DDT and other pesticides used over 50 years ago are still affecting the environment today. Scientists have found these substances in recent glacier runoff. Glacier runoff occurs during the summer, when
precipitation that has fallen on glaciers during the winter is released. Ice layers from existing glaciers
have been analyzed. The results of this analysis show that the concentrations of DDT and other
pesticides were highest about 10 years after the use of these substances was banned.