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Going, going, gone? Vanishing DDT is big surprise at ocean deposit off Los Angeles

A DDT deposit in the ocean off Los Angeles County has rapidly shrunk, shocking experts and casting doubt on the need to mount a controversial $60-million Superfund cleanup, according to new data.

For decades, government officials and scientists have estimated that 110 tons of the banned pesticide – the world's largest deposit of DDT – have been sprawled on the ocean floor, where it was discharged by a now-defunct Los Angeles company.

But now only about 14 tons remain, according to the latest testing by the U.S. Environmental Protection Agency.

What has happened to the DDT off Palos Verdes Peninsula is, for now, a scientific mystery. Scientists have no explanation for how almost 90 percent might have vanished in a mere five-year period – between tests in 2004 and 2009 – after decades of a slow, gradual decline.

“It’s a dramatic decrease,” said EPA site manager Judy Huang. “It’s a lot smaller. We don’t fully understand why.”

Mark Gold, associate director of the UCLA Institute of the Environment and Sustainability, said he was in “absolute shock.”

“There was no foreshadowing of this,” said Gold, who has served on the site’s technical review committee since the 1990s. “There’s an order of magnitude less DDT today than what was there five years ago. It doesn’t make sense to me that this degree of a change would have occurred within the last five years. It’s very difficult to assess where it went.”

To read the full story by Marla Cone click here.

Additional coverage:

http://www.scientificamerican.com/article.cfm?id=the-mystery-of-the-vanishing-ddt-in-the-ocean-near-los-angeles