California Air Resources Board

SACRAMENTO– The California Environmental Protection Agency's (Cal/EPA) Air Resources Board (ARB) will begin a second round of air monitoring for hexavalent chromium (chromium 6) near Hinkley July 26. The additional monitoring will determine the background concentration of chromium 6 in the area's air. Soil sampling will also be done in the area.

ARB Executive Officer Michael Kenny said, "We are concerned that residents near the PG&E facility may have been exposed to chromium 6 blown from the fields under irrigation. This added testing will give us more information with which to decide if other actions are needed to protect the citizens of Hinkley."

During the past eight years, groundwater contaminated with chromium 6 has been used to irrigate two alfalfa fields in Hinkley.  Chromium 6 is converted to far less toxic chromium 3 upon contacting organic matter in the alfalfa and the soil.

Concerns about airborne chromium 6 near fields irrigated with contaminated groundwater from a Pacific Gas and Electric (PG&E) facility prompted the ARB to conduct preliminary tests that revealed heightened levels of the compound. In May, the ARB found chromium 6 levels of 0.2 to 0.6 nanograms per cubic meter (ng/m3) at the edge of a sprayed field. As a result of those tests, the Lahontan Regional Water Quality Control Board shut down the irrigation program as a "threatened nuisance."  The chromium 6 concentrations in Hinkley were detected more frequently and at higher levels than is commonly found in California cities.

This round of testing will use more monitors for a more comprehensive picture of where chromium 6 can be detected in the area's air. Any decision on what actions should be taken will be made after the next series of tests are analyzed.

Kenny said, "We will extend our testing to get a more refined impression of how far chromium 6 can travel from its source and how many people may be exposed."

The ARB identified chromium 6 as a toxic air contaminant with no identifiable safe threshold in 1986. Used mainly to prevent rusting in air conditioners and cooling towers and to plate engine parts and ornaments, chromium 6 is known to cause lung cancer in humans. The ARB has adopted regulations that prevent its use as a rust inhibitor and other regulations to protect chrome plating shop workers.