U.S. Water News Online
TUCSON, Ariz. -- Residents are excreting trace amounts of the medications they take -- from birth control to antibiotics to steroids -- into the sewer system, preliminary results of a study found.
The substances are not necessarily stripped from the wastewater when it leaves treatment plants to head down the Santa Cruz River or to irrigate some golf courses and schoolyards around Tucson. Ultimately, some of it seeps into the aquifer that is pumped for drinking, the survey found.
Researchers are trying to determine the implications of the findings, particularly with water officials contemplating the use of highly treated wastewater as a new source of drinking water in decades to come.
``We really need to have a better understanding about the potential for it to get to the groundwater, because groundwater eventually is our drinking water,'' said Gail Cordy, a supervisory hydrologist with the U.S. Geological Survey.
In one lab test performed by the U.S. Geological Survey, chemical-laden water was pushed through an 8-foot column of soil. A number of the chemicals, including a drug used to treat epilepsy, could still be detected at the other end.
A survey of 139 steams across the country, including four in Arizona, found at least 80 percent of the bodies of water had one of 95 chemicals. And, half of the stream waters tested last year contained seven or more of the chemicals, the U.S. Geological Survey found.
Nonprescription drugs, insect repellant and steroids were the most frequently detected. Antibiotics and hormones were often found too.
Since antibiotics combat bacteria, some question whether the quantities found will increase bacterial resistance rates. Also, reproductive hormones may have greater implications to aquatic life because even low-level exposure can cause problems.
The chemicals detected were generally found in very low concentrations. But the government hasn't set safety limits for most of them and scientists don't know enough about the potential health effects in humans.
A scientist at the University of Arizona's Environmental Research Lab received approval for a three-year study that aims to further explore the issue. David Walker will study the effects of pesticides, herbicides and hormones on Arizona's native fish.
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