Researchers say a thick, smoky haze caused by man-made forest fires in Indonesia is the likely cause of more than 100,000 premature deaths in the country, as well as neighboring Malaysia and Singapore.
Scientists from Harvard and Columbia universities, using a complex analytical model, came up with a death toll that far exceeded Indonesia's official toll of just 19 deaths from the smog.
The study is scheduled to be published in the journal Environmental Research Letters.
The fires are set annually in Indonesia's forests and on carbon-rich peat land as quick and cheap ways to clear land for palm oil and pulpwood plantations.
Rajasekhar Bals, an environmental engineering expert at the National University of Singapore, told the Associated Press the study is hopefully a "wake-up call" for Indonesia to take action to curb the fires and for regional cooperation to deal with the fallout on public health.
The haze has strained relations between Indonesia and its neighbors.
Researchers estimated there were 91,600 deaths in Indonesia, 6,500 in Malaysia and 2,200 in Singapore from the haze.
Greenpeace said the study is "groundbreaking," but also cautioned that the approximated death toll is a "conservative estimate."
The study did not include the impact the haze has on children and future generations.
Nursyam Ibrahim, from the Indonesian Medical Association's West Kalimantan chapter, said "We are the doctors who care for the vulnerable groups exposed to toxic smoke in every medical center, and we know how awful it is to see the disease symptoms experienced by babies and children in our care."
Last year's fires were the worst since 1997.