...For those not familiar with the various cities that make up the Los Angeles metropolitan area, Artesia does have the appearance of a place you would find good water. Highly carcinogenic industrial waste? Yes. Clean, pure water? No.
You can add the entire West side, large portions of the San Gabriel Valley, and a myriad of locally affected areas to that list. I definitely wouldn't go around, drinking shallow groundwater!

Within the next 10 to 20 years though the tap water in most of the US is set to become THE major issue. Thanks to fracking my company stands to make a fortune making water potable again. Carbon is good but check with the NSF or WQA website to make sure your filter is rated to remove contaminents that may be in your water, not all do.