Editing Rare-earth element (section)

==Environmental considerations==
REEs are naturally found in very low concentrations in the environment. Mines are often in countries where environmental and social standards are very low, leading to human rights violations, deforestation, and contamination of land and water.<ref name=rizk>{{cite web |title=What colour is the cloud? |first1=Shirley |last1=Rizk |date=21 June 2019 |url=https://www.eib.org/en/stories/digital-footprint |access-date=2020-09-17 |website=European Investment Bank |language=en |archive-date=April 14, 2021 |archive-url=https://web.archive.org/web/20210414035732/https://www.eib.org/en/stories/digital-footprint |url-status=live}}</ref><ref name=standaert>{{cite web |title=China Wrestles with the Toxic Aftermath of Rare Earth Mining |url=https://e360.yale.edu/features/china-wrestles-with-the-toxic-aftermath-of-rare-earth-mining |first1=Michael |last1=Standaert |date=2 July 2019 |access-date=16 June 2021 |publisher=Yale School of the Environment |work=Yale Environment 360 |archive-date=July 9, 2022 |archive-url=https://web.archive.org/web/20220709042527/https://e360.yale.edu/features/china-wrestles-with-the-toxic-aftermath-of-rare-earth-mining |url-status=live}}</ref> Generally, it is estimated that extracting 1 metric ton of rare earth element creates around 2,000 metric tons of waste, partly toxic, including 1 ton of radioactive waste. The largest mining site of REEs, [[Bayan Obo Mining District|Bayan Obo]] in China produced more than 70,000 tons of radioactive waste, that contaminated ground water.<ref>{{cite web |last1=CHO |first1=RENEE |title=The Energy Transition Will Need More Rare Earth Elements. Can We Secure Them Sustainably? |url=https://news.climate.columbia.edu/2023/04/05/the-energy-transition-will-need-more-rare-earth-elements-can-we-secure-them-sustainably/ |website=State of the planet |date=April 5, 2023 |publisher=Columbia Climate School |access-date=27 September 2023}}</ref>

Near mining and industrial sites, the concentrations of REEs can rise to many times the normal background levels. Once in the environment, REEs can leach into the soil where their transport is determined by numerous factors such as erosion, weathering, pH, precipitation, groundwater, etc. Acting much like metals, they can speciate depending on the soil condition being either motile or adsorbed to soil particles. Depending on their bio-availability, REEs can be absorbed into plants and later consumed by humans and animals.<ref name="Volokh"/>

The mining of REEs, use of REE-enriched fertilizers, and the production of phosphorus fertilizers all contribute to REE contamination.<ref name="Volokh">{{cite journal |date=1990-06-01 |title=Phosphorus fertilizer production as a source of rare-earth elements pollution of the environment |journal=Science of the Total Environment |language=en |volume=95 |pages=141–148 |doi=10.1016/0048-9697(90)90059-4 |pmid=2169646 |issn=0048-9697 |bibcode=1990ScTEn..95..141V |last1=Volokh |first1=A. A. |last2=Gorbunov |first2=A. V. |last3=Gundorina |first3=S. F. |last4=Revich |first4=B. A. |last5=Frontasyeva |first5=M. V. |author6=Chen Sen Pal}}</ref> Strong acids are used during the extraction process of REEs, which can then leach out into the environment and be transported through water bodies and result in the acidification of aquatic environments. Another additive of REE mining that contributes to REE environmental contamination is [[cerium(IV) oxide|cerium oxide]] ({{chem|Ce|O|2}}), which is produced during the combustion of diesel and released as exhaust, contributing heavily to soil and water contamination.<ref name="Kyung">{{cite journal |last=Rim |first=Kyung-Taek |s2cid=17407586 |date=2016-09-01 |title=Effects of rare earth elements on the environment and human health: A literature review |journal=Toxicology and Environmental Health Sciences |language=en |volume=8 |issue=3 |pages=189–200 |doi=10.1007/s13530-016-0276-y |bibcode=2016TxEHS...8..189R |issn=2005-9752}}</ref>

