Air quality in the Mexican capital has deteriorated to such an extent that unless emergency measures are taken soon the lives of 1.5 million elderly people and children could be at risk, ecologists say.

As the winter nears, ozone levels in Mexico City have soared to three times the maximum level recommended by the World Health Organization."We must not risk the lives of more than 1.5 million people by turning a blind eye to this emergency," said Juan Manuel Guerra, director of the Autonomous Institute for Ecology Studies.

Pollution has become so acute that new President Carlos Salinas de Gortari was forced to admit the problem in his inaugural address Dec. 1.

"Mexico City dwellers are tired of promises from the government . . . while their children suffer the effects of pollution," he said.

Salinas said he had given immediate orders to federal district authorities to clean up the air.

The warning signs have been evident for more than a year, after birds began falling out of the sky - choked and poisoned as they flew in the smog.

Industry and three million vehicles are throwing up six to seven million tons of toxic matter a year into the Mexico City atmosphere.

Air filter systems are being marketed everywhere. One, called "Protecto Smog," is publicized on the radio with a famous Mexican song "Cielito Lindo (Beautiful Sky)," which is interrupted with the sharp reminder that Mexico City skies are scarcely seen these days.

The grey-brown smog covering Mexico City has thickened this winter and the government has been urging schools to curb sports and joggers to exercise early in the morning.

The measures aim to mitigate the world's worst urban pollution, which is endured by more than 18 million people, but ecologists say the government has shied away from sanctions on polluters and deliberately minimized the problem.

"We have not applied any contingency plan because pollution has not yet hit emergency levels," Urban Development Minister Gabino Fraga Muret said just before the new government took over.

The plan, under which industry would cut fuel oil processing by 30 percent and government vehicles would be taken off the roads, is supposed to take effect when ozone levels hit 200 on the Mexican scale. Between Nov. 9 and 18 they did so on seven days.

Some officials have begun to acknowledge the urgency of the problem. Former Health Minister Guillermo Soberon said late in November a new phase must begin in which pollution measures are energetically applied and sanctions issued to offenders.