Project No: 16308722

Title: Rethink ozone management - modification of the EKMA diagram to quantify the overall health effects of NOx and VOCs emission controls and its implication for decarbonization

Principal Investigator: Prof. Alexis LAU

Co-Investigator: Dr. Changqing LIN


Since the implementation of the clean air plan in 2013, ozone (O3) pollution has become prominent in China. Conventional guideline to address the O3 pollution issue relies on a deep cut in volatile organic compounds (VOCs) emission in a region deemed to be VOC-limited. This guideline is experiencing great challenges due to the widespread nature of VOCs emission sources. Compared to the VOCs, NOx emission control exhibits several different features. First, NOx emission control measures align closely with national decarbonization policies because stringent controls of combustion sources are expected to substantially reduce both carbon and NOx emissions. Second, as a common precursor of both O3 and particulate matter, the reduction in NOx emission would bring co-benefits on reducing concentrations of both pollutants. Third, a subsequent transition to the NOx-limited regime is helpful for O3 attainment in the long run. From a health protection perspective, which is the key objective of pollution controls, health burden caused by the increasing O3 can be offset by health benefits brought by the decreasing nitrogen dioxide (NO2). In this new era of achieving carbon neutrality, the proposed study rethinks the ozone management guideline and aims to explore the overall health effects of NOx and VOCs emission controls. The empirical kinetics modeling approach (EKMA) diagram has been widely used to examine the dependence of O3 concentration on VOCs and NOx emissions. The proposed study will focus on changing the assessment paradigm of O3 pollution control from using concentrations to using health risks. To accomplish risk evaluation, time-series analyses will be performed based on long-term local health data to estimate the risk coefficients of different air pollutants. These risk coefficients, along with the Air Quality Health Index model in Hong Kong, will be used to evaluate the overall health risk of pollution mixtures (e.g., from decreasing NO2 and increasing O3). Based on the O3 EKMA diagrams, we will develop health risk EKMA diagrams to explore the dependence of the health risks of pollution mixtures on variations in pollutant emissions. Spatiotemporal variations in the sensitivity of health risks toward emission variations in Hong Kong and the Greater Bay Area of China will be analyzed. The health risk EKMA diagrams will then be applied to explore the net health effect of pollution variations toward carbon neutrality by 2060. The project’s deliverables will provide positive incentives for policy makers to improve air pollution control and climate change mitigation strategies.