**8. Prospectus concerning research needs**

New rare earth element mines are in various states of development across the United States and in many other nations. Given that rare earth element mines and ore processing operations span a range of locations, the climate, and physical settings will vary. The environmental impact assessment must include (i) mine conditions, (ii) ore geochemistry, (iii) local geology and hydrology, and (iv) physiographic settings and geomorphology. Mine and processing sites may disturb or accentuate (i) surface water because of drilling fluids, acid, and neutral mine discharge water, and influence aquatic organisms, (ii) groundwater impacts because of mine pit lakes, evaporation ponds, (iii) air pathways involving fugitive dust, aerosols and chemical vapors, radioactivity, and (iv) tailing storage facilities [44]. The environmental assessment must consider (i) current and future construction workers/employees (ingestion and inhalation), (ii) traditional tribal lifeways, and (iii) on-site and off-site residents. The documentation of potential health effects requires a greater research emphasis. Pulmonary toxicity of inhaled rare earth elements, and expanded investigations, involving integrated risk information systems and provisional peer-reviewed toxicity values are necessary [44].

Pollution indices need to be verified for the rare earth elements. Additionally, substantial research in assessing the biological availability of the rare earth elements in ecosystems is warranted as the total rare earth element concentrations may not accurately describe the environmental risk.
