Editing Perchlorate (section)

===Water===
In 1998, perchlorate was included in the U.S. EPA [[Safe Drinking Water Act#Unregulated contaminants|Contaminant Candidate List]], primarily due to its detection in California drinking water.<ref>EPA (1998-03-02). "Announcement of the Drinking Water Contaminant Candidate List." ''Federal Register,'' {{usfr|63|10274}}</ref><ref name="Kucharzyk"/>

In 2002, the EPA completed its draft toxicological review of perchlorate and proposed an [[reference dose]] of 0.00003 milligrams per kilogram per day (mg/kg/day) based primarily on studies that identified neurodevelopmental deficits in rat pups. These deficits were linked to maternal exposure to perchlorate.<ref name="greer" />

In 2003, a [[United States District Court for the Central District of California|federal district court]] in California found that the [[CERCLA|Comprehensive Environmental Response, Compensation and Liability Act]] applied, because perchlorate is ignitable, and therefore was a "characteristic" hazardous waste.<ref>''Castaic Lake Water Agency v. Whittaker,'' 272 F. Supp. 2d 1053, 1059–61 (C.D. Cal. 2003).</ref>

Subsequently, the U.S. National Research Council of the [[National Academy of Sciences]] (NAS) reviewed the health implications of perchlorate, and in 2005 proposed a much higher reference dose of 0.0007&nbsp;mg/kg/day based primarily on a 2002 study by Greer ''et al.''<ref name="greer">{{cite journal | vauthors = Greer MA, Goodman G, Pleus RC, Greer SE | title = Health effects assessment for environmental perchlorate contamination: the dose response for inhibition of thyroidal radioiodine uptake in humans | journal = Environmental Health Perspectives | volume = 110 | issue = 9 | pages = 927–937 | date = September 2002 | pmid = 12204829 | pmc = 1240994 | doi = 10.1289/ehp.02110927 }}</ref> During that study, 37 adult human subjects were split into four exposure groups exposed to 0.007 (7 subjects), 0.02 (10 subjects), 0.1 (10 subjects), and 0.5 (10 subjects) mg/kg/day. Significant decreases in iodide uptake were found in the three highest exposure groups. Iodide uptake was not significantly reduced in the lowest exposed group, but four of the seven subjects in this group experienced inhibited iodide uptake. In 2005, the [[Reference dose|RfD]] proposed by NAS was accepted by EPA and added to its integrated risk information system (IRIS).

# The NAS report described the level of lowest exposure from Greer ''et al.'' as a "no-observed-effect level" ([[NOEL]]). However, there was actually an effect at that level although not statistically significant largely due to small size of study population (four of seven subjects showed a slight decrease in iodide uptake).
# Reduced iodide uptake was not considered to be an adverse effect, even though it is a precursor to an adverse effect, [[hypothyroidism]]. Therefore, additional safety factors, would be necessary when extrapolating from the point of departure to the RfD.
# Consideration of data uncertainty was insufficient because the Greer, ''et al.'' study reflected only a 14-day exposure (=acute) to healthy adults and no additional safety factors were considered to protect sensitive subpopulations like for example, breastfeeding newborns.

Although there has generally been consensus with the Greer ''et al.'' study, there has been no consensus with regard to developing a perchlorate RfD. One of the key differences results from how the point of departure is viewed (i.e., NOEL or "lowest-observed-adverse-effect level",  [[LOAEL]]), or whether a benchmark dose should be used to derive the RfD. Defining the point of departure as a NOEL or LOAEL has implications when it comes to applying appropriate safety factors to the point of departure to derive the RfD.<ref>{{cite web | title = EPA's Perchlorate Drinking Water Preliminary Remediation Goal (Prg). | url = http://www.epa.gov/region10/pdf/sites/euclid/eroad-perchlorate-memo-071307.pdf | archive-url = https://web.archive.org/web/20170303012904/http://www.epa.gov/region10/pdf/sites/euclid/eroad-perchlorate-memo-071307.pdf | archive-date = 3 March 2017 | work = Office of Environmental Health Assessments | publisher = Washington State Department of Health | date = 13 July 2007 }}</ref>

