Editing Great Lakes (section)

==== Sewage ====
The amount of raw sewage dumped into the waters was the primary focus of both the first Great Lakes Water Quality Agreement and federal laws passed in both countries during the 1970s. Implementation of secondary treatment of municipal sewage by major cities greatly reduced the routine discharge of untreated sewage during the 1970s and 1980s.<ref>{{cite web |url = http://ohioseagrant.osu.edu/_documents/publications/FS/FS-046%20Lake%20Erie%20water%20quality%20past%20present%20future.pdf |archive-url = https://web.archive.org/web/20060902100228/http://ohioseagrant.osu.edu/_documents/publications/FS/FS-046%20Lake%20Erie%20water%20quality%20past%20present%20future.pdf |archive-date = September 2, 2006 |url-status = live |title = Lake Erie Water Quality Past Present and Future |access-date = December 4, 2013 }}</ref> The [[International Joint Commission]] in 2009 summarized the change: "Since the early 1970s, the level of treatment to reduce pollution from waste water discharges to the Great Lakes has improved considerably. This is a result of significant expenditures to date on both infrastructure and technology, and robust regulatory systems that have proven to be, on the whole, quite effective."<ref name="ijc.org">{{Cite book |url = http://www.ijc.org/php/publications/pdf/ID1631.pdf |archive-url = https://web.archive.org/web/20100924165650/http://ijc.org/php/publications/pdf/ID1631.pdf |archive-date = September 24, 2010 |url-status = live |title = 14th Biennial Report on Great Lakes Water Quality }}</ref> The commission reported that all urban sewage treatment systems on the U.S. side of the lakes had implemented secondary treatment, as had all on the Canadian side except for five small systems.{{Citation needed|date=September 2012}}

Though contrary to federal laws in both countries, those treatment system upgrades have not yet eliminated [[combined sewer]] overflow events.{{citation needed|date=December 2013}} This describes when older sewerage systems, which combine storm water with sewage into single sewers heading to the treatment plant, are temporarily overwhelmed by heavy rainstorms. Local sewage treatment authorities then must release untreated effluent, a mix of rainwater and sewage, into local water bodies. While enormous public investments such as the [[Deep Tunnel]] projects in Chicago and [[Milwaukee]] have greatly reduced the frequency and volume of these events, they have not been eliminated. The number of such overflow events in Ontario, for example, is flat according to the International Joint Commission.<ref name="ijc.org"/> Reports about this issue on the U.S. side highlight five large municipal systems (those of Detroit, Cleveland, Buffalo, Milwaukee and [[Gary, Indiana|Gary]]) as being the largest current periodic sources of untreated discharges into the Great Lakes.<ref>{{cite web |url = http://healthylakes.org/press-releases/new-report-solving-region%E2%80%99s-sewage-crisis-will-create-jobs-restore-great-lakes/ |title = New Report: Solving Region's Sewage Crisis Will Create Jobs, Restore Great Lakes |archive-url = https://web.archive.org/web/20141129035802/http://healthylakes.org/press-releases/new-report-solving-region%E2%80%99s-sewage-crisis-will-create-jobs-restore-great-lakes/ |archive-date = November 29, 2014 |work = Healthylakes.org |date = August 9, 2010 |access-date = December 7, 2016 }}</ref>
[[File:Diatoms_through_the_microscope.jpg|thumb|upright=1.3|Diatoms of different sizes seen through the microscope. These minuscule [[phytoplankton]] are encased within a [[silicate]] [[cell wall]].]]

The fish of the Great Lakes have anti-depressant drugs meant for humans in their brains, which has caused concerns. The number of American adults who take anti-depressant drugs rose from 7.7% of all American adults in 1999–2002 to 12.7% in 2011–2014. As the anti-depressant drugs pass out of human bodies and through sanitation systems into the Great Lakes, this has resulted in fish in the Great Lakes with twenty times the level of anti-depressants in their brains than what is in the water, leading to the fish being exceedingly happy and hence less risk-averse, to the extent of damaging the fish populations.<ref name="The Economist">{{cite news |title = Antidepressants are finding their way into fish brains |url = https://www.economist.com/united-states/2018/02/08/antidepressants-are-finding-their-way-into-fish-brains |access-date = January 15, 2023 |newspaper = The Economist |date = February 8, 2018 }}</ref>