Spring 2000
Where Be-ist Mercury?
by Michael Stanley-Jones
How toxic is the Bay? Many toxic metals occur naturally in the soils of the South San Francisco Bay Area. When disturbed or artificially increased by human activity, these metals can be released to the waters of the San Francisco Bay, causing impairment of habitat and threats to human health. Over the years of human activity, the Bay has become a Toxic Soup.
Take mercury, please! Many soils of the Santa Clara Basin are rich in cinnabar, a cinnamon to brick-reddish colored ore also known as mercury sulfide (HgS). When cinnabar breaks down under the “right” aquatic conditions it turns into methyl mercury, a highly toxic substance. Methyl mercury can be taken up in the tissues of fish, which when eaten in quantity, pose a threat to human health.
Mercury is especially dangerous to pregnant women, as it can damage fetal development. Mercury is also suspected of retarding the cognitive development of children.
According to the San Francisco Regional Water Quality Control Board, the Guadalupe River watershed is the most mercury contaminated river basin in the nation, based on samples of mercury in bedded sediments taken from the mouth of the river, where the Guadalupe enters the Bay. Public Health officials have warned Bay Area communities not to consume fish caught in the Guadalupe (nor in the Bay itself) as these may contain toxic levels of mercury. Many people do eat fresh Bay-caught fish in spite of the warnings.
What is the cause of the contamination of our basin’s waters and fish? For more than one and a half centuries, humans have extracted mercury ore from South Bay mining works to make quicksilver, a form of mercury useful for extracting gold from its natural ores.
Santa Clara County Quicksilver mines were once the 8th largest producers of mercury in the world. The Gold Rush that made San Francisco “The Gilded City” has made Santa Clara Basin the state’s leading Mercury Hot Spot. More than a million pounds of released mercury line our Basin’s streams and rivers.
Silicon Valley Toxics Coalition’s Sustainable Water Program is currently working to decrease contamination of the Lower South San Francisco Bay from three toxic metals: copper, nickel and mercury. All three metals occur naturally in smaller or greater amounts in our Basin. Human recklessness has multiplied their release into the waters of the Bay and its upstream sources, causing impairment to species and, in the case of mercury, to humans consuming contaminated fish. Humans have introduced many new sources of these metals into the watershed. For example, high-tech industry plating technologies have discharged nickel into wastewater; brake pads used in autos and trucks release copper particles to the roadways; dental amalgams (fillings) and cement manufacturing contribute incinerated mercury to the air.
Regulatory measures to reduce sources of copper and nickel entering the South Bay have been largely successful. In recent years, clam populations living in the Bay offshore from Palo Alto’s wastewater treatment facility show signs of recovery. SVTC is working with city officials, CLEAN South Bay and the Santa Clara Basin Watershed Management Initiative to plan for continued reductions of the use and release of these metals.
We believe similar progress can be made to reduce mercury in the Bay. Air release of mercury must be eliminated. Terrestrial Hot Spots must be identified and cleaned up. Consumer products containing mercury, such as thermometers and thermostats, need to be taken off the market and replaced with safer, sustainable alternatives. Crematoriums will have to cease incinerating dental amalgam (fillings are 56% mercury). But most importantly, mercury lining our streams and rivers must be removed or isolated from the system. The era of treating our waters as a Toxic Soup are over.
Michael Stanley-Jones is SVTC’s Senior Researcher
Editor’s Note: Silicon Valley Toxics Coalition’s participation in the Santa Clara Basin Watershed Management Initiative is supported through two grants from the City of San Jose Watershed Program and South Bay Copper/Nickel Total Maximum Daily Load (TMDL) process. We wish to thank the City of San Jose for its generous support of community efforts to reduce toxic contamination of the San Francisco Bay and upland watersheds.
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