Nearly 50 days into the new year Mexico City residents have experienced only three “good” air quality days so far.
The Mexico City Environment Ministry reported that the situation is even worse for those living in the greater Valley of Mexico and México state where not a single good air quality day has been recorded.
So far in 2026, capital authorities have declared four Phase 1 environmental alerts, primarily due to high ozone levels. Last year, the fourth Phase 1 alert was not declared until early April.
Tuesday marks the fifth day that the city’s environmental contingency has been activated in less than a week, bringing the total to more than 100 hours in which transit restrictions have been applied to reduce ozone levels in the environment.
The Environmental Commission of the Megalopolis (CAMe) has called on the public to heed health recommendations to avoid exposure to pollution peaks between 1 p.m. and 7 p.m., especially for minors, the elderly, pregnant women and people with respiratory and cardiovascular diseases.
The most recent stretch of bad air saw the CAMe declare an alert last Thursday that was maintained for more than 40 hours before it was suspended. Then, just 15 hours later, the Phase 1 alert was reissued and remains in place for a third straight day.
The current Phase 1 alert is a reaction to solar radiation and high temperatures, with conditions further impacted by a huge fire consuming the grasslands in Ciudad Nezahualcóyotl to the east of Mexico City.
Today, ground-level ozone remains the air pollutant of greatest concern for health officials.
A high concentration of ozone typically occurs through late winter and early spring. The phenomenon is directly linked to the climate in the Valley of Mexico, which is dry this time of year, creating the perfect conditions for ozone to form.
Ground-level ozone is formed through the interaction of nitrogen oxides with volatile organic compounds, and ultraviolet radiation from the sun accelerates the reaction. This month’s unseasonably high temperatures — and the forecast is for highs between 83 (28.3 °C) and 86 degrees Fahrenheit (29.4 °C) the rest of this week — have resulted in high ozone levels.
Live in Mexico City? Here’s what you need to know about air quality
President Sheinbaum also pointed out on Tuesday morning that seasonal factors are mainly responsible for the current contamination levels, including thermal inversion.
“It happens at this time of year because it is still cold (but only) at night,” said Sheinbaum, who is a climate scientist with a PhD. “Normally, the warmest air is on the ground and as you go higher, it is colder, but what happens in the metropolitan area is that at night the lower part cools down while above it is hot as the sun begins to rise.”
Therefore, the pollutants concentrated in the lower layer stagnate, right at the level where people breathe.
The so-called “ozone season” typically ends with the first rains in June, when weather conditions change and the dispersion of pollutants improves.
CAMe has forecast between five and 11 ozone contingencies for the 2026 dry season in the Metropolitan Area of the Valley of Mexico.
With reports from El Financiero, El Universal, La Jornada and Sopitas