[[File:Baiyunebo ast 2006181.jpg|thumb|300px|A false-color satellite image of the [[Bayan Obo Mining District]], 2006]]
Mining, refining, and recycling of rare earths have serious environmental consequences if not properly managed. Low-level radioactive [[tailings]] resulting from the occurrence of [[thorium]] and [[uranium]] in rare-earth ores present a potential hazard<ref>Bourzac, Katherine. [http://www.technologyreview.com/energy/26655/?p1=MstCom "Can the US Rare-Earth Industry Rebound?"] {{Webarchive|url=https://web.archive.org/web/20120514220351/http://www.technologyreview.com/energy/26655/?p1=MstCom |date=May 14, 2012}} ''Technology Review''. October 29, 2010.</ref><ref>{{Cite web |date=2015-03-20 |title=Thorium - Cancer-Causing Substances - NCI |url=https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/thorium |access-date=2024-02-14 |website=www.cancer.gov |language=en}}</ref> and improper handling of these substances can result in extensive environmental damage. In May 2010, China announced a major, five-month crackdown on illegal mining in order to protect the environment and its resources. This campaign is expected to be concentrated in the South,<ref>{{cite web |url=http://www.chinamining.org/News/2010-05-21/1274404411d36358.html |title=Govt cracks whip on rare earth mining |publisher=China Mining Association |date=May 21, 2010 |access-date=June 3, 2010 |archive-url=https://web.archive.org/web/20110725170447/http://www.chinamining.org/News/2010-05-21/1274404411d36358.html |archive-date=2011-07-25}}</ref> where mines&nbsp;– commonly small, rural, and illegal operations&nbsp;– are particularly prone to releasing toxic waste into the general water supply.<ref name=Wikinvest/><ref>{{cite web |author=Lee Yong-tim |url=http://www.rfa.org/english/news/china_pollution-20080222.html |title=South China Villagers Slam Pollution From Rare Earth Mine |date=22 February 2008 |website=Radio Free Asia |access-date=16 March 2008 |archive-date=April 20, 2022 |archive-url=https://web.archive.org/web/20220420055708/https://www.rfa.org/english/news/china_pollution-20080222.html |url-status=live}}</ref> 

The major operation in [[Baotou]], in Inner Mongolia, where much of the world's rare-earth supply is refined, has caused major environmental damage.<ref name="NYT">{{cite news |title=After China's Rare Earth Embargo, a New Calculus |author=Bradsher, Keith |newspaper=The New York Times |date=October 29, 2010 |url=https://www.nytimes.com/2010/10/30/business/global/30rare.html |access-date=October 30, 2010 |author-link=Keith Bradsher |archive-date=June 25, 2022 |archive-url=https://web.archive.org/web/20220625155338/https://www.nytimes.com/2010/10/30/business/global/30rare.html |url-status=live}}</ref> China's Ministry of Industry and Information Technology estimated that cleanup costs in Jiangxi province at $5.5 billion.<ref name=standaert/>

It is possible to filter out and recover any rare-earth elements that flow out with the wastewater from mining facilities. Such filtering and recovery equipment may not always be present on the outlets carrying the wastewater.<ref>{{cite journal |last1=Pereao |first1=Omoniyi |last2=Bode-Aluko |first2=Chris |last3=Fatoba |first3=Olanrewaju |last4=Laatikaine |first4=Katri |last5=Petrik |first5=Leslie |title=Rare earth elements removal techniques from water/wastewater: a review |journal=Desalination and Water Treatment |date=2018 |volume=130 |pages=71–86 |doi=10.5004/dwt.2018.22844 |bibcode=2018DWatT.130...71P |url=https://www.researchgate.net/publication/328637201 |issn=1944-3994}}</ref><ref>{{cite journal |title=Recovery of Rare Earth Elements from Wastewater Towards a Circular Economy |first1=Óscar |last1=Barros |first2=Lara |last2=Costa |first3=Filomena |last3=Costa |first4=Ana |last4=Lago |first5=Verónica |last5=Rocha |first6=Ziva |last6=Vipotnik |first7=Bruna |last7=Silva |first8=Teresa |last8=Tavares |date=March 13, 2019 |journal=Molecules |volume=24 |issue=6 |page=1005 |doi=10.3390/molecules24061005 |pmid=30871164 |pmc=6471397 |doi-access=free}}</ref><ref>{{cite web |url=https://lirias.kuleuven.be/retrieve/325732 |title=Towards zero-waste valorization of rare earth elements |access-date=June 7, 2021 |archive-date=June 7, 2021 |archive-url=https://web.archive.org/web/20210607160620/https://lirias.kuleuven.be/retrieve/325732 |url-status=live}}</ref>

