1) Its a play on words following up Pompeo's "CLEAN NETWORK" propaganda when in fact the US network is most backdoored by far..."Dirty steel" is whatever the US/EU want it to be.
Same with dirty bikes. Dirty scooters. Dirty batteries. Dirty companies. Dirty factories. Dirty cotton. Dirty chips etc
Just change "Dirty" with "Chinese" and suddenly everything makes sense
Whatever is Chinese-made is to excluded from their market. The start is steel and aluminum. In due time other Chinese exports will follow
2) the insinuation is that China is the worst carbon polluter so any country that buys steel from China is contributing to global pollution so by buying steel from non-Chinese sources it is less dirty etc