Historical
The following question was answered by an expert in the appropriate field:
Q: How and when was the magenta trefoil radiation symbol designed?
A: The now standard familiar radiation warning symbol first appeared in the latter half of the 1940s, and its origins and evolution (including some excellent color photos) have been documented in an article by Lloyd Stephens and Rosemary Barrett that appeared in both the Health Physics journal and in the book Health Physics: A Backward Glance. The symbol, in essentially its modern, form first appeared in late 1946 at the University of California Radiation Laboratory in Berkeley where it was used internally as a radiation warning symbol. The familiar trefoil was apparently a collective effort of a number of staff members of the Health Chemistry group at that facility. In April 1948, at the instigation of J. H. B. Kuper of Brookhaven National Laboratory, an Atomic Energy Commission Information Meeting was held at which the now familiar trefoil was adopted along with the unique magenta and light blue color scheme; the light blue was later changed to yellow for better visible contrast. Acceptance was good, and on September 11, 1953, ASA Z53.1-1953, specifiying the design details and colors, was adopted.
The original Berkeley design can be found on the Oak Ridge Associated Universities Web site along with earlier signs and later versions and some excellent commentary by Paul Frame of the Oak Ridge Institute of Science and Education.
