Deep sea fish are contaminated with the pesticide DDT and other related chemicals off the Palos Verdes Peninsula coast and beyond, according to a study released this week.
The fish, as well as sediments, researched by scientists at UC San Diego’s Scripps Institution of Oceanography and San Diego State University are “contaminated with numerous DDT-related chemicals,” according to a press release. The study was published in the journal Environmental Science and Technology Letters and was funded by the National Oceanic and Atmospheric Administration.
“It’s providing the link that there’s a potential that the source of DDT to the food web could be coming from deep ocean sediments,” said Margaret Stack, a research specialist at San Diego State and one of the study’s authors.
“It’s possible,” she added in an interview, “that some of this DDT is still coming off of the Palos Verdes Shelf.”
The fish samples that were tested came mostly from the San Pedro Basin, which is located between the Palos Verdes Peninsula and Catalina Island. There was also testing from the Santa Cruz Basin, which is approximately 60 miles away from the San Diego Basin.
These basins are separated by miles, which, the study says, shows “this broad distribution of DDT pollution in the Southern California environment where we still maybe don’t know the boundary of where DDT pollution is occurring.”
The fish that were contaminated live in the deep sea, so they don’t spend much time at the surface, Lihini Aluwihare, a professor of ocean chemistry at Scripps and co-author of the study, said in a press release this week.
“Establishing the current distribution of DDT contamination in deep-sea food webs,” Aluwihare said, “lays the groundwork for thinking about whether those contaminants are also moving up through deep-ocean food webs into species that might be consumed by people.”
In recent years, the extent of DDT pollution off the Peninsula is coming to light thanks to scientific discoveries and research.
Known as the Southern California Bight, the hundreds of miles of coastline along the West Coast of the United States and Mexico, has “some of the highest recorded concentration of DDT in the world due to the discharge of DDT manufacturing waste from 1947 to 1982 by the Montrose Chemical Corporation,” according to the study, released on Monday, May 6.
The “discharged waste, composed of industrial acid waste with trace amounts of DDT,” according the study, “contaminated the Palos Verdes Shelf.”
This study is the latest in years of research into toxic chemicals off the Peninsula.
About 27,000 barrels that were thought to potentially contain DDT were found on the ocean floor in 2011 and 2013 by survey researchers, which included David Valentine, a professor of microbiology and geochemistry at UC Santa Barbara. The insecticide has been banned for many years, but the now-defunct Montrose Chemical Corporation was dumping its waste into the Pacific Ocean legally for decades.
“Offshore dumping of various chemical waste products was a legal practice in the 1900s, and there are 14 known deep ocean disposal sites off the coast of southern California,” according to the new study, including in the San Pedro Basin.
The EPA named Montrose a Superfund site, defining it as one of the nation’s most toxic collections of pollutants, on its “National Priorities List” in 1989.
Montrose closed in 1982, but around 20 years later, it reached a $140 million settlement with federal agencies for dumping harmful chemicals in the Pacific Ocean for decades.
Scientists also uncovered recently that Montrose was probably dumping the waste directly into the ocean, without the use of barrels.
In January, scientists from Scripps said they found fewer barrels that possibly contain DDT than previously believed, but they also uncovered World War II-era military munitions as well as a whale graveyard.
In February, researchers published another study that found potential evidence of low-level radioactive waste that was also dumped into the Pacific.
“Substantial amounts of DDT remain in these sediments, which are largely unaltered after more than 70 years,” according to a different study, published in February in the journal Environmental Science & Technology under the title “Disentangling the History of Deep Ocean Disposal for DDT and other Industrial Waste off Southern California.”
DDT-related pollution is well known, but the study released this week said more investigation needs to be done on the role of the dumpsites as a source of DDT in the food web.
Scientists are still discovering DDT-related compounds, which now reach nearly 50 in total, Stack said.
“The 45 or more DDT-plus compounds haven’t really been analyzed in a lot of sport fish that people might be consuming, but that is some work that we are undertaking right now,” Stack said. “But we don’t have any results to share yet.”
