Air pollution caused by phthalates and cyclic siloxanes in Hanoi, Vietnam: Levels, distribution characteristics, and implications for inhalation exposure

Highlights: • Phthalates and cyclic siloxanes were analyzed in indoor/outdoor air of Hanoi, Vietnam. • Concentrations of phthalates and siloxanes in indoor air were higher than in outdoor air. • DEP, DnBP, DiBP, DEHP, D5, and D6 were major compounds detected. • Most compounds were abundant in the gas phase than in particulate phase. • Non-cancer and cancer risks of airborne phthalates were relatively low. Contamination status and distribution characteristics of ten phthalic acid esters (PAEs) and three cyclic volatile methyl siloxanes (CSs) were determined in the air (gas and particle) samples collected from indoor and outdoor spaces of several chemistry laboratories, offices, and homes from urban area of Hanoi, the capital city of Vietnam. Air concentrations of Σ10PAEs (median 688; range 142–2390 ng m⁻³) and Σ3CSs (171; not detected–1100 ng m⁻³) in the indoor air samples were significantly higher than those measured in the outdoor ones (Σ10PAEs: 161; 34.1–515 ng m⁻³ and Σ3CSs: 43.2; not detected–258 ng m⁻³), partly suggesting the predominance of indoor emission sources of these substances. There were significant positive correlations in total air concentrations of phthalates and siloxanes between the indoor and outdoor air samples. The most predominant phthalates were diethyl-, di-n-butyl-, diisobutyl-, and di(2-ethylhexyl) phthalate. For siloxanes, D5 and D6 were more abundant than D4 in most samples. Except for di(2-ethylhexyl)- and di-n-octyl phthalate in some locations, almost all the compounds were likely associated with gas phase than particle phase. Daily intake doses of airborne phthalates and siloxanes, and non-cancer and cancer risks of selected phthalates were estimated for different exposure groups such as adults, children, and university subjects (e.g., laboratory staff and students), indicating relatively low levels of risk.