The Comisión Ambiental de la Megalópolis (CAMe) announced the suspension of Phase 1 of the environmental contingency for ozone in Mexico City and the State of Mexico on Wednesday, March 19, 2025, at 19:00 hours. This decision was made after 26 hours of activation, as the ozone concentrations fell below the limits established in the air quality program.
"The most recent information from the Air Quality Monitoring System of Mexico City indicates that for tomorrow, the high-pressure system that has been affecting the atmospheric basin of the Valley of Mexico will move away..." reported CAMe. This shift is expected to allow a moderate influx of humidity into the area and decrease atmospheric stability, forecasting increased ventilation, partly cloudy skies, and lower temperatures compared to the preceding day.
The contingency was set off on March 18, 2025, when atmospheric stability in the Zona Metropolitana del Valle de México (ZMVM) reached critical levels after 14:00 hours, which hindered the dispersion of ozone precursor pollutants. The intense solar radiation prevailing in the valley intensified ozone formation from accumulated contaminants, while weak wind conditions persisted throughout the day.
This recent environmental emergency followed closely after another contingency activated on February 26, 2025, which lasted 24 hours due to similarly elevated ozone levels. This brings the total number of environmental contingencies in 2024 to 12, marking a significant record for the area.
As a direct result of the ozone contingency, the Hoy No Circula program continues to restrict vehicle circulation on Thursday, March 20, 2025. Vehicles with a green sticker, license plates ending in 1 and 2, and those with holograms 1 and 2 will not be allowed to circulate between 5:00 and 22:00 hours. Those not in compliance may face penalties.
However, certain vehicles are exempt from these restrictions. Those eligible to circulate include electric and hybrid vehicles, those with a “0” or “00” hologram, and designated vehicles for emergency medical response, public safety, and other critical services. Additionally, vehicles needed for school transport and individuals with disabilities meeting the requisite conditions are permitted to operate under specified guidelines.
The implementation of the Doble Hoy No Circula will also remain effective in Mexico City and 18 municipalities of the State of Mexico, reinforcing the ongoing measures to combat air pollution. The restrictions affect major areas including municipalities like Ecatepec, Naucalpan, and Tlalnepantla
With temperatures in the Valley of Mexico exceeding 28°C and weak winds contributing to poor air quality, authorities are urging the public to remain vigilant regarding air quality reports and to limit outdoor activities, especially physical exercises. Residents are encouraged to utilize public transport as a way to minimize the number of cars on the road during this ongoing air quality issue.
As air quality is continually monitored, environmental authorities, including the Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT), are committed to providing updates on atmospheric conditions and potential future contingencies. The public is advised to access the Index of AIR and HEALTH on www.aire.cdmx.gob.mx or via the AIRE app available for both iOS and Android devices.
