Concentrations of CO2 in the atmosphere : 440 ppm
Convert parts per million to a percentage : 0.044%
Now round it up to a whole number : 0.0
CO2 is a trace gas. Any excess gets soaked up by plant life or the oceans. It is beneficial to the environment.
Most of the smog in China is due to dust coming in from the Gobi Desert (been happening since the days of Marco Polo) and also due to the tradition of burning rice fields.
See Dr. Happer's most recent video about 7:20 in:
https://www.youtube.com/watch?v=CA1zUW4uOSw