How An Ocean Dumping Ground Was Exposed

Diving around Catalina Island and off the Los Angeles coast may feel like a wonderful communion with nature. But there is a hidden pollution spreading sickness among the living creatures who share the water with you.


Dichloro-diphenyl-trichloroethane, also known as DDT, is one of the most environmentally poisonous insecticides. It can kill birds and fish. It was used during World War II to protect soldiers from malaria and typhus, prevent crop failures, and dust for mosquito elimination, all before its toxicity became evident. It was officially banned in the U.S. in 1972 due to mounting evidence it would have a negative impact on human health.


DDT can take generations to break down. Most worrisome is how it accumulates in animal tissue. Scientists have noted how its concentrations increase as it moves up the food chain. You would think preventing its impact on land and ocean ecosystems would be a priority. But that has not always been the case. Some industrial companies in Southern California prior to 1972 were less concerned with dumping DDT leftovers into the ocean than being cautious about its long-term effects on nature.


Eventually the Marine Protection, Research and Sanctuaries Act was enacted in 1972 to prevent dumping such toxins. Unfortunately, damage had already been done. And we didn’t know until recently just how vast that damage was.


Discovery of a dumping site


UC Santa Barbara marine scientist David Valentine verified what he had long suspected was hidden in the depths of more than 36,000 acres of sea between Catalina and Los Angeles. Thanks to the convenience of an on-loan deep sea robot, he was able to do more than study methane seeps on that memorable day in 2011. He had a few hours to spare and used his time to look for the environmental abuse he felt certain lurked in the deep.


His borrowed robot skimmed the ocean floor 3,000 feet below the waves. The images it sent up were as expected at first. Until the barrels appeared. One by one those rusted barrels, filled with toxic waste banned decades earlier, filled his screen. They oozed blue poison across the ocean floor. That poison was DDT. It had largely gone under the radar when it was dumped so many years before. Manufacturers had not dumped it through sewage pipes but had actually barged barrels of the stuff out to sea. It wasn’t known how much was being dumped back then... Until now.


"It's a feeling of — how does nobody know about this? How is it that we are the first people to ever see this with our eyes?" Valentine told CBS Los Angeles in April 2021.


Why would this happen?


The damage occurred largely between 1947 and 1982. The nation’s largest DDT manufacturer was based in Los Angeles and had been sending DDT barrels out to the ocean for dumping. It was believed poisons would be diluted in the deep waters near Catalina in those days. It took some sleuth work to look back on old shipping logs to better understand the magnitude of the toxins.


Dumping in the deep waters was bad enough. But workers often took shortcuts and simply dropped the barrels closer to shore. Even worse, they punctured barrels that seemed inclined to float, making them sink and spew poison as they did so.


Valentine and his researchers eventually counted 60 barrels along with samples between 2011 and 2013. The bad news didn’t end there, however. University of California San Diego Scripps Institution of Oceanography researchers continued exploration with underwater drones and have now identified 27,000 possible barrels. While not all the barrels may be DDT, they did estimate between 350 and 700 tons of DDT were dumped in the area between Los Angeles and Catalina Island.


Going forward


Scientists are now tasked with how to best solve this issue. Chemistry professor Diana Aga from University of Buffalo speculates the barrels may be moved to a safer disposal site. Leaking barrels may pose a different challenge, but water, sediment, and marine life samples could indicate the depth of damage done.


Research has already identified several impacts throughout the decades from DDT dumping, such as tumors in bottom-feeding fish. Brown pelican eggs with elevated DDT levels had eggshells so thin the chicks could not survive. Southern California jack mackerel had double the DDT levels considered safe for consumption. Sea lions with detectable levels of DDT delivered premature pups.


Teams of researchers and scientists will carry this project forward and hopefully find a solution to this terrible tragedy from the past. This story only underscores how vital it is we work together to protect our environment, to minimize the impact of chemical manufacturing, and to preserve all life for generations to come.


Looking for more like this? Read 5 Ways You Can Save the Ocean Environment.


SlipIns participates in marine conservation by supporting the Turtle FoundationSave the Reef Foundation, shark research, and abalone research. We are passionate about preserving marine ecology and the many colorful species that inspire us to create distinctive water sports wear.



Xia, Rosanna (2020). L.A.’s coast was once a DDT dumping ground. Los Angeles Times. October 25, 2020.


CBS News (2021). “Staggering”: 25,000 barrels found at toxic dump site in Pacific Ocean off Los Angeles Coast. April 27, 2021.

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