EnvironmentNews Most Spanish cities exceed WHO’s new nitrogen standard by Lorraine Williamson Published: September 24, 2021 Published: September 24, 2021 MADRID – The World Health Organisation (WHO) recently lowered the threshold for a safe concentration of nitrogen dioxide (NO2) in the air. But 7 of the 80 largest Spanish cities have NO2 concentrations in the air that fall within this new standard. Read more