===Recycling and reusing REEs===
{{Further|Circular economy|Renewable energy#Conservation areas, recycling and rare-earth elements}}

REEs are amongst the most critical elements to modern technologies and society. Despite this, typically only around 1% of REEs are recycled from end-products.<ref>{{Cite journal |last1=Jowitt |first1=Simon M. |last2=Werner |first2=Timothy T. |last3=Weng |first3=Zhehan |last4=Mudd |first4=Gavin M. |date=2018-10-01 |title=Recycling of the rare earth elements |url=https://www.sciencedirect.com/science/article/pii/S2452223617301256 |journal=Current Opinion in Green and Sustainable Chemistry |series=Reuse and Recycling / UN SGDs: How can Sustainable Chemistry Contribute? / Green Chemistry in Education |language=en |volume=13 |pages=1–7 |doi=10.1016/j.cogsc.2018.02.008 |bibcode=2018COGSC..13....1J |s2cid=135249554 |issn=2452-2236}}</ref> Recycling and reusing REEs is not easy: these elements are mostly present in tiny amounts in small electronic parts and they are difficult to separate chemically.<ref name="Balaram2019">{{Cite journal |last=Balaram |first=V. |date=2019-07-01 |title=Rare earth elements: A review of applications, occurrence, exploration, analysis, recycling, and environmental impact |journal=Geoscience Frontiers |language=en |volume=10 |issue=4 |pages=1285–1303 |doi=10.1016/j.gsf.2018.12.005 |bibcode=2019GeoFr..10.1285B |issn=1674-9871|doi-access=free }}</ref> For example, recovery of  neodymium requires manual disassembly of hard disk drives because shredding the drives only recovers 10% of the REE.<ref>{{Cite journal |last1=Sprecher |first1=Benjamin |last2=Xiao |first2=Yanping |last3=Walton |first3=Allan |last4=Speight |first4=John |last5=Harris |first5=Rex |last6=Kleijn |first6=Rene |last7=Visser |first7=Geert |last8=Kramer |first8=Gert Jan |date=2014-04-01 |title=Life Cycle Inventory of the Production of Rare Earths and the Subsequent Production of NdFeB Rare Earth Permanent Magnets |url=https://pubs.acs.org/doi/10.1021/es404596q |journal=Environmental Science & Technology |language=en |volume=48 |issue=7 |pages=3951–3958 |doi=10.1021/es404596q |pmid=24576005 |bibcode=2014EnST...48.3951S |issn=0013-936X}}</ref>

REE recycling and reuse have been increasingly focused on in recent years. The main concerns include environmental pollution during REE recycling and increasing recycling efficiency. Literature published in 2004 suggests that, along with previously established pollution mitigation, a more circular supply chain would help mitigate some of the pollution at the extraction point. This means recycling and reusing REEs that are already in use or reaching the end of their life cycle.<ref name="Ali 123–134">{{cite journal |last=Ali |first=Saleem H. |date=2014-02-13 |title=Social and Environmental Impact of the Rare Earth Industries |journal=Resources |language=en |volume=3 |issue=1 |pages=123–134 |doi=10.3390/resources3010123 |doi-access=free|bibcode=2014Resou...3..123A }}</ref> A study published in 2014 suggests a method to recycle REEs from waste [[nickel-metal hydride batteries]], demonstrating a recovery rate of 95.16%.<ref>{{cite journal |last1=Yang |first1=Xiuli |last2=Zhang |first2=Junwei |last3=Fang |first3=Xihui |date=2014-08-30 |title=Rare earth element recycling from waste nickel-metal hydride batteries |journal=Journal of Hazardous Materials |language=en |volume=279 |pages=384–388 |doi=10.1016/j.jhazmat.2014.07.027 |issn=0304-3894 |pmid=25089667|bibcode=2014JHzM..279..384Y }}</ref> 

