Study finds mysterious DDT chemicals in California condors

When Christopher Tubbs joined an ambitious multinational effort to save California’s electrical conductors from the brink of extinction, he knew the odds of success were long.

There are wind turbines that can attack giant birds, and lead shrapnel from hunted animals that can sicken and kill.

But Tubbs, who studies hormone-disrupting chemicals, suspects that there is another threat to condor’s existence – a particularly problematic pesticide. dumped off the coast of California decades ago.

Now, after years of research, Tubbs and a team of environmental health scientists have identified more than 40 DDT-related compounds that – along with several unknown chemicals – have circulated through the ecosystem. sea ​​and accumulate in this iconic bird. top of the food chain.

In a complex chemical analysis published Tuesday in the journal Environmental Science & Technology, the team found that DDT-related chemicals were seven times more abundant in the venous ducts. ocean compared to transmitters farther inland. Looking at the birds’ coastal food sources, the researchers found that the carcasses of dolphins and sea lions that washed ashore in Southern California were also contaminated with seven times more DDT than marine mammals. breasts they analyzed along the Gulf of California in Mexico.

A mysterious chemical potentially linked to DDT waste in California is 56 times more abundant in coastal conduits and 148 times more likely in California dolphins.

Close-up of an adult in California.

The California orcas, a critically endangered species, are at the top of the food chain in coastal ecosystems.

(Ken Bohn / San Diego Zoo Wildlife Alliance)

“The story of this DDT, and the pollutants that interfere with reproduction, we call exposure,” said Tubbs, a reproductive science specialist at the San Diego Zoo Wildlife Alliance. with a septic tank”. “They don’t kill a bird immediately, but… they can interfere with estrogen receptors or any other endocrine pathway.”

This latest study builds on study the toxic – and insidious – legacy of DDT in California. Public calls to action have grown since The Times reported that the nation’s largest pesticide producer once dumped its waste into the deep ocean. According to old records and a UC Santa Barbara study, about half a million barrels may still be under water today, providing the first real glimpse of this pollution bubbling up 3,000 feet below the sea. near Catalina Island.

Significant amounts of DDT-related compounds are still accumulating in Southern California dolphins, and a recent study has linked the presence of dichlorodiphenyltrichloroethane to aggressive cancer in sea lions. Another Oakland-based study shows that the hormone-disrupting effects of DDT are affecting a new generation of women – passed on from mother to daughter, and now the nieces.

Just because we banned DDT 50 years ago doesn’t mean it’s gone, said Eunha Hoh, whose lab at the San Diego State School of Public Health led the chemical analysis in the new study. – especially in California. If California waters are accumulating such high levels of DDT, that means every link of the coastal food chain – including humans – is exposed.

“Availability is very high in Southern California,” said Hoh, who continues to discover that the chemical is forever reappearing in new and unexpected ways. “We can’t go on… our oceans are so much more polluted with DDT.”

A California falcon spreading its wings.

California Condors are the largest land birds in North America.

(Ken Bohn / San Diego Zoo Wildlife Alliance)

Condors commanded the skies as early as the Pleistocene, when mammoths, saber-toothed cats, and other dinosaurs stalked California. Many natives like Chumash have come to see giant birds as central to their culture. The Yuroks know they are prey.

With a prehistoric bald head and a wingspan of nearly 10 feet, Gymnogyps californianus remains the largest land bird in North America and a sight to behold in the wild. However, its numbers have plummeted due to trophy hunting and increasingly polluted environment. By 1982, there were only 22 California conductors left on the planet.

Federal and state wildlife officials, with the support of conservation advocates, agreed to capture every last bird in the hope of bringing the population back to life.

Saving this critically endangered species is particularly difficult: It takes more than six years before a sparrow is ready to breed, and even then, the bird tends to lay only one egg a year. After decades of hard work, there are now 537 breeders in California, supported by a network of breeding centers and reintroduction sites from Baja California to Northern California.

Because lead poisoning is more common among scavengers farther inland, it is widely believed that marine mammals are an important food source for their long-term survival in the wild. course.

