The question is, do the benefits outweigh the costs. This is one question that has not yet been answered. The United States government has been trying to use a cost/benefit scale, but they are not sure of all of the problems, especially on humans. Some of the biggest problems that they have seen already include bioaccumulation, reproductive failure, many types of cancer, and many other health problems. .
Bioaccumulation is the term used to describe the build-up of toxins in the environment. Fat-soluble toxins are often very difficult to break down. These types of toxins accumulate (in plants, animals, or humans) as lower organisms are consumed by those higher on the food chain. It is easy for people to see that wind, rain, and run-off can spread pesticides. What is hard to understand is the idea of bioaccumulation. If DDT is sprayed on a field in Africa to kill mosquitoes it will end up in the soil and on all of the plants. When it rains, the DDT can be washed into a nearby stream, which feeds into a big river and then into the ocean. The stream, river, and ocean will now contain the toxin. Plankton in the ocean will ingest the DDT. A small fish might then eat the plankton and then a bigger fish might eat the small fish. By this time, the toxins may have traveled hundreds of miles, and could be off the coast of America. Since the molecule that makes up DDT is fat-soluble, the fish will store the DDT in its body forever, or until it is eaten by something else. If a fisherman catches that fish a human will eat it, and it will be stored in the human. Each time DDT is ingested by an animal, the toxicity increases. John Wargo, a leading expert in environmental policy, gives a very good example of bioaccumulation. In 1949, a lake in California was treated with DDD, which is very closely related to DDT. The concentration of DDD in the lake was one part DDD to every 70 million parts water.
