DDT Levels Set Record in Mussels at Newport

Transplanted mussels in two Newport Bay locations were found to have the highest saltwater levels of the banned pesticide DDT ever recorded, with Monterey Bay’s Watsonville Slough running a close third, state water officials said Thursday.

By far the highest concentrations of DDT ever found in the state’s 8-year-old monitoring program, however, were in freshwater clams from the Espinosa Slough, the Old Salinas River and the Salinas River Lagoon in Monterey County, officials for the state Water Resources Control Board said.

In Orange County, results of the long-awaited 1983-84 State Mussel Watch (SMW) also showed elevated levels of heavy metals, a variety of pesticides and organic chemicals in mussels transplanted to Anaheim Bay, Huntington Harbour and Newport Bay.

While the results are considered disturbing, especially when combined with results of similar tests for DDT and other toxics in freshwater fish in these areas, state officials said they do not appear to be a direct threat to human health.

Not Concerned About Health

“In terms of the public health risk--and that’s perhaps the most pertinent question --we do not believe the data indicates any reason for concern,” said Joanne Schneider, environmental specialist for the California Water Quality Control Board, Santa Ana region.

“We are concerned about the possible impacts on the aquatic habitat and on wildlife,” Schneider said Thursday. “We remain concerned about (biological) accumulation of DDT (in wildlife) through the food chain.”

Similar tests of freshwater fish in Newport Bay’s main tributary, San Diego Creek, show that DDT levels, while still among the highest ever found, are declining, according to 1984 results of the state Toxic Substances Monitoring Program released Wednesday along with the mussel studies.

Small bait fish called red shiners sampled in April, 1984, in the San Diego Creek near MacArthur Boulevard contained 5.1 parts per million of DDT. Samples of red shiners collected the previous year contained 9.5 ppm of DDT.

The U.S. Food and Drug Administration maximum tolerance level for DDT in fish sold for human consumption is 5.0 parts per million. However, the National Academy of Sciences says that concentrations as low as 1.0 part per million pose potential dangers to wildlife.

Banned in 1972 after it was conclusively linked to drastic declines in the population of two bird species, the brown pelican and peregrine falcon, DDT is an insecticide from the family of mostly banned pesticides known as chlorinated hydrocarbons. It dissolves not in water, but in oils or lipids. It accumulates in the fatty tissues of many animals and can reach very high concentrations in predators that feed on smaller animals.

DDT also is slow to break down in the environment. But most of the chemical was expected to have all but disappeared after 13 years.

That has made the finds in Newport Bay and its watershed, along with a number of other coastal areas, especially baffling.

The operative theory now is that DDT can stay relatively untouched in soil far longer than scientists ever believed possible. And as former farming areas are developed and the soil turned over, then washed downstream, the deadly pesticide is again released into the environment.

Blamed on Residue

“There is no evidence that (the DDT found) is due . . . to illegal use,” said Evan Nossof, spokesman for the state Water Resources Control Board. “The best evidence is that it’s a residue of practices that ended a decade ago. Everywhere there was a mosquito, it appears DDT was used.

“So we’re left, to some extent, to documenting a legacy,” Nossof said.

The mussel watch program--begun in 1977 and expanded to freshwater shellfish such as clams, which tend to build up higher concentrations of the pesticide than mussels--is considered an early warning signal to water quality specialists.

“It’s a reconnaissance program with very small samples taken at a large number of locations,” Nossof said. “The results are difficult to characterize because of the small number of samples, and we are just now building the type of data base to do studies of the statistical significance and to look for possible trends . . . .

“It does give us preliminary warning of water quality problems so that we can intensify our monitoring, and so that we can take action before things get out of hand,” he said.

The highest DDT levels recorded in the 1983-84 mussel watch program were found in California mussels transplanted to Bay Island and at the Pacific Coast Highway bridge in Newport Bay. At Bay Island, DDT levels were at 4.378 parts per million; at Pacific Coast Highway, DDT levels measured 3.833 ppm.

At Watsonville Slough in Monterey County, DDT levels in transplanted California mussels measured 3.244 ppm.

(The above dry weight measurements are well below the FDA standard of 5.0 parts per million, which is a wet weight measurement. If converted into wet weight measurement, the highest DDT level, found at Bay Island, equals .60 parts per million--or less than one-fifth the FDA limit.)

Other Test Results

DDT levels at other test stations in Newport Bay included, 1.911 ppm found in the Crows Nest area near Lido Island; 1.578 ppm found in the Upper Rhine Channel, and 1.370 ppm found in the bay entrance.

Elsewhere in Orange County, DDT was found in Anaheim Bay and Huntington Harbour. In Huntington Harbour, DDT levels measured 1.696 ppm at the Warner Avenue bridge and 1.189 ppm at the Edinger Avenue bridge. Both were near storm drains carrying outflows from the East Garden Grove and Wintersburg channels. In Anaheim Bay, DDT levels were lower at .773 ppm in the naval harbor and .739 ppm in the naval marsh.

The filter-feeding mussels, which were transplanted from Bodega Bay waters where there is relatively little pollution and harvested after about five months, were collected between November, 1983, and January, 1984. Nossof said the sheer volume of samples from stations throughout the coast of California makes testing a lengthy procedure.

Although the current thinking is that DDT is taking longer to degrade in the natural environment, Schneider said, “Nobody is going to say definitively that DDT is not being used illegally.”

“I believe the weight of evidence justifies that opinion. But I don’t think it excludes the possibility that DDT is being used illegally,” she said.

The soil and sediment in the Upper Newport Bay watershed is currently being extensively tested in an effort to determine the amount of DDT lingering in Orange County, she said.

And while reduced levels of DDT found in April, 1984, in San Diego Creek freshwater red shiners was encouraging, Schneider said one possible explanation is that 1984 was a year of relatively light rains compared to the rainy season of 1982-83.

Schneider said local health experts also remain concerned that the high level of toxics and pesticides could have some effect on sportfish. But because edible sportfish caught off Orange County have not been tested, she said it is not known whether they carry high levels of DDT and PCBs, as have been found recently in fish caught in coastal waters from Santa Monica Bay south to the Los Angeles-Long Beach Harbor.

Both the Orange County Health Care Agency and the regional water quality control board have asked the state Deparment of Fish and Game to include Orange County in future studies.