Evaluation of nitrate contents in regulated and non-regulated leafy vegetables of high consumption in the Canary Islands, Spain: Risk assessment

Abstract

The nitrate content of the most consumed green leafy vegetables in the European Region of the Canary Islands was determined. The sampling included chard and watercress, which are not regulated but highly consumed in this region. The levels of nitrates in organic vegetables were significantly higher than those of conventional cultivation. However, no seasonal differences were observed, and overall nitrate levels were lower than those reported in other studies. Median nitrate levels in the analyzed vegetables were: lettuce (3 varieties) = 573.7 mg/kg; ready-to-eat salad mixes = 595.0 mg/kg; spinach = 1044.2 mg/kg; arugula = 3144.2 mg/kg; watercress = 450.5 mg/kg; and chard = 1788.4 mg/kg. In general, the nitrate levels of watercress and chard were significantly higher than those of regulated vegetables with similar culinary uses. The average per capita daily intake of nitrates through regulated vegetables was 17.5–32.5% of acceptable daily intake (ADI). On the contrary, the consumption of unregulated vegetables in this archipelago represents a similar, or even higher, percentage of ADI (23.6–44.3%). We, therefore, consider that the establishment of maximum limits of nitrate by the EU regulatory authorities would be appropriate for chard and watercress and similar to those set for spinach.