Editing DDT (section)

===Eggshell thinning{{anchor|Effects_on_wildlife_and_eggshell_thinning}}===
The chemical and its breakdown products DDE and DDD caused eggshell thinning and population declines in multiple North American and European [[bird of prey]] species.<ref name="ATSDRc5"/><ref>{{cite journal | vauthors = Vos JG, Dybing E, Greim HA, Ladefoged O, Lambré C, Tarazona JV, Brandt I, Vethaak AD | title = Health effects of endocrine-disrupting chemicals on wildlife, with special reference to the European situation | journal = Critical Reviews in Toxicology | volume = 30 | issue = 1 | pages = 71–133 | date = January 2000 | pmid = 10680769 | doi = 10.1080/10408440091159176 | s2cid = 11908661 }}</ref><ref name=Stokstad07/><ref name="Lundholm, 1997"/><ref name=Tubbs2016>{{cite journal |doi=10.1080/23273747.2016.1173766 |title=California condors and DDT: Examining the effects of endocrine disrupting chemicals in a critically endangered species |journal=Endocrine Disruptors |volume=4 |pages=e1173766 |year=2016 |last1=Tubbs |first1=Christopher W. | name-list-style = vanc |doi-access=free }}</ref><ref name="ibis">{{cite journal |doi=10.1046/j.1474-919X.2003.00132.x |title=California Condors and DDE: A re-evaluation |journal=Ibis |volume=145 |issue=1 |pages=136–151 |year=2002 |last1=Snyder |first1=Noel F. R. |last2=Meretsky |first2=Vicky J. | name-list-style = vanc }}</ref> Both laboratory experiments and field studies confirmed this effect.<ref>{{cite news | url = https://www.epa.gov/caddis-vol1/case-ddt-revisiting-impairment | title = The Case of DDT: Revisiting the Impairment | work = US Environmental Protection Agency (EPA) | access-date = August 5, 2021 | archive-date = August 5, 2021 | archive-url = https://web.archive.org/web/20210805060600/https://www.epa.gov/caddis-vol1/case-ddt-revisiting-impairment | url-status = live }}</ref> The effect was first conclusively proven at [[Bellow Island]] in [[Lake Michigan]] during [[University of Michigan]]-funded studies on [[American herring gull]]s in the mid-1960s.<ref name="mynorthscience">{{cite web |last1=Smith |first1=Jeff |title=The Science Behind Northport's Gull Island |url=https://mynorth.com/2017/05/the-science-behind-northports-gull-island/ |website=MyNorth.com |access-date=8 September 2020 |date=9 May 2017 |archive-date=May 19, 2021 |archive-url=https://web.archive.org/web/20210519235311/https://mynorth.com/2017/05/the-science-behind-northports-gull-island/ |url-status=live }}</ref> DDE-related eggshell thinning is considered a major reason for the decline of the [[bald eagle]],<ref name=Stokstad07/> [[brown pelican]],<ref>"Endangered and Threatened Wildlife and Plants; 12-Month Petition Finding and Proposed Rule To Remove the Brown Pelican (Pelecanus occidentalis) From the Federal List of Endangered and Threatened Wildlife; Proposed Rule", Fish and Wildlife Service, U.S. Department of the Interior, February 20, 2008. {{Federal Register|73|9407}}</ref> [[peregrine falcon]] and [[osprey]].<ref name="ATSDRc5" /> However, birds vary in their sensitivity to these chemicals, with [[birds of prey]], [[waterfowl]] and [[passerine|song birds]] being more susceptible than [[chicken]]s and [[Galliformes|related species]].