Ambient BTEX levels over urban, suburban and rural areas in Malaysia

Benzene, toluene, ethylbenzene and xylene isomers (BTEX) are volatile organic air pollutants of concern which arise from natural and anthropogenic sources. This study aims to determine and evaluate the BTEX levels in ambient air in selected areas of Malaysia, namely: Kuala Lumpur (KL-urban), Penang (PG-urban), Bangi (BG-suburban), Langkawi (LGK-suburban) and the Danum Valley (DV-rural). Active sampling with sorbent tubes was applied in this study and samples were analysed using thermal desorption (TD) coupled with gas chromatography-mass spectrometry (GC-MS). The results show that the urban area of KL had the highest ΣBTEX (40.36 ± 6.99 μg/m 3 ) followed by PG (30.82 ± 8.06 μg/m 3 ). ΣBTEX concentrations in the suburban areas of LGK and BG were measured as 20.22 ± 11.42 μg/m 3 and 12.36 ± 2.26 μg/m 3 , respectively. The rural area of DV had the lowest concentration of ΣBTEX (5.55 ± 2.54 μg/m 3 ). The average toluene to benzene (T:B) ratio at KL, PG and LG were found to be within the range of 2.00–5.00 thus indicating vehicle emissions as the main source. The benzene level at both KL (7.43 μg/m 3 ) and PG (5.12 μg/m 3 ) were found to be slightly higher than the annual benchmark of 5 μg/m 3 as suggested by the European Union (EU). The results of health risk assessments found that the cancer risk (CR) based on benzene concentrations in urban, suburban and rural areas was > 10 −6 thus indicating a link between human cancer risks and ambient benzene exposure.