About 90% of the global population in 2022 experienced unhealthy air quality, and only six countries met the World Health Organization’s recommendations of safe air pollutant levels, according to a new report from Swiss air quality technology company IQAir.

IQAir measured air quality levels based on the concentration of lung-damaging airborne particles known as PM 2.5. Research shows that exposure to such particulate matter can lead to heart attacks, asthma attacks and premature death. Studies have also linked long-term exposure to PM 2.5 with higher rates of death from Covid-19.

When the WHO first published air quality guidance in 2005, it said the acceptable levels of air pollution were less than 10 micrograms per cubic meter. In 2021, the WHO changed its benchmark guidelines to below 5 micrograms per cubic meter.

The report found that the top five most polluted countries in 2022 were Chad, Iraq, Pakistan, Bahrain and Bangladesh. The most polluted cities globally were Lahore, Pakistan; Hotan, China; Bhiwadi, India; Delhi, India; and Peshawar, Pakistan.