Editing Rare-earth element (section)

===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>