Occurrence and Risk Assessment of Personal PM 2.5 -Bound Phthalates Exposure for Adults in Hong Kong.

We performed personal PM 2.5 monitoring involving 56 adult residents in Hong Kong. Additionally, paired personal and residential indoor fine particle (PM 2.5 ) samples were collected from 26 homes and from 3 fixed monitoring locations (i.e., outdoor samples). Six PM 2.5 -bound phthalate esters (PAEs)-including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DnOP)-were measured using a thermal desorption-gas chromatography/mass spectrometer method. Average ∑ 6 PAEs (i.e., summation of six PAE congeners) concentrations in personal PM 2.5 exposure (699.4 ng/m 3 ) were comparable with those in residential indoors (646.9 ng/m 3 ), and both were slightly lower than the outdoor levels. DEHP was the most abundant PAE congener (80.3%-85.0%) and found at the highest levels in different exposure categories, followed by BBP, DnBP, and DnOP. Strong correlations were observed between DEHP with DnBP ( r s : 0.81-0.90; p < 0.01), BBP ( r s : 0.81-0.90; p < 0.01), and DnOP ( r s : 0.87-0.93; p < 0.01) in each exposure category. However, no apparent intercorrelations were shown for PAE congeners. Higher indoor concentrations and a stronger correlation between DMP and DEP were found compared with outdoor concentrations. Principal component analysis affirmed heterogeneous distribution and notable variations in PAE sources across different exposure categories. The average daily intakes of ∑ 6 PAEs and DEHP via inhalation were 0.14-0.17 and 0.12-0.16 μg/kg-day for adults in Hong Kong. A time-weighted model was used to estimate PAE exposures incorporating residential indoor and outdoor exposure and time activities. The inhalation cancer risks attributable to measured and estimated personal exposure to DEHP exceeded the U.S. EPA's benchmark (1 × 10 -6 ). The results provide critical information for mitigation strategies, suggesting that PAEs from both ambient and indoor sources should be considered when exploring the inhalation health risks of PAEs exposure.