When scientists investigated the seabed off the coast of California with high-resolution cameras in March, they made a disturbing discovery: between the coast near Los Angeles and the island of Santa Catalina 35 kilometres away, they mapped 27,000 barrels containing chemicals, predominantly DDT, over an area of 15,000 hectares at depths of up to 900 metres. In between, they observed more than 100,000 other debris fragments, under which the scientists suspect further barrels of DDT lie. DDT (dichlorodiphenyltrichloroethane) was used as an insecticide in agriculture in the 20th century, particularly against malaria-transmitting mosquitoes. When its use was linked to severe health damage in humans and animals, most countries banned the use of DDT starting in the 1970s.
Now, scientists fear that large quantities of DDT off the coast of California will affect marine food chains - and could ultimately end up on our plates in the form of fish. The Pacific region off L.A. has been used by chemical companies since the mid-20th century as a dumping site, for the cheap disposal of everything that was no longer wanted. The logbook of one of the American vessels from 1947 to 1961 shows that up to 2,000 barrels of sludge contaminated with DDT were dumped per month. This highly environmentally damaging mindset and practice was the global standard for a long time; the US government only banned it in 1972. Previous studies in 2011 and 2013 assumed there were about 60 barrels of DDT in this region; what an understatement! The true extent only became clear in 2021 and is a wake-up call: many of the barrels are damaged, and the sediment shows high concentrations of DDT. Research on dolphins and sea lions in the area revealed, among other things, very high concentrations of DDT in the adipose tissue. An increased rate of cancer was detected in the sea lions.
The scientists estimate that there are at least one hundred thousand barrels (nearly 16 million litres) of DDT in the ocean off the coast of Los Angeles. And further chemical substances must be feared.
Sources:
V. Kivenson et al.: Ocean Dumping of Containerized DDT Waste Was a Sloppy Process. Environmental Science and Technology, 2019. http://doi.org/10.1021/acs.est.8b05859
S.A. Mackintosh et al.: Newly Identified DDT-Related Compounds Accumulating in Southern California Bottlenose Dolphins. Environmental Science & Technology, 2016. http://doi.org/10.1021/acs.est.6b03150
N. Randhawa et al.: Sentinel California sea lions provide insight into legacy organochlorine exposure trends and their association with cancer and infectious disease. One Health, 2015. https://doi.org/10.1016/j.onehlt.2015.08.003
https://www.abc.net.au/news/science/2021-04-30/barrels-leaking-insecticide-ddt-la-coast-dumping-ground/100100912
