PM_2.5 and ozone in office environments and their potential impact on human health

It is important to have good indoor air quality, especially in indoor office environments, in order to enhance productivity and maintain good work performance. This study investigated the effects of indoor office activities on particulate matter of less than 2.5 μm (PM_2.5) and ozone (O₃) concentrations, assessing their potential impact on human health. Measurements of indoor PM_2.5 and O₃ concentrations were taken every 24 h during the working days in five office environments located in a semi-urban area. As a comparison, the outdoor concentrations were derived from the nearest Continuous Air Quality Monitoring Station. The results showed that the average 24 h of indoor and outdoor PM_2.5 concentrations were 3.24 ± 0.82 μg m^-3 and 17.4 ± 3.58 μg m^-3 respectively, while for O₃ they were 4.75 ± 4.52 ppb and 21.5 ± 5.22 ppb respectively. During working hours, the range of PM_2.5 concentrations were 1.00 μg m^-3 to 6.10 μg m^-3 while for O₃ they were 0.10 ppb to 38.0 ppb. The indoor to outdoor ratio (I/O) for PM_2.5 and O₃ was <1, thus indicating a low infiltration of outdoor sources. The value of the hazard quotient (HQ) for all sampling buildings was <1 for both chronic and acute exposures, indicating that the non-carcinogenic risks are negligible. Higher total cancer risk (CR) value for outdoors (2.67E-03) was observed compared to indoors (4.95E-04) under chronic exposure while the CR value for acute exposure exceeded 1.0E-04, thus suggesting a carcinogenic PM_2.5 risk for both the indoor and outdoor environments. The results of this study suggest that office activities, such as printing and photocopying, affect indoor O₃ concentrations while PM_2.5 concentrations are impacted by indoor-related contributions.