A coalition of water agencies reports it has found more evidence of pharmaceuticals, caffeine and other trace chemicals in the region’s water supply, including Orange County’s.

And while the amounts are considered far too small to pose a health risk, they could harm aquatic habitat or wildlife, a possibility being investigated by other researchers.

“The concentrations we’re seeing are many, many times lower than the normal dosage of these particular drugs,” said Kurt Berchtold, executive officer of the Santa Ana Regional Water Quality Control Board, which received the report this week. “So we certainly don’t think there is any potential for human effects due to this.”

The $50,000 report, from the Santa Ana Watershed Project Authority, found 10 “emerging constituents” — drugs or chemicals for which water-quality standards do not yet exist — at a variety of sampling sites within the 2,650-square mile area that drains into the Santa Ana River.

The substances included the active ingredient in pain relievers like Tylenol, the plastic contaminant known as BPA, anti-convulsion medication, antibiotics and flame retardant.

The results came from 23 sampling sites at wastewater treatment plants that feed into the Santa Ana River, two sites on the Santa Ana River, and one each on the Colorado River Aqueduct and the State Water Project. The samples were collected last spring.

Much of Santa Ana River is composed of treated effluent; as it flows downstream, some of it is captured for storage in Orange County’s deep drinking-water aquifer.

“Nobody wants drugs in their drinking water,” said Mark Norton, water resources and planning manager at the Watershed Project Authority. “But these things have no doubt been in the water for years and years. Now we’ve finally been able to detect these things.”

The contaminants appear at the parts per trillion range, he said.

“Imagine one drop in 20 Olympic-size swimming pools,” he said.

The researchers looked for 11 contaminants, and found 10. Many were found in a high percentage of samples, though all were at trace concentrations.

A flame retardant known as TCEP, for example, was found in 93 percent of the samples. The insecticide, DEET, was found in 89 percent.

The anti-convulsant Carbamazepine was found in 85 percent of the samples, caffeine in 48 percent.

There are a variety of reasons experts do not believe the pharmaceuticals and other trace substances, invisible to water-quality agencies before sampling technology improved in recent years, pose a threat.

First, the amounts are vanishingly small. Among the surrealistic comparisons to prove the point: a water consumer would have to drink some 2 million gallons of the recycled water straight from the river to swallow the equivalent of a single Tylenol.

It would take 370,000 gallons to equal the amount of caffeine in a cup of coffee.

Another reason not to worry, water experts say, is that the water percolates through layers of rock and sand before reaching the deep aquifer, a process that tends to clear the water of contamination.

The sampling effort was not meant as a comprehensive search for trace constituents, but to find those that are easily tracked and can be used as “indicators” of human waste.

Norton said state officials also are looking at stepped up sampling for the new, emerging constituents.

“This is a very forward step to take action and begin to look at these constituents before we’re required to,” Norton said. “We’re wanting be on top of assuring the safety of the public. This will be an ongoing, annual sampling program.”

The report’s findings are similar to those of a National Water Research Institute study released in May, which found 27 “constituents of emerging concern” out of 49 sought.

Those also included pharmaceuticals at extremely tiny levels.