Table 3.
Comparison from the current study and the ones of Chirizzi et al. (2021) and Setti et al. (2020b).
| Operative conditions | Current study | Chirizzi et al. (2021) | Setti et al. (2020b) |
|---|---|---|---|
| Sampling size | 44 samples from 10 sites | 60 samples from 2 sites | 34 samples from 2 sites |
| Positive samples | 0 samples | 0 samples | 20 samples |
| Period of sampling | From February 24th to March 9th 2020 (14 days) | From 13th to 27th of May 2020 (14 days) | From February 21st to March 13th 2020 (21 days) |
| Location of sampling | Padua province (NE Italy) | two different Italian regions: Veneto (NE Italy) and Apulia (in the SE Italy) | Bergamo Province (North Italy) |
| Typology of sampling point | Different: urban and rural background sites; traffic and industrial sites | Urban background site | Industrial site |
| Filter used | Quartz fiber filters (47 mm Ø, Whatman QMA, GE Healthcare, USA) | Quartz fiber filters | Quartz fiber filters |
| Sampler typology | Two different samplers were used: Low-volume aerosol sampler (Skypost PM-TCR Tecora) equipped with a sequential sampler (Charlie) that operates at flow rate of 38.3 L min−1 for 24 h; it was used for the following sites: BO, TO, ES, PO, SA. Low volume aerosol sampler (SWAM 5a Dual Channel Monitor-FAI Instruments) that operates at flow rate of 38,3 L min−1 for 24 h; it was used for the following sites: PD1, PD2, PD3, SG. |
Two different samplers were used per site: In Veneto: low volume aerosol sampler (Skypost PM-TCR Tecora) equipped with a sequential sampler (Charlie) that operates at flow rate of 38.3 L min−1 for 48 h; model 110 MOUDI cascade impactor with an average flow of 30 L min−1 for about 6 d. In Apulia: low volume aerosol sampler (SWAM 5a Dual Channel Monitor-FAI Instruments) that operates at flow rate of 38 L min−1 for 48 h; a rotating model 120 MOUDI-II™ cascade impactor, operating at 30 L min−1 for about 6 d. |
Low-volume gravimetric air sampler (38.3 L/min for 24 h) |
| Average air collected per sample | 55.2 m3 | 110 m3 or 250 m3 | 55.2 m3 |
| Particulate matter retention | >99.95% for particles with an aerodynamic diameter of 0.3 μm | Not reported | 99.9% |
| Sampling procedure | EN 12341:2014 | Not reported | EN 12341:2014 |
| Meteorological conditions | Temperature; irradiation; precipitation; wind intensity | Temperature; relative humidity; precipitation | Temperature; relative humidity; irradiance |
| Solid phase extraction | Quick-RNA™ Fecal/Soil Microbe Microprep Kit, Zymo Research, USA |
Total RNA Purification Kit, Norgen Biotek Corp. | Quick-RNA™ Fecal/Soil Microbe Microprep Kit, Zymo Research, USA |
| Internal Positive Control | SARS-CoV-2 (E gene) aRNA, EVA, Marseille, France. | Not reported | Not reported |
| RT-PCR reference protocol | Chu et al., 2020 | Corman et al., 2020 | Corman et al., 2020 |
| RT-PCR oligos | Custom oligos, Thermofisher | Diatheva commercial kit | Not reported |
| RT-PCR molecular targets | Genes N and Orf1b-14nsp | Genes RdRp and E | Genes E, RdRP and N |
| Limit of Detection | 2.5 gc/μL | 10 gc/μL | Not reported |
| Detection threshold | 1.2 gc m−3 | <0.8 gc m−3 | 1.5 gc m−3a |
a
Detection threshold for the method of Setti et al. (2020b) was calculated assuming a LOD for their molecular assay of 2 gc/μL (Corman et al., 2020) and that the RNA extraction protocol strictly followed the kit manufacturer's instructions, with a 90% purification efficiency.