For a month Mike Yamashita and I tracked the burning, experiencing its baleful effects. Then, shortly after I returned home, I began feeling as though my head were stuffed with cotton batting. I became dizzy and even fell down the stairs. I couldn't concentrate. One doctor guessed that pollution had affected the inner ear, disturbing my balance. I recalled that a farmer I'd spoken with had complained of similar problems. After two months my symptoms cleared up.

Accompanied by a pair of local guides and a succession of truck drivers and boat and ferry pilots, we traveled some 1,200 miles in Kalimantan through smoke and fire. We also visited the Malaysian capital, Kuala Lumpur, one of Southeast Asia's most glittering cities. Even in normal times this low-lying city contends with industrial and automotive pollution. But Kuala Lumpur was in the flight path of the smoke coming across the South China Sea from Indonesia, and its residents were choking beneath a smelly, yellow-gray shroud.

As we drove through the jungle of Indonesian Borneo, rarely were we out of blackened terrain. Often we were ringed by open flames and smoldering peat, which pumped out particularly noxious smoke. Mike, ever mindful of light levels, pointed out that even though we were astride the Equator, the sun never pierced the smog sufficiently to cast a shadow. When the sun was at all visible, it seemed as small and pale as a brassy sequin pasted to a sheet of gray cardboard. Early mornings, midday, and late afternoons were indistinguishable—just gray. Visibility was so limited that we were continually startled by motorcycle and bicycle riders, cars, trucks, and pedestrians suddenly popping out of the gloom. Only a few wore flimsy cloth or paper masks, largely ineffective against the poisonous air.

One evening in the market town of Ketapang, a clerk at the Taruna hardware store was hanging a dozen paper masks on a wooden rack. This was the only shipment received in four months, and he doubted he'd sell many.

"We haven't been told about the haze being harmful," he said. "I don't think it's dangerous."

The next morning I couldn't see more than 20 yards up Jalan Merdeka, the main street. Children in blue-and-white uniforms held rags to their noses as they jounced along behind their parents, who were scootering them to school. The hardware man reported that he'd sold two masks.

We drove for hundreds of miles at a stretch, past rows of spiky green oil palms, some as tall as two-story buildings. At first the plantations seemed attractive, the trees heavy with clusters of the purple egg-size fruit that is the source of the rich oil. But as we traveled on, it became evident that entire forests had been destroyed to make way for these industrial gardens and that thousands more acres were going up in flames daily.