Chris Johnson, Singapore – Choking yellow-grey smog over Southeast Asia has already closed factories, cancelled flights and lengthened queues in doctors' waiting-rooms.
But much worse could be in store if the raging forest fires across Indonesia are not put out soon – and for good.
Business executives and analysts say tourists may shun the entire region, badly damaging a US$26 billion dollar industry, if it gets a reputation for polluted air during the September-November season.
"If it is a constant thing, the whole area at that time of the year will be a no-go zone," said John Koldowski, director of strategic information at the Pacific Asia Tourist Association.
Industry is only beginning to count the cost of the fires, which have now been burning across Indonesia's Sumatra and Kalimantan for three months. Analysts say the total bill for the disaster is likely to run into billions of dollars.
They note a growing anger that the problem is partly self-inflicted, since many of the fires were caused deliberately to clear forests for agriculture or plantations.
Aside from accidents in which smog has been a factor – at least two shipping collisions and the crash of a Garuda Indonesia aircraft which killed all 234 people on board – experts say a big casualty will be lost working days.
Some 20 million people live in the worst-affected parts of Indonesia and many millions more in the east Malaysian state of Sarawak and the cities of Kuala Lumpur and Singapore, which have been blanketed by the suffocating pollution.
Although the onset of the northerly monsoon has now begun to blow the smoke away from some of these areas, many cities continue to report outbreaks of breathing disorders and skin ailments as a result of the poor air quality.
Singapore's air Pollutants Standard Index (PSI) was at unhealthy levels for much of the last week with the three-hour measurement reaching a peak of 175 at 1100 GMT on October 23.
A reading of zero to 50 is considered good, 51-100 moderate, 101-200 unhealthy and 201-300 very unhealthy.
The Singapore Environment Ministry advises the old and sick to stay indoors and all citizens to avoid vigorous outdoor activities while the PSI is in the unhealthy range.
"We estimate that hospital visits for upper respiratory type problems were up two to three times above their normal levels when the smog was at its worst in Indonesia," said Steve Tamplin at the World Health Organisation Philippine's office in Manila.
"This has an impact on days off work but we are just now beginning to collect the data," he said.
The picture in Singapore was similar with some hospitals reporting a doubling of respiratory complaints.
"This would mean a significant decline in man-hours because people are falling ill and calling in sick," said Keven Scully, managing director of Schroder Securities in Singapore.
The smog has reduced visibility across the region, closing at least a dozen Indonesian airports and delaying or halting completely air traffic to and from some Malaysian cities.
Malaysia Airlines System (MAS) says it has lost 6.5 million ringgit ($1.95 million) due to cancellations of flights caused by the smog. A total of 890 domestic flights and 34 international trips were scrapped last month alone.
Other airlines, including Singapore's Silkair and Garuda, have also been hit by the poor visibility.
The effect on tourism appears to have been almost immediate and threatens to be much more long-lasting.
Industry executives say Southeast Asia's inter-regional tourist industry was already suffering from the collapse in the region's currencies and the air pollution is now also reducing visits from some long-haul origins.
Some of Singapore tourist hotels report bookings down by as much as a third and five-star hotels have reported a reduction in business customers. Singapore's Ritz-Carlton, one of the city's most expensive hotels, says occupancy rates are down 10 percent.
Hoteliers say they expect to be able to ride out the problem this year and hope the seasonal rains will put out the fires in Indonesia by December.
Their nightmare scenario would be for the fires to keep smouldering or to be started again next year, destroying the essential tourist brochure image of sunshine and sandy beaches.
"Reputation for blue skies is vital," Citibank said in its monthly Asian Market View. United Nations climate experts in Geneva said on Friday that rains in Indonesia could be delayed far beyond the normal start of the monsoon due to the El Nino phenomenon, a periodic upswelling of warmer water in the Pacific Ocean which distorts normal weather patterns.
One climate scientist said the rains could be suppressed for three months.
Koldowski said the long-term effect will depend on whether the problem persists or recurs next year.
"The media are issuing stories on the problem throughout Europe and the U.S.," he said. "It is no longer a localised problem. It's obvious to the whole world."