Like many of their neighbors near Plant City, Dana Shores and his fiancee, Nicole Fulwood, fear what their well water might do to them.
Recent tests show it's tainted with arsenic, a metal tied to phosphate and pesticides and known to cause cancer.
"I moved out in the country to get away from the city, and came out to this," said Shores, 29, a construction worker who previously lived in Tampa.
Shores and Fulwood own one of 20 wells near the Coronet Industries plant that shows elevated levels of toxins, and one of 10 that exceeds federal drinking water standards. The couple took that to mean the worst, yet health officials told them the risk was low.
How bad is it?
The truth is hard to pin down.
Drinking water standards are based on complicated formulas, and the risk levels they represent aren't listed in a simple chart on a government Web site. Even health officials get confused.
In August, Hillsborough County Health Department Director Doug Holt told the St. Petersburg Times that a lifetime of consuming water with 10 parts per billion of arsenic in it - which is the incoming federal standard - would increase a person's odds of getting cancer by 1 in 1-million. His comments were printed in an Aug. 31 story about mounting pollution fears in Plant City.
But Holt turned out to be way off. The risk factor at that level is more like 1 in 2,500, according to U.S. Environmental Protection Agency officials who set the standard.
Holt admitted the mistake.
Even with the revised risk number, Holt says the pollution levels showing up in Plant City wells do not appear to be a major threat - a preliminary conclusion that is just not registering with frightened families.
To figure out drinking water standards, federal scientists weigh the health effects of a particular pollutant, then factor in the economic costs of preventing those effects. Their calculations are based on the assumption that somebody weighing about 150 pounds will drink 2 liters of water every day for 70 years.
The final number represents "acceptable risk," said Edward Ohanian, who directs the EPA department that oversees risk assessment for drinking water standards.
The number is not the level at which the water becomes acutely toxic, but a gauge to measure long-term threat. Ohanian said conservative assumptions, such as lifetime exposure, are built in to the number "so there are several layers of safety cushions."
Still, the risk behind the number varies, depending on the pollutant.
For many cancer-causing substances, the risk factor is a relatively safe 1 in 1-million. But for arsenic, the risk has been left higher because the substance is so potent in even the tiniest amounts, and the cost of removing it from water supplies is so high, EPA officials said.In order to have a health standard for arsenic that is as safe as the ones for other pollutants, the level would have be so low the arsenic would be nearly undetectable. And achieving it would be economically impractical, they said.
The risk is assumed to increase in proportion to the amount of pollution. If a family has 20 parts per billion of arsenic in their well - which is double the standard - their risk would double, to 1 in 1,250.
Eight wells within one-quarter mile of Coronet exceeded the arsenic standard, with numbers ranging from 10.8 to 49.7 parts per billion. Shores' well came in at 44.4 parts per billion.
In response, authorities are delivering bottled water, a step some residents have taken as a sign that the wells are an immediate threat.
Authorities say it only means they are being extra cautious.
So far, a team of investigators led by Holt say there is no evidence to support the widely held notion that pollution from Coronet is causing a cancer epidemic.
The team says it is too early to tell what is responsible for the pollution. Arsenic is a byproduct at Coronet, which turns phosphate into an animal feed additive, but it was also widely used for decades in pesticides. Investigators are looking at nearby landfills, too.
A few years ago, the state Department of Environmental Protection found evidence that natural arsenic levels could exceed drinking water standards when it looked at 22 wells in West Central Florida.
The wells were selected in areas where neither pesticides nor industrial pollutants were expected to be a factor, said Geof Mansfield, a senior DEP water analyst.
Four showed levels beyond 10 parts per billion.
Arsenic in groundwater might be higher in this part of Florida because there is so much phosphate - which contains trace amounts of arsenic - beneath the surface, Mansfield said. But there weren't enough wells tested to draw any meaningful conclusions, he said.
The government's standard-setting process has its critics.
The standards don't consider the effects pollutants have when they're combined, or the susceptibility of people who might be more vulnerable to pollution, such as pregnant women and the elderly, said Paul Schwartz with Clean Water Fund, an environmental group based in Washington, D.C.
The standards can also be shaped by political pressure, he said.
Two years ago, the Bush administration tried unsuccessfully to undo the incoming arsenic standard, which the Clinton administration had reduced from 50 parts per billion to 10 parts per billion. Utility and mining companies were among those pushing for a roll-back.
Debate continues, with some scientists concluding the cancer risk at 10 parts per billion is a much-scarier 1 in 500.
"There's a range of scientific opinion about every standard," Schwartz said.
Near Plant City, talk about relative risk probably won't matter to those who have been drinking well water. Shores said county health officials explained the numbers when the broke the news last week.
But when you hear "arsenic," he said, "all you see is toxic."
- Ron Matus can be reached at 226-3405 or email@example.com Times researcher John Martin contributed to this report.