Edward Calabrese, Professor of Toxicology, Department of Public Health Environmental Health Sciences, University of Massachusetts, Amherst, MA. The first Earth Day, in 1970, was celebrated after a wave of environmentalism swept the nation. Many give credit to Rachel Carson's 1962 book, "Silent Spring," which popularized the notion of large-scale chemical pollution, for igniting the movement.The "linear model" assumes that just a single molecule of a carcinogen or a single ionization from an X-ray can induce cancer. The enthusiasm spawned by Earth Day soon gave us brand new regulatory agencies such as the Environmental Protection Agency. The linear model is rigid, absolute and wrong. The resulting environmental regulations are having a negative impact, not only on societal costs, but on our health as well.