The World Health Organization (WHO) on Wednesday strengthened its air quality guidelines, saying air pollution is now one of the biggest environmental threats to human health, causing seven million deaths a year.
It said urgent action was needed to reduce exposure to air pollution, ranking its burden of disease on a par with smoking and unhealthy eating.
The WHO’s new guidelines recommend air quality levels for six pollutants, including ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide.
The other two are PM10 and PM2.5 — particulate matter equal or smaller than 10 and 2.5 microns in diameter.
Both are capable of penetrating deep into the lungs but research shows PM2.5 can even enter the bloodstream, primarily resulting in cardiovascular and respiratory problems, but also affecting other organs, said the WHO.
In response, the PM2.5 guideline level has been halved.