In early 2006, EPA issued a "Cleanup Guidance" and recommended a [[Drinking Water Equivalent Level]] (DWEL) for perchlorate of 24.5&nbsp;μg/L.{{Citation needed|date=December 2020}} Both DWEL and Cleanup Guidance were based on a 2005 review of the existing research by the [[National Academy of Sciences]] (NAS).<ref name="NAS1">{{cite book |title=Health Implications of Perchlorate Ingestion |author=Committee to Assess the Health Implications of Perchlorate Ingestion, National Research Council |year=2005 |publisher=The National Academies Press |location=Washington, DC |isbn=978-0-309-09568-6 |url=https://archive.org/details/healthimplicatio00nati |doi=10.17226/11202 }}</ref>

Lacking a federal drinking water standard, several states subsequently published their own standards for perchlorate including Massachusetts in 2006{{citation needed|date=November 2017}} and California in 2007. Other states, including Arizona, Maryland, Nevada, New Mexico, New York, and Texas have established non-enforceable, advisory levels for perchlorate.{{citation needed|date=May 2017}}

In 2008, EPA issued an interim [[Safe Drinking Water Act#Health advisories|drinking water health advisory]] for perchlorate and with it a guidance and analysis concerning the impacts on the environment and drinking water.<ref name="EPA-perchlorate">{{cite web |url=https://www.epa.gov/dwstandardsregulations/perchlorate-drinking-water |title=Perchlorate in Drinking Water |author=<!--Not stated--> |date=2017-03-31 |website=Drinking Water Contaminants—Standards and Regulations |publisher=EPA}}</ref> California also issued guidance{{when|date=November 2017}} regarding perchlorate use.<ref>{{cite web |url=http://www.cdph.ca.gov/certlic/drinkingwater/Pages/Perchlorate.aspx |title=Perchlorate in Drinking Water |date=2012-12-07 |website=Drinking Water Systems |publisher=California Department of Public Health |location=Sacramento, CA |archive-date=2013-02-06 |archive-url=https://web.archive.org/web/20130206064109/http://www.cdph.ca.gov/certlic/drinkingwater/Pages/Perchlorate.aspx}}</ref> Both the [[United States Department of Defense|Department of Defense]] and some environmental groups voiced questions about the NAS report,{{citation needed|date=November 2017}} but no credible science has emerged to challenge the NAS findings.{{citation needed|date=November 2017}}

In February 2008, the U.S. [[Food and Drug Administration]] (FDA) reported that U.S. toddlers on average were being exposed to more than half of EPA's safe dose from food alone.<ref>{{cite journal |last1=Renner |first1=Rebecca |date=2008-03-15 |title=Perchlorate In Food |journal=Environ. Sci. Technol. |volume=42 |issue=6 |page=1817 |doi=10.1021/es0870552|pmid=18409597 |bibcode=2008EnST...42.1817R |doi-access=free }}</ref> In March 2009, a [[Centers for Disease Control]] study found 15 brands of infant formula contaminated with perchlorate and that combined with existing perchlorate drinking water contamination, infants could be at risk for perchlorate exposure above the levels considered safe by EPA.

In 2010, the [[Massachusetts Department of Environmental Protection]] set a 10 fold lower RfD (0.07&nbsp;μg/kg/day) than the NAS RfD using a much higher uncertainty factor of 100. They also calculated an Infant drinking water value, which neither US EPA nor [[CalEPA]] had done.<ref name="ma">{{cite journal | vauthors = Zewdie T, Smith CM, Hutcheson M, West CR | title = Basis of the Massachusetts reference dose and drinking water standard for perchlorate | journal = Environmental Health Perspectives | volume = 118 | issue = 1 | pages = 42–48 | date = January 2010 | pmid = 20056583 | pmc = 2831965 | doi = 10.1289/ehp.0900635 }}</ref>

