A new study by Stanford University suggests that air quality for countries across the world would deteriorate even further in 21st century. Main reason behind the worsening act would be the occurrence of atmospheric stagnation events.

Many regions could experience more frequent pollution exposures that may lead to a rise in cardiovascular and respiratory illnesses. "The World Health Organization estimates 3.7 million premature deaths per year are attributable to poor air quality. As such, it's a substantial public health issue facing the world today", said first author Daniel Horton.

In the new study, resaerchers have focused on air stagnation. It is a condition in which pollutants can collect in the atmosphere. Researchers wanted to know the frequency and duration of future stagnation events.

For which, Diffenbaugh's group used the National Climatic Data Center's air stagnation index and applied the same to the collection of global climate models using computers to mimic earth's climate and environmental condition in the 21st century.

Researchers focused on a scenario that assumed that greenhouse gas concentrations would accumulate in the atmosphere at the same. By which, the global mean temperature will increase around 4 degrees Celsius by the year 2100.

Researchers got to know that more frequent air stagnation will affect areas in late 21st century covering around 55% of the current global population. Some regions will experience even stagnations like up to 40 stagnation days per year.

Not only the frequency, but duration of the event would also increase, said researchers. Researchers said the trend could impact the level of pollutant management needed to meet air quality targets.