Bioaerosols in ambient air particulates: a review and research needs

Fine (< 2.5 microns) and inhalable (< 10 microns) ambient particles are associated with increased morbidity and mortality. In addition to a variety of organic chemicals, salts, and metals, inhalable ambient particles may contain biological species, such as proteins, lipids, and so on, from plants, bacteria, and fungi. In airborne particles, the total mass of biological species is small, but their allergenic and inflammatory potential is strong. This paper provides an overview of the bioaerosols found in ambient air particles. Pollen grains are the strongest aeroallergens and have a size > 10 microns. Major pollen allergens have also been identified in size fractions smaller than that of intact pollen. Special atmospheric conditions (such as rainfall) or interactions between air pollutants and pollen may produce allergenic fine particles. Endotoxin (LPS), another important biological species of particles, may play a role in proinflammatory effects. In this review, we discuss the possible interactions between pollen and pollutants and suggest several directions for future research.