In the 1920s, surveys of factory workers who painted watch dials with luminous paint found an alarming incidence of anemia, loss of teeth, bone fractures and death from cancer. This paint contained radium, a radioactive element. As a result, the industrial use of radioactive luminous paint was completely stopped by 1960. However, radium stays active for hundreds of years. Therefore, those watch-collectors who own watches that have luminous dials and were made before 1960 should either bury these watches in the ground or store them in thick lead boxes to protect themselves and the people around them from anemia, loss of teeth, bone fractures and death from cancer.
Which one of the following, if true, LEAST strengthens the argument above?