10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Comparison of Physicochemical Properties and Toxicity of Particles Found Indoors and Outdoors in Occupied Residences – Measurement Methodology
ANETA WIERZBICKA, Yuliya Omelekhina, Nicklas R. Jacobsen, Anne Thoustrup Saber, Erica Bloom, Patrik Nilsson, Axel C. Eriksson, Joakim Pagels, Lund University
Abstract Number: 1382 Working Group: Indoor Aerosols
Abstract Surprisingly little is known about toxicity and physicochemical characteristics of airborne particles found in residences, even though we spend about 65% of our time in homes. Characteristics and toxicity of outdoor particles have been studied and adverse health effects due to exposure have been confirmed. Outdoor particles infiltrate to indoor environments and we are exposed to them indoors but they change their physicochemical characteristics upon infiltration and mix and transform with particles and gas pollutants from indoor sources. Many indoor sources generate particles in amounts that exceed levels observed outdoors by far, for example during cooking or candle burning. There is a need to better understand exposures in homes. The aim of this study was to develop measurement methodology that would allow studying toxicity and physicochemical differences between particles found indoor and outdoor occupied residences.
Week-long measurements were conducted simultaneously indoors and outdoors in sixteen occupied residences in southern Sweden during winter time 2016/17. Residences included in the study were detached single family houses with natural ventilation and apartments with both natural and mechanical ventilation. Occupants kept logbooks of performed activities that were prone to generate particles.
Two identical sets of instruments for indoor and outdoor measurements were used. Instruments were placed in specifically designed enclosures to minimise the noise and disturbance for the occupants. Measurements comprised online assessment of physical characteristics of particles and collection of particles for off-line chemical analysis and toxicological studies in mice. Measured time-resolved physical characteristics were: number concentration and mean size (Nanotracer, 10-300 nm), PM2.5 mass concentration (DustTrack DRX), and black carbon concentration (Microaethelometer). Filters from Dustracks DRX were used firstly for gravimetric analysis (corrections for DustTrack readings), then split into three parts and used for the following analysis: policyclic aromatic hydrocarbons quantification (GS-MS), metal analysis (ICP-MS) and ion chromatography. Particles were also collected on a Teflon filter for endotoxin analysis (PM2.5 cyclone at flow 15 l/min). PM2.5 particles for the toxicological studies were collected using Dekati Gravimetric Impactor (70 l/min).
Particles collected for toxicological studies were extracted and evaporated according to method described by Jalava et al 2005. In short each PTFE sample filter, was extracted twice in 30 ml methanol in ultrasonic water bath for 30 min below 35 degree C. All extracts of particles of one type namely: indoor, outdoor and blanks, were pooled together, sonicated and dried in a vacuum evaporator at 35deg C and 150 mbar.
During the measurement period we collected time-resolved data about physical characteristics of airborne particles indoor and outdoor occupied residences. Average particle number concentration (10-300 nm) was higher indoors than outdoors, and accounted to 6700 cm-3 (STD 4700 cm-3) and 2400 cm-3 (STD 900 cm-3), respectively. Gravimetrically assessed PM2.5 mass concentration was higher outdoors than indoors, average outdoor concentrations were 8.5 μgm-3 (STD 6.1 μgm-3) while indoors 4.9 μgm-3 (STD 3.7 μgm-3). Extracted mass of particles collected for toxicological studies accounted in total to about 70 mg for indoor and outdoor separately, which was sufficient for conducting toxicological studies in mice, the results are being analysed. Preliminary tests of PAHs, endotoxin and metal analyses confirmed sufficient amounts of particle mass on split filters for the analysis, which are currently ongoing.
Applied measurement methodology proved its suitability for assessment of physicochemical characteristics and toxicity of particles found indoor and outdoor occupied residences. Collected and extracted PM2.5 particle mass was also sufficient to perform toxicological studies in mice. These characteristics are needed to increase our understanding of the mixture of particles found indoors, in order to assess health effects and minimize exposure.
ACKNOWLEDGEMENT This work was financed by the Swedish Research Council FORMAS (Project Dnr 942-2015-1029).