Editing San Francisco Bay (section)

==Pollution==

San Francisco Bay faces many of the same water quality issues as other urban waterways in industrialized countries, or downstream of intensive agriculture. According to state water quality regulators, San Francisco Bay waters do not meet water quality standards for the following pollutants:<ref>{{Cite conference| last = California State Water Resources Control Board| title = 2024 California Integrated Report: Surface Water Quality Assessments to Comply with Clean Water Act Sections 303(d) and 305(b)| location = Sacramento, California| access-date = 2024-08-15| date = 2024-03-24| url = https://www.waterboards.ca.gov/water_issues/programs/water_quality_assessment/2024-integrated-report.html}}</ref>

* [[DDT]]
* [[Mercury (element)|Mercury]] 
* [[Selenium]]
* [[Polychlorinated biphenyls]] (PCBs)
* [[Polychlorinated dibenzodioxins|Dioxin]] compounds
* [[Polychlorinated dibenzofurans|Furan]] compounds 
* [[Litter|Trash]]
* [[Diazinon]]
* [[Chlordane]]
* [[Dieldrin]]

===Mercury===
Industrial, mining, and other uses of [[Mercury (element)|mercury]] have resulted in a widespread distribution in the bay, with uptake in the bay's [[phytoplankton]] and contamination of its sportfish.<ref>{{cite book|doi=10.1007/978-0-387-74816-0_2 |journal=Rev Environ Contam Toxicol |year=2008 |volume=194 |pages=29–54 |last1=Conaway |first1=CH |last2=Black |first2=FJ |last3=Grieb |first3=TM |last4=Roy |first4=S |last5=Flegal |first5=AR |title=Reviews of Environmental Contamination and Toxicology |chapter=Mercury in the San Francisco Estuary |pmid=18069645 |isbn=978-0-387-74815-3}}</ref>

===Oil spills===
In January 1971, two [[Standard Oil]] tankers collided in the bay, creating an {{convert|800000|USgal|L|abbr=off|sp=us|adj=on}} [[1971 San Francisco Bay oil spill|oil spill disaster]], which spurred environmental protection of the bay. In November 2007, a ship named ''[[MSC Venezia|COSCO Busan]]'' collided with the [[San Francisco–Oakland Bay Bridge]] and spilled over {{convert|58000|USgal|L|abbr=off|sp=us}} of [[fuel oil#Bunker fuel|bunker fuel]], creating the largest [[oil spill]] in the region since 1996.<ref>{{cite news|url=https://www.latimes.com/archives/la-xpm-2007-nov-09-me-bay9-story.html |work=Los Angeles Times |first=Eric |last=Bailey |title=Oil oozes in S.F. Bay after ship hits bridge |date=November 9, 2007 |archive-url=https://web.archive.org/web/20190322094319/https://www.latimes.com/archives/la-xpm-2007-nov-09-me-bay9-story.html |archive-date=March 22, 2019 |url-status=live}}</ref>

===Nutrients===
The bay also has some of the highest levels of dissolved inorganic nitrogen known from any coastal water body, mostly originating from treated wastewater from [[Publicly owned treatment works]].<ref>{{cite journal|title=Nutrient Status of San Francisco Bay and Its Management Implications|journal=Estuaries and Coasts|year=2020|volume=43|pages=1299–1317|doi=10.1007/s12237-020-00737-w |last1=Cloern |first1=James E. |last2=Schraga |first2=Tara S. |last3=Nejad |first3=Erica |last4=Martin |first4=Charles |issue=6 |doi-access=free |bibcode=2020EstCo..43.1299C }}</ref> In other bays, such nutrient levels would likely lead to [[eutrophication]], but historically, the bay has had less [[harmful algal blooms]] than other water bodies with similar nutrient concentrations. Potential explanations have included the presence of intensive "top-down control" from grazing clams like ''[[Potamocorbula]]'', high sediment supply limiting light availability for the algae, and intensive tidal mixing. The occurrence of an unprecedented harmful algal bloom of ''[[Heterosigma akashiwo]]'' in 2022, resulting in mass fish deaths and anoxia,<ref>{{cite news|url=https://abc7news.com/sf-bay-toxic-algae-turning-water-brown-heterosigma-akashiwo-area-waters/12135158/|title=Harmful algae bloom spreading across San Francisco Bay, turning water brown|author=Liz Kreutz|publisher=ABC7 News|access-date=February 28, 2024|archive-date=February 28, 2024|archive-url=https://web.archive.org/web/20240228190932/https://abc7news.com/sf-bay-toxic-algae-turning-water-brown-heterosigma-akashiwo-area-waters/12135158/|url-status=live}}</ref> suggests that the mechanisms of control on algal growth may be eroding.

