Yes China produce more air pollution and CO2 over all then any other single country, but far less than any fully developed country per capita. The smog problem is concentrated in and around the big population and industrial centers, in China like in any other country.
Another reason for the problem in Beijing especially is the climate. Very cold winter days without wind , but with heavy traffic cause levels of particle pollution that is WAY above WHO limits, sometimes for days.
But China is doing more about it than most countries, spending huge amounts on infrastructure and clean energy: http://money.cnn.com/2017/07/18/technology/china-us-clean-energy-solar-farm/index.html
But what this discussion was about was pollution of a different kind, in the form of imported scrap being contaminated with pollutants such as PBCs, heavy metals and other dangerous materials. As China is getting richer they don’t need to accept other people’s trash and the pollution that comes with it.
Rich countries like to do so, but they will now have to find other countries to export their problems to. (Africa is open for business)
BTW: The Chinese are already getting a taste for beef, just look at the number of McDonald’s in China and growing by the day: http://money.cnn.com/2017/08/08/investing/mcdonalds-china-new-restaurants/index.html
Luckily for China they can import beef from abroad, thus exporting the problem of methane pollution and water shortage to other countries.
Now also from US, provided the producers there meet certain criteria, incl. against use of growth hormones, which is banned in China: https://www.reuters.com/article/us-usa-china-beef/u-s-finalizes-talks-to-resume-beef-exports-to-china-after-ban-idUSKBN1932ID