Mexico City hit by worst air pollution in decades

Mexico City's government has advised people to stay indoors and restricted traffic due to air pollution, Dw.com reports.

Ozone levels have been measured at nearly twice the acceptable limit, triggering the first alert in over a decade.

Authorities said Monday that the alert stemmed from an "extraordinary increase" in ozone concentration due to the presence of a high pressure weather system and intense solar radiation around greater Mexico City. The Mexican capital is home to more than 20 million inhabitants.

An advisory posted by the city authorities recommended that people stay off the streets between 1 pm and 7 pm, refrain from vigorous exercise in the open and curb sporting activities, in order to avoid respiratory problems.

The last time a phase one alert was issued for particle pollution was on New Year's Day 2005. Then, air quality was likely affected by heavy use of firecrackers, a city official said. Ozone, which is a key ingredient of air pollution, is a form of oxygen created by the reaction of sunlight with air containing other pollutants such as hydrocarbons and nitrogen oxide.