Friday, December 10, 2004
Copyright © Las Vegas Review-Journal

Perchlorate in river 'poses no threat'

Arizona governor calls levels acceptable

PHOENIX -- A study intended to gauge the safety of drinking water from the Colorado River found some amounts of a chemical component of rocket fuel, but Arizona Gov. Janet Napolitano said Thursday the levels were acceptable.

Perchlorate can interfere with thyroid function and hormone balance, but the level of perchlorate found in Arizona drinking water "poses no threat to the public," Napolitano said in announcing the findings of a state task force.

The lower Colorado River provides drinking water for central and southern Arizona, Southern Nevada and Southern California.

A chemical plant near Las Vegas that produced ammonium perchlorate for the space shuttle program and rocket engines has been identified as the primary source of perchlorate contamination in the river. Water containing perchlorate was discharged into unlined evaporation ponds. It then seeped into the aquifer and then Lake Mead and the Colorado River. The Henderson plant, owned by Kerr-McKee Chemical Corp. is being cleaned up.

A process deployed near the Kerr-McKee plant in May using a single-celled organism that breaks down perchlorate is cleaning up about 1,000 gallons of contaminated water per minute, replacing a less-efficient process known as ion exchange.

The Arizona task force recommended continued monitoring of water quality and oversight of the plant cleanup as well as review of a National Academy of Science study to determine whether Arizona should stand by its nonbinding "health-based guidance level" of 14 parts per billion.

Napolitano formed the task force in April from the state Departments of Environmental Quality, Water Resources, Health Services and Agriculture to analyze more than 100 water samples.

In forming the task force, Napolitano said she was heeding a report by the American Rivers conservation group that perchlorate, human waste and uranium tailings made the Colorado River the nation's most threatened.

American Rivers spokesman Eric Eckl called the study findings "reassuring news." He complimented Napolitano for keeping an eye on the question of how much exposure is acceptable.

The issue "remains the subject of some pretty fierce debate in the scientific community," Eckl said.

The study said tests found perchlorate levels generally ranging from zero to 7.4 parts per billion. One monitoring well in Yuma, in southwestern Arizona on the Colorado River, recorded 15 ppb.

The results generally showed "slow, steady declines" of concentrations from 1999 tests at sites along the river as well as places in central and southern Arizona where Colorado River water is used, the study said.

That suggests benefits from the continuing cleanup of the contamination at the Henderson factory site, the study said.

While Arizona has its nonbinding "health-based guidance level" at 14 ppb, California environmental officials last spring proposed a standard of 6 ppb. The U.S. Environmental Protection Agency is studying whether to establish a nationwide limit. An EPA draft suggests allowing no more than 1 ppb of perchlorate in drinking water.

Locations sampled for the Arizona review included groundwater, surface water, agricultural areas, groundwater recharge facilities and treatment plants throughout Arizona.

When ingested, perchlorate can disrupt the thyroid gland and its production of hormones that regulate metabolism and growth. Infants and pregnant women are particularly at risk to the health effects caused by the disruption of thyroid functions.

Review-Journal writer Keith Rogers contributed to this report.