A Cobalt-60 contamination incident in Taiwan 21 years ago demonstrated once again that sometimes a little poison is good for you:
The contamination occurred during the recycling of metal scrap when a Co-60 source was mixed with metal scrap, melted and drawn into steel bars in the mill. Unaware of the contamination, the steel bars were ultimately used in construction of more than 180 buildings in 1982-84. Most buildings were partitioned into about 1,700 apartments for dwelling, and some buildings for other purpose. The first contaminated apartment was discovered in 1992. The residents in the apartments totaled 10,000 individuals who had been exposed to chronic radiation for at least 9 years and as long as 21 years.The annual average dose received by the residents in the first year (1983) was about 50 mSv/y with the maximum dosage as high as 600 mSv/y. The residents’ total doses accumulated in 21 years could be calculated using the half-life of 5.3 years for Co-60 and resulted in the average total dosage of 0.4 Sv (the highest total dosage was 6 Sv). These values are higher than the average doses received by the atomic bomb survivors in a short period of time in Japan and higher than the doses received by the Russian recovery workers in two years after Chernobyl accident.
If the linear-no-threshold (LNT) model constructed based upon data from the atomic explosions in Japan is appropriate for evaluating chronic radiation, such excessive doses received by the contaminated apartment residents could induce at least 35 excess leukemia and 35 solid cancer deaths after 21 years. However, actually no increase cancers were observed. On the contrary, the spontaneous cancer deaths of the residents totaled 243 over 21 years based upon the vital statistics provided by the Taiwanese government. The mortality rate from these cancers dropped to only 3% of the general population as shown in the following graph.
The chronic radiation received by the residents in the contaminated apartments had not only reduced their cancers, but also seemed to reduce the hereditary malfunctions of their children (though the hereditary effects had not been obviously observed in the Japanese bomb survivors). The 46 hypothetical hereditary defected children predicated among the residents based on the LNT model, and the 21 congenital hereditary defects among the apartment children were reduced to only 3, (6.5% of the general population). Therefore, the health effects of chronic radiation observed from the residents revealed that chronic radiation is greatly beneficial to the residents, even with their doses accumulated to high level.
The beneficial health effects of radiation observed in the Taiwan Co-60 contamination incident are so unique, they could also coincidentally explain the theory developed by Dr. T.D. Luckey, and his Complete Dose-Response Curve as shown in the last page of his book, “Radiation Hormesis 1991.” The dose of chronic radiation of about 100 mSv/y is optimum to health with up to 10 Sv/y still being in the hormetic range. Dr. Luckey predicted in his paper at the 1999 American Nuclear Society annual meeting in Boston that if the American population received a supplemental radiation dose through the public health service of about 55 mSv, 49 % of the cancer deaths of the US population (about 200,000 Americans) could be prevented every year. Of course, many people were shocked by his suggestion. However, findings from this study suggest the potential of radioactive vaccines to prevent cancers.