Mercury in the Environment
Most of the mercury in San Francisco Bay entered during the Gold Rush years. It was used to extract gold from surrounding rocks and after use it was released to the air or washed downstream to the Bay.
The levels of Mercury have been declining in the bay since those times but more is being added each year from other sources. The major sources of new mercury are;
- Erosion of sediments already in the Bay
- Mercury in the rivers flowing from the Guadalupe and Central Valley Watersheds
- Urban stormwater runoff
- Direct atmospheric deposition
- Dental Amalgam
Mercury may be converted from elemental Mercury to Methyl Mercury which is readily absorbed by fish and wildlife. As you move up the food web the concentration of mercury increase as the fish have no way to remove it from their bodies. As a consequence, larger fish have a higher level of mercury contamination. The risk for people is when they eat fish that has a high level of mercury contamination.
The health effects of mercury poisoning are neurological meaning they affect the brain and spinal cord. They can be especially dangerous in pregnant women and young children as the mercury can affect brain size in the child or growing fetus.