The persistence of DDT is a problem—and not just in the countries that use it.DDT and several other common chlorine-containing pesticides are sturdy molecules that can stay intact for decades. They evaporate into the atmosphere and are blown by the wind all over the globe. They condense and fall to theground in cold weather, especially in higher altitudes. Some of the highest
concentrations of DDT are found in polar bears, penguins and the Inuit people of
northern Canada.