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Airborne bacteria are components of the atmospheric aerosol particles and can be responsible of allergic disease, regardless of their viability. In this paper, we report a method for the determination of total (viable and nonviable) bacterial content in airborne particles, using muramic and dipicolinic acids as biomarkers of bacteria and bacterial spores, respectively. The analytical procedure was optimized with bacteria and spores of Bacillus subtilis. After extraction and purification, the two biomarkers were analyzed by HPLC-ESI-MS/MS and their percentage was evaluated to be used as conversion factor. The present method for the determination of the total bacterial content was then applied to environmental samples, after a proper collection in an urban site. Thanks to the use of a low pressure impactor, capable of fractionating particles into the range of 0.03-10 μm, it was also possible to study the bacterial content in ultrafine, fine, and coarse particulate matter. The results from this study showed that muramic and dipicolinic acids can be determined together in one chromatographic run in reversed phase ion pair chromatography. Bacteria were more abundant than bacterial spores in the urban atmosphere, both showing a higher concentration in the coarse fraction of particles, although bacteria and bacterial spore amounts per unit mass of ultrafine particles were higher than in fine and coarse particles.

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Both regulated and unregulated air pollutants were detected during an intensive seasonal sampling campaign in a mixed industrial/semi-rural area on the outskirts of Rome, Italy, at two sites located opposite a hospital waste incinerator, downwind according to the direction of the prevailing local winds. Concentrations of pollutants were significantly lower than in urban atmospheres. The composition of particulate organic material indicated a heavy biogenic impact, accompanied by a lower contribution from petroleum-related processes. Both PAH and nitro-PAH group compositions of particulates were used to assess the nature and relative importance of sources. Both sites showed that different and diffuse sources contributed to local pollution with a significant contribution from traffic, proving that the hospital waste incinerator was not the main pollution source in this area. Among unregulated compounds, a series of positional isomers of nitro-PAHs and other organic compounds associated with particulate matter were investigated. In particular, 1- and 3-nitrophenanthrene identification was carried out, and they proved to be the most abundant nitro-PAHs.

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