Etermination of daily dietary exposure with nitrate through food and water in Shabestar and Khamneh cities

Abstract

Introduction: Nitrate is one of the important water and food contaminants.The concentration of nitrate in surface and underground water, agricultural products such as fruits, vegetables and meats. Due to natural sedimentary dissolution containing nitrates, animal waste and chemical industry activities, urban and industrial waste water as well as the increasing use of chemical fertilizers, its concentration is increased. Although nitrate is non-toxic to human in less amounts than the standard, it may be converted to nitrite in the human body and combined with the amides, amines and amino acids and produce nitrosamine compounds which can lead to stomach or intestine cancer and dangerous blood diseases. According to guidelines of World Health Organization (WHO), acceptable daily intake (ADI) of nitrate is zero to 3.7 mg per kilogram of body weight per day.As water and food are the most important sources of nitrate in human which has negative on public health therefore measuring and monitoring the concentration of nitrate in drinking water and foods to reduce the amount of daily nitrate intake is crucial. Thus, this study aimed to determine the nitrate concentration in food and drinking water in Khameneh and Shabestar cities in northwest of Iran. Materials and methods: IN this study, dietary intake of people living in Shabestar and Khameneh were obtained via Azar cohort study by skilled nutritionists. Twelve samples of drinking water were taken randomly from the drinking water network points of each city (total 24 samples) in two seasons (low rainfall and high rainfall). Nitrate concentration in drinking water was analyzed using standard methods. Sixty kinds of food samples were taken from 5 retile centers and transferred to the environmental chemical laboratory of Health faculty. Food samples were separately prepared and mixed together and were dried at 70 ° C. The dried samples were milled and then passed through a 20 mesh sieve. Then, two sub-samples were taken from each initial sample. Finally, 24 drinking water samples and 236 food samples were analyzed. The data were analysed by SPSS and descriptive t- test and samples. Results: The concentration of nitrate in drinking water was less than the maximum limit recommended (50 mg) in both cities. The results of this study showed that acceptable daily intake of nitrate was 751.58 mg in Shabestar. If the average weight of each person be considered 70 Kg, the amount of received nitrate per person per kg of body weight achieves 10.74 mg. Also, ADI of per the person was calculated to be 650.90 mg, or 9.30 mg per Kg of body weight in Khameneh. In addition, based on the results of present study, the highest daily intake was related to fruits and vegetables in both cities of Shabestar and Khameneh.II The highest and lowest concentrations of nitrate in vegetables in both cities were related to garlic and savory, respectively. Also, the highest concentration of nitrate in fruit related to apple in both cities and the lowest concentration was for mandarin in Shabestar and orange in Khameneh. Discussion and conclusion: Acceptable daily intake of nitrates was more than the maximum limit recommended by the WHO in both cities (In Shabestar 2.9-fold and 2.5-fold in Khameneh). Considering the results of most studies on the negative health effects of nitrate on public health, it is suggested that nitrate sources of drinking water and agricultural soils be identified. Also, it is recommended that the concentration of nitrates in food and drinking water continuously be monitored and planned to decrease the amount to the under standard level.