The World Health Organization (WHO) maintains that reducing the average outdoor air pollution in a city can lead to substantial long term reductions in mortality.

By reducing the annual mean outdoor concentration of PM10 from 70 to 20 µg/m3, the target level set out in the 2005 WHO Air Quality Guidelines, WHO estimates that 15% of long term mortality (i.e. deaths) from air pollution can be averted. Reaching these lower levels of air pollution will also reduce respiratory and cardiovascular diseases as well as increase life expectancy among local populations.

In addition, action to reduce urban air pollution will also cut emissions of greenhouse gases and other pollutants contributing to climate change. Climate change produces a number of adverse effects on health (other health impacts). This includes those from drought and extreme weather events (e.g. windstorms, floods), such as water-borne and food-borne diseases. It also increases the prevalence of vector-borne diseases like dengue or malaria.