A new study has found that people living in South and Central Asia experience some of the highest levels of air pollution in the world .
The air in these areas has the highest amounts of the most kind of air pollution .
A micron is one millionth of a meter .
PM2.5 is so small that it can enter human lungs and the blood .
The Switzerland-based company IQAir released its latest study on Tuesday .
The company operates an air quality information system .
The yearly IQAir reports began in 2017 .
Glory Dolphin Hammes is chief of IQAir North America .
She told VOA : "PM2.5 actually kills more people than any other air quality pollutant .”
Based on data from IQAir's worldwide network , Bangladesh is the country with the highest levels of PM2.5 air pollution .
Chad , Pakistan , Tajikistan and India are also among the five nations with the lowest air quality .
IQAir found that New Delhi , India , is the capital city with the most PM2.5 pollution .
Dhaka , Bangladesh ; N'Djamena , Chad ; Dushanbe , Tajikistan ; and Muscat , Oman , are the other capital cities rated as having extremely polluted air .
People seeking the world's cleanest air will find it in the French overseas territory of New Caledonia .
The territory's main city , Noumea , is at the top of IQAir's clean air ranking .
Other places where the air is very clean include the U.S . Virgin Islands and Puerto Rico in the Caribbean .
Cape Verde , in the Atlantic Ocean off the coast of Africa , also has very little air pollution .
Some parts of the developing world lack enough monitoring , Dolphin Hammes said .
Those areas include parts of Africa , the Middle East and South America .
Developed countries usually have a greater number of air quality monitors than developing countries and areas .
Monitoring is at a higher level than in past years in some countries , she said .
In 2021 , air pollution levels increased from those of a year earlier : the first year of the COVID-19 pandemic .
In 2020 , the world saw a decrease in air pollution because of less ground and air transportation .
Another reason for the rise in air pollution last year was an increase in wildfires , Dolphin Hammes said .
The WHO said the reduction would prevent millions of deaths worldwide .
Scientists supported the new recommendations .
But they worry that some countries would have trouble reaching them .
Much of the world was already failing to meet the 10-microgram limit , Reuters news agency reported .
IQAir's yearly reports are based on PM2.5 measurements from what is now a total of 6,475 cities in 117 countries , regions and territories .
The worldwide information comes from "tens of thousands of regulatory and low-cost air quality monitoring stations ,” the company said .
The stations are operated by governments , nonprofit organizations , research centers and citizen scientists .