As a side note, there are some water shore beaches in areas of the world that are black sand, and have high amounts of magnetic particles in the sand. I have been told, a conveyer with a magnetic end roller is used to separate the material. Very little processing on site required, load on ship and off to the smelter, China, Korea?
I don't see where cutting steel with water jet would be a large problem with byproduct, other materials possibly more so. The fumes from oxy-ac, plasma, and laser cutting are also problems as are some slag leftovers. Hell, even cuttings, shavings, grit, from lathe, mill, drill press, grinders could and do cause fires/melt downs of equipment, buildings. Can anyone say magnesium, or aluminum, iron grit/power! I am not saying "don't be worried about leftovers, just be aware of the effects, and concecences that maybe caused as we know them/learn of them.
Floride comes to mind, it may be a manufacturing leftover byproduct?, so put it in toothpaste, and feed it to the people! ( there appears to be some evidence ,it stripes calcium and possibly causes some cancers).
There seems to be a get rid of companies that manufacture (pollute),( send them to other places), policy.
Very few people want less these days, very few of the things we want these days cause little/no after effects or manufacturing after effects somewhere, some time.
Enough of that rant, any of the above maybe disagreed with, and is subject to possibly, only a little, or no knowlage.