Research article INVESTIGATION OF COOKING METHOD ON NITRATE AND NITRITE CONTENTS IN CROPS AND VEGETABLES AND ASSESS THE ASSOCIATIED HEALTH RISK

According to the recent studies southern parts of Tehran have the highest levels of pollution of environmental contaminants. A descriptive - analytical and cross-sectional study was conducted for determination nitrate and nitrite in vegetable and crops in Tehran's farmlands. 1650 samples of 13 varieties of vegetables: Potato, Onion, Carrot, Iceberg lettuce, Romania Lettuce, Celery( petioles and leaves), Cauliflower, Broccoli, Beetroot, Eggplant, Spinach, and cabbage during 12 consecutive months of 2012and 2013 cultivated in the 40 important agricultural areas in the south of Tehran were collected. The study indicated that size of crops in onion, potatoes, beetroots, carrot, cabbage and lettuces has an effect on its nitrate content as mostly in large crops the nitrate content was less. Large size onion, carrot, beetroot and potato had significantly ( p<0.01) lower nitrate levels than small size. In accordance of the result of nitrate and nitrite content after boiling samples finding that the nitrate content were reduced with boiling by approximately: 54% in cabbage, 36% in potato, 43% in cauliflower, 19% in onion, 39% in celery and 11% in carrot samples, while the contents of nitrite in most of samples were the same and only in potato and onion were reduced with boiling approximately 9.6% and 10.3% respectively. Considering the high levels of nitrate in leafy vegetables especially lettuces, the ingestion of only 100 g of raw vegetables with the nitrate concentration of 2500 mg/kg will already lead to an intake of 250 mgNO3. Consuming this item alone, for a person of 60 kg, would exceed the ADI for nitrate by 13%. Chinese lettuce, Iceberg Lettuce, Onion, potato, spinach samples were 100 % higher than standard levels of ECR especially they are in the highest level in the cold seasons. Nitrate levels in these vegetables and crops of southern Tehran are higher than maximum acceptable ECR levels.