Background: the city of Milan introduced a traffic charging zone in city center in January 2008, named Ecopass.
Aim of the study: to compare PM1, PM2,5 and PM10 levels in and outside the restricted area before and after the enforcement of the charging scheme.
Methods: PM1, PM2,5 and PM10 exposures were measured by means of pre-calibrated portable laser-operated particle analyzers. PM10 data from the ARPA official monitoring stations were also evaluated.
Results: during a walking trip from Piazza Loreto (outside) to Piazza Duomo (inside Ecopass zone) and back, mean (SD) PM1, PM2,5 and PM10 were 31 (6), 68 (24) and 93 (37) microg/m3 inside the Ecopass zone, and 32 (6), 70 (37), 98 (48) microg/m3 in the outer area, respectively (not significant, ns). In another trip walking from Piazza Buonarroti to Piazza Duomo and back, PM1, PM2,5 and PM10 levels were 56 (2), 183 (14) and 245 (28) microg/m3 inside the Ecopass zone, and 58 (3), 197 (13) and 247 (24) microg/m3 in the outer area, respectively (ns). In the measurements taken from a car moving in three ring belts--one inside the restricted zone, and two outer radial orbitals--PM1, PM2,5 and PM10 levels were found 41 (1), 110 (8) and 148 (16) microg/m3 inside the Ecopass area, 42 (3), 116 (14) and 152 (28) microg/m3 along the middle belt, and 39 (4), 102 (15) and 127 (23) microg/m3 along the greater Milan orbital ("Tangenziale"), respectively (ns). Mean (SD) PM10 levels from ARPA in the two months before the enforcement were 71.2 (32.6) and 74.8 (38.4) microg/m3, in the Ecopass zone and outside, respectively while after the enforcement were 67.3 (36.4) and 70.9 (38.3) microg/m3 of PM10, respectively (ns).
Conclusions: no signficant improvement in air quality was observed after the enforcement of the Ecopass charging zone in Milan. In spite of their limitations, the present data confirm that small scale reductions in particle emissions are not sufficient to reach the goal of an improvement in air quality. Large scale, coordinated interventions on an inter-regional basis are envisioned.