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
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
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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