1. Radon
- naturally occurring radioactive gas that is invisible and odorless, it forms from the radioactive decay of small amounts of uranium and thorium naturally present in rocks, mainly black shales and certain igneous rocks.
2. Mercury
-A neurotoxin (to humans), mainly entering the body through certain species of fish (biomagnification) as methyl mercury.
-Natural sources of mercury: volcanoes, hot springs, and natural mercury deposits.
-Sources related to human activities: include coal combustion, waste incineration, certain industrial activities and some mining activities.
-Cinnabar (mercury sulfide, HgS) can be found in New Almaden district, Santa Clara County, California.
3. Asbestos
Chrysotile and amphibole asbestos (such as tremolite) occur naturally in certain geologic settings in California, most commonly in association with ultramafic rocks and along associated faults.
|