Water, average intake values

In mammals, arsenic intake derives from food and drinking water, inspired air and absorption through the skin. The chemical form of arsenic and its solubility affect the absorption of the element in mammals and its transfer into the bloodstream. According to Leonard (1991), the normal arsenic content in human blood is about 4 ng/ml. However, an average arsenic value of 7.9 ng/ml and a range of 0.4-70.5 ng/ml were reported by Minoia et al. (1990), who analyzed blood samples of 470 healthy Italians. 

Only a small proportion of the salt added to water for cooking foods is eaten. A value of 24% was obtained by the lithium method for the average intake per head of the purchased cooking salt used in cooking in the UK. The only other data using traditional methods come from Hungary where 41% of the salt purchased by households was actually ingested. 

This value is only slightly higher than the estimated lead intake of 54 pg/day found in a Canadian 24-hour duplicate diet study conducted during 1981. The average lead content of the 10 food groups used in the Canadian study ranged from 0.088 pg/g for drinking water to 0.654 pg/g for cheese (Dabeka et al. 1987). 

Data for humans show that adverse effects occur at concentrations in air >1.0 mg PCP/m3 and in tissues at more than 8 mg/kg fresh weight (Table 23.7). No adverse effects were noted at daily intakes of 2.1 mg per 70-kg adult or 30 pg/kg BW, up to 1.01 mg/L in drinking water, <0.5 mg/m3 in air, <0.5 mg/L in blood plasma, and <1.0 mg/L in blood (Table 23.7). It is noteworthy that the recommended PCP air concentration of 0.5 mg/m3 results in a daily intake of 2.5 to 3.8 mg (based on 15 to 23 m3 of air inhaled daily, 8-h exposure), equivalent to 42 to 63 pg/kg BW for a 60-kg female. These levels are higher than the currently recommended no-adverse-effect level of 30 pg/kg BW daily (Table 23.7), and overlap or exceed the 58 to 74 pg/kg BW daily range — a level recommended by Williams (1982). Air concentrations >1.0 mg PCP/m3 can produce respiratory irritation in unacclimatized individuals, but concentrations as high as 2.4 mg/m3 can be tolerated by conditioned individuals (USEPA 1980). The biological tolerance value of <1000 pg PCP/L in blood, recommended by Ziemsen etal. (1987), is based on occupational air exposure studies exposure to maximum average air concentrations of 0.18 mg PCP/m3 for up to 34 years produced blood PCP residues of 23 to 775 pg/L, with no measurable adverse effects. The authors concluded... 

ECETOC (2001) has collected exposure data in the Exposure Factors Sourcebook for European Populations. In this Sourcebook, average values for drinking water intake of 1.1 L/day for adults and 0.5 L/day for children (1-11 years) are reported. These values are based on a British survey (Hopkins and Ellis 1980 - cited in ECETOC 2001). Selected data from this study are presented in Table 7.11. 

Serum nickel levels in hospital workers averaged 0.6 0.3 pg/L in Sudbury, Ontario, versus 0.2 0.2 pg/L in Hartford, Connecticut (Hopfer et al. 1989). Measurements of nickel content of tap water in these communities were reported as 109 46 and 0.4 0.2 pg/L, respectively (Hopfer et al. 1989). Concentrations of nickel in the blood and urine of workers at a rolling mill in Poland were 18.5 4.0 and 25.7 5.1 pg/L, respectively (Baranowska-Dutkiewicz et al. 1992). Nickel concentrations in the urine of preschool children in Poland were 10.6 4.1 and 9.4 4.7 pg/L for children from an industrial region and a health resort, respectively (Baranowska-Dutkiewicz et al. 1992). After reviewing studies of nickel concentrations in humans, Templeton et al. (1994) indicated that the most reliable reference values were 0.2 pg/L for nickel in serum of healthy adults and 1-3 pg/L for nickel in urine. These values are dependent on food and fluid intake and environmental factors. Fewer studies of nickel in whole blood were identified, and a reference value was not suggested. 

Table I shows average values for the levels of these contaminants obtained from various national surveys undertaken by the Department of National Health and Welfare. Some water supplies showed significantly higher concentrations of these substances than those in Table I, and in these cases the contribution via water to the total daily intake would be proportionally greater.

The MPC values for water and for a 168-hour week can be applied to foods if appropriate care is taken—for example, the MPC values assume an average daily intake of 2200 grams of water for a standard man. If 2200 grams of radioactive food are consumed every day for 50 years, the referenced MPC values for water are applicable. This situation is obviously not the case, and correction factors that account for the intake of various foods are needed. Intake estimates are obtainable from data such as shown in Table VI (15). The correction factor is roughly the ratio of 2200 grams to the grams of daily intake of the irradiated or radioactive food. 

Notes-. Concentrations of tl4 and tTs in sera were determined by radioimmunoassay (RIA) using commercial RIA kits for rat sera or human sera. The effect of a high bromide intake in the dams was more pronounced in their pups, as is evident from markedly decreased concentrations not only of tl4, but also of tTa in the sera of the young whose mothers drank water with the highest bromide concentration. Average values determined in duplicate in three repeated assays in samples from two independent experiments are shown. The values are means SD, n = 3-6. Modified with permission from Pavelka et at. (2002). 

According to the Drinking Water Directive, lead monitoring at the tap should be based on representative sampling at the consumer s tap. The lead value determined by a monitoring protocol should be very close to the true average weekly intake. This approach ensures the safety of individual consumers. The sampling method should be representative and accurate. 

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