The air quality crisis continues to plague Mexico City and the surrounding State of Mexico as authorities recently activated Fase 1 of the Environmental Contingency due to alarming concentrations of ozone recorded on February 26, 2025. The Comisión Ambiental de la Megalópolis (CAMe) reported highest levels of ozone at 157 parts per billion (ppb) at the Tlalnepantla monitoring station. This severe air quality notification requires immediate action from residents and local officials alike.
Weather conditions across the region have become increasingly detrimental, attributed to the presence of a high pressure system generating light winds and intense solar radiation. According to CAMe, these conditions have been conducive to the accumulation of ozone precursors, leading to its dangerous formation. "This has persisted throughout the day, which, combined with intense solar radiation, favored the accumulation of the precursors of ozone for the formation of the contaminant," explained the commission.
To combat this health hazard, the CAMe has instituted the "Doble Hoy No Circula" measure, effective on Thursday, February 27, from 5:00 AM to 10:00 PM. This regulation establishes strict traffic restrictions aimed at curtailing pollution levels, significantly affecting personal vehicles across the metropolitan area.
The restrictions detail which vehicles must refrain from circulation: those with verification hologram 2, personal vehicles with verification hologram 1 ending with digits 1, 2, 4, 6, 8, and 0, as well as vehicles bearing holograms 00 and 0 with green stickers ending in numerals 1 and 2. Even older model vehicles and those lacking verification stickers face similar restrictions. It’s estimated this action will reduce the number of vehicles on the road, thereby improving air quality.
The plan also imposes limitations on LPG distribution trucks lacking the necessary safety valves, along with local and federal cargo vehicles during specific early morning hours. Public transportation, such as taxis, will also be regulated, with the most affected taxis being those bearing verification holograms “00”, “0”, “1” or “2.” Taxis can nevertheless operate from 5:00 AM to 10:00 AM to assist public mobility, as specified by the authorities.
Exceptions to the Doble Hoy No Circula include electric and hybrid vehicles, as well as those with valid exemption stickers, which serve as incentives for cleaner modes of transportation. CAMe has also noted how vehicles used for emergency medical transport and public services, including ambulances and police vehicles, remain exempt from these restrictions.
Alongside vehicular restrictions, CAMe advises the public to take necessary precautions to minimize exposure to the polluted air. Officials strongly recommend avoiding outdoor activities between 1:00 PM and 7:00 PM when ozone levels are forecasted to be highest. This public health caution is particularly pertinent for vulnerable populations, including children, the elderly, and individuals with pre-existing health conditions.
Other recommended measures include canceling outdoor events such as sports or cultural activities and avoiding practices like smoking indoors, which contributes to air quality degradation. Local officials are urging the public to stay informed and comply with advisories to protect health and welfare during this environmental crisis.
This environmental contingency situation is concerning, especially following previous years marked by similar air quality issues. For 2025, officials anticipate multiple occasions of high ozone levels resulting from Mexico City’s unique geographical and climatic conditions, emphasizing the necessity of maintaining active measures to safeguard health.
The multi-disciplinary approach to control pollutants—encompassing traffic measures, public advisories, and increased monitoring—reflects the urgent need to rally community participation alongside government intervention to handle atmospheric pollution. These measures seek to not only alleviate immediate health risks but to address longstanding air quality challenges across the sprawling metropolitan region.
With millions of residents relying on effective transportation and clean air, the need for continued vigilance during these contingencies is clear. Ensuring comprehensive educational campaigns and effective policy measures proves imperative for sustainable air quality management as Mexico City endeavors to improve its environmental conditions.
Therefore, as residents prepare for the Doble Hoy No Circula regulations, they must also adapt to the surrounding environmental challenges, recognizing the importance of air quality on overall public health. With collaboration between leadership and community members, Mexico City moves toward creating healthier environmental standards for all.