Electric lighting has become an integral part of modern society. When such light is inefficient, annoying, or unnecessary, it is known as light pollution. Many environmentalists, naturalists, and medical researchers consider light pollution to be one of the fastest growing and most pervasive forms of environmental pollution. Moreover, a growing body of scientific research suggests light pollution can impair biologic functions in both humans and wildlife. Researchers are working to determine the extent and nature of associations between light pollution and human health effects such as cancer, cardiovascular disease, depression, and insomnia.