Cadmium and other metals in Swedish wheat and rye flours: Longitudinal study, 1983-1997

Wheat flour (sifted), wheat bran, and rye flour were sampled annually in se veral different areas in Sweden for 15 consecutive years (1983-1997) for a total of 105, 90, and 30 samples, respectively. These samples were analyzed for their content of Cd, Co, Cr, Cu, Fe, Mn, NI, Pb, and Zn by atomic abso rption spectrophotometry with background correction after dry ashing at 450 degreesC. As part of the quality control procedures, an in-house reference material was analyzed in parallel to the samples to ensure reliability of the results. In addition, a certified reference material was analyzed to mo nitor accuracy of the results. The Cd level in wheat and rye flours (mean 0 .029 and 0.017 mg/kg dry wt, respectively) correlated significantly with ti me (p < 0.05) in 2 phases, tending to increase during the first half of the period and decrease during the latter half. In wheat bran, Cd (mean 0.15 m g/kg) levels did not correlate significantly with time. In wheat flour, Cu, Mn, and Zn (means 1.7, 6.2, and 7.6 mg/kg, respectively) showed a signific ant linear increase (p < 0.05) in concentration over time. In rye flour, th e levels of Cu, Fe, Mn, and Zn (means 3.8, 36, 31), and 28 mg/kg, respectiv ely) all decreased significantly (p < 0.05) over time. Similarly, in wheat bran Cu (mean 14 mg/kg) increased and Pb (mean 0.027 mg/kg) decreased signi ficantly (p < 0.05) over time, whereas Ni and Zn showed a significant curve d correlation with time and peaked at about the middle of the measurement p eriod.