This kind of reminds of when we dump tons of salt on the roads when winter storms come around the east coast. It solves one problem but what other problems is it causing? It would be incredibly naive to think dumping all these chemicals on the ground wouldn't cause some type of negative externality.
You are confusing different classes of chemical contaminants. Rock salt which is spread on roads consists of a chemical subset of seasalt - which is completely safe to humans as evidenced by healthy coastal communities. The contaminants discussed here are of an entirely different class, they are toxic at trace levels. Sea salt and rock salt are ubiquitous natural materials, if they were toxic at low levels plagues of…
Whether it's directly benign to humans is one thing, but the indirect effects are hard to account for.