LOS ANGELES (CBS) — A study of 195 well water samples taken from across Los Angeles County found three times as many sites with detectable levels of chromium as 10 years ago, though none were in excess of regulatory limits, county officials reported Tuesday.
The wells were tested between March and September for arsenic, lead and chromium.
Twelve were found to have concentrations of arsenic in excess of federal and state maximum contaminant levels of 10 parts per billion. The wells with the highest concentration, which ranged up to 72 ppb, were found in Saugus.
Wells in Lancaster, Tujunga, Glendora and Acton also had arsenic in excess of regulated limits.
Just one well, in Castaic, was found to have lead concentration in excess of federal and state limits of 15 ppb.
The concentration there, 37 ppb, was attributed by officials to pipe corrosion.
The study also tested for chromium. Chromium salts are widely used in industrial applications such as corrosion control and electroplating and as catalysts in petroleum refineries. It exists in two forms, trivalent chromium and hexavalent chromium, also known as chromium 6.
While it is generally agreed that chromium 6 poses the highest risk to animal and human health and can cause cancer, no federal or state limit for the specific contaminant has been set. Total chromium is limited to 50 ppb by state law.
While none of the county samples were in excess of this level, three times as many sites as in 2001 had some level of detectable total chromium. The highest concentration, 13.9 ppb, was found near Lake Hughes.
Agricultural Commissioner Kurt Floren called this the most significant finding of the study.
The county’s top health official speculated that the increase may be due either to industrial operations near the areas being tested or drier weather that leaves the same amount of contaminant in less water.
Dr. Jonathan Fielding, director of the county’s Department of Public Health, said it was important to continue to monitor levels, but sought to reassure residents about the results of the study.
“Arsenic and chromium are naturally occurring, so they will always be there to some degree in our water supply,” Fielding said.