OAK HILLS — Two prominent experts have weighed in on the high levels of hexavalent chromium recently found in all five wells that supply water to Oak Hills residents, signaling a possible lack of consensus nationwide as to what constitutes a danger zone with regard to the levels of the known carcinogen commonly called chromium-6.

Water samples from Oak Hills tested in October showed chromium-6 levels of 18-23 parts per billion, according to a previous Daily Press report. Those levels are higher than the state’s new regulation of 10 ppb enacted with the passage of Senate Bill 385, but much lower than the Environmental Protection Agency’s regulation of 100 ppb.

The obvious disparity between those two regulations is not lost on chromium-6 expert Dr. Max Costa, who chairs the department of environmental medicine at New York University.

Costa commended California’s new standard, which went into effect Jan. 1, 2015, but told the Daily Press any regulatory standard is “all relative.”

“So it’s safe to drink 99 (ppb), but you’re gonna die when you drink 101 (ppb)?” Costa asked with regard to the EPA’s standard. “I mean come on … The risks are high when the levels of chromium-6 are high.”

For perspective, one part per billion is the equivalent of one drop of water in an Olympic-size swimming pool, according to the Association of California Water Agencies.

Costa said most of the chromium-6 that ends up in water supplies — especially elevated levels — stems from human activity.

“In point of fact,” Costa said, “everyone who knows about chromium-6 knows that most of the contamination with chromium-6 comes from human intervention.”

Those remarks contradict statements made by Acting Deputy Director of the Water and Sanitation Division of San Bernardino County’s Special Districts Department Steve Samaras, who told Oak Hills residents at a recent meeting that the levels found in October were naturally occurring as far as he knew.

Samaras’ comments are in line, however, with the Environmental Protection Agency, which said in 2011 that “the major source of hexavalent chromium in drinking water is oxidation of naturally occurring chromium present in igneous geologic formations.”

The EPA noted though that there are locations where chromium compounds have been released into the environment via leakage, poor storage or improper industrial disposal practices, as was the case in Hinkley in the 1990s when Pacific Gas & Electric’s long-term use of ponds to store water allowed extremely high levels of chromium-6 to seep into Hinkley’s groundwater supply.

And UC Berkeley professor and chromium-6 expert Dr. Allan Smith told the Daily Press that — Hinkley aside — Oak Hills residents should not be alarmed by the concentrations of chromium-6 in the water supply.

“At these concentrations,” Smith said via email, “even with exposure for 50 years, I would not expect to find cancer rates (noticeably) increased. The reason I say this is that water concentrations of several hundred ppb, which occurred in an area in China, produced possible increase in cancer, in particular stomach cancer, but the findings were not clear cut.”

Smith prefaced that statement by calling Oak Hills’ elevated chromium-6 levels “unfortunate,” and said it needs to be corrected.

A pilot test of technology that collects chromium-6 from water samples and provides results as to how much of the metal is being removed from those samples is scheduled for the second week of February, according to Samaras, who reiterated during the meeting with Oak Hills residents that the levels are not a cause for concern.

During that meeting, the Mojave Water Agency’s Water Resources Supervisor Matt Howard — an Oak Hills resident — told those in attendance that he personally had not changed his drinking habits as a result of the October tests.

A draft compliance plan submitted to the State Water Resources Control Board last year will allow Samaras and his team at the Water and Sanitation Division until Jan. 1, 2020, to lower chromium-6 levels into compliance with the state regulation.

Meanwhile, Costa preferred to err on the side of caution.

“I don’t need to drink something that will increase my risk for cancer if I have other options,” he said. “It’s impossible to live in our society without making compromises, (but) chromium-6 is a human carcinogen. It causes cancer. Why would you want any of it in your drinking water? Anything higher than 10 (ppb), I wouldn’t drink it.”

Matthew Cabe can be reached at MCabe@VVDailyPress.com or at 760-951-6254. Follow him on Twitter @DP_MatthewCabe.