Cancer from Surfing in Southern California? Scientists Assess Risk from Massive Suspected DDT Ocean Dumping

Forget sharks. In Southern California this summer, beachgoers may fear another perceived yet invisible threat — contracting cancer after splashing in the blue Pacific.

After seeing possible links to cancer in sea life, scientists are assessing the health threat to humans following the discovery of more than 27,000 barrels of suspected DDT or other chemicals deep in the Pacific off Los Angeles.

Not to worry, experts say. So far, no connection has been made between the sunken pesticides, scattered for miles on the seafloor some 3,000 feet below the surface, and cancers in humans. But scientists say they have much more to learn about the extent of dumping and its ramifications.

Related: DDT Could Be Causing Breast Cancer In Some Women

Some of the barrels have broken open and scattered their contents into sediments. A solution isn’t in sight. It’s considered too early to discuss whether the drums should be dredged up, covered over or just left alone in hopes of minimizing further damage to the environment.

For now, the waters off the Southern California coast should be considered safe for swimmers, surfers and others, said Dr. Lihini Aluwihare of the Scripps Institution of Oceanography at the University of California, San Diego, in a webinar on the issue Thursday. A bigger immediate concern is seafood.

“We are quite confident the primary route of exposure to human populations is through consuming seafood just because of the chemical behavior of these molecules,” Aluwihare said. But even that risk is minimal: “Unless you’re going down and eating a bunch of sediment, I think you’re good,” she quipped.

However, another expert was more hesitant. Toxic chemicals can accumulate in the tissue of oily fish like anchovies, which are tasty not only to humans but are a favorite meal for larger fish and mammals, said Dr. Pádraig Duignan of The Marine Mammal Center, which sponsored the webinar.

“Those are the fish that will accumulate those fat-soluble chemicals,” he said. “If you eat those, you are more than likely going to get exposed.”

Some of the same concerns were raised regarding ocean dumpsites at a hearing of Congress’ House Subcommittee on Water, Oceans, and Wildlife earlier this week. Asked about potential toxicity to people arising from chemicals believed to be deteriorating at underwater dumping sites, Dr. Eunha Hoh, division head of Environmental Health at San Diego State University, replied "we don't really know about it" yet.

Finding out will be expensive. The committee was told that next phase of site investigation will cost between $10 million and $20 million. Costs of the probe "will pale in comparison to the actual cleanup costs," said Jared Blumenfeld, California's secretary of environmental projection.

But if the effects seen so far on wildlife are any indicator, the cleanup may be necessary if it's found DDT is working its way into the food chain.

DDT was first developed in the 1940s and was used extensively to try to control a variety of common pests. But as DDT's effects on wildlife became known, including development of tumors in some animals, it was banned in the U.S. in 1972. It is classified as a "probable human carcinogen."

A study released last December points to a link between a high rate of cancer found during necropsies of sea lions in California and a high level of contaminants in their blubber, which can include DDT.

Another study found high levels of DDT-related compounds in bottlenose dolphins.

California didn't step in to prevent dumping of chemical waste into the ocean until 1961. Authorities have records from chemical companies documenting how many barrels they legally dumped. There were several different dumping sites and mapping of underwater dumpsites is far from complete.

There's another big concern, too. Not all of the chemicals may have been in drums. DDT could have been dumped directly into the ocean from massive shipboard tanks, making it that much harder to determine which sediments are contaminated.

The contents of the barrels that have been discovered haven't been fully assessed to figure out what exactly is inside of them.

But it's going to take time. With the barrels spilled out more than a half-mile deep, "this is an incredibly complex place to investigate anything," Blumenfeld explained to the House subcommittee.

What is Known About DDT & Cancer?

A March 2019 study found that women who were exposed to the chemical in the womb or in infancy periods of high developmental growth have a increased risk of developing breast cancer. The degree of increased risk depended on the amount of exposure to the chemical and age of initial exposure.

The findings are based on research involving three generations of women in the San Francisco Bay Area. Women who had been exposed to high levels of DDT during these periods were usually diagnosed with breast cancer about 40 years after their initial exposure.

"Nearly everyone alive has been exposed to this very persistent chemical, particularly women currently being diagnosed with breast cancer through early post-menopause who were alive in the 1950s and 1960s before DDT was banned in many countries," study author Barbara Cohn, Director of Health and Development Studies at the Public Health Institute in Berkeley, California told Reuters.

According to the CDC, people are most likely to be exposed to really small doses of DDT, or to the toxic chemical in DDT called DDE, through their food meat, fish and dairy products.

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