Air pollution in Asia, which already kills at least 800,000 people each year, will likely lead to even higher death rates as the region's air quality worsens, an environmental group warned Wednesday.

Energy consumption and rising vehicle emissions amid Asia's rapid economic growth are the main driving force behind the region's increasingly acute air pollution, according to air quality group Clean Air Asia.

"What we are worrying is that we are seeing the PM10 concentration (level) is on the rise again," the group's executive director Sophie Punte told a regional conference on air pollution in Hong Kong.

"Seven out of 10 cities in developing Asia are breathing air that is harmful to their health," she told 600 environmentalists and government officials gathered at the "Better Air Quality" conference organised by the group.

PM10 are air particles that are 10 micrometres, or 10 millionths of a metre (0.0004 of an inch), across.

The group says air pollution will rise as the number of vehicles in Asia is expected to exceed one billion by 2035, while its fuel consumption and resulting carbon dioxide emissions will grow by 400 percent compared to its 2005 levels.

A World Health Organization study in 2008 found 800,000 out of 1.3 million premature deaths each year due to air pollution are in Asia, and experts warn the figure could rise if no urgent action is taken.

"Our concern is that as pollution begins to rise, the toll -- which is already significant -- will start to escalate again," US-based Health Effects Institute vice chairman Robert O'Keefe said.

O'Keefe, who is also Clean Air Asia's trustees board chairman, said research had shown the deaths attributed to air pollution could double by 2050 if "business is as usual".

Asian countries like China -- which suffers from industrial pollution, increasing traffic and lax protection measures -- has come under pressure in recent years to tighten its air quality standards.

In Hong Kong, where its famed skyline is often covered in smog, the government has vowed to cut emissions from power plants and phase out polluting diesel vehicles as part of an ongoing effort to tackle air pollution.

Tehran residents urged to escape 'dangerous' pollution
Tehran (AFP) Dec 5, 2012 - Residents of Tehran were on Wednesday urged to leave the city, if possible, to escape a stagnant stew of choking air pollution that officials warned had reached "dangerous" levels.

Health Minister Marzieh Vahid Dastjerdi made the appeal as her services recorded a 15 percent increase in hospital admissions in recent days by people suffering headaches, respiratory difficulties and nausea.

"If Tehran's inhabitants are able to leave the city, it would be good for them to do so," Vahid Dastjerdi was quoted as saying by the Arman newspaper.

The pollution, blamed mainly on the city's bumper-to-bumper traffic, is a constant woe for Tehran's eight million residents.

It often peaks around this time of year, when autumnal weather traps the hazy fumes in the city, which is bordered by mountains acting as a bowl. This year, though, appeared worse than ever, according to some inhabitants.

Authorities effectively called holidays this week, ordering Tehran schools, universities and government agencies closed on Tuesday and Wednesday because of the pollution.

A regular government cabinet meeting in the capital was also cancelled, the Fars news agency reported.

Despite the efforts to reduce vehicle emissions in Tehran, "air quality remains at dangerous levels and the concentration of polluting emissions has increased in the past 24 hours," the head of the city's air monitoring services, Youssef Rashidi, told the ILNA news agency on Wednesday.

The shutdowns to try to contain the pollution are proving costly, economically.

"Each day of holiday in the five biggest cities (Tehran, Mashhad, Isfahan, Arak and Karaj) costs the economy" $275 million, a lawmaker, Mohammed Reza Tabesh, told the ISNA news agency.

Efforts by Tehran officials to boost public transport, including extending the subway lines and establishing lanes for buses only, have barely dented the problem because of the ever-growing number of cars, many of which are inefficient and old.

Western sanctions on fuel imports to Iran have also forced the country to rely on its own production of petrol -- of a lower grade, and therefore more polluting, than in many other countries.

Iran's meteorological services said they expected the worst of the pollution in Tehran to dissipate from Thursday because of forecast rain.