Assuming a substance is harmful merely because it contains chlorine is akin to assuming water is flammable simply because it contains hydrogen, a highly flammable element. Different compounds with the same elements often have very different properties. Clearly, certain chlorinated substances, such as PCBs, DDT and dioxin, do harm wildlife at sufficiently high concentrations. However, PCBs and DDT were banned years ago and today dioxin emissions are kept to virtually undetectable levels. The ad hoc reasoning used by Greenpeace and others is no substitute for careful risk analysis.
Harm varies with the extent of exposure and disappears entirely below certain threshold doses.
In the Great Lakes, bald eagles, double-crested cormorants and other predator bird populations rebounded as DDT and PCBs were phased out and emission regulations reduced dioxin concentrations. Moreover, at the concentrations typically found in our environment, no organochlorines seem to cause identifiable human health problems. Industrial uses aside, it is worth remembering that until chlorination became widespread, dirty water was the most serious public health problem, spreading cholera, typhoid fever and dysentery. Contaminated water supplies still kill 25,000 children a day in the Third World. The substitutes Greenpeace favors are more costly and much less effective at maintaining water purity.