In the mid-20th century, numerous containers of the pesticide DDT were dumped into the ocean and have yet to decompose, posing a significant hazard to the environment.
DDT (Dichloro-Diphenyl-Trichloroethane) is a synthetic organic compound containing chlorine, appearing as a white powder with a distinct odor, and is insoluble in water.
DDT exhibits high stability and toxicity, taking a long time to break down in the natural environment.
A DDT container at the bottom of the ocean, near the coast of Catalina Island, California. (Photo: AP).
Decades ago, industrial companies in Southern California used the coastline as a dumping ground for hazardous chemical waste for many years, including the pesticide DDT. In a recent study, scientists discovered that DDT remains at high concentrations on the ocean floor and has not decomposed, as reported by the Guardian on March 24.
“We still find original DDT on the seabed from 50, 60, 70 years ago. This shows that the substance does not degrade in the way we once thought,” said David Valentine, a scientist at the University of California, Santa Barbara, on March 23. The contaminated area on the ocean floor is even larger than the city of San Francisco.
DDT was widely used in the United States as an agricultural pesticide and was sprayed in large quantities on beaches to kill mosquitoes. This compound has been linked to cancer, various other human diseases, and mass animal deaths.
In the 1970s, DDT was banned in the U.S. due to its harmful effects on wildlife and potential risks to humans. Research has also shown a connection between exposure to this chemical and breast cancer as well as reproductive issues. Near the central California coast, which was also a dumping ground for DDT, a 20-year study found that exposure to this contaminant was associated with higher rates of cancer and herpes infections in sea lions.
Southern California is the center of DDT production in the U.S. The Montrose Chemical Corporation in Torrance, Southern California, produced large quantities of DDT from the end of World War II until 1982, before the U.S. Congress banned the practice. During that time, up to 2,000 barrels of waste acid containing DDT were dumped into the sea each month. Workers sometimes drilled holes in the barrels to make them sink faster.
In 2021, a team of experts from the Scripps Institution of Oceanography at the University of California San Diego and the National Oceanic and Atmospheric Administration (NOAA) conducted a two-week survey using underwater robots, sonar imaging, and other data. The survey uncovered over 25,000 barrels of waste. Scientists also found more than 100,000 artificial objects throughout the surveyed area.
According to the latest analysis by scientists, the densest layer of DDT lies only about 6 centimeters below the seabed sediments. “Trawling nets and cables can bring this substance back to the surface. Animals foraging, such as a whale diving down and stirring up the seabed, can disturb everything,” Valentine stated.
