The water in the ocean surrounding Bermuda may be crystal clear, but the water in Bermuda's ponds appears to be a whole other story ? one that could be affecting human health.

Fortunately, the warning signs are already in place, with one species in particular taking the brunt of the contamination ? Bermuda's toads.

The story began with the Bermuda Amphibian Research Project (the Toad Project) in 1995. It took on a sinister twist in 1998, however, when scientists noticed that three of 12 toads collected had minor limb deformities.

With increasing reports of deformed frogs in North America, the Bermuda Zoological Society's Dr. Jamie Bacon wondered if Bermuda was following suit.

What she has found so far is alarming. Nearly 50 percent of the toads found in some ponds were deformed in some way. Of the six ponds that contained the most deformed toads, four were nature reserves. Deformities included missing or extra limbs and strange development of eyes.

Mortality rates also set off alarm bells. "At 40 percent (mortality rate) you get nervous," Dr. Bacon said. The first time she tested one pond, the mortality rate was 86.5 percent.

The second time she tested that pond, the mortality rate was 55 percent. Other ponds have shown mortality rates of 60 and 71 percent.

Through tests scientists have determined chemicals ? namely total petroleum hydrocarbons (TPH, derived from crude oil) and metals including arsenic, copper, lead and mercury ? are present in the ponds at such levels as to make them prime suspects.

Not only are TPH and the metals likely causing the deformities, they have a "synergistic" relationship ? meaning that while normally adding one and one will cause two, in this case one and one causes "ten or 20", Dr. Bacon said.

But where are the pollutants coming from? Dr. Bacon explained that many of Bermuda's ponds are man-made and were previously dumps which would have contained these chemicals. Another cause could be modern-day pollutants, such as road run-off and air emissions. One of the aims now is to determine how much of the cause is historical, and how much is current.

Since amphibians are considered monitors of environmental health, the next logical questions were were effects of this trend on other wildlife and, especially, on humans.

Most of the information The Toad Project has now about the effect on humans is strictly anecdotal, Dr. Bacon said. "We need hard data to see if this will be a problem."

Fortunately it is unlikely Bermudians are ingesting these pollutants through the water they drink. "The water distributed to people is distilled with chlorine added ... In theory any contaminant is removed by the process."

Humans could be exposed to the chemicals if they are drinking well water or if the chemicals are airborne and infiltrate tanks, she said.

Government, and especially Environment Minister Neletha Butterfield, have shown a strong interest in the project, as have non-Governmental organisations such as the Audubon Society and the National Trust. "I'm pleased with Government's interest.

"It's been a four-year long detective story and we're getting there, we've made huge strides," she said. "We're not at the end yet and we're not sure where they are coming from, so we're not sure they can be reversed."

But how did it get so bad without anyone noticing? "You could theorise it just finally reached a threshold so that it became noticeable," Dr. Bacon said. "Sometimes you don't find it unless you look for it."

Most people are "dismayed" when they hear her tale, she said. "Toads are not at this point threatened with extinction, there are places where they are plenty. But they're not very healthy.

"The problem is so big. The concern is, 'Can we turn it around?'"