The World Health Organisation's representative in Indonesia said yesterday that the health of thousands of people would be affected by smog enveloping large tracts of South East Asia.
"When you have these levels of pollutants in the air, there are increases in acute respiratory ailments, including pneumonias, and in asthma," said Mr Robert KimFarley. "There are also long-term effects from carcinogens, which will be known 20-30 years down the line."
He said the number of people suffering from the catastrophe ran "certainly into the thousands".
International relief organisations have begun to assess the smog disaster and how best to use the offers of aid which have begun pouring in, officials said.
Weeks of prayers asking for wind and rain in Borneo and Malaysia to clear the choking toxic haze were finally answered yesterday. But the polluted smog remained as thick as ever in other parts of South East Asia, prompting many foreigners to flee.
Life returned to near normal for the first time in weeks in the city of Kuching in the Malaysian half of Borneo and the air pollutant index dropped by almost one third in the capital, Kuala Lumpur.
Mohammad Dfari, a Muslim preacher in Kuching, said: "We are all rejoicing. Our prayers have been answered. I am looking at blue sky, and sunshine pouring in through my front door. I cannot tell you how happy I am."
For weeks the city has endured thick smog caused by raging forest fires in Sumatra and Kalimantan lit by palm oil plantation owners wanting to clear land. Health experts say that breathing the toxic cocktail of smoke, sulphur dioxide, carbon monoxide and other chemicals was equivalent to smoking more than 50 cigarettes a day.
Meteorologists in Jakarta however warned against celebrating too much. The winds are predicted to swing round to the south and east and bring more smog from Indonesia.
In Sumatra the haze remained as thick as ever. The Caltex oil company, a joint venture between Texaco and Chevron, evacuated hundreds of employees, their families and patients in company hospitals from its bases in the province of Riau in the west of the island.
Indonesian plantation owners are refusing to take responsibility for the crisis but yesterday they contributed £154 million to the fire-fighting fund. The government is also saying it should not be blamed. Ministers have said it is a natural disaster and that neighbouring countries should not sue Jakarta, as Malaysian opposition politicians have suggested.
In the city of Medan grieving relatives wept uncontrollably as unidentified victims of Indonesia's worst plane crash, in which all 234 people aboard died, were buried in a mass grave.
The search continued for the plane's black box recorders to determine the cause of Friday's crash, which occurred minutes after the pilot of the Airbus A300B4 reported low visibility because of a smoky haze.
Aviation experts in Japan discounted the theory that zero visibility in dense smog could have caused the crash, but have not ruled out the possibility of engine failure caused by smog intake.
"Haze is an ordinary thing for pilots," said Mr Shadrach Nababan, the head of the Garuda Indonesia Communications Forum for Pilots. "There are instruments in the plane and on the ground which can be used." The bodies were buried alongside another mass grave containing 62 unidentified victims of a 1979 air crash in North Sumatra.