Mercury in the Sierra

How did mercury get here?

Millions of pounds of mercury were brought to the Sierra for use in gold processing, and approximately 10%-30% was lost to the environment. Today, mercury affects people and wildlife that eat fish from the Sierra, all the way down to the San Francisco Bay.

Toxic in the Body

  • Mercury can damage the brain, central nervous system, immune system, kidneys and heart.
  • Pregnant women need to be especially careful because mercury (even at very low levels) can cause permanent learning disabilities in the developing child.
  • Children are particularly vulnerable.
  • If you feel you, your baby or your child may be at risk, talk to your doctor.
  • Pregnant or planning on becoming pregnant? Mercury stays in the human body for about one year. Start making healthy choices now.

What can I do?

1.       Look up safe eating guidelines.

Go to and click on the places where you go fishing for advice about how much fish of each kind you can safely eat from that location.

No information? – Not necessarily safe. If the location or kind of fish you are interested in is not listed, it does NOT mean it’s safe to eat.  It just means that not enough information has been collected to tell either way.  Follow OEHHA’s General Guidelines for lakes and reservoirs that lack a fish advisory:

2.         Know your fish.

Learn how to make good choices about the fish you catch, based on which fish generally contain more mercury than others.

  • Smaller, younger fish have less mercury than older, larger fish.
  • Predatory fish (ones that eat other fish) have higher mercury.
  • Fish that have been planted generally have lower mercury.
  • Avoid large predatory fish whether wild-caught or store bought.
  • Eat smaller younger fish, which generally contain less mercury.
  • Mercury is stored in the entire fish. You cannot clean the head guts, fat and skin to get rid of it. Other toxins, like PCBs may be stored there so trimming off these areas is still a good idea.
  • Check fish you plan to eat at the EPA and OEHHA websites. You can also visit a mercury calculator website such as the one at

 3.       Make your voice heard!

We all deserve to eat fish we catch, and to have good information about how to protect ourselves and our families. Tell your elected officials we need to clean up mercury from lakes and rivers in the Sierra, and we need more information about which fish are safe to eat.

Interested in learning more?

Great! Check out our publications:

  • Fish, Mercury and You educational brochure
  • Mining’s Toxic Legacy – The Sierra Fund’s comprehensive report on the health, environmental and cultural effects of legacy mining toxins including mercury
  • Gold Country Angler Survey – The Sierra Fund’s study that contacted over 150 Sierra anglers to learn about mercury exposure potential – and it also includes in depth information about Sierra mercury sources and extent of the pollution

Or, for further information, read our Frequently Asked Questions or check out these external resources about mercury.

See Also:

Peer-reviewed journal articles about mercury in the human body – Compiled by partner organization CIEA, and provided as part of their Mercury Health Toolkit

Fish Consumption Advisories – State-issued fish consumption advisories for lakes, reservoirs and rivers in California, many based on high mercury levels in fish

Gold Country Angler Survey – A study The Sierra Fund has been conducting since 2010 to look at exposure potential to mercury through eating locally caught fish

Get the Mercury Out Campaign – The Sierra Fund is spearheading a campaign to increase public funding for cleanup of mercury from legacy mines.

Frequently Asked Questions – For concerned citizens

Malakoff Diggins – The Sierra Fund has been working to assess and address the ongoing sediment and mercury discharge from one of California’s largest and most iconic hydraulic mines, Malakoff Diggins