Potential for Exposure to Toluene Secondary Organic Aerosol and Health Effect

HYEON-JU OH, Jiwoo Jeong, Yanfang Chen, Hwajin Kim, Seoul National University

     Abstract Number: 573
     Working Group: Aerosol Exposure

Abstract
Secondary organic aerosols (SOAs), the major components of fine particle contamination (PM_2.5), are currently receiving considerable attention as those cause lung and heart problems and other health effects. In particular, toluene emitted from automobiles is the most abundant aromatic compound in the atmosphere and is an important precursor of SOA. This study evaluates SOA exposure generated on the roadside and its potential health effects using a reaction model of toluene photooxidation within a reaction chamber. Scanning Mobility Particle Sizer (SMPS) was used for quantitative exposure evaluation of SOA produced by toluene photooxidation with different NOx concentrations (max. 70ppb). The health effects of aerosol induced by the toluene-SOA were simulated by the modeling methods of the International Commission on Radiological Protection (ICRP) and Multiple-Path Particle Dosimetry (MPPD). The average mass concentrations and the average number concentration of produced SOA were within 120.63–225.64 µg/m³ and 5.28x10⁴–1.11x10⁵ µg/m³, respectively. The SOA reached maximal mass concentration at about 2 hours post toluene injection and maintained the same level thereafter. Although the yield of SOA increased with the NOx concentration, the SOA number concentration decreased, which is attributed to particle agglomeration and wall loss in the chamber. Using the result of SOA mass concentration in the chamber, the inhalable aerosol doses were 2,470–4,620 ng/kg-bw/application in the ICRP model, and the deposited aerosol was 500–900 ng/kg-bw/application in the MPPD. Of the aerosol deposit, 34.0% were deposited in the head airways, 42.6% in the alveolar, and 23.5% in the tracheobronchial regions. This study shows the potential health effect of toluene-SOA, an ultrafine aerosol, mediated by toluene as a precursor. Therefore, further studies are needed to investigate the physicochemical/cytological properties of toluene-SOA and other precursors of SOA in the air environment.

This work was funded by the Korean Government through the National Research Foundation of Korea Grant (NRF–2022R111A1A01063383) and FRIEND (Fine Particle Research Initiative in East Asia Considering National Differences) Project.