Only 12 per cent of the people living in cities for which air quality data is available, are breathing “safe” air, reveals World Health Organization’s Urban Air Quality database.

About half urban population being monitored is exposed to air pollution that is at least 2.5 times higher than the levels recommended by the WHO, putting those people at additional risk of serious, long-term health problems.

According to the WHO, air quality in most cities worldwide that monitor outdoor (ambient) air pollution fails to meet the organisation’s guidelines for safe levels.

WHO’s Urban Air Quality database that covers 1,600 cities across 91 countries has revealed that more cities worldwide are monitoring outdoor air quality, reflecting growing recognition of air pollution’s health risks. More than 120 Indian cities, including Delhi, Mumbai, Ahmedabad, Agra and Varanasi also figure in the list of cities with high pollution levels.

In most cities where there is enough data to compare the situation today with previous years, air pollution is getting worse. The factors contribute to this increase are reliance on fossil fuels such as coal-fired power plants, private transport motor vehicles, inefficient use of energy in buildings and the use of biomass for cooking and heating.

But some cities are making notable improvements, demonstrating that air quality can be improved by implementing policy measures such as banning the use of coal for “space heating” in buildings, using renewable or “clean” fuel for electricity production and improving efficiency of motor vehicle engines.

The latest available data have prompted WHO to call for greater awareness of health risks caused by air pollution, implementation of effective air pollution mitigation policies and close monitoring of the situation in cities worldwide.

In April 2014, WHO issued new information estimating that outdoor air pollution was responsible for deaths of some 3.7 million people under the age of 60 in 2012. The organization also emphasised that indoor and outdoor air pollution together are among the largest risks to health worldwide.

Measurement of fine particulate matter of 2.5 micrometers or less in diameter (PM2.5) is considered to be the best indicator of the level of health risks from air pollution.

In high-income countries, 816 cities reported on PM2.5 levels with another 544 cities reporting on PM10, from which estimates of PM2.5 can be derived.