However, after a short time of use, it became clear that the chemicals were disturbing the balance which exists in the environment. Scientists soon realized that chemicals like DDT killed useful insects as well as the harmful ones. It also became clear that some of the most harmful insects were quickly developing resistance to DDT. As a result, farmers had to use even stronger and more poisonous chemicals against the new “super-insects.” Another problem Was that the chemicals did not disappear: They remained in the ground; they found their way into rivers, lakes, and oceans. They were absorbed into the bodies of fish and animals, and the animals began to suffer from new types of diseases. The
chemicals were poisoning them. Humans also began to experience serious health problems, especially in areas which were sprayed with 2,4,5-T. In these areas doctors reported an increase of heart disease.