Rocket fuel's spread in water could be worse than thought. (Up Front).

Even with costly efforts under way to clean up the rocket-fuel chemical perchlorate in Los Angeles groundwater supplies, there are concerns that contamination could be more widespread than previously thought.

Last month, several samples of lettuce irrigated with tainted water from the Colorado River were discovered to contain the chemical.

In terms of local groundwater contamination, the Los Angeles region, home to decades of aerospace manufacturing activities, is among the hardest hit in the U.S. A chemical in solid rocket fuel, munitions and other applications, perchlorate has contaminated 128 wells in the region, according to the Los Angeles Regional Water Quality Control Board.

Most of the wells contaminated with perchlorate, which has been linked to thyroid problems in humans, have been closed. A handful have been treated, and some are being blended with uncontaminated sources to bring perchlorate content to acceptable levels.

"Perchlorate is something we are definitely keeping an eye on," said Pankaj Parkej, director of water quality compliance with the Los Angeles Department of Water and Power.

Most perchlorate contamination occurred during the 1950s, '60s and '70s, but it wasn't found to be a health problem until the early-1990s. The local groundwater contamination largely arises from six known sites in the region, including a former Aerojet rocket manufacturing facility in Azusa, the Jet Propulsion Laboratory in La Canada-Flintridge and a former munitions manufacturing site in the Santa Clarita Valley.

In the San Gabriel Valley, site of the region's worst problem, GenCorp. Inc., Aerojet's parent, and seven other companies reached a $250 million agreement last year to clean up perchlorate and other toxins in the vast underground aquifer that is the valley's primary water supply. The agreement is being hailed as a model for other Superfund sites. However, the pact took five years to reach after perchlorate was first detected, and treatment will last decades.

"It's very expensive," said Carol Williams, executive officer of the Main San Gabriel Basin Watermaster, the agency that manages the groundwater basin and brokered the deal.

The city of Pasadena, meanwhile, has had to shut down nine of its 12 drinking water wells from contamination traced to the Jet Propulsion Laboratory, another Superfund site. The lab is currently seeking permits to build a treatment facility, said Kevin Mayer, the Environmental Protection Agency's regional perchlorate coordinator.

Groundwater clean-up has yet to begin in Santa Clarita, where perchlorate contamination has been linked to a former weapons production and testing facility operated by Whittaker Corp. as late as 1987. Five wells have been contaminated so far, officials said.

Questions and complications

Meanwhile, efforts to clean up the local groundwater have been complicated by concerns that the chemical may be more toxic than first thought -- and more widespread.

Last year, the Environmental Protection Agency released a draft proposal that called for a national drinking water standard as low as I part per billion. That is equivalent to a single drop of perchlorate in a home swimming pool.

However, the Pentagon and defense contractors objected, saying levels as high as 200 parts per billion should be allowed. The issue has been sent to a National Academy of Sciences panel for review.

The state of California, meanwhile, is working to establish its own drinking water standard, and in the interim has established a temporary standard of 4 parts per billion.

Last year, when the state lowered that number from 18 parts per billion, West Covina-based Southwest Water Co. took an additional well out of service, and now has nine wells contaminated with perchlorate.

Perchlorate is suspected of causing thyroid cancer at very high levels, but even at trace amounts some scientists fear that it can interfere with the production of thyroid hormones, which govern brain development in fetuses and infants.

Last month, tests conducted by the Environmental Working Group, a Washington, D.C.-based research and advocacy group, found perchlorate in four out of 22 samples of winter lettuce -- 90 percent of which is grown in the Imperial Valley and Arizona, with tainted Colorado River water.

The Colorado River is contaminated with low levels of perchlorate -- on average about 5 parts per billion -- that was traced about five years ago to a former Nevada rocket fuel factory near Lake Mead.

A clean-up is under way, but given the size of the Colorado River system scientists say the existing contamination could take years to flush out. In the mean time, the Metropolitan Water District of Southern California, which supplies water to some 18 million people, has taken to blending its Colorado River supplies with those from Northern California.

The result is that the agency ships water still contaminated with some perchlorate but not a detectable level, since even the most modern labs can only detect perchlorate at levels of 4 parts per billion.

Mark Beuhler, the MWD's associate vice president for water quality strategies, said he believes the agency's water is safe at those levels but conceded its discovery in food could change things.

"At some point it may result in stricter standards if it turns out people are exposed to other sources," he said.