Levels of the carcinogen chromium-6 are rising in groundwater at a UC Davis site used as an animal-testing laboratory during the Cold War, and university officials are at a loss to explain why.
Currently, 42 of the 100 monitoring wells at the former Laboratory for Energy-Related Health Research, or LEHR, do not meet state standards for safe levels of chromium-6, a heavy metal also known as hexavalent chromium.
Exposure to chromium-6 can lead to skin irritation, occupational asthma, and kidney and liver damage, according to the National Institute for Occupational Safety and Health. The carcinogen came to the fore in the 2000 film “Erin Brockovich,” in which the lead figure sued Pacific Gas and Electric over chromium-6 found in a Mojave Desert community’s drinking water.
Many wells at the LEHR site – where the effects of low-level radiation were tested on laboratory animals – have five times the state standard of 10 parts per billion for chromium-6.
The chemical is but one of many found at the LEHR site, where research on the biological effects of radiation was conducted for agencies including the U.S. Department of Energy from 1960 to 1989, according to the U.S. Environmental Protection Agency. The 15-acre location off Old Davis Road south of Interstate 80 has been a federal Superfund site since 1994, and millions of dollars have gone toward cleanup efforts.
Research at the site involved exposing hundreds of beagles to strontium-90, dousing them with cobalt-60 and injecting them with radium-226 to determine how humans might survive nuclear exposure. But chromium wasn’t involved.
“This is a conundrum for us,” said Sue Fields, environmental manager at UC Davis. “There is really no indication that there was any dumping of chromium at the LEHR site.”
Fields believes the answer will not be found anytime soon.
“Part of the problem is, the more we look the more we find,” she said.
Chromium-6 is typically found in areas where there has been a lot of industrial activity, such as electroplating. That type of activity has never occurred at the LEHR site or in Davis, Fields said.
Moreover, the pattern of wells with high chromium levels at LEHR do not match areas where toxic waste was disposed at the site.
“We’re finding that chromium-6 seems to be more widespread than just our disposal areas at the site,” Fields said.
UC Davis has enlisted Stanford University expert Scott Fendorf to help solve the puzzle.
“It’s not easy to identify the source, but the distribution of chromium-6 does not parallel other known contaminants introduced at the LEHR site,” said Fendorf, who has been studying chromium for 25 years.
“As such, it seems more likely that it is of natural origin,” Fendorf said.
However, naturally occurring chromium-6 cannot fully explain the rising levels at the LEHR, Fields said.
One theory she believes is that changes are happening in the soil where naturally existing chromium-3 is mixing with sludge dumped into three landfills at the site over the years.
Another theory is that chromium-6 may have been introduced into the ground or the groundwater by years of dumping rust inhibitor chemicals used to clean out underwater pipes serving the many cooling and heating towers on the UC Davis campus.
“The reality is, we’ve not found any evidence of any such kind of release on the campus,” Fields said. “If someone had dumped a bunch of chromic acid or corrosion inhibitors into the ground, it would still be in the soil.”
Fields said UC Davis is doing remediation on the LEHR site where it is extracting groundwater from wells and treating it at a nearby wastewater plant so that it can be converted to naturally occurring chromium-3.
The university has spent $20 million on cleaning up the site since the early 1990s, Fields said. The University of California system has spent an additional $6 million. The university shares the cleanup costs at LEHR with the Department of Energy.
While workers and visitors at the LEHR site do not face exposure risks, the danger is that chromium-6 could contaminate aquifers and groundwater in the rural area nearby. Fields said most farms there likely use deeper wells that do not have chromium-6 problems, but there is not much data because those wells are private.
Establishing why chromium-6 levels are rising at LEHR may shed some light on why the toxic metal is being found in groundwater regionally, Fields said.
New state standards for chromium were set in 2014 and apply to public wells and drinking water. The new standards put the majority of Davis’ drinking wells over the limit for chromium-6. The city is joining Woodland in building a new surface-water project that will tap the Sacramento River for drinking water by the end of 2016.
One private well in the Binning tract area of Davis has recorded five times the standard set by the state. Property owner Martha Daschbach said that she is no longer able to use the well on her property because of the high chromium-6 levels and is forced to use bottled water to replace well water.
Wells in Woodland and Dixon are also over state standards, according to data provided to The Sacramento Bee from the State Water Resources Control Board.
Editor’s note: An earlier version of this story incorrectly referred to an area in Davis as the Benning tract. The correct name is the Binning tract.