A little-known environmental disaster is lurking off the coast of southern California. In the mid-20th century, the seabed somewhere between Long Beach and Catalina Island became the site of a deepsea dumping ground. While the practice stopped decades ago, the seafloor is still littered with hundreds of thousands of waste-laden barrels, including many holding the now-banned pesticide dichlorodiphenyltrichloroethane (DDT).
Once a widely used insecticide, DDT became infamous for its environmental impacts and its effect on both animal and human health. While much of its effects on health are still not deeply understood, DDT has been linked to a host of reproduction issues and is thought to be carcinogenic in humans. After these numerous issues came to light, the US banned the use of DDT in 1972. However, that was certainly not the end of the story. DDT is notorious as it builds up in food chains and lingers with ecosystems for decades — even today, most people have traces amounts of DDT in their bodies.
California was a global hub of this nasty stuff. In the post-war period, Montrose Chemical Corporation of California became the world's largest supplier of DDT from their plant in Los Angeles. Not only did they leak tons of DDT into the ocean through the local sewer system, they also dumped an estimated 2,000 to 3,000 barrels of DDT-related waste into the ocean every month between 1947 to 1961, according to a report produced by a California Regional Water Quality Control Board in the 1980s. In total, they estimated 500,000 barrels laced with DDT were sitting on the ocean floor off the coast of Los Angeles.
While certainly shocking, the report was largely forgotten about until the troubled dumping site was brought to public attention once again by David Valentine and a team of marine scientists at the University of California, Santa Barbara. As reported in the journal Environment Science & Technology in 2019, they used submersible submarines and chemical samples to document and start to understand the effect of the waste dumped at the site. Through their survey, they saw around 60 waste barrels located at a depth of around 900 meters (~2,950 feet). All in all, they concluded: the "disposal process was inherently sloppy," and "there is evidence to suggest that the waste was dumped purposefully."
It's not yet clear what effect this is having on the marine life around southern California and beyond, but some worrying hints are starting to emerge. In December 2020, researchers from Marine Mammal Center Sausalito published a study on almost 400 wild California sea lions (Zalophus californianus) and found that just under 25 percent had cancer. Most of the sea lions were infected with herpes, which is likely to have played a factor in the cancer rates, but the researchers also found a surprisingly high amount of DDT and PCBs, another environmental pollutant, in their blubber. The study even concluded that their findings are likely to have implications for human health too.
The sea lions of California are just one example of marine life potentially suffering the impacts by the dumpsite, but it looks unlikely to be the last.
[H/T: CBS News]