Sources and Toxicity of Mercury in the San Francisco Bay Area, Spanning California and Beyond

Table 1

Environmental methylmercury concentrations measured in air, water, and sediments.

Location of mercury	Amount or range of MeHg concentrations	Air, water, and sediment transport	Literature source
Air in Europe	Occurs in picograms/m^3. Picograms are equivalent to parts per trillion (ppt).	Mercury is transported worldwide, regionally, and locally.	[40]
Water from Sacramento River Basin, CA (where most gold mining took place during 1849–1981)	0.27–2.84 ng/g, which is equivalent to parts per billion (ppb).	Serves as distribution source of Hg via rain, streams, and run-off from lakes and oceans. Hg becomes CH3Hg through microbial processes in water.	[41]
Sediments collected from within SFO Bay and at Oakland estuary	SFO Bay samples analyzed 2.3 ppm (dry weight) in SFO Bay’s Oakland Estuary.	Hg trapped in aquatic sediment allows sulfate-reducing bacteria to transform elemental Hg to organic CH3Hg.	[42]