Some have called it the “airpocalypse.” Others portrayed the cloud of dark smog that rolled into Beijing, China, this week as Godzilla.

Godzilla appears in #Beijing? Netizens turn creative amidst #smog in Beijing recently, adding Godzilla, Ironman and aliens in their photos pic.twitter.com/QeMHlUUqJe

— People's Daily,China (@PDChina) December 24, 2016

Either way, it was an unhappy New Year for China’s air quality.

A thick haze of pollution covered northern and central China Sunday and Monday, prompting a “red alert” in 25 cities that led to school, factory, and construction site closures. On Monday Beijing declared an “orange alert,” delaying flights and shutting down highway travel, according to the Associated Press.

Read More: How Toxic Is Your City’s Air? Now You Can Find Out

A dramatic time-lapse video showed Beijing being completely engulfed by a dark cloud in just 20 minutes:

The particles making up the smog were many times over the safe level declared by the World Health Organization. The readings exceed 400 micrograms of PM 2.5 per cubic meter, when the WHO recommends 25 micrograms as a safe level, according to the AP. The particles damage lung tissue.China’s ongoing battle with air pollution stems from its reliance on coal, its factories, and its reliance on older cars for travel.

Throughout the world, 6.5 million deaths each year can be linked to air pollution, making it the fourth-biggest threat to human health after a poor diet, smoking, and high blood pressure.

Air pollution is recognized as the world’s worst environmental carcinogen, and it’s considered more dangerous than second-hand smoke.

But while China may be starting 2017 under a cloud of a deadly smog, the country will also begin to devote major resources this year to curtailing its pollution under the Paris climate agreement.

Read More: Air Pollution is Killing 6.5 Million People Each Year

China will try to cut carbon emissions by 60 to 65% per unit of GDP by 2030, compared with 2005 levels, under the agreement.

Perhaps by New Year’s Day of 2018, “red alerts” will have become part of the country’s history.