The insecticides kill the black flies, but also destroy much of the food chain for the bird, fish, and animal life which also inhabit those regions. The fish of the Great Lakes are laced with mercury from industrial plants, and fluoride from aluminum plants poisons the land and the people. Sewage from the population centers is mixed with PCBs and PBS in the watershed of the great lakes and the Finger Lakes, and the water is virtually nowhere safe for any living creatures.