MTBE has been determined to be a carcinogen in laboratory animals, said Chet Auckly, director of Water Quality and Environmental Affairs for the California Water Service Company in a phone interview.
The state does not allow MTBE levels to exceed 5 parts per billion based on aesthetic value - or its secondary standard - to maintain taste and odor standards.Federal regulations based on health - known as the primary standard - are more lenient and allow 13 parts per billion of MTBE.
"We're very conservative," Auckly
said."We want to meet both primary and secondary standards."
Arsenic is defined as a carcinogen, however precise levels safety are still debated.
Limits on contaminants, or maximum contaminant levels, are typically based on the assumption a person drinks 2 liters of water a day for 70 years, he