Mexico State activated Phase I of the Atmospheric Environmental Contingency on December 25, 2025, in the metropolitan areas of Valle de Toluca and Santiago Tianguistenco, due to high levels of PM2.5 particles. Mexico City also reports poor air quality in several boroughs, though no contingency has been declared there. Authorities attribute the issue to fireworks burning and adverse weather conditions.
On December 25, 2025, the Secretariat of Environment and Sustainable Development of Mexico State declared Phase I of the Atmospheric Environmental Contingency in the Metropolitan Areas of Valle de Toluca and Santiago Tianguistenco, after detecting elevated PM2.5 particle concentrations. At 11:00 a.m., monitoring stations in Almoloya de Juárez and Xonacatlán recorded 84 and 82 micrograms per cubic meter, respectively, exceeding health risk thresholds.
In Mexico City, the Secretariat of Environment (SEDEMA) reported poor air quality at 3:00 p.m., with high PM10 and PM2.5 indices in boroughs such as Azcapotzalco, Cuauhtémoc, Venustiano Carranza, Álvaro Obregón, Benito Juárez, Magdalena Contreras, Coyoacán, Iztapalapa, Tlalpan, Xochimilco, and Milpa Alta. Affected municipalities in Mexico State include Nezahualcóyotl, Chimalhuacán, Chicoloapan, La Paz, and Texcoco.
The contingency activates when pollutants reach 150 points on the Metropolitan Air Quality Index (IMECA). Factors like fireworks and bonfire burning during Christmas festivities, combined with thermal inversion preventing dispersion, worsened the situation.
Measures in Mexico State include suspending construction, demolition, and industrial operations using wood or coal without emission controls, plus a 40% reduction in manufacturing emissions. For December 26, from 5:00 a.m. to 10:00 p.m., vehicular restrictions apply: hologram 2 vehicles, hologram 1 with endings 1, 3, 4, 5, 7, and 9, and hologram 0 and 00 with blue sticker endings 9 and 0 are banned.
Recommendations for the public: sensitive individuals should stay indoors, avoid open burns, postpone outdoor events, and perform wet sweeping on streets. In Mexico City, avoid physical activities from 1:00 p.m. to 7:00 p.m. and suspend mass events during that time. Authorities urge avoiding fireworks to reduce health risks and accidents.
