(Beyond Pesticides, February 1, 2007) Thirty-five years after the banning of DDT, extremely high concentrations of the pesticide are being found in fish caught in California’s Los Angeles county waters. According to a newly released federal survey by the National Oceanic and Atmospheric Administration (NOAA) and Environmental Protection Agency (EPA), the fish caught in the area contain the world’s highest-known DDT concentrations.
The survey was conducted in order to update health advisories on which fish are unsafe to eat and to help EPA decide whether to attempt a costly operation to reduce continued contamination from a deposit of DDT on the ocean floor. The findings contradict the belief held by some scientists that DDT on the ocean floor has been breaking down into less-toxic compounds and would soon disappear from marine life.
The contamination, most severe in the middle of San Redondo Bay, stems from a 100-ton deposit of DDT released by the Montrose Chemical Co. beginning in the late 1940s, which still covers several square miles of the ocean floor. The pesticide manufacturer had a plant near Torrance, California, from 1947 to 1971, releasing about 2,000 tons of DDT into county sewers that subsequently emptied into the ocean. The banned pesticide, classified as a probable human carcinogen and linked to liver disease, reproductive damage and altered hormones in lab animals and wildlife, adheres to sediment and continues to seep into marine creatures. EPA must now decide whether to attempt to seal off the ocean deposit with a thick cap of sand, which could cost tens of millions of dollars.
The survey looked at data from 2002, and identified the bottom-feeding white croaker the most contaminated fish, especially when caught in the middle of San Pedro Bay, about 1.5 miles offshore in an area called Horseshoe Kelp. Also highly contaminated were kelp bass, barred sandbass, scorpionfish and rockfish, some containing above half a part per million (ppm) of DDT. The average at Horseshoe Kelp was 3.2 ppm of DDT, with one fish reaching almost 13 ppm. Waters at the southern end of Santa Monica Bay, between Redondo Beach and Palos Verdes Estates, also had some highly contaminated croaker and barred sandbass. Pacific mackerel, opaleye and jacksmelt had the lowest concentrations.
In the past, the state of California has used 100 parts per billion of DDT as the threshold for acceptable cancer risk from eating fish, indicating that one of every 100,000 people who regularly eat such fish could contract cancer. The amount found in the average San Pedro Bay croaker was 30 times higher than this threshold. In response to the new federal findings, California’s environmental health agency is reevaluating the risks of eating locally caught fish, which could result in updates to a health advisory and a commercial fishing ban that have been in effect since 1991. Robert K. Brodberg, chief of fish and water quality evaluation at the Office of Environmental Health Hazard Assessment, said the agency will launch a reevaluation of the health risks this year, as soon as a federal report detailing the new data is complete. The aim is to develop new fish consumption recommendations and advise the Department of Fish and Game in updating its commercial no-fishing zone.
The data from the federal survey suggest that there has been no improvement in DDT contamination since the late 1980s, when the last regional fish survey was conducted. “Things have not changed a whole lot in the last decade or so,” said David Witting, a NOAA fish biologist who directed the survey. “The biggest concern is still lower Santa Monica Bay, Palos Verdes Shelf and much of San Pedro Bay. The species that is consistently the most highly contaminated is still white croaker.”
Mark Gold, executive director of the Santa Monica-based environmental group Heal the Bay, said the scope of the contamination revealed by the new fish data was worse than he thought. “Not only have things not improved for contaminated fish off Palos Verdes, but this data shows that the concern is more far-ranging than we originally thought,” Gold said. “Hot fish [highly contaminated fish] off Palos Verdes is no surprise, but we’re finding hot fish all the way from the Redondo Pier throughout San Pedro Bay, and it’s for a wide variety of species, not just the bottom-dwelling ones.”
An annual test of fish by the county sanitation department off the Palos Verdes Peninsula indicate conditions may have improved at the DDT deposit in the four years since the federal survey was conducted. David Montagne, supervising environmental scientist at the Los Angeles County Sanitation District, said that at least another year of data is needed before officials could be confident that the drop was permanent and not a temporary flux. “The trend we see ”” and we don’t know if it’s real or not ”” suggests that concentrations over the area of greatest DDT contamination are dropping,” he said. If that proves to be true, Mr. Montagne said, it supports the theory that the pesticide is degrading into less toxic compounds. For the past two years, average DDT concentrations in white croaker there declined substantially, from 33 ppm in 2002 to 4 ppm in 2005 ”” still a worldwide high.
In September 2006, the World Health Organization announced a new policy to support indoor application of DDT for malaria control in developing countries, despite the fact that it is classified as a class B “probable human carcinogen” by EPA and numerous studies have shown other adverse effects, such as endocrine disruption. Beyond Pesticides went on record disputing the logic behind continuing its use despite its known adverse health effects and persistence in the environment.
Source: Los Angeles Times