===PBDEs===
The bay was once considered a hotspot for polybrominated diphenyl ether ([[PBDE]]) flame retardants used to make upholstered furniture and infant care items less flammable. PBDEs have been largely phased out and replaced with alternative phosphate flame retardants. A 2019 [[San Francisco Estuary Institute]] (SFEI) study assayed a wide range of these newer flame retardant chemicals in Bay waters, bivalve [[California mussel]]s (''Mytilus californianus''), and [[harbor seal]]s (''Phoca vitulina'') which haul out in Corkscrew Slough<ref>{{cite gnis|233719|Corkscrew Slough}}</ref> on [[Bair Island]] in [[San Mateo County]], with phosphate flame retardant contaminants such as [[tris(1,3-dichloro-2-propyl)phosphate]] (TDCPP) and [[triphenyl phosphate]] (TPhP) found at levels comparable to thresholds for aquatic toxicity.<ref>{{cite journal |title=Characterization of brominated, chlorinated, and phosphate flame retardants in San Francisco Bay, an urban estuary |first1=Rebecca |last1=Sutton |first2=Da |last2=Chen |first3=Jennifer |last3=Sun |first4=Denise J. |last4=Greig |first5=Yan |last5=Wu |journal=Science of the Total Environment |volume=652 |year=2019 |pages=212–223 |url=https://www.sfei.org/news/rmp-journal-article-characterization-brominated-chlorinated-and-phosphate-flame-retardants-san#sthash.nPaHsoyk.dpbs |access-date=March 16, 2019 |doi=10.1016/j.scitotenv.2018.10.096 |pmid=30366322 |bibcode=2019ScTEn.652..212S |doi-access=free |archive-date=April 3, 2019 |archive-url=https://web.archive.org/web/20190403133425/https://www.sfei.org/news/rmp-journal-article-characterization-brominated-chlorinated-and-phosphate-flame-retardants-san#sthash.nPaHsoyk.dpbs |url-status=live }}</ref>

===Emerging contaminants===

Thousands of man-made chemicals are found in Bay water, sediment, and organisms. For many of these, there is little or no data on their impacts on the environment or human health, and they are not regulated by state or federal law. These are often referred to as "contaminants of emerging concern." The [[San Francisco Estuary Institute]] has studied these chemicals in the Bay since 2001.<ref>{{Cite conference| publisher = San Francisco Estuary Institute| pages = 98| last = SFEI| title = 2013 Pulse of the Bay: Contaminants of Emerging Concern| location = Richmond, California| date = 2013}}</ref> Scientists have identified the following most likely to have a negative impact on Bay wildlife:<ref>{{Cite conference| publisher = San Francisco Estuary Institute| last1 = Miller| first1 = Ezra| last2 = Mendez| first2 = Miguel| last3 = Shimabuku| first3 = Ila| last4 = Buzby| first4 = Nina| last5 = Sutton| first5 = Rebecca| title = Contaminants of Emerging Concern in San Francisco Bay: A Strategy for Future Investigations 2020 Update| location = Richmond, California| access-date = 2021-03-16| date = September 2020| url = https://www.sfei.org/sites/default/files/biblio_files/CEC%20Strategy%20-%202020%20Update%20-%20Final_92320.pdf}}</ref>

* [[PFOS]]
* [[fipronil]]
* [[nonylphenol]]s
* nonylphenol ethoxylates

{{wide image|San_Francisco_with_two_bridges_and_the_low_fog.jpg|1200px|City skyline through the fog, from the [[Golden Gate National Recreation Area]]}}