Bioaerosol Release, Transport, and Fate During Land Application of Manure and Biosolids Residuals.

Bioaerosols (biological aerosols) are environmentally ubiquitous, both in rural and urban settings.  Aerosol transport is a critical, mostly un-accounted for, and unseen mechanism of microbial environmental dispersal.  Agriculture and other anthropogenic activities contribute to this transport system, exposing the personnel and the public to microbial loads consisting of pathogenic and non-pathogenic bacteria, viruses, fungi, protozoa, and microbial by-products.  Agricultural activities such as concentrated animal feeding operations, crop-harvesting, and land-application of manure and municipal wastes are key to bioaerosol formation.  This review focuses on manure and biosolids land application operations which are capable of generating large intermittent microbial pulses, or plumes, which can disperse over large swaths of land.  Microbial constituents associated with these plumes will be diluted, inactivated, or deposited once released from the source.  Despite knowing that pathogens are released from these operations; transport, and ultimately fate is largely unknown.  Empirical data suggests transport is largely limited to onsite locations (< 500 m) and modeling suggests carriage at or near to these distances, though variability is inherent to climatic conditions and organism.  Aerosol transport and quantitative microbial risk assessment models have been applied to these exposure scenarios and suggest significant risks are limited to the occupationally exposed.  Bioaerosol sampling is one of the most demanding and difficult environmental matrices to work with, despite the recent advances in this research area.  Novel techniques in microbial ecology, polymerase chain reaction, and sample collection may further expand the breadth of our knowledge and should help overcome deficiencies associated with the field.