Mexico Issues Emergency Air Quality Regulation for Cars

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By Emily Pickrell

June 10 — Mexico has issued emergency emissions standards rules for cars in the greater Mexico City area in response to concerns about worsening air quality and ineffective emissions standards tests for vehicles.

The Environmental Ministry issued a temporary emergency regulation (NOM-EM-167) June 7 that requires an internationally accepted diagnostics testing of cars for emissions inspections to ensure that they are not being passed without meeting the standards.

The emergency ruling is partially as the result of unseasonably dry weather this spring that has worsened air quality and partially the effect of changes to a program intended to limit cars in Mexico City. Under that program, Hoy No Circula, or No-Drive Days, cars over eight years old could not be driven on certain days. Newer cars, depending on their age and emissions standards performance, faced either fewer or no reduction requirements. In 2015, the Mexican Supreme Court ruled that this approach was discriminatory and effectively gave permission to 1.4 million car owners to take to the roads again.

“Normally, these emergency standards are for something unexpected and disastrous, like an oil spill,” said Jorge Macias, urban development director of the Mexican Cities Program of the World Resources Institute. “However, for the air quality and the emissions, you can say there is an emergency because there are 1 million more vehicles on the street. If you successfully argue that it is an emergency, then you can skip some steps in developing a new standard.”

Ozone Levels

The new regulation comes as Mexico's sprawling capital city, which swells to a population of more than 20 million during the day, tries to contain its air pollution issues, which reached its first Phase 1 emergency due to high ozone levels in mid-March. Under Mexico's air quality standard, pollution levels exceeding 100 are considered potentially dangerous to human health. Phase 1 is activated when the air quality index reaches 150. A Phase 2 alert would begin when levels reach 200.

The emergency legislation also requires the use of the European On-Board Diagnostics system and the OBD-II emissions testing program in an effort to discourage false verifications. In the U.S., this self-diagnostic emissions software has been required on all new vehicles since 1996.

Mexico's new regulation also includes stricter maximum emissions standards for gas and diesel cars and now requires private and public buses to comply with emissions standards.

It will apply to nearly 2 million vehicles in the Valle de Mexico area, which includes Mexico City, Hidalgo, the State of Mexico, Morelos, Puebla and Tlaxcala.

And while the regulation are in effect only for the next 12 months, environmental groups believe it will be the template for a longer lasting standard.

“In the end, it needs to be a standard for all the whole fleet,” Macias said. “The emergency regulation cannot extend forever, so we need to translate into a federal ruling that is not only applicable for Mexico City, it should be extended for the whole country.”

Other Recommended Steps

Several Mexican civil society groups have proposed additional steps that could be taken to improve air quality, such as updating other existing emissions standards laws.

Mexico's emissions standards for cars and trucks were first established in 1988 and implemented in 1993. The current standard for trucks allows compliance with either U.S. 2004 or Euro IV equivalent standards, but has not been enforced, largely due to an insufficient national supply of ultra-low sulfur diesel fuel. Mexico's fuel market will be fully open to private vendors by 2018, at which time a sufficient quantity of the needed diesel to meet the emissions standards is expected.

In addition, the Environmental Commission of the Megalopolis of Mexico City has established a temporary regional regulation limiting all cars to one no-drive per week through the end of June 2016.

To contact the reporter on this story: Emily Pickrell in Mexico City at

To contact the editor responsible for this story: Greg Henderson at