Implications of photochemical losses of VOCs: An integrated approach for source apportionment, ozone formation potential and health risk assessment

The increasing ozone (O₃) concentration has received significant attention recently, yet the health risks posed by volatile organic compounds (VOCs) cannot be ignored. Accurately identifying the primary sources of VOCs contributing to health risks and O₃ formation has been challenging due to their high reactivity with oxidants in ambient air. This study conducted field measurements of VOCs seasonally and diurnally in an urban area of central Taiwan, aiming to elucidate the effects of photochemical loss of VOCs on the source apportionment of O₃, as well as health risks of VOCs under different levels of O₃. The results revealed that O₃ formation was sensitive to VOCs, which was diagnosed using the regional threshold of the observed VOCs/NO_X ratio and was further supported by a significant positive correlation between O₃ concentrations and initial O₃ formation potential. The dispersion normalized positive matrix factorization model, applied to initial mixing ratios of VOCs, identified six VOC sources, with the synthetic rubber industry and solvent usage being prominent contributors to O₃ formation potential. A source-attributed health risk assessment approach was developed that incorporates the effects of photochemical losses and observed mixing ratios of VOCs, enabling a more accurate evaluation of health risks from different sources. Non-carcinogenic risks associated with VOC sources remained within acceptable thresholds, while the carcinogenic risks posed by vehicle exhaust and solvent usage were above acceptable levels, particularly on O₃ non-polluted days. This study highlights the importance of establishing concurrent control strategies for VOCs and O₃ to effectively mitigate air pollution and improve public health.