On top of Victoria Peak in Hong Kong, groups of tourists find themselves staring down at an apocalyptic vision of a towering city clouded in a menacing grey smog.
The haze blurs one of the world's most famous skylines and veils the ships dotting the harbour, disappointing visitors who made the trip to the Peak for a glimpse of what can be a spectacular panorama.
When a scene like this was captured on the cover of the Hong Kong edition of the "Lonely Planet" travel guide in 2002, shocked and embarrassed policymakers claimed the image did not truly reflect the southern Chinese city.
But a hazy sky has become an inescapable part of life for Hong Kong's population of seven million.
Statistics from the Hong Kong Observatory show that the annual number of hours of "reduced visibility" jumped from 295 in 1988 to 1,100 in 2008.
The term refers to visibility of less than eight kilometres (five miles) in the absence of fog, mist or rain.
"Blue skies are very rare in Hong Kong today," Professor Anthony Hedley of the Department of Community Medicine at the University of Hong Kong told AFP.
"There are very few days in which our air quality meets the safety guidelines promulgated by the World Health Organisation."
The haze in Hong Kong is formed by a combination of particles and gases generated by power plants, ships, vehicles and tens of thousands of factories in neighbouring Guangdong province in mainland China, experts say.
"It is a very toxic cocktail. The suspended particulates are so fine that they can penetrate to the very lowest region of our lungs, even cross into our (blood) circulation and damage our arteries as well as the air sacs," Hedley said.
Natural mist or fog was only a tiny component of the haze in times of high humidity, he said.
The problem is particularly acute in a city as densely packed as Hong Kong, as pollutants are often trapped between the buildings.
Although the government has in recent years pledged increased efforts to clean the air, critics say it is not aggressive enough.
"At this rate we are going, it's going to be 50 years before we get clean air," Hedley said.
The professor and a team at the university launched the Hedley Environmental Index last year to provide real-time measurements of the health and financial impacts of air pollution in Hong Kong.
The index showed that between January and mid-December this year health care and lost productivity related to air pollution illnesses had cost the city about 1.8 billion Hong Kong dollars (231 million US).
The team estimated that a total of 5.9 million doctor visits and 793 premature deaths were related to air pollution over the same period.
Hedley said he had found a direct correlation between visibility and health in his latest research.
His findings, due to be released within a few months, will allow anybody to estimate the number of expected air pollution-related deaths based on the visibility level on that day.
Meanwhile, another group of environmental scientists is travelling to all 18 districts of the city in a van to measure daily roadside pollution levels. One of their objectives is to compare their data with those collected by the government's roadside air quality measuring stations.
Chak Chan, acting head of the environment division at Hong Kong University of Science and Technology and leader of the project, said the levels of carbon monoxide, sulphur dioxide and nitrogen dioxide they recorded in Central -- the city's business hub -- were often two or three times higher than the government figures.
"We believe our measurements can more accurately reflect the roadside situation because ours is a mobile measuring device and theirs are mounted at fixed spots," Chan told AFP.
A spokesman for the Environmental Protection Department said air pollution was a regional problem.
"Reduced visibility is part of the regional air pollution problems in the Pearl River Delta region," he said in a statement to AFP.
However, a study conducted by the Civic Exchange think-tank showed that Hong Kong's own emissions -- not those from the factories in mainland China -- are the dominant sources of air pollution, affecting the city 53 percent of the time.
Although the government in 2006 imposed a requirement for newly-registered vehicles to meet European vehicle emission standards, Civic Exchange found that 99 percent of the 6,000 franchised buses are below the Euro IV standard.
Christine Loh, chief executive of Civic Exchange, warned that dirty air is now driving away the people who are instrumental to the success of the city.
"The biggest shocker of all was that our surveys showed that half a million Hong Kong people -- usually in the professional classes -- are planning to leave because of air pollution," she said.
Hedley urged Hong Kong people to pressure the government to take faster and more aggressive action.
"My advice to Hong Kong people is to write to the chief executive and tell him we want clean air now," he said. "We are all paying a heavy cost for it."