How would this have changed if we were mining our own coal? If they're using an amount that far outstrips everyone else combined, the environmental damage would be largely the same with or without US coal.
I'm not sure why this is confusing.
I'm also not sure why people are modding down factual posts. That type of behavior is exactly what's given you President Trump.
http://www.reuters.com/article/us-column-russell-steel-china... http://www.ita.doc.gov/steel/countries/pdfs/imports-us.pdf