Nitrate in foodstuffs : analytical standardisation and monitoring and control in leafy vegetables

Abstract: The potential harm to human health and the environment of compounds derived from nitrate is an issue that occasionally awakens media and public concern. Recent studies provide a new understanding of the role of nitrate and nitrite in our body and motivate revision of the long-held view that nitrate poses a health risk. Coincidently, national authorities are performing research, surveys and risk assessments to provide scientific support for the regulations laid down in the 1990s setting limits on nitrate in lettuce and spinach. In addition to the health factor, the economic (market unity) and environmental (agricultural contamination) aspects of the issue are being considered in this legislative work. In order to obtain data of appropriate and comparable quality in this study, a standardised method was needed for analysing nitrate and nitrite in foodstuffs. The standardisation process comprised three stages: a) comparative evaluation of the performance of three liquid chromatography methods; b) internal validation of the selected ion chromatography method; and c) external validation across an international collaborative study. The validated analytical method is now a Nordic and European standard method. The standardised analytical method was then used in a European monitoring programme of nitrate levels in green leafy vegetables. Our participation involved obtaining data on nitrate in Swedish-produced lettuce and spinach over the past ten years (1995-2005). The satisfactory levels of nitrate found in Swedish lettuce and spinach are partly explained by the prevention measures taken by Swedish farmers to reduce the content of nitrate in vegetables. These ten years of Swedish data confirm that the European maximum limits are reasonable. Implementation and enforcement of the current regulation are advisable from an environmental point of view.