Modelling public health benefits of various emission control options to reduce NO2 concentrations in Guangzhou

The local government of the megacity of Guangzhou, China, has established an annual average NO 2 concentration target of 40 μ g m −3 to achieve by 2020. However, the Guangzhou Ambient Air Quality Compliance Plan does not specify what constitutes compliance with this target. We investigated a range of ambition levels for emissions reductions required to meet different possible interpretations of compliance using a hybrid dispersion and land-use regression model approach. We found that to reduce average annual-mean NO 2 concentration across all current monitoring sites to below 40 μ g m −3 (i.e. a compliance assessment approach that does not use modelling) would require emissions reductions from all source sectors within Guangzhou of 60%, whilst to attain 40 μ g m −3 everywhere in Guangzhou (based on model results) would require all-source emissions reduction of 90%. Reducing emissions only from the traffic sector would not achieve either interpretation of the target. We calculated the impacts of the emissions reductions on NO 2 -atttributable premature mortality to illustrate that policy assessment based only on assessment against a fixed concentration target does not account for the full public health improvements attained. Our approach and findings are relevant for NO 2 air pollution control policy making in other megacities.