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Sunday, October 17, 2021

High chromium-6 concentrations on campus

A 15-acre federal Superfund site on the edge of the UC Davis campus has been linked with cancer-causing carcinogenic chromium-6 contaminants.

The carcinogen, which has been linked with having high solubility rates, has been primarily noted to cause lung cancer.

The current contamination site was formerly home to the Laboratory for Energy-Related Health Research. The lab was in use from 1958 to 1988 and primarily studied the effects of radioactivity on animals. Many link the radioactive elements in use at this site to be the major proponent of the chromium, but scientists disagree.

“Our current theory is that organic waste deposited at one of the landfills decades ago acted to convert naturally occurring nontoxic chromium-3 into chromium-6,” said Sue Fields, environmental manager at the Office of Environmental Health and Safety at UC Davis in an e-mail interview.

Under oxidizing conditions, alkaline pH range, presence of manganese oxide and minerals containing chromium, chromium-3 is made into chromium-6.

Chromium-6 is a natural component of rocks in the mineral form of chromite. It is commonly found in the rock serpentine at the Sierra Hills and the Coast Ranges. From there it flows down the valleys and integrates into the soil. It can also be generated from industrial methods.

Some researchers believe this is how the contaminate made its way to the Superfund site.

“In and near the UC Davis campus, it was carried from the Coast Ranges largely as chromium-3 to the valley by Cache and Putah Creeks,” said Martin Goldhaber, a senior scientist of the U.S. geological survey in an e-mail interview.

The chromium-6 is primarily found in the groundwater, which poses a threat to the drinking water of residents in the Sacramento Valley. The reason for this is linked to the high solubility rate that chromium-6 has in comparison to chromium-3. According to the State Water Resources Control Board, drinking water can be treated by different pumps and treat remediation systems. Chromium-3 and chromium-6 can be removed by reverse osmosis or ion exchange resins.

However, UC Davis researchers say there is no indication that the contamination has affected drinking water in the Sacramento Valley.

Chromium-6 can also threaten health by means of inhalation. “Chromium-6 is known to cause lung cancer when breathed in as dust. There is no dispute about that,” Goldhaber said.

UC Davis researchers have begun efforts to clean up the contaminates by converting chromium-6 back into chromium-3 by pumping calcium polysulfide into the soil, Fields said. The pilot project was recently launched.

Calcium polysulfide can re-oxidize chromium-6 to chromium-3 by producing aqueous manganese.

The project hopes to submit a plan for clean-up to the federal Environmental Protection Agency this fall.

SADAF MOGHIMI can be reached at campus@theaggie.org.

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