Atmospheric aging processes of bioaerosols under laboratory-controlled conditions: A review

Abstract

We present a comprehensive update on the studies of atmospheric aging processes for airborne bioaerosols under various laboratory-controlled conditions. We reviewed changes in physical, chemical, and biological properties of aerosolized biological organisms suspended in air under different simulated environmental parameters or open air factors (OAFs). These changes were scrutinized by measuring viability, inactivation, infectivity, DNA damage, qPCR signal, fluorescence spectral profile and intensity, or/and Raman spectral features. The OAFs considered here are the solar or ultra-violet (UV) radiation, heat or temperature, ozone (O3), free radicals, pollutants, relative humidity, and volatile organic compounds. Most times, especially in actual environmental conditions, far more than one of these factors were involved in the aging processes under various mixed conditions with different levels of individual factors and procedures applied. It is extremely challenging to quantitatively describe these changes of airborne bioaerosols under various combined influences of multiple OAFs. To date, there is not yet sufficient knowledge to enable us to quantitatively express relationships among viability, PCR signals, and spectral features for the atmospheric aging processes, except for some simple changes under particular conditions. Therefore, more comprehensive studies are strongly encouraged to be carried out to address those challenges in the field.