Linking Volatile Organic Compounds (VOCs) in the Ambient Air of Malaysia with its Sources, Environmental Impacts, and Potential Health Risks

Volatile organic compounds (VOCs) are significant air pollutants emitted from both anthropogenic and biogenic sources, impacting atmospheric photochemical processes and human health. This study aimed to determine the variations and potential sources of VOCs concentration in ambient air across various land-use types, including urban, industrial, and background areas in Malaysia. It also evaluated the impact of VOCs on photochemical processes and assessed health risks. The concentrations of ∑₃₀ VOCs were measured between January 2018 and December 2019 at ten continuous air quality monitoring (CAQM) stations operated by the Malaysian Department of Environment (DOE). The positive matrix factorisation (PMF) model was used to identify the VOCs source apportionment. The VOCs contributions to ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) were quantified. Non-carcinogenic and carcinogenic risks of specific VOCs species were assessed using the health risk assessments (HRA) for both children and adults. The results revealed the highest VOCs concentrations in urban areas (125 ± 116 µg m^-3 at the S3 station), followed by industrial (112 ± 112 µg m^-3 at the S4 station and 95.4 ± 87.1 µg m^-3 at the S1 station), while the lowest concentrations were recorded at the background site (55.5 ± 65.4 µg m^-3 at the S9 station). Fuel evaporation (28.5%) was the major contributor in both urban (S3 station) and industrial (S4 station) areas, whereas combustion and biogenic sources (29.7%) dominated in background areas (S9). For the VOCs photochemical reactivity, alkenes (182 µg m^-3, 59.0%) and aromatics (79.8 µg m^-3, 25.9%) had the highest mean contributions to ozone (O₃)formation across all monitoring stations. Aromatic VOCs recorded the highest SOAFP levels at all stations, ranging from 351 µg m^-3 (88.1%) to 2312 µg m^-3 (96.7%). The hazard quotient (HQ) and hazard index (∑HI) for non-carcinogenic risk were below 1.00 for both children and adults. The excess lifetime cancer risk (ELCR) for adults was above the regulatory threshold of 1.00 × 10^-⁶ at all monitoring stations, indicating potential carcinogenic risk due to benzene exposure. Given the limited research on VOCs in Malaysia, the outcomes of this study will be vital for informing nationwide policy and standards for ambient VOCs monitoring.