A two-mile thick cloud of pollution shrouding southern Asia is threatening the lives of millions of people in the region, according to a United Nations study.
It said the cloud, a toxic mix of ash, acids, aerosols and other particles, was damaging agriculture and changing rainfall patterns across the region, which stretches from Afghanistan to Sri Lanka.
The lives of millions of people were at risk from drought and flooding as rainfall patterns were radically altered, with dire implications for economic growth and health.
"We have an early warning. We have clear information and we already have some impact. But we need much, much more information," UN Environment Programme chief Mr Klaus Toepfer said.
"There are also global implications not least because a pollution parcel like this, which stretches three kilometres high, can travel half way round the globe in a week," he said.
Mr Toepfer said the cloud was due to forest fires; burning of agricultural wastes; dramatic increases in the burning of fossil fuels in vehicles, industries and power stations; and emissions from millions of inefficient cookers.