Mexico City is in the grips of a pollution crisis.

Authorities have issued the first smog alerts for the city in more than a decade and recently implemented restrictions on when cars can be on the road. On Wednesday, for example, two-in-five cars were ordered off the road, because the pollution reached such high levels.

In addition, Mexico City closed a loophole in its existing rules that kept about 20 percent of cars off the road each day. Now, even vehicles certified as low-emissions will also be banned on designated days, typically based on a number on their license plates.

But the pollution problem isn't new for Mexico City. Some driving restrictions have been in place for years. But still, according to the Wall Street Journal, the Mexican Institute for Competitiveness estimates that 1,823 people each year die prematurely in Mexico City because of air pollution. The city's geography is a major factor in the city's bad air. Surrounded by mountains, during the city's dry season, smog just sits and accumulates.

Warmer tempeatures — it's been in the mid-80s this week — also contribute to the thick smog.

The new, tighter restrictions are set to remain in place until the rainy season arrives this summer.

In the meantime, the city is offering free bus and subway rides as a way to get people off the road. And it's also proving to be a proft center for some businesses. Uber has a major presence in the city and is setting high surge prices.

According to a story in Quartz, Uber was charging a 9.9x surge on rides in Mexico City on Wednesday. In response, the app has been pushing its UberPool service, which allows users to share a ride with others going the same direction.

In the meantime, environmentalists and scientists wonder if the new restrictions will actually reduce the pollution at all. They blame new freeways and a court decision that reversed a ban on older model cars for getting more vehicles moving on the streets.

So what are residents to do? The World's Global Nation editor Monica Campbell, who lives in Mexico City, said there are a few options that really boil down to this: Stay indoors, and try to escape the city for some fresh air.