Mitigating the Air Pollution Effect? The Remarkable Decline in the Pollution-Mortality Relationship in Hong Kong

Using transboundary pollution from mainland China as an instrument, we show that air pollution leads to higher cardio-respiratory mortality in Hong Kong. However, the air pollution effect has dramatically decreased over the past two decades: before 2003, a 10-unit increase in the Air Pollution Index (API) could lead to a 3.1% increase in monthly cardio-respiratory mortality, but this effect has reduced to 0.5% using recent data and become statistically insignificant. Exploratory analyses suggest that a well-functioning medical system and immediate access to emergency services can help mitigate the contemporaneous effects of pollution on health