New research suggests that disease from air pollution has increased in the last 25 years, and prevention measures in the most polluted countries are needed to prevent more loss of life.
An international study has found air pollution caused 4.2 million deaths in 2015, making it the fifth biggest health risk factor for that year. 
The findings come from an analysis of data from the 2015 Global Burden of Diseases study, funded by the Bill & Melinda Gates Foundation. 
Exposure to ambient air pollution increases morbidity and mortality, and is a leading contributor to global disease burden. To find out just how great this burden is, experts have estimated global population-weighted mean concentrations of particle mass with aerodynamic diameter less than 2·5 μm (PM2·5) and ozone at an approximate 11 km × 11 km resolution with satellite-based estimates, chemical transport models, and ground-level measurements. 
Using integrated exposure–response functions for each cause of death, the team was able to estimate the relative risk of mortality from ischaemic heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, lung cancer, and lower respiratory infections from epidemiological studies using non-linear exposure–response functions spanning the global range of exposure.
They found that ambient PM2.5 was the fifth-highest mortality risk in 2015, causing 4.2 million deaths, up from an estimated 3.5 million in 1990. 

The team suggests that this increase was due in part to increasing air pollution in low and middle income countries in particular. 

The modelling suggests that reduction in this mortality rate is possible even in the most polluted countries, if PM2.5 values are decreased substantially.