Bomb 14C and human radiation burden

Following the publication (Stenhouse and Baxter, Nature; 267:828 (1977)) of the levels of bomb 14C and the residence times of carbon in the human body, excess radiation burdens from this radioisotope are evaluated under the assumption that no radiation dose, however small, can be regarded as entirely harmless biologically. The estimated annual absorbed dose attributable to 14C both natural and man-made for 1953-1973 and similar predicted figures for 1975-2025 are shown graphically. The cumulated doses to gonads (over 30 yr) and to bone marrow and bone-lining cells (over 60 yr) and also estimates of the biological damage to reproductive cells from 14C β-irradiation (30 yr accumulated dose) are presented. It is concluded from both genetic and somatic considerations, that the potential human radiation burden due to artificially produced 14C calculated using the assumptions stated is certainly significant and, therefore, cannot be dismissed. However, relative to the world population and in view of the time span over which this dose is delivered, some three to four generations, the conclusion of this study must be that such effects will occur unnoticed. (U.K.)