Rare-earth elements could also be recovered from industrial wastes with practical potential to reduce environmental and health impacts from mining, waste generation, and imports if known and experimental processes are scaled up.<ref>{{cite news |title=Rare earth elements for smartphones can be extracted from coal waste |work=New Scientist |url=https://www.newscientist.com/article/2307608-rare-earth-elements-for-smartphones-can-be-extracted-from-coal-waste/}}</ref><ref>{{cite journal |last1=Deng |first1=Bing |last2=Wang |first2=Xin |last3=Luong |first3=Duy Xuan |last4=Carter |first4=Robert A. |last5=Wang |first5=Zhe |last6=Tomson |first6=Mason B. |last7=Tour |first7=James M. |year=2022 |title=Rare earth elements from waste |journal=Science Advances |volume=8 |issue=6 |pages=eabm3132 |bibcode=2022SciA....8M3132D |doi=10.1126/sciadv.abm3132 |pmc=8827657 |pmid=35138886}}</ref> A 2019 study suggests that "fulfillment of the circular economy approach could reduce up to 200 times the impact [[Climate change mitigation|in the climate change category]] and up to 70 times the cost due to the REE mining."<ref>{{cite journal |last1=Amato |first1=A. |last2=Becci |first2=A. |last3=Birloaga |first3=I. |last4=De Michelis |first4=I. |last5=Ferella |first5=F. |last6=Innocenzi |first6=V. |last7=Ippolito |first7=N. M. |last8=Pillar Jimenez Gomez |first8=C. |last9=Vegliò |first9=F. |last10=Beolchini |first10=F. |date=1 May 2019 |title=Sustainability analysis of innovative technologies for the rare earth elements recovery |journal=Renewable and Sustainable Energy Reviews |language=en |volume=106 |pages=41–53 |doi=10.1016/j.rser.2019.02.029 |bibcode=2019RSERv.106...41A |issn=1364-0321 |s2cid=115810707 |hdl-access=free |hdl=11566/264482}}</ref> In 2020, in most of the reported studies reviewed by a [[scientific review]], "secondary waste is subjected to chemical and or bioleaching followed by solvent extraction processes for clean separation of REEs."<ref>{{cite journal |last1=Jyothi |first1=Rajesh Kumar |last2=Thenepalli |first2=Thriveni |last3=Ahn |first3=Ji Whan |last4=Parhi |first4=Pankaj Kumar |last5=Chung |first5=Kyeong Woo |last6=Lee |first6=Jin-Young |date=10 September 2020 |title=Review of rare earth elements recovery from secondary resources for clean energy technologies: Grand opportunities to create wealth from waste |journal=Journal of Cleaner Production |language=en |volume=267 |page=122048 |doi=10.1016/j.jclepro.2020.122048 |bibcode=2020JCPro.26722048J |issn=0959-6526 |s2cid=219469381}}</ref>

