Fingerprints of Airborne Plastics in Urban PM2.5: Applications and Implications

To better identify emission sources of airborne plastics, we employed nine plastic-associated chemicals (PlsACs) in 240 daily PM2.5 samples collected in Singapore during 2018–2020. A unique PlsAC, tris(2,4-ditert-butylphenyl) phosphate (I168O), is most abundant, accounting for 90% of the total quantified PlsACs and identifying at least 40% more PM2.5 linked to respirable airborne PlsACs. A newly resolved source of plastic production, use, and burning (PlasticPub) accounts for the highest fraction (37%) of the quantified PlsACs among the seven apportioned PM2.5 sources. Nearly all di-iso-butyl phthalate (DIBP) and more than half of di-n-butyl phthalate (DNBP) are attributed to two factors of Background and Marine aerosols, indicating their potential worldwide transport. More than 90% of diethyl phthalate (DEP) is associated with transported peat forest (PF) burning smoke, demonstrating involvement of anthropogenic activities. Following PlasticPub, Traffic & road dust is the second predominant source responsible for >20% of the near-range PlsACs and featured with a DNBP/di-2-ethylhexyl phthalate (DEHP) concentration ratio of 2.2. The DNBP/DEHP concentration ratio higher than 1 can indicate nonexhaust emissions from on-road traffic due to abrasion of tires, brakes, and road markings. The average enrichment ratio of quantified PlsACs within PM2.5 (ng PlsACs per μg PM2.5) for each resolved source provides a basis for assessing strategies to cocontrol airborne plastics and PM2.5.