The tap water that Tampa residents consume is contaminated with low levels of antibiotics, nicotine byproducts and a chemical used to produce firefighting foams.
City and state officials say the levels of the contaminants - found in recent tests of the city's drinking water system - are miniscule and that the city's water is safe to drink.
But the presence of the contaminants raises questions about what is coming out of the faucets in tens of thousands of households served by the city's water system.
State and federal environmental regulators say they know little about possible health risks from the cocktail of contaminants that in recent years have been found in water supplies across the country. They are only beginning to study the long-term effects.
Without any regulation of these types of contaminants, the city isn't required to report the findings of the recent tests to state and local environmental regulators, or the public.
Elias Franco, distribution division manager for Tampa's water department, said the city began voluntarily testing its water for pharmaceutical contaminants two years ago.
He said the contaminants found in tests conducted in May 2009 include the antibiotic drug sulfamethoxzole; cotinine, a nicotine byproduct; and perfluorooctane sulphonate, a chemical commonly used for metal plating, photography and firefighting foams.
The contaminants were found in samples of treated drinking water taken from the city's treatment plant, indicating that the existing filtration process doesn't remove them.
Franco said the city meets all federal and state regulations for drinking water quality and, for now, doesn't intend to make any wholesale changes to the water treatment system.
"The industry continues to evaluate the latest technologies available that could prove reliable in evaluating the effects of these contaminants," Franco said in a statement, "and the City of Tampa will continue to stay abreast of these developments."
Neither the state nor federal government requires testing for unregulated contaminants such as those found in Tampa's drinking water and regulators haven't set safety limits.
Only one of the contaminants found in Tampa's drinking water, perfluorooctane sulphonate, is regulated by federal heath officials. Even then, a health advisory is required to be issued only when the contamination levels exceed 200 micrograms per liter. The level of the chemical found in the city's drinking water system was only 1.4 micrograms per liter.
"At this time, no research has shown that concentrations of these substances reported in recent studies pose a threat to drinking water supplies," Dee Ann Miller, a spokeswoman for the Florida Department of Environmental Protection. "Research is ongoing, especially on the effects of multiple chemical constituents at low concentrations."
How does it get into the water?
Tampa officials attribute the contaminants found in the recent tests to pollution from the Hillsborough River, the city's primary source of drinking water.
When people take medicine or smoke, some of the chemicals are absorbed by the body, but the leftovers end up getting flushed down the toilet and into the water supply.
The wastewater is treated before it is discharged into reservoirs, rivers or lakes.
Leaking septic tanks also can eventually send contaminants into drinking water systems, and regulators say pharmaceuticals can also permeate aquifers deep underground, a source of about 90 percent of the state's drinking water supplies.
State environmental regulators say despite the recent emphasis on pharmaceuticals in the drinking water supplies, it's likely people have been consuming them for a long time.
"It is inevitable that small amounts of these compounds will be released to the environment," the DEP's Miller said. "It is also likely that these compounds have been there for decades and have remained undetected until the recent development of analytical methods to enable their identification and quantification."
And Tampa is not alone.
Two years ago, an Associated Press investigation revealed how scientists have found that water piped to millions of people nationwide contains minute concentrations of contaminants ranging from tranquilizers to painkillers to antibiotics.
While scientists have not established that people are harmed by these drugs, the AP reported, laboratory tests conducted by research teams at universities in the U.S. and Europe have shown that tiny amounts can have ill effects on human cells, especially when ingested over decades, possibly in combination with other drugs or in sensitive populations such as children and pregnant women.
Since the AP report stirred congressional hearings and legislation, the U.S. Environmental Protection Agency has launched a survey to check for 200 chemical and microbial contaminants at 50 water treatment plants across the nation, and health agencies are conducting research to clarify how humans might be harmed by drugs at low environmental levels.
This research will help federal officials decide whether regulations are needed.
Locally, few local governments test for pharmaceuticals on their own, relying instead on Tampa Bay Water, which provides water to Hillsborough, Pinellas and Pasco counties.
From 2002 to 2005, the U.S. Geological Survey tested groundwater supplied by Tampa Bay Water to its members for pharmaceuticals and other contaminants, but didn't find anything, according to Chris Owen, the authority's water quality assurance officer.
Hillsborough County has for several years tested for herbicides and other unregulated contaminants under an agreement with the EPA, but not for antibiotics, steroids, growth hormones and other pharmaceuticals that have been detected in other water systems.
"Even if we found something, we don't yet know what the health risks are from these types of contaminants," said Luke Mulford, Hillsborough's water quality engineer.
"And it's going to be a long time before we know."
Contaminants in drinking water
Recent tests of Tampa drinking water system found the following contaminants:
Sulfamethoxzole: An antibiotic used to treat bacterial infections. Level found in recent tests: 1.1 nanogram per liter ng/L
Cotinine: Created by the breakdown of Nicotine in the human body. Level found in recent tests: 2.3 nanogram per liter ng/L
Perfluorooctane Sulphonate: Used to produce fire fighting foams and coatings for fabrics, leather, and some paper products, this chemical is known to persist in the environment and to accumulate in human and animal tissues. Level found in recent tests: 1.4 nanogram per liter ng/L
Sources: City of Tampa; Environmental Protection Agency; Physician's Desk Reference