Water discharged from fracking sites in California contained levels of benzene and chromium-6 well in excess of federal standards, according to a recent report by an Arizona environmental group.
Fracking operations use a highly pressurized solution to crack shale rock and access oil or natural gas, and the resulting wastewater is often sent to injection wells or open pits.
The Center for Biological Diversity analyzed hundreds of chemical tests of that flowback fluid conducted by the California Division of Oil, Gas and Geothermal Resources since April of 2014, finding 320 tests showed benzene levels above the federal threshold for drinking water and 118 tests revealed chromium-6.
Testing also showed benzene levels at more than 1,500 times the federal limit and chromium-6 levels at more than 2,700 times the level recommended by the Office of Environmental Health Hazard Assessment. Both chemicals, the group said, can cause cancer.
The group also said levels of toluene, which it said can affect the nervous system, exceeded federal limits in 118 tests, while data from 100 flowback tests were missing from the state reporting website.
Regulators had recently announced changes to regulations of those wells following a report showing more than 2,500 wells had been improperly created in aquifers that could be used for drinking water or irrigation.
"Cancer-causing chemicals are surfacing in fracking flowback fluid just as we learn that the California oil industry is disposing of wastewater in hundreds of illegal disposal wells and open pits," said CBD attorney Hollin Kretzmann, calling on Gov. Jerry Brown to immediately halt production at those wells.