Air pollution in Mexico City worsened overnight, triggering an emergency alert.

The Environmental Commission of the Megalopolis (Came) issued an Extraordinary Environmental Contingency for the Mexico City metropolitan area after measuring extremely high levels of PM2.5 — fine particulate matter — at different points around the city in the early hours of the morning.

The commission warned the public to avoid outdoor activities.

The city’s Imeca index, which measures air quality, reached 158 at 5:00am at the Nezahualcóyotl Metro station, up from 144 yesterday evening. An environmental contingency is declared when the index reaches 151.

The municipality of Nezahualcóyotl often suffers from the poorest air quality in the region because of its location at the lowest point of the Valley of Mexico’s dried lake beds.

At least 23 fires were reported in Mexico City yesterday, affecting nearly all of the capital’s 16 boroughs and contributing to poor air quality.

To avoid possible respiratory ailments, the commission recommended that residents remain indoors with windows and doors shut, and avoid intense exercise or other outdoor recreational activities.

The environmental commission also warned against smoking and cooking over an open fire and urged that drivers restrict vehicle use.

Source: El Financiero (sp)