US challenging China on rare earth elements., page-2

Amigo, the grades of rare earths at Mountain Pass are really spectacular. But rare earth operations that have these types of grades, have an achilles heel - radioactivity. MP has high grades of radioactive elements, uranium and thorium. Wikiedia has a summary of previous environmental problems at MP (copied below). In China radioactive dust is also problem. In Malaysia where they process the ore from Lynas' Mount Weld (WA) mine, there have been similar issues which the local communities have rallied against (see copy below from a Human Rights article). So, although ARR's very large deposit at La Paz has a relatively low grade, it doesn't suffer from radioactive issues.

"Mountain Pass - Environmental impact
In the 1980s, the company began piping wastewater up to 14 miles to evaporation ponds on or near Ivanpah Dry Lake, east of Interstate 15 near Nevada. This pipeline repeatedly ruptured during cleaning operations to remove mineral deposits called scale. The scale is radioactive because of the presence of thorium and radium, which occur naturally in the rare-earth ore. A federal investigation later found that some 60 spills—some unreported—occurred between 1984 and 1998, when the pipeline and chemical processing at the mine were shut down.[21] In all, about 600,000 gallons of radioactive and other hazardous waste flowed onto the desert floor, according to federal authorities. By the end of the 1990s, Unocal was served with a cleanup order and a San Bernardino County district attorney's lawsuit. The company paid more than $1.4 million in fines and settlements. After preparing a cleanup plan and completing an extensive environmental study, Unocal in 2004 won approval of a county permit that allowed the mine to operate for another 30 years. The mine passed a key county inspection in 2007.[10]"

"Lynas ARE- Malaysian operation
...radioactive waste from the ARE refinery was first dumped by the company before inadequate storage led to leakage into local rivers and lakes. As a result, nearby land, air and water was severely contaminated by hazardous and dangerous radioactive materials, including Thorium 232, which has a half-life of more than 14 billion years. It can cause cancers in cases of overexposure. At the time, the levels of radioactivity near the site were measured to be from fifty times to more than seven hundred times higher than what is considered normal."