@inproceedings{01JWTP6R0K64NQW0EP5RCXEQQH,
  abstract     = {{INTRODUCTION
In Vietnam, children aged 6 and under are commonly enrolled in nursery schools, kindergartens, or childcare centers, where they spend approximately 10 hours daily receiving care and education. This prolonged exposure in classrooms raises concerns about their exposure towards air pollutants. According to the World Health Organization (WHO), Benzene, Toluene, Ethylbenzene, and Xylene isomers (BTEX) have been linked to a range of health issues of children, impacting respiratory, nervous, and immune systems, as well as cognitive development. The International Agency for Research on Cancer (IARC) classifies benzene as class 1 (carcinogen to humans), ethylbenzene as group 2B (possibly carcinogenic to humans), and toluene and xylenes as class 3 (not classifiable as to its carcinogenicity to humans). However, to date, no studies have been conducted in Vietnam to determine 7-days BTEX levels in the indoor air of public spaces dedicated to children. Therefore, the primary objective of this study was to measure and assess the concentrations of BTEX in classrooms at a nursery school in both urban and rural areas in Hanoi, Vietnam using passive sampling and TD-GC-MS analysis. 

METHODS
A sampling campaign was conducted in August 2023 to collect air samples in classrooms at nursery schools located in Hanoi, the capital of Vietnam. Air samples were passively collected (exposure time was 7 days) from 10 classrooms, 10 sleeping rooms (excluding the rural school) and two different locations within the schoolyard of each school. 
Axial tube samplers packed with Tenax TA (poly(2,6-diphenyl-p-phenylene oxide)) were utilized in the campaign. Prior to use, the samplers were conditioned at 300 °C for 1 hour, followed by 320°C for another 15 minutes, under a clean and dry Helium flow of at least 50 mL/min through each tube. The conditioned samplers placed in the field were loaded with 8.5 ng Tol-d8 as internal standard. Standards comprising BTEX, were made by dissolving the pure compounds in MeOH. 1uL of stock solution was loaded in triplicate onto conditioned tubes via a home-made injector system under a 100 mL/min Helium flow (Demeestere et al. (2008)). 
Subsequently, both collected air samples, blank samples, and standards samples were analyzed using TD-GC-MS to quantify individual VOC concentrations. VOCs preconcentrated on the passively sampled Tenax TA sorbent was desorbed in a Unity Series 2 Thermal Desorption system (Markes International, Llantrisant, UK) by heating the tube at 50 °C (1 min) followed by 260 °C (7 min) under a Nitrogen flow of 20 mL/min. Next, VOCs were refocused on a microtrap filled with 22 mg of Tenax TA 35/60 and 34 mg of Carbograph 1TD sorbent (volumetric ratio 50/50), and cooled at −10 °C. After flash-heating of the microtrap at 280 °C (3 min), VOCs were carried by a Nitrogen-flow and injected onto a 30 m FactorFour VF-1 ms low bleed bounded phase capillary GC column (Varian, Sint–Katelijne–Waver, Belgium; 100% dimethylpolysiloxane, internal diameter 0.25 mm, film thickness 1 μm). Then, the GC oven temperature (Trace 2000, Thermo Finnigan, Milan, Italy) was initially set at 35 °C (10 min), and then increased gradually up to 240 °C in three steps at different heating rates:  35 °C - 60 °C at 2 °C/min; 60 °C - 170 °C at 8 °C/min; 170 °C - 240 °C at 15 °C/min. After that, the oven temperature was held at 240 °C for 10 min before cooling down at 35 °C.  The MS-transfer line was also heated to 240 °C. Masses from m/z 29 to 300 were recorded in full scan mode (5 scans per sec) on a DSQ II Quadrupole MS (Thermo Scientific, Austin, TX, USA), hyphenated to the GC, and operating at an electron impact energy of 70 eV. Chromatograms and mass spectra were processed using XCalibur (Thermo Scientific™, version 2.2), and TraceFinder (Thermo Scientific™, version 4.2) software was used for the data processing. 

RESULTS
In addressing the critical concern of indoor air quality within nursery school classrooms in Vietnam, this study successfully measured concentrations of Benzene, Ethylbenzene, Toluene, and Xylene isomers (BTEX) through a meticulous sampling campaign and subsequent TD-GC-MS analysis. The findings underscore the absence of prior investigations on BTEX levels in such educational settings in Vietnam, emphasizing the novelty and importance of this research. The results reveal that the 7-days concentrations ranged from 2.85 µg/m³ to 19.96 µg/m³ for benzene, 1.54 µg/m³ to 20.45 µg/m³ for ethylbenzene, 10.17 µg/m³ to 115.86 µg/m³ for toluene, 0.66 µg/m³ to 14.39 µg/m³ for o-xylene, and 1.38 µg/m³ to 29.61 µg/m³ for m-/ p-xylene for both the schools. 

CONCLUSIONS
Results, revealing the concentrations of BTEX compounds over a 7-days period, now provide a foundation for further interpretation. Exposure levels, and non-carcinogenic and carcinogenic risks are estimated, and sources of these compounds (indoor and outdoor) are identified. The significance of these results lies not only in recognizing potential health risks for children but also in formulating actionable suggestions to enhance air quality within nursery school environments. As a step forward, recommendations for improvements will be proposed, aiming to create an optimal atmosphere conducive to the growth and development of children in these educational spaces.}},
  author       = {{Hoang Tuan, Viet and Demeestere, Kristof and Van Langenhove, Herman and De Coster, Gynaika and Le, T.T. and Nguyen, Duc-Luong and Walgraeve, Christophe}},
  booktitle    = {{14th International Conference on Air Quality, Abstracts}},
  keywords     = {{Passive sampling,TD-GC-MS,Indoor BTEX,Nursery schools,Hanoi, Vietnam}},
  language     = {{eng}},
  location     = {{Helsinki, Finland}},
  title        = {{Utilizing passive sampling and TD-GC-MS analysis to determine BTEX levels in the indoor air of nursery schools in Hanoi, Vietnam}},
  year         = {{2024}},
}