HONG KONG: Hong Kong's air pollution soared to record levels Monday, the Environmental Protection Department said, warning that a toxic stew enveloping the city was a danger to the public.

The government agency said it found Air Pollution Index (API) readings that in one case were double the level that the general public is advised to stay indoors or avoid prolonged exposure to heavy traffic areas.

"Today's API is at record high levels," an agency spokeswoman said in an email to AFP.

Hong Kong's famed skyline and harbour is often shrouded in a blanket of haze which has been criticised as a public health disaster and blamed for driving some expatriates away from the international financial hub.

In July 2008, the city's environmental agency recorded air pollution levels as high as 202, it said, well below Monday's record numbers which ranged from a low of 179 to a record 413 reading at one roadside station.

"As the sandstorm from northern China is moving southward with the northeast monsoon and is now affecting Hong Kong, the Air Pollution Index is expected to reach the "very high" or "severe" level," it said in a statement.

On the API index, people with heart or respiratory problems are advised to stay indoors at a reading of more than 100. The public is advised to stay indoors or avoid prolonged exposure to heavy traffic areas at more than 200.

On March 5, a group of businesses - including Starbucks, Pacific Coffee, Ben & Jerry's and Pure Fitness ' launched an unprecedented petition campaign to combat Hong Kong's worsening air pollution.

The organisers also ran ads in newspapers, warning that the city's smog "kills three people a day" and its air is "three times dirtier than New York City's."

Data from the Hong Kong Observatory on March 2 showed that the annual number of hours of "reduced visibility" - defined as visibility of less than eight kilometres (five miles) in the absence of fog, mist or rain - skyrocketed to 1,139 last year from 295 in 1988.

Authorities often blame deteriorating air quality on emissions from the southern Chinese factory belt over Hong Kong's northern border.

But a study by the Civic Exchange think-tank last year said that Hong Kong's own road emissions were the dominant source of air pollution in the densely populated city of seven million.