New Devices for Measuring Indoor and Outdoor Ultra-Fine Particulates - A Case Study

摘要

Evidence mounts that Ultrafine Particles (UFPs) are contributors in the range of environmental pollutants that affect respiratory and cardiovascular health. While ambient particulate concentrations may be a measure out of doors for exposure dose, many populations, in urban and suburban areas, spend more time indoors where indoor UFP sources add to exposure. Such exposures are not often monitored. Thus, UPF indoor concentrations may be a good measure of personal exposure but it does not necessarily provide for a complete understanding of a building's air handling system. One indicator is the Indoor/Outdoor (I/O) ratio calculated by simultaneous monitoring. New technology ultrafine particulate monitoring devices were used to report Lung Deposited Surface Area (LDSA), particle number concentration and PM mass concentration. These were deployed to characterize the I/O ratio at a local public library that is located near a major traffic pollution source, namely the George Washington Bridge. The devices employed use a diffusion charging method to accurately detect UFPs in the range of 10 nm - 800 nm. A Pegasor AQUrban (PE-14) was placed on the roof of the Library at 60 feet height from the ground, near a PM2.5 FRM device operated by the NJDEP. A Pegasor AQIndoor unit (PIAQ-119) was placed in the Children's Reading Room of the Library on the ground floor (west side) within a short distance from the building entry doors. PE-14 and PIAQ-119 measured concomitantly during the period March 28 to May 9, 2016. The PM concentrations provided by PE-14 also showed a fair correlation (R2=0.58) with the PM2.5 data of a co-located European FEM device (optical method). During the study period we calculated an average I/O value of 1.25 which is in line with the I/O values reported by other similar studies and indicates an optimal removal of the UFPs from outside air by the Library's air handling system. We found a correlation factor of 0.34 between the outdoor and indoor UFP concentrations, which further supports this conclusion. However, there are episodes occurring almost daily in the early afternoon hours where the calculated I/O ratio values, sometime exceeding 1, clearly indicate elevated levels of indoor generated UFPs. Also, subsets of the indoor and outdoor concentration data seem to be more strongly associated than the overall period correlation. A follow up study in the Library is planned to identify the origin of the internal UFP source(s) and investigate their periodic occurrence.