Only about one in 10 urbanites across the world are breathing air that can meet the recommended safety levels set by the World Health Organization (WHO). Indian city-dwellers have it the worst, according to newly released statistics.

An updated version of the WHO's urban air database revealed earlier this week details the average air quality of nearly 1,600 cities across 91 countries.

Fifty percent of all urban citizens who were monitored across the globe are breathing air containing pollution levels that are at least 2.5 times higher than WHO recommended levels, according to an analysis of the database conducted by WHO experts prior to its release. Breathing air of such poor quality puts these people at additional risk of long-term health problems such as respiratory disease and unrestful sleep - a condition associated with oxygen deprivation during sleep.

Analysts also found that a mere 12 percent of the world's urbanites are living in cities reporting air quality that complies with the same WHO air-pollution guidelines.

Officials from India have already denied the statistics of this year's database, telling Reuters that the air or the city of Delhi -which was found to have the dirtiest air among all the world's urban regions - simply cannot be as dangerous as the WHO claims.

But Delhi is only one of India's worries. Of the top 20 most air-polluted cities in the world, 13 were found in India.

Still, some public health advocates are welcoming the study. The Center for Science and Environment (CSE) issued a statement on Thursday praising the WHO data and expressing their hope that such information will force the Indian government to take actions towards a cleaner urban environment.

The CSE also used the release as an opportunity to directly challenge India's Auto Fuel Policy Committee, which has been delaying setting uniform emissions standards for years. Many experts suggest that India's significant air pollution problem is cause by largely unregulated gasoline and diesel toxicity levels.

However, not every bit of the report is bad news. This year's version of the database contains information on about 500 more cities than the previous database released in 2011. According to the WHO, this reflects a "growing recognition of air pollution's health risks," as the database only includes data from regions that bother to monitor their outdoor air quality in the first place.

The WHO press release which revealed this year's updated database was published on May 7.