But in 2006, when prey released along the Big Sur coast finally began to mate, many of their eggs failed to hatch. Researchers began studying how DDT left in the environment might work.

“Our ongoing work has demonstrated that females live on the coast for many years and are therefore capable of living on the seashore,” said Myra Finkelstein, an environmental toxicologist at UC Santa Cruz, whose team worked on the study. ability to feed on marine mammals, the lower the probability that its eggs will hatch. It is also a tool in determining the cause of lead poisoning in electrical conduit.

A big challenge for her field, she said, is the overwhelming amount of chemicals that pollute the environment. Research like this new one, which Finkelstein reviewed but did not participate in, has gone a long way in helping toxicologists figure out where and how to focus their analyses.

For this latest study, researchers at the San Diego State School of Public Health teamed up with the San Diego Zoo Wildlife Alliance to connect more chemistry sites.

They took blood samples from 19 creatures that live on the coast of Big Sur and 20 that live mainly inland. Using a high-tech tool called a mass spectrometer, they sorted through hundreds of chemicals and methodically identified each DDT-related compound in blood samples – and applied the technique. The same applies to marine mammals on both the Southern California coast and the Gulf of California.

Nathan Dodder, an analytical chemist at SDSU, explains that they have cataloged a set of DDT compounds, which include two suspicious chemicals – TCPM and TCPMOH – that could be byproducts of the manufacturing process. export DDT. These currently unmonitored chemicals were also present in the dolphins they studied, as well as in sediment collected near barrels dumped into the deep ocean.

Little is known about these chemicals, said Margaret Stack, an environmental health scientist at SDSU and first author of the paper. She points to one study to date that tested TCPMOH on zebrafish – the aquatic version of lab rats – and found that the chemical was toxic to its embryos at high concentrations.

These are all the clues to look for when tracing DDT’s legacy through coastal ecosystems, says Lihini Aluwihare, a marine chemist at the Scripps Institute of Oceanography.

“We really need to understand where these animals are accessing DDT from. … What [this study] adds a more comprehensive look at the fingerprints of pollutants in the ducts,” said Aluwihare, who has synthesized the various sources of DDT that have infiltrated the food web. “This gives us something to compare, as we get the kind of data we’re looking for from the dumps.”

David Valentine, whose UC Santa Barbara research team first saw the craters underwater, says that detecting TCPM at such high concentrations is a big piece of the puzzle.

He will convene key scientists, regulators and policymakers in a conference this week to discuss next steps. The researchers recently received a grant from Congress to perform more chemical analyzes and collect more data — including more mapping of the seafloor to determine the extent of the seafloor. waste dump.

Many agree that better monitoring is needed overall – not only for the chemicals involved in DDT as we know them, but also those that can emerge from decades of interaction with the environment. .

“We now see it in marine mammals, especially dolphins. We already know about some fish in shallow water. We know that sea lions have a higher burden of DDT-related compounds, and now we see conductors are also accumulating both DDT and other DDT-related compounds in the form of TCPM,” said Valentine. speak. “For me, that said we had a problem. … Now we need to go back and understand what the legacy of those compounds really is – and understand where it came from, and what we can do in the future. “

Back at the southernmost tip of Condor’s historic habitat, Ignacio Vilchis led the Baja California restoration team – working across borders to help these endangered birds thrive back in the wild.

With the latest findings showing that the Gulf of California is less polluted by conductors, he hopes that releasing more bird species in Baja could help the general population stay well self-sustaining in the future.

As a trained oceanographer, Vilchis considers ships integral to the health and future of our oceans. If we can save the guide, it means we are also saving a lot of other lives along the way, he said.

His face lit up as he described the fear he felt when a spirit flew overhead. Their wings are so large that you can hear them beating in the air.

“It’s just… it’s so majestic,” he said, momentarily speechless. “There is something magical about them. You look up and there’s a 10 foot long bird flying overhead. It always gives me chills.”

https://www.latimes.com/environment/story/2022-05-17/study-finds-high-concentrations-of-ddt-in-california-condors Study finds mysterious DDT chemicals in California condors

Edmund DeMarche

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