Comparing cities can be tricky. Concentrations can fluctuate because of volumes of flow, time of day and how long waste travels through sewers, which gives drugs a chance to degrade.
"This has caught on only recently, and people are still trying to understand the uncertainties," said Field, who is currently analyzing data from 96 locations in Oregon.
Jennifer de Vallance, spokeswoman for the White House's Office of National Drug Control Policy, said the testing of sewage in 2006 was an experiment to see if it could provide useful data to federal drug officials at a low cost.
"It came back very favorable. Our determination was that it probably could be done on a larger scale," she said.
EPA Assistant Administrator Benjamin Grumbles said that the EPA and the national drug office are "working on the details" of a voluntary program at sewage plants that will test for illicit drugs.
"This is sensitive for various communities because these substances do have a stigma attached to them," Daughton said. San Diego, for example, refused to grant permission to researchers.
The Sanitation Districts of Los Angeles County don't test for illicit drugs because iDrug Enforcement Administration permits to handle controlled substances would be needed, said supervising engineer Ann Heil.
"It's too hard to test for it. We can't have morphine lying around to calibrate equipment," she said.
Some researchers are now checking the environment for illicit drugs. Traces of prescription drugs have been detected in some drinking water supplies, and cocaine and other drugs have been found in rivers. No one has tested drinking water for illicit drugs.
"Since most of these residues still have potent pharmacological activities, their presence in the aquatic environment may have potential implications for human health and wildlife," the scientists from Milan reported in February.
Although few researchers are studying the effect of these ultra-low doses, scientists say the threat to people is probably minimal. To get a typical dose of cocaine, someone would have to drink 1,000 liters of raw sewage, Field said.
For now, this new drug test remains anonymous. Wastewater from thousands, sometimes millions, of people is pooled at treatment plants, so it cannot be tracked to any individual or specific location.
But because waste also can be tested in local sewers, questions about privacy have been raised.
"You could take this down to a community, a street, even a house," Daughton said. "You can do all kinds of stuff with this. It's sort of unlimited."
--
marla.cone@latimes.com
