Quantitative parameters of nitrates in urine and N-nitrosodimethylamine in blood as markers of the oral exposure to nitrates introduced with drinking water

Introduction. The nitrate entry into the body with drinking water might lead to endogenous nitrotyrosine and N–nitrosamine formation. The study aims to prove quantitative measurement of N-nitrosodimethylamine in blood and nitrates in urine as markers of the exposure to nitrates entering the body with drinking water. 

Material and methods. Analysis of blood samples for N-nitrosodimethylamine was carried out using Agilent gas chromatograph with quadrupole mass spectrometric detector. When preparing blood samples, an automatic system for solid extraction Sepaths was used. Studies of urine samples for nitrates were carried out using the system of capillary electrophoresis “Kapel”. The target audience includes two groups. Children consuming drinking water with nitrate level exceeding hygienic norm by 1.2 times and N-nitrosodimethylamine level exceeding by 1.6 times. The second group included children consuming drinking water of satisfactory quality. The establishment of cause-effect relationships is carried out using the package of applied programs Statistica 6.0.

Results. The nitrate level in drinking water of target area was 51.7 mg/dm³, what is by 4.7 times higher than in comparison area of 10.9 mg/dm³. The N-nitrosodimethylamine level was at the level of 0.016 mg/dm³, which is by 2.5 higher than in the comparison area of 0.0065 mg/dm³.

Discussion. The long-term exposure to nitrate and N-nitrosodimethylamine in the drinking water was found out to form in the children’s blood of first group the N-nitrosodimethylamine accounted of 0.0045±0.0014 mg/dm³ i.e. by 1.5 times higher in comparison with the second group (0.003±0.0009 mg/dm³). In the urine of children from the first group, the nitrates were by 1.5 times more than in the urine of children in the second group. Experimental studies proved that the concentration of nitrates in the urine and N-nitrosodimethylamine in the blood might be considered as markers of the oral exposure and correspond to the permitted level for nitrates in the urine of 43.7 mg/dm³ and N-nitrosodimethylamine in the blood of 0.003 mg/dm³ when nitrate concentration in drinking water is from of 45-51.7 mg/dm³ and N-nitrosodimethylamine from of 0.01-0.016 mg/dm³.