Mexico City Extends Tighter Curbs on Smog : Pollution: Cars and industries are affected. The capital plays down the dangers, suggests taking vitamins.

After the worst week of ozone-laden smog in Mexico City’s history and a weekend that brought no relief to this smothered capital, the government Monday indefinitely extended stiff restrictions on driving and industry.

At the same time, however, city officials played down the danger of the pollution, pointing out that its lead, sulfur and carbon monoxide contents are under control.

And the Health Ministry weighed in with its recommendations for living in the noxious air: Tune up your car, close your windows and take vitamins “to counter the oxidizing agents that ozone produces in the organism.”

Indeed, throughout the city, the smog seemed to set eyes and lungs afire. Residents seeking relief from the capital Saturday had to drive north through an industrial inferno for nearly an hour before sighting blue sky and smelling fresh air.

On March 16, ozone levels in the city hit a record 398 points on the government’s Imeca scale, or 0.42 parts per million. That is 3 1/2 times the U.S. federal standard of 0.12 parts per million and the equivalent of a second stage smog alert, which has not occurred in the four-county South Coast Air Quality Management District in the past six years.

The AQMD would call a second-stage alert at 0.35 parts per million and a third-stage alert at .50.

On Friday, Mexico City’s ozone reading hit 360 points, and in the most afflicted area of the capital, its southern neighborhoods, five elementary school children were rushed to a hospital after experiencing breathing difficulties, according to police officials who had evacuated them from the playground of the Simitrio Ramirez Primary School. They were held overnight, then released.

Street vendors who normally peddle stuffed animals and chewing gum at busy intersections hawked surgical masks instead. Several cab drivers and pedestrians were seen wearing the blue paper masks.

The government imposed weekend driving restrictions for the first time on Saturday and Sunday but proceeded with the city’s annual spring parade, allowing children to march down traffic-choked Insurgentes Boulevard, the main north-south road bisecting the city.

Thousands of spectators also turned out to breathe exhaust fumes at the Mexican Grand Prix Formula One race on the edge of the capital.

On Monday morning, the valley in which the city sits, 7,000 feet above sea level and surrounded by mountains, remained shrouded in a bank of acrid smoke. In the course of the day, the ozone reached 229 points on the Imeca scale or about 0.25 parts per million.

Because of the record pollution, Mayor Manuel Camacho extended a ban on 40% of the city’s nearly 3 million automobiles until the climate improves. That is double the number of vehicles normally banned from the roads each day.

Under the system begun two years ago, all vehicles were issued a color-coded sticker based on the last digit of its license plate, and each weekday, cars with stickers of a specific color were banned from the streets. On Fridays, for example, cars with blue stickers could not be driven.

Officials estimated that this cut driving by about 20%.

Now, the ban applies to two colored stickers each weekday, and the limitations have been extended to weekends. This means drivers cannot use their cars two and sometimes three days a week.

In addition, 225 industries in the metropolitan area are required to operate at only 70% of their production capacity. There have been no estimates of the economic cost of the cutbacks so far.

“We are determined to make the necessary decisions, independent of the costs, in order to protect the environment,” said Fernando Menendez, the mayor’s smog expert. “These measures will be in effect as long as we have adverse conditions of dispersion. We have a stationary atmosphere, heat and no winds. There is a pressure (system) over the capital like a cap.”

Trying hard to find improvement, he and the mayor both stressed the good news about the capital’s air quality.

“Our unleaded gas has reduced lead, sulfur and carbon monoxide,” Menendez said. “We don’t have the daily cocktail of contaminants that we used to. No other city, not even Los Angeles, has been able to do that in two years.”

That provided little comfort to those suffering from burning eyes, hacking coughs and headaches, however. For residents of the capital, coping with the smog is a constant. Those who can afford to do so use air filters and air conditioning and find ways to exercise indoors; many who cannot afford to do those things say they work hard to put the foul air out of their minds.

President Carlos Salinas de Gortari is expected to announce today the closure of several industries in Mexico City and new restrictions on others.

Industrial leaders had complained about the government-ordered cuts in production last week, saying that industries produce only 4% of the capital’s smog.

“The worst contaminating agents are the automobiles,” Vicente Gutierrez, president of an industrial chamber, was quoted as saying.