Exposure to bioaerosols containing airborne microorganisms and their by-products from outdoor environments such as industrial, urban or agricultural sites is of a great concern as it is linked to adverse health effects in humans including respiratory diseases and infections. Yet the risk exposure from outdoor emissions is difficult to quantify in real-time as microbial concentration in air is low and varies depending on meteorological factors, anthropogenic activities and sampling conditions. In this study, bioaerosol markers including microbial volatile organic compounds (MVOCs) and phospholipid fatty acids (PLFAs) were used to characterise the distribution, abundance and diversity of airborne microorganisms across three contrasting sites, a wastewater treatment plant (WWTP), a compost facility and a farm respectively. Each site had a distinct MVOC and PLFA profiles. The site with the higher diversity and concentration of MVOCs and PLFAs corresponded to the compost facility containing 21 different PLFAs (∑PLFAs 8275 ng m-3) and 48 MVOCs (∑MVOCs 216914 ng m-3) and the site with the least diversity was the farm containing only 2 PLFAs (∑PLFAs 775 ng m-3) and 14 MVOCs (∑MVOCs 11855 ng m-3). The most predominant group of MVOCs in the WWTP were ketones (42%), in the compost facility were furans (41%) and in the farm there were 3 dominant MVOC groups: esters (23.%), aldehydes (22%) and alkanes (29%). The farm only had PLFAs from fungal origin, whereas in the WWTP and the compost facility PLFAs from Gram positive and Gram negative bacteria as well as from fungi were identified.