Background carbon-14 levels in UK foodstuffs, 1981–1995, based upon a 1992 survey

Knowledge of the current ‘natural’ background level is important to 14C-related studies, especially dose assessments in the vicinity of and distant from nuclear establishments since its value must be subtracted from measured levels to determine local enhancement. Although measurements have been made world-wide to monitor the decline of the background level, from its peak in the early 1960s to the present, there exists a paucity of precise data for UK natural materials. Accordingly this study was carried out to establish an average figure for the ‘natural’ 14C level in foodstuffs in 1992 from a survey of materials collected from a wide range of sites over England and Wales, using this single year value, to infill missing years prior to 1992 and to extrapolate for some years afterwards. Results are presented from the survey, and from the derived extrapolation with comparison made with measurements from other laboratories.