How do combustion and non-combustion products used outdoors affect outdoor and indoor particulate matter levels? A field evaluation near the entrance of an italian university library

Particulate Matter (PM) is a well-known health risk factor and pollutes both outdoor and indoor air. Using PM as an air pollution indicator, the aims were to assess outdoor and indoor air pollution due to combustion and/or non-combustion products used outdoors and to compare the PM levels emitted by different products. PM with an aerodynamic diameter ≤10, 4, 2.5 and 1 µm (PM10, PM4, PM2.5, PM1) was simultaneously measured in two areas, respectively, indoors (with smoking ban) and outdoors (where people commonly smoke) of a university library during the morning and the afternoon of two weekdays. Both combustion and non-combustion products determined a relevant worsening of outdoor air quality, with the highest PM1 levels achieved when a single traditional cigarette (9920 µg m−3), a single e-cigarette (9810 µg m−3) and three simultaneous traditional cigarettes (8700 µg m−3) were smoked. An increase of indoor PM1 levels was found during outdoor smoking/vaping sessions, persisting also after the end of sessions. The results highlighted the need for a revision of smoke-free laws, especially for outdoor areas, to include non-combustion products. In addition, it is essential to make society aware of the dangers of smoking outdoors by implementing health promotion interventions.