Officials in Mexico City have declared an environmental emergency after air pollution in the Mexican capital reached levels potentially dangerous to human health.
They urged those at particular risk to stay indoors and restricted the number of cars which can be driven in the city on Wednesday.
Smoke from nearby forest fires has contributed to the spike in pollution.
The city has been wrapped in a smoky haze for days.
Mexican photographer Santiago Arau tweeted video taken from a drone showing the extent of the pollution.
Particulate matter measuring 2.5 micrometres or less, known as PM2.5, reached 158 micrograms per cubic metre of air at one measuring station on Tuesday morning, more than six times the World Health Organisation daily mean recommended limit.
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PM2.5 particles are thought to be particularly damaging because they are so small, they can penetrate the deepest parts of the lungs.
More than 21 million people live in Mexico City's metropolitan area and it was once infamous for its poor air quality. Air pollution levels dropped in the late 1990s but have again been on the rise in recent years.
The city lies in a valley and when there is little wind, the air can quickly become stagnant.
Mexico City's envirRead More – Source