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Arsenic in Drinking Water (1999)

Chapter: Addendum to Chapter 9

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Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
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Page 302

Addendum to Chapter 9
Experimental Conditions for Nutritional Studies with Arsenic

EXPERIMENTS designed to induce deficiencies of trace elements in animals with very low requirements depend on strict control of contamination from diet, water, air, and caging (Smith and Schwarz 1967). Proteins and salts furnishing macrominerals are the major sources of dietary contaminants. Careful selection, backed by analysis, is routinely applied to the ingredients; the latter might have to be further purified by recrystallization or other means. Drinking water is of the highest attainable purity and is constantly monitored with resistance measurements. Animals are housed in plastic cages that are often isolated in laminar-flow hoods. These conditions of an "ultraclean environment" make it necessary to supply all essential micronutrients as supplements in an acceptable balance. Such complex diets have their own problems of contamination. Contamination from protein sources can be avoided by acid washing, by substituting chemically pure amino acid mixtures or by using ruminant animal species that can synthesize much of their protein needs from chemically pure urea.

Rats and Chicks

The animals are raised in plastic cages. In the earlier experiments, the cages were kept in laminar-flow hoods, but the extra protection was later found to be unnecessary when the arsenic content of the diets was consistently less than 20 ng/g. All ingredients are of the highest obtainable purity, but some sources of minerals, especially of potassium, calcium, and phosphate, require additional purification. The composition of representative diets, fed ad libitum, is given in Table A9-1.

Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
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Page 303

TABLE A9-1 Composition of Representative Diets for Rats and Chicksa

Ingredient

Rat Diet (g/kg)

Chick Diet (g/kg)

Milk powder

 

250

Casein, high protein

200

150

Ground corn, acid washed

673

230

Non-nutritive fiber

 

50

Dextrose, anhydrous

 

142.5

Corn oil

 

100

Soybean oil

70

 

CaCo3

15

14

KH2PO4

10

4

Choline bitartrate

2.5

 

A vitamin mix in cornstarch and a mineral mix in dextrose was added to the rat diet to furnish all known miconutrient requirements. The chick diet was slightly different to meet requirements of that species.

Vitamins added to diet: (mg/kg): Niacin (30); d-pantothenic acid calcium (16); pyridoxin HCI (7); thiamin HCI (6); riboflavin (6); folic acid (2); d-biotin (0.2); vitamin B12(0.02); d,l-a-tocopherol acetate (120); retinyl palmitate (16); vitamin D3 (2.5); vitamin K, (0.75).

Trace elements added to diet: (mg/kg): CaHPO4 (1,265); K2SO4 (1,632); CaCI2.2H2O (1,000); Na2CO3 (1,500); Mg(C2H3O2)2.4H2O (3,600); NaSiO3.9H2O (254); ferric citrate (220); zinc carbonate (58); manganese carbonate (22); copper acetate (11); KIO3 (0.35); Na2SeO4 (0.36 mg/kg); NH4MO7O24.4H2O (0.37); CrK(SO4)2.12 H2O (9.6); H3BO3 (2.9); NaF (2.2); NiCO3 (2.2); SnO (0.25); NH4VO3 (0.46).

aData from Nielsen et al. 1978; Nielsen 1980; Uthus et al. 1983; Uthus 1992.

Goats and Minipigs

The animals are kept in plastic-lined wooden cages with cellulose as bedding material. An estimated 100 g per day of cellulose (arsenic at less than 15 ng/g) is eaten by goats. Cellulose contributes to their energy intake and dilutes the arsenic content from less than 35 ng/g in the semisynthetic diet to less than 20 ng/g in the total. Table A9-2 gives the composition of the rations fed ad libitum to both species.

Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×

Page 304

TABLE A9-2 Composition of Representative Diets for Goats and Minipigsa

Ingredient

Goat Diet (g/kg)

Minipig Diet (g/kg)

Potato starch

483

570

Beet sugar

320

147

Casein

100

200

Urea

30

 

Sunflower oil

30

20

CaCO3

10

10

KH2PO4

13.4

22

Micronutrients added to goat diet: NaCI (3.5 g); A12(SO4)3 (2 g); MgO (2.2 g); K2SO4(3.5 g); ZnSO4.7H2O(0.5g); FeSO4.7H2O(0.45 g); MnSO4.7H2O(0.4 g); S (0.35 g); LiCO3 (106 mg); CuSO4.5H2O(40 mg); KBr (30 mg); Ni2SO4.7H2O (34 mg); Cr2(SO4)3.18H2O(6 mg); (NH4)VO3 (4.6 mg); NaF (2.2 mg); NaWO4.H2O(1.8 mg); KJ(1.0 mg); (NH4)6Mo7O24.4H2O (0.92 mg); SeO2 (0.8 mg); CoSO4.7H2O(0.8 mg); CdC12.H2O (0.36 mg); vitamin A (20 mg); vitamin D3 (4 mg); vitamin E (200 mg).