Currently, people take two essential resources into consideration for the secure supply of REEs: one is to extract REEs from primary resources like mines harboring REE-bearing ores, regolith-hosted clay deposits,<ref>{{Cite journal |last1=Borst |first1=Anouk M. |last2=Smith |first2=Martin P. |last3=Finch |first3=Adrian A. |last4=Estrade |first4=Guillaume |last5=Villanova-de-Benavent |first5=Cristina |last6=Nason |first6=Peter |last7=Marquis |first7=Eva |last8=Horsburgh |first8=Nicola J. |last9=Goodenough |first9=Kathryn M. |last10=Xu |first10=Cheng |last11=Kynický |first11=Jindřich |last12=Geraki |first12=Kalotina |date=2020-09-01 |title=Adsorption of rare earth elements in regolith-hosted clay deposits |journal=Nature Communications |language=en |volume=11 |issue=1 |page=4386 |doi=10.1038/s41467-020-17801-5 |issn=2041-1723 |pmc=7463018 |pmid=32873784|bibcode=2020NatCo..11.4386B }}</ref> ocean bed sediments, coal fly ash,<ref>{{Cite journal |last1=Liu |first1=Pan |last2=Huang |first2=Rixiang |last3=Tang |first3=Yuanzhi |date=2019-05-07 |title=Comprehensive Understandings of Rare Earth Element (REE) Speciation in Coal Fly Ashes and Implication for REE Extractability |url=https://pubs.acs.org/doi/10.1021/acs.est.9b00005 |journal=Environmental Science & Technology |language=en |volume=53 |issue=9 |pages=5369–5377 |doi=10.1021/acs.est.9b00005 |pmid=30912650 |bibcode=2019EnST...53.5369L |s2cid=85517653 |issn=0013-936X}}</ref> etc. A work developed a green system for recovery of REEs from coal fly ash by using citrate and oxalate who are strong organic ligand and capable of complexing or precipItating with REE.<ref>{{Cite journal |last1=Liu |first1=Pan |last2=Zhao |first2=Simin |last3=Xie |first3=Nan |last4=Yang |first4=Lufeng |last5=Wang |first5=Qian |last6=Wen |first6=Yinghao |last7=Chen |first7=Hailong |last8=Tang |first8=Yuanzhi |date=2023-04-04 |title=Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash |journal=Environmental Science & Technology |language=en |volume=57 |issue=13 |pages=5414–5423 |doi=10.1021/acs.est.2c09273 |issn=0013-936X |pmc=10077585 |pmid=36942728|bibcode=2023EnST...57.5414L }}</ref> The other one is from secondary resources such as electronic, industrial waste and municipal waste. E-waste contains a significant concentration of REEs, and thus is the primary option for REE recycling now{{when|date=July 2023}}. According to a 2019 study, approximately 50 million metric tons of electronic waste are dumped in landfills worldwide each year. Despite the fact that e-waste contains a significant amount of rare-earth elements (REE), only 12.5% of e-waste is currently being recycled for all metals.<ref name="Balaram2019"/>

===Impact of REE contamination===
====On vegetation====
The mining of REEs has caused the [[soil contamination|contamination]] of soil and water around production areas, which has impacted vegetation in these areas by decreasing [[chlorophyll]] production, which affects photosynthesis and inhibits the growth of the plants.<ref name=Kyung/> However, the impact of REE contamination on vegetation is dependent on the plants present in the contaminated environment: not all plants retain and absorb REEs. Also, the ability of the vegetation to intake the REE is dependent on the type of REE present in the soil, hence there are a multitude of factors that influence this process.<ref name="sciencedirect.com">{{cite journal |last=Chua |first=H |date=18 June 1998 |title=Bio-accumulation of environmental residues of rare earth elements in aquatic flora ''Eichhornia crassipes'' (Mart.) Solms in Guangdong Province of China |journal=Science of the Total Environment |language=en |volume=214 |issue=1–3 |pages=79–85 |doi=10.1016/S0048-9697(98)00055-2 |issn=0048-9697 |bibcode=1998ScTEn.214...79C}}</ref> Agricultural plants are the main type of vegetation affected by REE contamination in the environment, the two plants with a higher chance of absorbing and storing REEs being apples and beets.<ref name=Volokh/> 

There is a possibility that REEs can leach out into aquatic environments and be absorbed by aquatic vegetation, which can then bio-accumulate and potentially enter the human food chain if livestock or humans choose to eat the vegetation. An example of this situation was the case of the [[Eichhornia crassipes|water hyacinth]] (''Eichhornia crassipes)'' in China, where the water was contaminated due to a REE-enriched fertilizer being used in a nearby agricultural area. The aquatic environment became contaminated with [[cerium]] and resulted in the water hyacinth becoming three times more concentrated in cerium than its surrounding water.<ref name="sciencedirect.com"/>

