Passage 3All kinds of pollution as well as the depletion of natural resources (such as fuels, forests, and soil) by carelessly wasteful use, have worried scientists and other thoughtful people. Such persons are also disturbed about the effects of chemical fertilizers and of poisons which farmers use in order to destroy insects and weeds . Above all they are alarmed at the interference with the natural balance of the environment, and its possible consequences. As a result, there have been attempts to alert the public to these dangers and to control pollution, as well as to reduce the wasting of natural resources. One way of bringing these problems to the attention of the public is the yearly celebration of Earth Day, which began in 1970. There are also articles and books by environmentalists and organizations interested in ecology, the study of the interdependence of organisms and the environment. Federal laws to protect the environment date back to the late nineteenth century, after the conservationists exerted influence to save the forests and other resources from wasteful use and destruction.In the Los Angeles region, because of the particular weather conditions of that area, the exhaust from motor vehicles tends to create a dangerous accumulation of gases called smog. The United States government's Environment Protection Agency is studying various ways of avoiding danger to the population. By these and other antipollution studies and regulations, it is hoped that the environment can be prevented from deteriorating further.12. Federal laws to protect the environment date back to ____.