<ref name="ATSDRc5"/><ref name="EHC83" />   Even in 2010, [[California condor]]s that feed on [[sea lion]]s at [[Big Sur]] that in turn feed in the Palos Verdes Shelf area of the [[Montrose Chemical Corporation of California|Montrose Chemical]] [[Superfund]] site exhibited continued thin-shell problems,<ref>{{cite news | last = Moir | first = John | name-list-style = vanc | url = https://www.nytimes.com/2010/11/16/science/16condors.html | title = New Hurdle for California Condors May Be DDT From Years Ago | work = The New York Times | date = November 15, 2010 | access-date = February 7, 2017 | archive-date = September 21, 2017 | archive-url = https://web.archive.org/web/20170921194609/http://www.nytimes.com/2010/11/16/science/16condors.html | url-status = live }}</ref><ref>{{cite journal |vauthors=Kurle CM, Bakker VJ, Copeland H, Burnett J, Jones Scherbinski J, Brandt J, Finkelstein ME |title=Terrestrial Scavenging of Marine Mammals: Cross-Ecosystem Contaminant Transfer and Potential Risks to Endangered California Condors (Gymnogyps californianus) |journal=Environmental Science & Technology |volume=50 |issue=17 |pages=9114–9123 |year=2016 |pmid=27434394 |doi=10.1021/acs.est.6b01990 |bibcode=2016EnST...50.9114K |s2cid=206559840 |url=http://www.escholarship.org/uc/item/1646t91t |access-date=June 13, 2019 |archive-date=June 22, 2020 |archive-url=https://web.archive.org/web/20200622174112/https://escholarship.org/uc/item/1646t91t |url-status=live }}</ref>  though DDT's role in the decline of the [[California condor]] is disputed.<ref name="ibis"/><ref name=Tubbs2016/>

The biological thinning mechanism is not entirely understood, but DDE appears to be more potent than DDT,<ref name="ATSDRc5"/> and strong evidence indicates that ''p'',''p{{'}}''-DDE inhibits [[calcium ATPase]] in the [[Biological membrane|membrane]] of the shell gland and reduces the transport of [[calcium carbonate]] from [[blood]] into the eggshell gland. This results in a dose-dependent thickness reduction.<ref name="ATSDRc5"/><ref>{{cite book | vauthors = Walker CH, Sibly RM, Hopkin SP, Peakall DB | title = Principles of ecotoxicology | publisher = CRC/Taylor & Francis | location = Boca Raton, FL | isbn = 978-0-8493-3635-5 | year = 2006 | edition = 3rd | url = https://books.google.com/books?id=WxfSBQAAQBAJ&pg=PA300 | pages = 300 ff | access-date = August 29, 2022 | archive-date = July 31, 2020 | archive-url = https://web.archive.org/web/20200731135732/https://books.google.com/books?id=WxfSBQAAQBAJ&pg=PA300 | url-status = live }}</ref><ref name="Guillette, 2006">{{cite web |last=Guillette |first=Louis J. |name-list-style=vanc |year=2006 |url=http://www.ehponline.org/members/2005/8045/8045.pdf |title=Endocrine Disrupting Contaminants |access-date=February 2, 2007 |archive-url=https://web.archive.org/web/20090325085455/http://www.ehponline.org/members/2005/8045/8045.pdf |archive-date=March 25, 2009 |url-status=dead |df=mdy }}</ref><ref name="Lundholm, 1997">{{cite journal | vauthors = Lundholm CD | title = DDE-induced eggshell thinning in birds: effects of ''p'',''p{{'}}''-DDE on the calcium and prostaglandin metabolism of the eggshell gland | journal = Comparative Biochemistry and Physiology C | volume = 118 | issue = 2 | pages = 113–128 | date = October 1997 | pmid = 9490182 | doi = 10.1016/S0742-8413(97)00105-9 }}</ref> Other evidence indicates that o,p'-DDT disrupts female reproductive tract development, later impairing eggshell quality.<ref>{{cite journal | vauthors = Holm L, Blomqvist A, Brandt I, Brunström B, Ridderstråle Y, Berg C | title = Embryonic exposure to ''o'',''p{{'}}''-DDT causes eggshell thinning and altered shell gland carbonic anhydrase expression in the domestic hen | journal =Environmental Toxicology and Chemistry| volume = 25 | issue = 10 | pages = 2787–2793 | date = October 2006 | pmid = 17022422 | doi = 10.1897/05-619R.1 | s2cid = 9298213 }}</ref> Multiple mechanisms may be at work, or different mechanisms may operate in different species.<ref name="ATSDRc5"/>