Environmental context. Atmospheric biological particles have been largely overlooked in the past. While some microorganisms have been studied, the majority of other biological particles have not. The presence of these particles might force us to view the atmospheric aerosol differently.

Abstract. Measurements of biological particles in the atmosphere during the last decade indicate that the presence of these particles seems to have been underestimated by atmospheric scientists. On the average these primary aerosol particles might be present as much as 25% of the total mass (or number for particles with radius greater than 0.2 µm) concentration of the atmospheric aerosol. Such a large fraction certainly plays a major role in all processes affected by atmospheric aerosols, such as cloud and precipitation formation, climate forcing, visibility, turbidity, and so on. This disregard of the biological particles requires a new attitude in our opinion.