I think it's important in the context of this discussion to separate the mining of rare earths and the processing thereof. Both are generally environmentally hazardous, but in different ways. The mining process generally involves strip mines or open pit mines (such as Mountain Pass in California, iirc the only US rare earth mine), neither of which are particularly friendly to the environment. The processing is also hazardous due to the chemicals and processes necessary to separate the component elements of the ores which are effectively more tightly coupled than is the case in most metal mines. Domestically that means continued and heightened investment in Mountain Pass as well as potentially other sites, but also the development of domestic processing industry. So while the mine might be in California we're going to see the ancillary industry popping up in locations with notably lower standards, i.e. Texas.