Estimation of dietary intake of radioactive materials by duplicate diet method

The radioactive materials released in the accident at the Fukushima Dai'ichi Nuclear Power Plant have forced many residents in Fukushima Prefecture, including members of Co-op Fukushima, currently living as they do in an environment exposed to radiation, to live in the shadow of anxiety that they may be subject to internal radiation exposure. A dietary survey was therefore conducted using the duplicate diet method on 300 participating Co-op member families over three periods for the purpose of investigating the intake of radioactive materials through everyday meals and thereby providing accurate information about existing conditions of internal radiation exposure. Neither (134)Cs nor (137)Cs was detected in excess of the lower detection limit of 1 Bq/kg in the meals of 283 of the 300 families (i.e., 94%). In the meals of 17 families, (134)Cs or (137)Cs was detected in excess of 1 Bq/kg. Of these, the greatest internal exposure dose for both of the radionuclides was observed in the period " I winter" (November 2011 thru April 2012) of the three-period survey. This coincided with the implementation period of the Provisional Regulation Values, which set a maximum annual exposure dose of 5 mSv. On the supposition that the family in question had continued to eat the sample for a whole year, the resulting annual exposure dose would have amounted to 0.135 mSv. This is far below the current annual radiation dose standard of 1 mSv. Accordingly, we conclude that a sufficient level of dietary safety has been attained and that there are no grounds for concern that the consumption of foodstuffs currently on the market will have any adverse effects on health as a result of internal radiation exposure.