Although DDT is a (modestly) toxic substance, there is a world of difference between applying large amounts of it in the environment – as farmers did before it was banned – and using it carefully and sparingly to fight mosquitoes and other disease-carrying insects. (When it is used at all now, it is now sprayed indoors in small amounts to prevent mosquitoes from nesting.)
毒性学的一个基本原则是剂量造就毒药。虽然DDT是一种（较为）有毒的物质，但大量使用于环境中（就如同禁用前农民的使用方式）和小心谨慎地用来杀灭传播疾病的蚊虫（现今被极少量地喷洒于室内防止蚊虫孳生），其效果是完全不同的。