For years before the mid-1980s, groundwater in parts of Southern California was contaminated with toxic solvents, yet the federal body responsible for tracking this didn’t investigate the potential health threat to people who were drinking contaminated tap water. A congressional committee is now investigating why that neglect occurred.
Here’s a closer look at what scientists know about the main solvents of concern and their health effects.
Trichloroethylene (TCE) and the related compound tetrachloroethylene, also known as perchloroethylene (PCE or PERC), are industrial solvents still used to clean up grease and to dry-clean clothes. For a long time, their use was unregulated and many companies across the nation disposed of them in such a way that they leached into drinking water sources.
In 1980, the Environmental Protection Agency started a Superfund project to clean up a variety of chemical pollutants. The effort includes getting the perpetrators of improper TCE and PCE disposal, many of them defense contractors, to help remove the worst of the contamination across the country.
What problems do these closely related solvents cause?
Scientists know that TCE can cause cancer -- usually of the kidneys, liver and lungs -- at high doses. They have concluded this from studies on animals that were given contaminated water to drink, as well as from people exposed to TCE through their work or through contaminated drinking water.
They don’t yet understand how TCE causes cancer: Researchers studying the question say the process is pretty complicated, and the jury is still out on the exact mechanism.
Peter Preuss, director of the EPA’s National Center for Environmental Assessment, says that TCE breaks down into several different components, some of which are carcinogenic. “There are maybe three to five routes by which TCE might induce cancer,” he says.
But the cancer data are from animal and humans subjected to high doses of TCE. To understand what might happen at lower doses found in the environment, researchers have to extrapolate.
“There’s a fair amount of uncertainty,” Preuss says. And the kinds of new experiments that are needed to determine whether the levels found in Southern California water led to cancer are difficult to do. Preuss is leading an effort to determine what health effects the TCE might have had over the years by examining all the available, published data.
-- What about PCE?
Some of the best data on the health effects of these solvents come from Marines based at Camp Lejeune in North Carolina from November 1957 through February 1987. Those who lived in the base’s Tarawa Terrace family housing units drank water contaminated with PCE from a dry-cleaning operation near the water source.
Researchers with the Agency for Toxic Substances and Disease Registry -- a group within the Centers for Disease Control and Prevention concerned with toxic chemicals -- estimate that in 1985 the PCE in groundwater was at a concentration of approximately 800-1500 parts per billion. That’s far above the 5 ppb limit the EPA considers safe.
Over time, PCE breaks down into TCE; the researchers estimated that levels of TCE, which is subject to the same 5-ppb limit as PCE, were as high as 100 ppb.
The Marines drank considerably less of the solvents than were present in the groundwater, however. The water coming out of the water treatment plant contained about 200 ppb of PCE and up to 15 ppb of TCE.
The Camp Lejeune study found that older mothers (35 and older) and mothers who had a history of miscarriages generally gave birth to lower-weight babies than unexposed women. The Agency for Toxic Substances and Disease Registry is continuing to look at possible birth defects and childhood cancers linked to the exposures.
Should Southern Californians be drinking bottled water?
Researchers and the EPA say there’s no need, because even with the contamination, people in Southern California are drinking solvent-free water.
Not all water sources in the L.A. area are contaminated. Also, although not all of the groundwater in regions of concern in the L.A. area have been treated to contain less than the federal limit of 5 parts per billion, what comes out of your tap is not the same as what’s in the groundwater.
The treatment systems that clean up water before it reaches people’s faucets clear out the TCE, says EPA Superfund project manager David Stensby, who oversees water treatment in one of the Superfund sites, in Glendale.
The first treatment consists of blowing air through the water. Because TCE is volatile, it catches a ride on the air, and that removes about 98% of the TCE.
The water then flows through activated carbon filters, which removes the remaining solvent. Because the carbon filters can fill up just like carbon filters on home water filtration systems can, the water is checked at various points in the process to make sure there is no TCE.
“Our performance standard is zero, not at the end of the pipe, but before the last carbon filter,” Stensby says. He adds that the TCE-filled air also goes through carbon filters before it is released: “The TCE is captured one way or another.”
The groundwater being treated this way wasn’t being used before treatment. The EPA treatment systems were put in place when cities wanted to use the water from a contaminated source.
In parts of the L.A. area not covered by the Superfund effort, water is subject to the equally strict standards set out by the California Department of Public Health.
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For more information
Want to know more about water contamination in the Los Angeles area?
On its Superfund website, the Environmental Protection Agency identifies areas contaminated by the solvents.
In the San Gabriel Valley, contamination has been detected in groundwater underlying the cities of Alhambra, Arcadia, Azusa, Baldwin Park, Industry, Irwindale, El Monte, La Puente, Monrovia, Rosemead, South El Monte and West Covina.
The eastern portion of the San Fernando Valley, which supplies drinking water to the Los Angeles metropolitan area, Glendale, Burbank, San Fernando, La Canada Flintridge and La Crescenta, contains another large Superfund area.
* You can learn more about California’s Superfund sites at www.epa.gov/region09/waste/sfund/.
* For more general information about the Superfund effort, go to www.epa.gov/superfund /index.htm.
* To learn more about the exposure to TCE at Camp Lejeune, go to www.atsdr.cdc.gov/sites /lejeune/index.html.
-- Mary Beckman