The Union of Concerned Scientists (UCS) was founded by students and faculty at the Massachusetts Institute of Technology in 1969[1] and still exists today. The group has primarily focused on environmental and nuclear energy issues. In its founding document the UCS states that it intends:[2]

1. To initiate a critical and continuing examination of governmental policy in areas where science and technology are of actual or potential significance.
2. To devise means for turning research applications away from the present emphasis on military technology toward the solution of pressing environmental and social problems.
3. To convey to our students the hope that they will devote themselves to bringing the benefits of science and technology to mankind and to ask them to scrutinize the issues raised here before participating in the construction of destructive weapons systems.
4. To express our determined opposition to ill-advised and hazardous projects such as the ABM system, the enlargement of our nuclear arsenal, and the development of chemical and biological weapons.
5. To explore the feasibility of organizing scientists and engineers so that their desire for a more humane and civilized world can be translated into effective political action.

In the pamphlet shared in this post outlines the environmental and health risks that plutonium (used in power plants and atomic bombs) can cause if it is left unmonitored. It is hard to determine when this was published but they mention plutonium being a “recent” element (it was discovered in 1940). My guess is that this was printed in the 1950s or 1960s.

Union of Concerned Scientists

[1] http://en.wikipedia.org/wiki/Union_of_Concerned_Scientists

[2] http://www.ucsusa.org/about/founding-document-1968.html