastal birds. The results of this study suggest that the English sparrow might serve as a useful indicator of amospheric pollutants and as a model system for studying the effects of an adverse environment.