Assessment of the combined nitrate and nitrite exposure from food and drinking water: application of uncertainty around the nitrate to nitrite conversion factor

Figures & data

Table 1. Overview of nitrate and nitrite concentrations in the different exposure scenarios.

	Scenario 1	Scenario 2	Scenario 3	Scenario 4
Nitrite concentration drinking water	Mean NL (0.005 mg/l)	High regional (0.03 mg/l)	Mean NL (0.005 mg/l)	Mean NL (0.005 mg/l)
Nitrate concentration drinking water	Mean NL (4.7 mg/l)	Mean NL (4.7 mg/l)	High regional (35 mg/l)	Future high regional (50 mg/l)

Table 2. Overview of nitrate and nitrite concentrations in drinking water measured in on average 185 Dutch regions between 2012–2017.

	Minimum, mean and maximum concentrations per year for the Netherlands						Drinking water production station with highest mean annual concentrations
	Nitrate			Nitrite			Nitrate	Nitrite
	Min^a	Mean	Max	Min^a	Mean	Max	Mean	Mean
2012	0.10	5.1	40	0.0035	0.0054	0.10	39	0.03
2013	0.10	4.8	40	0.0035	0.0055	0.21	37	0.03
2014	0.10	4.6	48	0.0035	0.0053	0.11	37	0.02
2015	0.10	4.6	39	0.0035	0.0056	0.34	35	0.04
2016	0.10	4.6	39	0.0035	0.0055	0.09	35	0.02
2017	0.10	4.5	37	0.0035	0.0053	0.13	34	0.02
Av	0.10	4.7	48	0.0035	0.0054	0.34	36	0.03

^aFor non-detects, a middle bound approach was used where the samples were assumed to be equal to half of the value of the level of detection (LOD) or the level of quantification (LOQ; nitrate, 0,2–1 mg/l; nitrite, 0.007–0.016 mg/l).

Av: Average

Figure 1. Mean and high (upper 5^th percentile) exposure to nitrite resulting from the combined exposure to nitrate and nitrite from all dietary sources (including confidence interval) as a function of age. Lower panel describes the mean total dietary exposure and upper limits across all ages (1–79 years). Scenario 1 assumes the intake of nitrate and nitrite at mean concentration in food and at the national mean concentrations in drinking water. Scenario 2 assumes the intake of nitrate and nitrite at mean concentrations in food and high regional nitrite level and the national mean concentration for nitrate in drinking water. Scenario 3 assumes the intake of nitrate and nitrite at mean concentrations in food and high regional nitrate concentration and the national mean concentration for nitrite in drinking water. Scenario 4 assumes the intake of nitrate and nitrite at mean concentrations in food and possible future high regional nitrate concentration and the current national mean level for nitrite in drinking water.

Figure 2. The relative contribution of food groups to the total exposure of nitrite resulting from the combined dietary exposure to nitrate and nitrite from all dietary sources (food additive use, natural occurrence and as contaminant in food) for the Dutch population aged 1 − 79 years assuming four different scenarios for nitrate and nitrite concentrations in drinking water.

Table 3. Relative contribution of food categories to the exposure of nitrite resulting from the combined exposure (mean and P95) of nitrate and nitrite due to food additive use and contaminants in vegetables for the Dutch population aged 1 − 79 years.

	Total population	Upper 5^th exposure percentile
Contribution to combined exposure due to food additive use (%)
Meat products	56	62
Cheese	43	37
Herring and Sprat	1	1
Contribution to combined exposure due to presence in vegetables (%)
Legume vegetables	2	2
Brassica	15	16
Bulbs	3	1
Fruiting vegetables	39	36
Leafy vegetables	29	39
Legumes	0.2	0.1
Root vegetables	4	3
Stem vegetables	8	3
Fungi	0.4	0.2

Table 4. Overview of uncertainties in the current exposure assessment that could not be quantified and their assessed subsequent qualitative impact on exposure.

Sources of uncertainty	Direction
Food consumption data: under/over reporting, portion sizes	±
Mean drinking water concentration for breweries and soft drink producers	±
Drinking water concentration means for mineral water	+
Limited concentration data for some foods	±
Misclassification meat products	+
Nitrite to nitrate conversion as a result of high temperature cooking	±
Aggregation of some food categories (e.g. fruit) because of limited data of individual foods	±
Limited processing factors for nitrate and none for nitrite	±
Seasonal variation nitrate/nitrite in products/consumption	±
Fruit vs fruit juices	±
Left censored data substitution using the middle bound scenario	±

+ Potential over-estimation of risk or exposure – potential under-estimation risk or exposure