Several studies in literature have highlighted associations between airborne particulate matter and several adverse health outcomes, as a function of particle size.

Traditionally, PM studies have focused on particles less than 10 μm in diameter (PM₁₀) or particles less than 2.5 μm in diameter (PM_2.5), with each fraction characterized by a distinct source, and different composition and health effects.

Since, diffusion in the alveolar region of smaller particles with an aerodynamic diameter less than 0.1 μm (i.e. 100 nm and therefore also defined as nanoparticles) becomes an effective mechanism and the probability of deposition increases. There is a great debate whether ultrafine fraction (PM_0.1) is mainly responsible for negative cardiovascular effects caused by its high oxidative and mutagenic potential.

In the present study, size-fractionated airborne particulate matter was collected from outdoor urban and working environments and analyzed for 105 organic contaminants of different classes: polycyclic aromatic hydrocarbons (PAH) and their derivatives (nitro-PAH and oxy-PAH); polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and Novel Brominated flame-retardants (N-BFRs) selected for their toxicity and persistence in the environment.

The selected organic contaminants were subsequently divided into three different macro-groups based on chemical and physical properties (PAH/N-PAH/O-PAH; PCB and PBDE/N-BFR) and subjected to statistical analysis.

The monitoring campaigns were carried out in four sites: an urban atmosphere (RM), a wastewater treatment plant (WWTP) where aerosol is generated during the different phases of the processes, an intensive livestock farming activity, characterized by sheds serving as a shelter for cows (COW) and an area where feed is stored (FEED).

In each monitoring campaign PM was collected with a multistage low-pressure impactor able to sample 14 size intervals of PM on as many filters, subsequently joined to form three dimensional fractions (coarse, fine and ultrafine).

The results obtained from the organic contaminant analyses and from the Principal Component Analysis (PCA) showed a correlation between sites and classes of pollutants, allowing the identification of characteristic emission sources of each monitored site. Emission source studies are in fact a valuable tool for both identifying the type of emission source characteristic of a specific place and estimating the strength of each contamination source in the same place of interest.