The DDT came from the now defunct Montrose Chemical Corporation based in Torrance, California. Once North America’s largest DDT producer, according to the study, the company routinely and legally dumped its manufacturing waste containing residual DDT into the Southern California ocean before the chemical’s harmful effects were recognized and the bans took effect.
“In Southern California, extensive dumping of agrochemical waste, particularly chlorinated hydrocarbon contaminants such as DDT, via sewage outfalls and permitted offshore barging occurred for most of the last century,” researchers wrote in the article, and their research aimed to examine “how this unique legacy of regional ocean disposal translates into the contemporary contamination of the coastal ocean.”
“It is a terrible chapter in our history, treating our ocean as a giant garbage can,” David Valentine, professor and founding director of the Marine Science program in the College of Creative Studies at University of California—Santa Barbara, who did not work on the study, told The Epoch Times.
Most Fish Are Safe to Eat
While researchers found DDT contamination has not yet disappeared, they also found that contamination has decreased over time, and most fish caught in Southern California are safe to eat in terms of DDT content.Most of the fish samples—86 percent—had DDT levels below the threshold for safety consumption set by California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment, while 3 percent “exceeded the most restrictive threshold of consumption,” according to the study. The remaining 11 percent should only be consumed occasionally.
The data also suggested that DDT in the ocean floor sediment has become “less bioavailable due to degradation and burial,” resulting in less contaminated fish. The burial of DDT by new sediment over time is likely more substantial than its degradation, Brice Semmens, a professor in the Marine Biology Research Division at Scripps Institution of Oceanography and one of the researchers for the study, told The Epoch Times.
Because of the localization of the DDT, most fish that anglers catch throughout California, even throughout Southern California, are safe to eat, Semmens said.
“This is a great example to bring to the public’s attention to show what could happen when we acted without thinking, when we dumped all that stuff and didn’t care to think of the ramifications,” said Valentine of the study.
“It is important to have discussions about this—these chemicals benefit us but also cause harm—so that we can take a more balanced approach: How do we handle all these chemicals that we are making, how do we regulate them? These are difficult but important questions,” he said.
DDT Remains Localized
Semmens said he was surprised to find out from the study that “the spatial footprint of where the DDT is in the sediments off California is remarkably well conserved relative to where it was dumped into the ocean long, long ago.”This is contrary to what is generally believed, that the ocean disperses and dilutes out toxins, he said, for example, through ocean currents.
Part of the reason is that DDT is not water-soluble, Semmens said, “but we don’t know exactly why the ocean hasn’t done more to disperse the pollutants. That’s an interesting open question.”
He said some trial studies of other toxins and metals suggested similar trends, but more data is needed.
DDT in History
DDT was the first synthetic insecticide developed in the 1940s and was used to combat malaria, typhus, and other insect-borne human diseases.DDT is now “classified as a probable human carcinogen by U.S. and international authorities.”
It is also known to be very persistent in the environment and accumulate in fatty tissues, according to EPA.