Thousands of people in Brevard County drink or wash in water contaminated with chlorine byproducts at levels linked with increased risk of cancer and birth defects, Local 6 News partner Florida Today reported.

While chlorine makes the water safe from bacteria and other pathogens, tests show many systems repeatedly measure high in unintended and potentially cancer-causing chlorine compounds called trihalothemanes and haloacetic acids.

A Florida Today analysis of 2006 water data, the most recent available, found:

3,413 people in Brevard used tap water with trihalomethanes that exceeded the recommended federal limit of 80 parts per billion.

1,812 of those same people also had water with haloacetic acids over the recommended limit of 60 parts per billion. In some cases, it was more than six times over the limit.

Many small systems, serving mobile and manufactured homes, have been plagued for years by chlorine's cancer-causing compounds.

While Brevard's largest water suppliers -- Cocoa and Melbourne -- test well within federal limits for chlorine's byproducts, they still have levels that scientists now suspect could double one's risk of bladder and other cancers.

As legally required consumer water reports reached mailboxes, some residents worried what chlorine's complex compounds might do to their health over the long haul.

"We didn't know it until we moved in," Dave Rosinski, 50, said of the discolored water that flowed from his faucet at River Grove II Mobile Home Villa in Micco. "Yesterday, it came out pure yellow. It smelled like chlorine, really bad, pungent."

In September, River Grove's water tested 383 parts per billion haloacetic acids, about six times the federal standard.

One part per billion is analogous to an ink drop in an Olympic-sized swimming pool.

State regulators required River Grove II to notify homeowners and lower chlorine levels in the distribution system.

Subsequent tests showed improvement, bringing the overall average of quarterly tests closer to federal limits.

Water suppliers must measure chlorine byproducts quarterly. When averaged, haloacetic acids must not exceed 60 parts per billion.

The average for trihalomethanes (THMs) cannot exceed 80 parts per billion.

When levels cross those thresholds, the state Department of Environmental Protection first sends warning letters, then can ultimately use legal orders and penalties if water suppliers fail to fix the problem.

That rarely happens, officials said.

The state agency tends to allow such levels to persist in the water because chlorine byproducts are considered less threatening to health than contaminants such as bacteria or nitrates.

How They Form

Cancer-causing compounds form when chlorine bonds with microscopic bits of leaves and soil. Smaller water systems tend to be at greater risk because suppliers cannot afford the expensive filtering systems that cities use. They also often lack stable sources of clean water.

Cocoa's water measures within federal limits. But its highest level for THMs, 76 parts per billion in February 2006, neared the 80 part per billion federal threshold.

Scientists are now finding a twofold bladder cancer risk at THMs of 50 parts per billion or higher. Studies also have associated chlorine byproducts with increased risk of colon, rectal, brain and liver cancers.

No studies specifically link Brevard's water to increased cancer rates, but a state health department database shows an average of 200 cases of bladder cancer diagnosed yearly, putting the county in the top 10 for age-adjusted rate of bladder cancer in Florida.

Researchers warn, however, that when it comes to cancer risk from chlorine byproducts, there is much they still don't know.

Drinking water is not the only worry.

Recent research shows people might get a much higher dose of chlorine byproducts from showering and hand washing than from drinking the typical quarter to half gallon per day.

Studies at Colorado State University found that after showering, people can have anywhere from two to four times the level of chlorine byproducts that was in their blood before stepping under the shower head.

Worse In Florida?

Florida's warmer climate also can exacerbate chlorine's byproducts. And the byproducts can be even more prevalent in coastal cities, where groundwater, rivers and lakes are impacted by saltwater intrusion or natural salt deposits from ancient seas.

Most of Brevard's troubled water systems are in the far north or south rural reaches of the county, such as Micco, where many neighborhoods rely on septic tanks and shallow wells.

Some are growing neighborhoods too far from any large municipal water system.

In River Grove, which tested above limits for haloacetic acids, the Rosinskis spent $500 for a reverse osmosis filtering system to cleanse the water they don't trust.

But Dave Rosinski expects better, given the natural sand filter below.

"It's all sand here, and you would think the water would be pretty clean," he said.

Watch Local 6 News for more on this story.