Evaluation of measurement data for Cd, Cr and Pb in certain uncontaminated foodstuffs published in surveys: analytical quality vs. uncertainty of measurements

Results for Cd, Cr and Pb at trace levels, in the same type of uncontaminated foodstuffs, often vary with several orders of magnitude, which normally is not the case for metals occurring at macro levels. In this paper we have been able to show that surveys that display results spanning a great range are linked to poor analytical quality control (AQC). A model for grading the quality of analytical publications was tested on 105 surveys, published during the 10 last years, on Cd, Cr and Pb in milk and in muscle tissue from domestic animals and fish. The result showed that as the description of the quality procedures increased, the span of results in a given study decreased. This correlation was statistically significant for cadmium in meat and fish muscle and for lead in milk at p<0.05. The papers were then ranked according to their quality, in order to indicate the level of confidence a reader can have in the results. Papers published in journals specialising in food and analysis/chemistry generally got higher ranking than papers published in other fields of expertise, e.g. toxicology or environment. The results also showed that there is no visible trend towards improvement in how quality procedures are described over the last decade.