Unfortunately, fracking has become common in parts of California and many water wells have been contaminated by fracking chemicals. In addition, many people living near fracking sites are unaware that they are breathing in evaporated fracking waste.
If you smell something like rotten eggs in the air or your water quality has changed, you should find out if you live near a fracking site.
No one likes to be poisoned.
Good point re: the fracking. And watch out for earthquakes nearby also, if Oklahoma is any indication!