Laser printers are one of the common indoor equipment in schools, offices, and various other places. Laser printers have recently been identified as a potential source of indoor air pollution. This study examines the characteristics of ultrafine particles (UFPs, diameter <100 nm) and volatile organic compounds (VOCs) emitted from laser printers housed in a commercial printing center. The results indicated that apart from the printer type, the age of printers, and the number of pages printed, the characteristics of UFPs emitted from printers also depend on indoor ventilation conditions. It was found that at reduced ventilation rates of indoor air, there was a rise in the number concentration of UFPs in the printing center. Interestingly, the contribution of UFPs to the total number of submicrometer-sized particles was observed to be higher at a sampling point far away from the printer than the one in the immediate vicinity of the printer. Black carbon (BC) measurements showed a good correlation (rs = 0.82) with particles in the size range of 100-560 nm than those with diameters less than 100 nm (rs = 0.33 for 50-100 nm, and rs = -0.19 for 5.6-50 nm particles). Measurements of VOCs in the printing center showed high levels of m-, o-, and p-xylene, styrene, and ethylbenzenes during peak hours of printing. Although toluene was found in higher levels, its concentration decreased during peak hours compared to those during nonoperating hours of the printing center.

Assessment of integrated personal exposure (PE) to airborne particulate matter (PM) across diverse microenvironments (MEs) over 24 hours under different exposure scenarios is necessary to identify appropriate strategies to improve urban air quality and mitigate the health effects of PM. We carried out a collaborative study in a densely populated city-state (Singapore) to assess the integrated PE to fine particles (PM2.5), ultrafine particles (UFPs) and black carbon (BC) across diverse indoor and outdoor urban MEs, estimate related health risks and make suitable recommendations for healthy living in cities. Two volunteers with different lifestyles participated in the study by tracking their PE to particulate air pollution and the time-activity patterns over 24 hours using portable PM monitoring devices and recording their whereabouts using GPS coordinates. Home, transport and recreation (i.e., food court) MEs represented pollution hotspots of PM2.5 (21.0 μg/m3), BC (3.4 μg/m3) and UFP (33.0 × 103 #/cm3), respectively. Among the different modes of transport used by the participants (walking, cycling, e-scooter, mass rapid transport (MRT), bus, car and taxi), the air pollutants had elevated concentrations while commuting by public transport (bus and MRT) as well as during active modes of transport (walking and cycling). Air-conditioned cars and taxis, equipped with air filtration systems, represented the lowest PE. The health risk assessment revealed that there are potential carcinogenic risks associated with the long-term exposure to elevated levels of PM2.5-bound toxic trace elements. These risks can be mitigated with the introduction of low-carbon and active modes of transport in place of internal combustion engines and the use of indoor air pollution exposure mitigation devices.