Concentration and Source of dl-PCBs in PM2.5 in Central Hanoi, Vietnam

Abstract

Fine particulate matter (PM2.5) pollution is a major air quality concern in Hanoi, while information on PM2.5 - bound dioxin - like polychlorinated biphenyls (dl-PCBs) remains limited. This study investigated the concentrations, congener profiles, and potential sources of dl-PCBs associated with PM2.5 in central Hanoi during the dry season of 2025. Fourteen consecutive 24-h PM2.5 samples were collected from 4 to 19 April 2025 at an urban site influenced by traffic and other anthropogenic activities. Twelve dl-PCB congeners were analyzed according to U.S. EPA Method 1668B using high resolution gas chromatography high resolution mass spectrometry (HRGC - HRMS) with isotope-dilution quantification. The 24-h PM2.5 concentrations ranged from 32.4 to 83.1 µg/m3, averaging 60.3 µg/m3; 64.3% of samples exceeded the Vietnamese 24-h standard of 50 µg/m3, while the mean concentration was approximately four times the WHO guideline value of 15 µg/m3. Toxic equivalent concentrations of dl-PCBs ranged from 1 × 10-3 to 11 × 10-3 pgTEQ/m3, with an average of 4 × 10-3 pgTEQ/m3. Congener profiles were dominated by PCB-118 (36.3 - 52.9%) and PCB-105 (17.1 - 24.4%), together accounting for approximately 70% of total dl-PCBs, followed by PCB-77 (7.2 - 10.6%). This profile suggests that volatilization from PCB - containing products and materials may represent an important source of atmospheric dl-PCBs in central Hanoi, although contributions from thermal processes cannot be excluded. These findings provide baseline data on PM2.5 - bound dl-PCBs in central Hanoi, supporting future source apportionment studies, air - quality management, and environmental health assessments.