December 2, 2015 11:59 AM EST

As 150 world leaders meet in Paris to produce a landmark agreement that would set targets on reducing carbon emissions – and limit the rise of global temperatures – parts of China, including its capital, Beijing, recorded the worst smog of 2015.

On Nov. 30 and Dec. 1, some of the country’s air quality devices were unable to read such high level of pollutants, notes photographer Kevin Frayer who produced a series of before and after images showing the smog’s visual impact. In one scene, the mausoleum at Tiananmen Square completely disappears in the pollution as tourists wear surgical masks to protect themselves.

In Beijing, levels of fine particulate matters, considered the most hazardous, crossed 600 units, nearly 25 times the acceptable standard set by the World Health Organization.

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