Polonium were marketed by Firestone from 1940 to 1953. While the amount of radiation from the plugs was minuscule and not a threat to the consumer, the benefits of such plugs quickly diminished after approximately a month because of polonium's short half-life and because buildup on the conductors would block the radiation that improved engine performance. (The premise behind the polonium spark plug, as well as Alfred Matthew Hubbard's prototype radium plug that preceded it, was that the radiation would improve ionization of the fuel in the cylinder and thus allow the motor to fire more quickly and efficiently.) Polonium is
Isotopes of polonium Isotopes of polonium Polonium (Po) has 33 isotopes, all of which are radioactive, with between 186 and 227 nucleons. Po with a half-life of 138.376 days has the longest half-life of naturally occurring polonium. Po with a half-life of 125 years has the longest half-life of all isotopes of polonium. Po and Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron. Po is an alpha emitter that has a half-life of 138.376 days; it decays directly to stable Pb. A milligram of Po emits as many alpha particles