Radiocaesium activity concentrations in wheat grains in the Republic of Croatia for 1965-2003 and dose assessment.

Results of systematic, long-term measurements of (137)Cs activities in wheat for the period 1965-2003 are summarized. Radiocaesum fallout activities affect wheat activity concentrations, the coefficient of correlation being 0.91. In the observed period, the highest activity of (137)Cs deposited by fallout, 6321 Bq m(-2), was recorded in 1986, i.e., in the year of Chernobyl accident, causing peak (137)Cs activity concentration in wheat of 38.0 +/- 13.0 Bq kg(-1). After the Chernobyl nuclear accident the (134)Cs:(137)Cs activity ratio in wheat was approximately 0.5, and did not differ from the value found in other environmental samples. The transfer coefficient from (137)Cs fallout deposition to wheat was calculated to be 8.6 x 10(-3) Bq y kg(-1) per Bq m(-2), indicating the low transfer of radiocaesium from fallout to wheat. The upper limit for the collective effective dose for the Croatian population due to (137)Cs and (134)Cs ingestion by wheat and wheat products consumption for period 1965-2003 was estimated to be 665 person-Sv, the upper limit for the annual collective effective dose in 2003 being only about 0.061 person-Sv.