In addition to the Boomers, the generation of children born after about 1983 appears to be experiencing the same adverse immune-related health trends as the Boomers did. Before a cause-and-effect of a harmful substance is established, epidemiological studies involving statistical links between the offending substances and health effects are required. Perhaps the initial research showing effects on Hiroshima and Nagasaki survivors, indicating low levels were safe, was soothing to scientists and the public. In the case of low-level radiation's effects, anecdotes probably came before the theory as well. Even though national trends are influenced by many factors, environmental and nonenvironmental, identifying excess disease and death near nuclear plants clearly implicates radiation exposure as one of these causes. The environmental movement of the late 1960s and early 1970s took the growing body of evidence that certain chemicals were harming the population and engaged in highly public demonstrations, rousing state and federal governments to stop producing the offending substances.