On February 11, 2011, EPA determined that perchlorate meets the [[Safe Drinking Water Act]] criteria for regulation as a contaminant.<ref name="EPA-perchlorate"/><ref>EPA (2011-02-11). "Drinking Water: Regulatory Determination on Perchlorate." {{usfr|76|7762}}</ref> The agency found that perchlorate may have an adverse effect on the health of persons and is known to occur in [[public water system]]s with a frequency and at levels that it presents a public health concern. Since then EPA has continued to determine what level of contamination is appropriate. EPA prepared extensive responses to submitted public comments.<ref>[http://www.regulations.gov/#!searchResults;rpp=10;po=0;s=EPA-HQ-OW-2008-0692 EPA-HQ-OW-2009-0297] "Docket ID" for EPA</ref>{{better source needed|date=November 2017}}

In 2016, the [[Natural Resources Defense Council]] (NRDC) filed a lawsuit to accelerate EPA's regulation of perchlorate.<ref>{{cite web |title=Regulatory Update At-A-Glance |url=https://www.amwa.net/update-glance/regulatory-update-glance |access-date=2019-04-04 |publisher=Association of Metropolitan Water Agencies |location=Washington, DC |archive-date=2019-04-06 |archive-url=https://web.archive.org/web/20190406015412/https://www.amwa.net/update-glance/regulatory-update-glance |url-status=dead }}</ref>

In 2019, EPA proposed a [[Maximum Contaminant Level]] of 0.056&nbsp;mg/L for public water systems.<ref>EPA (2019-06-26). "National Primary Drinking Water Regulations: Perchlorate." Proposed Rule. ''Federal Register.'' {{usfr|84|30524}}.</ref>

On June 18, 2020, EPA announced that it was withdrawing its 2011 regulatory determination and its 2019 proposal, stating that it had taken "proactive steps" with state and local governments to address perchlorate contamination.<ref>{{cite web |title=Perchlorate in Drinking Water; Final Action |url=https://www.epa.gov/sdwa/perchlorate-drinking-water |date=2020-06-18 |publisher=EPA}}</ref> In September 2020 NRDC filed suit against EPA for its failure to regulate perchlorate, and stated that 26 million people may be affected by perchlorate in their drinking water.<ref>{{cite news |last=Slisco |first=Aila |title=EPA Sued For Not Regulating Rocket Fuel Chemical in Drinking Water |url=https://www.msn.com/en-us/news/us/epa-sued-for-not-regulating-rocket-fuel-chemical-in-drinking-water/ar-BB18GT1p |date=2020-09-04 |work=Newsweek}}</ref> On March 31, 2022, the EPA announced that a review confirmed its 2020 decision.<ref>{{cite web |title=EPA Announces Plan to Protect the Public from Perchlorate in Drinking Water |url=https://www.epa.gov/newsreleases/epa-announces-plan-protect-public-perchlorate-drinking-water |publisher=U.S. Environmental Protection Agency |access-date=18 April 2022 |date=March 31, 2022}}</ref> Following the NRDC lawsuit, in 2023 the [[United States Court of Appeals for the District of Columbia Circuit|US Court of Appeals for the DC Circuit]] ordered EPA to develop a perchlorate standard for public water systems.<ref>{{cite magazine |last=Erickson |first=Britt E. |title=Court orders EPA to regulate perchlorate in drinking water |url=https://cen.acs.org/environment/pollution/Court-orders-EPA-regulate-perchlorate-drinking-water/101/web/2023/05 |date=2023-05-11 |magazine=Chemical and Engineering News |publisher=American Chemical Society}}</ref> EPA stated that it will publish a proposed standard for perchlorate in 2025, and issue a final rule in 2027.<ref>{{cite web |title=Perchlorate in Drinking Water |url=https://www.epa.gov/sdwa/perchlorate-drinking-water |date=2024-01-05 |publisher=EPA}}</ref>