For several months during the unusually dry El Niño winter of 1997-98, a thick pall of smoke covered much of Southeast Asia. Generated primarily by thousands of forest fires on the Indonesian islands of Kalimantan (Borneo) and Sumatra, the smoke spread over eight countries and 75 million people, covering an area larger than Europe (fig. 1). The air quality in Singapore and the city of Kuala Lumpur, Malaysia, just across the Strait of Malacca from Indonesia, was worse than any industrial region in the world. In towns such as Palembang, Sumatra, and Banjarmasin, Kalimantan, in the heart of the massive conflagration, the air pollution index frequently passed 800, twice the level classified in the United States as an air quality emergency, hazardous to human health.