Will 2024 Be the Year with the Most Environmental Contingencies? Mexico City Metropolitan Area Breaks Historical Record with 12


With 12 environmental contingencies announced by the Environmental Commission of the Megalopolis (CAMe) so far this year, 2024 has already reached the record for the highest number of alerts issued due to high pollution levels in the Mexico City Metropolitan Area.

This figure matches the record for environmental contingencies set in 1993, 31 years ago, when Phase 1 was also activated 12 times.

May has become one of the most problematic months in this regard, with seven activations. Practically the entire month has experienced high concentrations of pollutants, both in Mexico City (CDMX) and the State of Mexico (Edomex).

The most recent contingency was activated on Thursday, May 30th, after the Pedregal monitoring station detected a maximum ozone concentration of 160 parts per billion (ppb), and the Centro de Ciencias de la Atmósfera station recorded 155 ppb. These stations are in the Álvaro Obregón and Coyoacán boroughs, respectively.

As a result, Phase 1 of the environmental contingency was activated, leading to vehicle restrictions under the “Hoy No Circula” program.

Heatwaves have largely contributed to this series of environmental contingencies. The combination of high temperatures and an anticyclonic system that has prevented sufficient rainfall has favored the concentration of pollutants.

So far this year, the high temperatures in Mexico—currently experiencing its third heatwave of the year—have caused 61 deaths nationwide and 1,346 cases of heatstroke as of the last week of May, according to the federal Ministry of Health (SSA).

Which Years Have Had the Most Environmental Contingencies?

According to historical records from the Mexico City Environmental Secretariat, these are the years with the highest number of environmental contingencies in the metropolitan area:

  1. 1993: A total of 12 contingencies were reported during this year. February and December were the worst months, each with four contingencies.
  2. 2024: After surpassing the previous record, this year is now tied with 1993, having accumulated 12 contingencies in just five months. More than half of them were activated in May.
  3. 2016: This is now the third year with the most contingencies, totaling 10. May was its worst month, accounting for 60% of the contingencies.
  4. 1992: Eight environmental contingencies were reported throughout this year, with half of them occurring in March.
  5. 2022: In this year, there were six contingencies in total. Three of them were activated in May, while the last one occurred in November.

Why Are There More Environmental Contingencies Than Before?

While it may seem that there are more environmental contingencies now, this is due to changes in the Atmospheric Monitoring System over the past three decades.

Previously, in 1990, Phase 1 of the contingency was activated only when pollutant levels reached 294 ppb. Over time, this concentration was gradually reduced to “make the values stricter and protect public health,” as detailed by the Environmental Secretariat.

From 2011 to 2015, the activation threshold was 199 ppb, while from 2016 to the present, it was changed to 155 ppb.

“Between 2013 and 2018, there were 62 days with ozone concentrations equal to or greater than 155 ppb in the Mexico City Metropolitan Area. During that period, 29 environmental contingency events were implemented. However, before 2016, the limits were set at 185 ppb. In other words, if the current 155 ppb threshold had been in place during that period, the number of contingencies would have been even higher,” stated the Environmental Secretariat in a press release.

Source: El Financiero