The unrelenting smog here is reaching record levels, leading one expert to warn of an environmental disaster on the scale of the 1952 London fog that killed more than 4,000 people.
Taxi drivers, street vendors and other residents complained Tuesday of watery eyes, hacking coughs and headaches as the pollution by Monday reached three times the level considered safe by international health organizations.
Despite a multitude of measures--from twice-yearly automobile exhaust checks to improved gasoline--ozone and general pollution levels have continued to rise. Both the level of pollution and the number of days with high pollution levels have increased.
A first-stage smog alert has been in effect here since Friday, when authorities ordered factories to cut production by one-third, halved the use of government vehicles and halted street repairs to minimize pollution-causing traffic jams.
Nevertheless, pollution levels have remained high.
A thermal inversion combined with heavy holiday traffic drove ozone levels to a peak of 0.39 parts per million Monday. The level dropped Tuesday but remained high.
An ozone level of 0.35 parts per million is considered dangerous and would prompt officials to declare a second-stage smog alert in Los Angeles. Mexico City does not declare a second-stage alert until smog reaches 0.42 parts per million.
Los Angeles has not experienced second-stage-alert pollution levels since the early 1980s, except for one hour in 1988 in the San Gabriel Valley, according to a spokesman for the South Coast Air Quality Management District.
In contrast, the number of days with ozone levels above the dangerous level here increased from six in 1991 to 10 so far this year. Six weeks ago, a team of environmental researchers measured smog levels on the south side of the city at 0.60 parts per million--comparable to the Los Angeles record set in 1955 and well above the level at which healthy adults are susceptible to asthma attacks.
"Unless we are lucky and the wind starts to blow, we are going to have a disaster comparable to the 1950s London fogs," warned Luis Manuel Guerra, who lead the environmental research team and heads a consulting firm here.
Mexico City--the hemisphere's largest city with 18 million inhabitants--sits in a mile-high mountain valley. Pollution is a problem year-round because of the thin air and the large number of old cars.
Health problems related to pollution--mainly respiratory diseases--have become so severe that the National Human Rights Commission has taken up the cause, developing recommendations last year and sending government agencies reminders about them in recent weeks.
In 1952 in London, a freakish combination of foul weather (fog and a thermal inversion) and the practice of burning heavily sulfurous coal resulted in an environmental catastrophe that forever altered public perceptions about the problem of air pollution. The choking air severely limited visibility and claimed more than 4,000 lives. Most victims had previously suffered cardiopulmonary disorders. But many children also died in the crisis, which led Britain to take major steps to control pollution.