====On human health====
The chemical properties of the REEs are so similar that they are expected to show similar toxicity in humans.
Mortality studies show REEs are not highly toxic.<ref name=HiranoSuzuki1996>{{Cite journal |last1=Hirano |first1=S |last2=Suzuki |first2=K T |date=March 1996 |title=Exposure, metabolism, and toxicity of rare earths and related compounds. |journal=Environmental Health Perspectives |language=en |volume=104 |issue=suppl 1 |pages=85–95 |doi=10.1289/ehp.96104s185 |issn=0091-6765 |pmc=1469566 |pmid=8722113|bibcode=1996EnvHP.104S..85H }}</ref> Long term (18 months) inhalation of dust containing high levels (60%) of REEs has been shown to cause [[pneumoconiosis]] but the mechanism is unknown.<ref name=HiranoSuzuki1996/>

While REEs are not major pollutants, the increase application of REEs in new technologies has increased the need to understand their safe levels of exposure for humans.<ref name=Rim>{{cite journal |last1=Rim |first1=Kyung Taek |last2=Koo |first2=Kwon Ho |last3=Park |first3=Jung Sun |title=Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review |journal=Safety and Health at Work |volume=4 |issue=1 |pages=12–26 |doi=10.5491/shaw.2013.4.1.12 |pmid=23516020 |year=2013 |pmc=3601293}}</ref> One side effect of mining REEs can be exposure to harmful radioactive [[Thorium]] as has been demonstrated at large mine in Batou (Mongolia).<ref>Chen, X. A., et al. "A twenty-year follow-up study on health effects-following long-term exposure to thorium dusts." HEIR 2004 (2005): 139.</ref> 
The rare-earth mining and smelting process can release airborne fluoride which will associate with total suspended particles (TSP) to form aerosols that can enter human respiratory systems. Research from Baotou, China shows that the fluoride concentration in the air near REE mines is higher than the limit value from WHO, but the health effects of this exposure are unknown.<ref>{{cite journal |last1=Zhong |first1=Buqing |last2=Wang |first2=Lingqing |last3=Liang |first3=Tao |last4=Xing |first4=Baoshan |date=October 2017 |title=Pollution level and inhalation exposure of ambient aerosol fluoride as affected by polymetallic rare earth mining and smelting in Baotou, north China |journal=Atmospheric Environment |language=en |volume=167 |pages=40–48 |doi=10.1016/j.atmosenv.2017.08.014 |bibcode=2017AtmEn.167...40Z}}</ref>

