Dietary exposure to nitrate and nitrite of the Hong Kong population through a total diet study

Nitrate and nitrite are part of the nitrogen cycle, and are ubiquitous in the environment including soil, water, and air. Nitrate plays an important role in the nutrition and function of plants. Dietary exposure assessment of the Hong Kong adult and younger populations to nitrate and nitrite was included in the second Hong Kong Total Diet Study (TDS). A total of 187 commonly consumed food items were collected and prepared 'as consumed'. A total of 374 composite food samples were analysed for nitrate and nitrite by ion chromatography-ultraviolet detection (IC-UV). Dietary exposure to nitrate and nitrite was estimated based on the analytical results and the food consumption data of the local residents. Nitrite was found at low levels in about one-third of food items and the dietary exposure estimates of the average and high consumers (90th percentile) of Hong Kong adult and younger populations to nitrite were below its acceptable daily intake (ADI) which indicated a low health risk. On the other hand, nitrate was found widely across all TDS food groups, with the highest mean concentration detected in the food group 'Vegetables and their products'. The dietary exposure estimates of the average and high consumers of Hong Kong adult and younger populations to nitrate fell within the range of ADI values derived by the European Food Safety Authority and lower than the threshold for elevated methaemoglobin levels in the blood of infants, children and adults identified by the Food Standards Australia and New Zealand, indicating that the general population was unlikely to experience any immediate health risk.