Decades of research by environmental scientists shows that not only do some chemicals persist in the environment for 40 years or more, some may never go away, according to a recent article in Chemical and Engineering News.
Ronald Hites of the University of Indiana and other researchers have tracked the movements through the environment of persistent chemicals such as DDT, PCBs and PAHs. Scientists were surprised to find evidence of DDT 40 years after it was banned, contradicting the previous notion that the chemical broke down in the atmosphere in a matter of days.
Instead of a simple atmospheric breakdown, scientists found DDT and other chemicals could go into the atmosphere, collect in water, soil, sediment, urban areas or landfills and then be released back into the atmosphere later. The chemicals can also persist in animal and human blood and tissue for decades.
Much of the research Hites and others have done on the persistence of chemicals is based on data obtained in the Great Lakes region through decades of study. Although the concentrations of the phased out or banned chemicals have been shown to gradually decline, Hites and others wonder if their concentrations will ever reach zero.