17 eerie photos that show just how polluted China's air has become

Although no one knows the exact amount of carbon that China emits each year, it's a well-known fact that the country has some of the most polluted air in the world. A recent study from UC Berkeley found that 4,000 people die every day because of complications from air pollution in China.

In March, Chen Jining, the country's minister of environmental protection, said that while China cannot hold back on efforts to address the pollution, the turnaround is not going to be immediate.

On November 9, the country was once again blanketed in acid smog from burning coal, breaking the record for the highest amount of pollution ever recorded in China. That weekend, the levels of airborne harmful particles were more than 50 times the number that the World Health Organization deems safe. The smog is estimated to remain lingering in the air throughout the rest of this week.

Here are a selection of photos that illustrate the escalation of China's pollution problems over recent years.