Analysis of people living near mines in China had many times the levels of REEs in their blood, urine, bone, and hair compared to controls far from mining sites, suggesting possible [[bioaccumulation]] of REEs. This higher level was related to the high levels of REEs present in the vegetables they cultivated, the soil, and the water from the wells, indicating that the high levels were caused by the nearby mine. However the levels found were not high enough to cause health effects.<ref>{{cite journal |date=2013-10-01 |title=A human health risk assessment of rare earth elements in soil and vegetables from a mining area in Fujian Province, Southeast China |journal=Chemosphere |language=en |volume=93 |issue=6 |pages=1240–1246 |doi=10.1016/j.chemosphere.2013.06.085 |pmid=23891580 |issn=0045-6535 |bibcode=2013Chmsp..93.1240L |last1=Li |first1=Xiaofei |last2=Chen |first2=Zhibiao |last3=Chen |first3=Zhiqiang |last4=Zhang |first4=Yonghe |doi-access=free}}</ref> 
Analysis of REEs in street dust in China suggest "no augmented health hazard".<ref name=sun>{{cite journal |last1=Sun |first1=Guangyi |last2=Li |first2=Zhonggen |last3=Liu |first3=Ting |last4=Chen |first4=Ji |last5=Wu |first5=Tingting |last6=Feng |first6=Xinbin |s2cid=31655372 |date=2017-12-01 |title=Rare earth elements in street dust and associated health risk in a municipal industrial base of central China |journal=Environmental Geochemistry and Health |language=en |volume=39 |issue=6 |pages=1469–1486 |doi=10.1007/s10653-017-9982-x |pmid=28550599 |bibcode=2017EnvGH..39.1469S |issn=0269-4042 |url=http://ir.ihb.ac.cn/handle/342005/30223 |access-date=September 6, 2019 |archive-date=February 25, 2021 |archive-url=https://web.archive.org/web/20210225013613/http://ir.ihb.ac.cn/handle/342005/30223 }}</ref>
Similarly, analysis of cereal crops in mining areas in China found levels too low for health risks.<ref>{{cite journal |last1=Zhuang |first1=Maoqiang |last2=Wang |first2=Liansen |last3=Wu |first3=Guangjian |last4=Wang |first4=Kebo |last5=Jiang |first5=Xiaofeng |last6=Liu |first6=Taibin |last7=Xiao |first7=Peirui |last8=Yu |first8=Lianlong |last9=Jiang |first9=Ying |date=2017-08-29 |title=Health risk assessment of rare earth elements in cereals from mining area in Shandong, China |journal=Scientific Reports |language=En |volume=7 |issue=1 |page=9772 |doi=10.1038/s41598-017-10256-7 |pmid=28852170 |pmc=5575011 |issn=2045-2322 |bibcode=2017NatSR...7.9772Z}}</ref>

====On animal health====
Experiments exposing rats to various cerium compounds have found accumulation primarily in the lungs and liver. This resulted in various negative health outcomes associated with those organs.<ref name=Pagano>{{cite journal |last1=Pagano |first1=Giovanni |last2=Aliberti |first2=Francesco |last3=Guida |first3=Marco |last4=Oral |first4=Rahime |last5=Siciliano |first5=Antonietta |last6=Trifuoggi |first6=Marco |last7=Tommasi |first7=Franca |title=Rare earth elements in human and animal health: State of art and research priorities |journal=Environmental Research |volume=142 |pages=215–220 |doi=10.1016/j.envres.2015.06.039 |pmid=26164116 |bibcode=2015ER....142..215P |year=2015 |hdl=11586/148470 |hdl-access=free}}</ref> REEs have been added to feed in livestock to increase their body mass and increase milk production.<ref name=Pagano/> They are most commonly used to increase the body mass of pigs, and it was discovered that REEs increase the digestibility and nutrient use of pigs' digestive systems.<ref name=Pagano/> Studies point to a dose-response when considering toxicity versus positive effects. While small doses from the environment or with proper administration seem to have no ill effects, larger doses have been shown to have negative effects specifically in the organs where they accumulate.<ref name=Pagano/> 

The process of mining REEs in China has resulted in soil and water contamination in certain areas, which when transported into aquatic bodies could potentially bio-accumulate within aquatic biota. In some cases, animals that live in REE-contaminated areas have been diagnosed with organ or system problems.<ref name=Kyung/> REEs have been used in freshwater fish farming because it protects the fish from possible diseases.<ref name=Pagano/> One main reason why they have been avidly used in animal livestock feeding is that they have had better results than inorganic livestock feed enhancers.<ref>{{cite thesis |url=https://edoc.ub.uni-muenchen.de/5936/ |title=Rare Earth Elements in Agriculture with Emphasis on Animal Husbandry |last=Redling |first=Kerstin |date=2006 |type=Dissertation |location=LMU München |publisher=Faculty of Veterinary Medicine |access-date=2018-04-05 |archive-date=June 15, 2022 |archive-url=https://web.archive.org/web/20220615124341/https://edoc.ub.uni-muenchen.de/5936/ |url-status=live}}</ref>

