There's a common culprit between contamination from Moffett Field, old semiconductor sites, and even old dry cleaning sites: chlorinated solvents, trichloroethy

There's a common culprit between contamination from Moffett Field, old semiconductor sites, and even old dry cleaning sites: chlorinated solvents, trichloroethylene in particular. TCE is non-corrosive, non-flammable, cheap, a great solvent for many non-water-soluble compounds, and it evaporates cleanly and rapidly. It also has a relatively low acute toxicity to humans. It was commercialized in the 1920s as a surgical anesthetic, and still sees some medical use: http://apps.who.int/medicinedocs/en/d/Jh2929e/4.5.html http://apps.who.int/medicinedocs/en/d/Jh2929e/4.5.html I even found it sold by the can in a hardware store as recently as 2002. Unfortunately, it's a carcinogen and can cause neurological problems with heavy or chronic exposure. It breaks down slowly in soil or water. (Though it breaks down rapidly once volatilized into the atmosphere - half life of one week.) It migrates easily through soil and into water. As of 2005, TCE was detected in 5% of American public water systems supplied by groundwater and in 15% supplied by surface water. https://www.atsdr.cdc.gov/toxprofiles/tp19.pdf https://www.atsdr.cdc.gov/toxprofiles/tp19.pdf