One illustration of the seriousness of Mexico City's air pollution problem is the fact that it is a world center for research into bronchial and other respiratory ailments.

Sixty per cent of that orange-brown haze hovering over the capital at least half the year is created by cars, buses and trucks that blow their poisonous fumes freely into the air. (City authorities say the area has 1.5 million vehicles of its own and another half million floating vehicles). Private cars, often 10 years old, as well as trucks and buses owned by the federal and city government, are equally guilty.

The second sinner is industry. While Mexico City is the nation's main industrial center, factories rarely adhere to government emissions standards. In addition, about one-third of the 11 million inhabitants of the Valley of Mexico live in one-room dwellings where heating is improvised with whatever will burn.

To be fair, much of the chronic pollution results from the city's geography. It is stiuated at 7,400 feet above sea level, where the air is thin and photosensitivity more intense. Moreover, surrounding mountains trap pollution within the valley. Only in the windy winter months, and sometimes in the summer rainy season, are sometimes in the summer rainy season, are the skies blown clear.

In 1972, the previous administration turned the environment commission into a full-fledged Undersecretariat "For Environment Improvement." Between 1972 and 1975, the new body has been able to accomplish little else besides making a nationwide inventory of smoke, gas, dust and water pollution. In the last year, it began to give technical assistance and set standards for industrial polluters, even producing attractive tax incentives to woo industry away from the urban-districts.

Sixteen monitors have been placed in the valley and city to register pollution and warn the authorities. Recently, the Enviroment Undersecretariat says, it has launched patrol cars which stop and fine cars with emission or noise problems.

"We cannot solve Mexico City pollution 100 per cent," said spokesman Gomes Noguera, "but we are determined to first stop it from getting worse and then reduce it."

Critics of the environment programs say that efforts so far have been timid and halfhearted, and widespread corruption of government officials has often let sinners off the hooks.