===Remediation after pollution===
{{Update section|date=May 2019}}
After the [[1982 Bukit Merah radioactive pollution]], the mine in [[Malaysia]] has been the focus of a US$100 million cleanup that is proceeding in 2011. After having accomplished the hilltop entombment of 11,000 truckloads of radioactively contaminated material, the project is expected to entail in summer, 2011, the removal of "more than 80,000 steel barrels of radioactive waste to the hilltop repository."<ref name=NYT01/>

In May 2011, after the [[Fukushima nuclear disaster]], widespread protests took place in Kuantan over the [[#Production|Lynas refinery]] and radioactive waste from it. The ore to be processed has very low levels of thorium, and Lynas founder and chief executive Nicholas Curtis said "There is absolutely no risk to public health." T. Jayabalan, a doctor who says he has been monitoring and treating patients affected by the Mitsubishi plant, "is wary of Lynas's assurances. The argument that low levels of thorium in the ore make it safer doesn't make sense, he says, because radiation exposure is cumulative."<ref name=Bl01>Lee, Yoolim, [https://www.bloomberg.com/news/2011-05-31/malaysia-rare-earths-in-largest-would-be-refinery-incite-protest.html "Malaysia Rare Earths in Largest Would-Be Refinery Incite Protest"] {{Webarchive|url=https://web.archive.org/web/20140911001724/http://www.bloomberg.com/news/2011-05-31/malaysia-rare-earths-in-largest-would-be-refinery-incite-protest.html |date=September 11, 2014}}, ''[[Bloomberg L.P.|Bloomberg Markets Magazine]]'', May 31, 2011 5:00 PM ET.</ref> Construction of the facility has been halted until an independent [[United Nations]] [[IAEA]] panel investigation is completed, which is expected by the end of June 2011.<ref>[https://www.bbc.co.uk/news/world-asia-pacific-13593213 "UN investigation into Malaysia rare-earth plant safety"] {{Webarchive|url=https://web.archive.org/web/20220622010100/https://www.bbc.co.uk/news/world-asia-pacific-13593213 |date=June 22, 2022}}, [[BBC]], 30 May 2011 05:52 ET.</ref> [[#Production|New restrictions]] were announced by the Malaysian government in late June.<ref name=B01/>

An [[IAEA]] panel investigation was completed and no construction has been halted. Lynas is on budget and on schedule to start producing in 2011. The IAEA concluded in a report issued in June 2011 that it did not find any instance of "any non-compliance with international radiation safety standards" in the project.<ref>[http://www.iaea.org/newscenter/news/2011/malaysiamissionreport.html IAEA Submits Lynas Report to Malaysian Government] {{Webarchive|url=https://web.archive.org/web/20121007140824/http://www.iaea.org/newscenter/news/2011/malaysiamissionreport.html |date=October 7, 2012}}. Iaea.org (2011-06-29). Retrieved on 2011-09-27.</ref>

If the proper safety standards are followed, REE mining is relatively low impact. Molycorp (before going bankrupt) often exceeded environmental regulations to improve its public image.<ref>{{cite magazine |magazine=High Country News |title=Why rare-earth mining in the West is a bust |url=http://www.hcn.org/issues/47.11/why-rare-earth-mining-in-the-west-is-a-bust |author=Tim Heffernan |date=June 16, 2015 |access-date=September 26, 2017 |archive-date=November 3, 2021 |archive-url=https://web.archive.org/web/20211103103815/https://www.hcn.org/issues/47.11/why-rare-earth-mining-in-the-west-is-a-bust |url-status=live}}</ref>

In Greenland, there is a significant dispute on whether to start a new rare-earth mine in [[Kvanefjeld]] due to environmental concerns.<ref>{{cite news |title=Greenland votes, split on rare earth metals mining |newspaper=Deutsche Welle |date=2021-06-04 |url=https://www.dw.com/en/greenland-votes-split-on-rare-earth-metals-mining/a-57113587 |access-date=2021-04-07 |language=en-GB |archive-date=June 21, 2022 |archive-url=https://web.archive.org/web/20220621090757/https://www.dw.com/en/greenland-votes-split-on-rare-earth-metals-mining/a-57113587 |url-status=live}}</ref>