Saturday, October 16, 1999 Published at 09:19 GMT 10:19 UK
Mexico pollution alert
Mexico City: shadowy skyline
By the BBC's Mexico correspondent, Peter Greste
The authorities in Mexico City are taking action against pollution levels that have become quite literally breathtaking.
The city's health officials declared a general pollution alert when they found the ozone levels had reached 272 micrograms per cubic metre - almost triple the 100 micrograms that most industrialised countries consider to be the maximum acceptable.
But now is the time when people normally feel they can breathe easy.
Meteorologists say an unusually clear dry spell has helped attract huge amounts of ozone into the Mexico City basin.
Buildings several blocks away are now just shadowy outlines.
But the authorities have acted: by declaring the alert, they triggered an all too familiar drill.
They have ordered hundreds of thousands of cars off the streets and told factories to work at 30% capacity to fight soaring pollution levels. Hundreds of thousands of cars are off the streets and factories have cut production.
But environmentalists say what is really needed is drastic action to reduce the four million tonnes of toxic emissions released into the air each year.