CHICAGO (CBS) — The pesticide DDT is still killing robins 50 years after Rachel Carson started the environmental movement with DDT warnings in her book: “Silent Spring.”

Back in September 1962, Carson wrote that robin populations were rapidly dwindling because the birds were eating worms laced with DDT–sprayed to control Dutch Elm disease.

And just this year, 50 years later, Terri Kniffen found several robins dead in her yard in Saint Louis, poisoned by DDT from an abandoned Velsicol chemical plant site.

The site has been designated for Superfund Cleanup but work won’t begin for another year or two.

Federal Fish and Wildlife Contaminant Specialist Lisa Williams says the 1972 DDT ban has resulted remarkable comebacks for bald eagles, ospreys and brown pelicans.

But she says DDT has a half-life of 15 to 30 years and still remains dangerous to wildlife feeding in high concentrations.

Williams says just because DDT and other older contaminants have been banned doesn’t mean the job is done preserving the environment.

She says there are still concerns about newer contaminants like pharmaceuticals which wash right through water treatment plants into the environment where their long-term impact remains unknown.

LISTEN: WBBM Newsradio’s John Cody Reports