Almost all our modern tech has extremely long tails measured in decades.

It's basic economics to exploit one source for as long as possible before feasibility changes, but that's a hard argument to make for anyone, even the most experienced personnel because it's all so site specific.

If the particular impurities of this source can be chelated out with safer or cheaper chemicals, maybe in fewer steps, then the cost goes down.

Of course jurisdictions with poor worker conditions can just use the less safe chemicals and externalize the human toll instead of using more complex safety procedures.