Micronutrients added to minipig diet: MgSO4.7H2O(5.0 g); NaCI (5.2 g); K2SO4(12.4 g); FeSO4.7H2O(0.5 g); MnSO4.4H2O(0.25 g); ZnSO4.7H2O(50 mg); CuSO4.5H2O(40 mg); Ni2SO4.7H2O (48 mg); NaHSO3 (1.6 mg); Ni2SO.7H2O (34 mg); Cr2(SO4)3.18H2O (6 mg); KI (0.6 mg); CoSO4.7H2O(0.5 mg); NaWO4.2H2O(1.8 mg); NaF (2.2 mg); KBr (30 mg); (NH4)Mo7O24.4H2O(0.92 mg); choline (2 g); vitamin C (80 mg); vitamin E (100 mg); Ca pantothenate (80 mg); Niacin (80 mg); vitamin E (20 mg); vitamin D (40 mg); vitamin B1 (4 mg); vitamin B2 (6 mg); vitamin B6 (4 mg); vitamin B12(0.05 mg); folic acid (2 mg); ethoxyquinolin (200 mg).

aData from Anke 1986, 1991; Anke et al. 1976.

References

Anke, M. 1986. Arsenic. Pp. 347-372 in Trace Elements in Human and Animal Nutrition, Vol. 2, 5th Ed., W. Mertz, ed. Orlando, Fla.: Academic.

Anke, M. 1991. The essentiality of ultra trace elements for reproduction and pre-and postnatal development. Pp. 119-144 in Trace Elements in Nutrition of Children—II, R.K. Chandra, ed. New York: Raven.

Anke, M., M. Grün, and M. Partschefeld. 1976. The essentiality of arsenic for animals.  Pp. 403-409 in Trace Substances in Environmental Health—X, Proceedings of the University of Missouri's Tenth Annual Conference on Trace Substances in Environmental Health, D.D. Hemphill, ed. Columbia, Mo.: University of Missouri Press.

Nielsen, F.H. 1980. Evidence of the essentiality of arsenic, nickel, and vanadium and their possible nutritional significance. Pp. 157-172 in Advances in Nutritional Research, Vol. 9, H.H. Draper, ed. New York: Plenum.

Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×

Page 305

Nielsen, F.H., D.R. Myron, and E.O. Uthus. 1978. Newer trace elements—Vanadium (V) and arsenic (As) deficiency signs and possible metabolic roles. Pp. 244-247 in Trace Element Metabolism in Man and Animals, Vol. 3, M. Kirchgessner, ed. Freising-Weihenstephan, Germany: Technische Universitat Munchen

Uthus, E.O. 1992. Evidence for arsenic essentiality. Environ. Geochem. Health 14:55-58.

Uthus, E.O., W.E. Cornatzer, and F.H. Nielsen. 1983. Consequences of arsenic deprivation in laboratory animals. Pp. 173-189 in Arsenic: Industrial, Biomedical, Environmental Perspectives, W.H. Lederer and R.J. Fensterheim, eds. New York: Van Nostrand Reinhold.

Smith, J.C., and K. Schwarz. 1967. A controlled environment system for new trace element deficiencies. J. Nutr. 93:182-188.

Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×

Page 306

Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×
Page 302
Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×
Page 303
Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×
Page 304
Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×
Page 305
Suggested Citation:"Addendum to Chapter 9." National Research Council. 1999. Arsenic in Drinking Water. Washington, DC: The National Academies Press. doi: 10.17226/6444.
×
Page 306
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The U.S. Environmental Protection Agency (EPA) has been considering a more stringent regulation of arsenic in water. A significant reduction in the maximum contaminant level (MCL) could increase compliance costs for water utilities. This book discusses the adequacy of the current EPA MCL for protecting human health in the context of stated EPA policy and provides an unbiased scientific basis for deriving the arsenic standard for drinking water and surface water.

Arsenic in Drinking Water evaluates epidemiological data on the carcinogenic and noncarcinogenic health effects of arsenic exposure of Taiwanese populations and compares those effects with the effects of arsenic exposure demonstrated in other countries—including the United States.

The book also reviews data on toxicokinetics, metabolism, and mechanism and mode of action of arsenic to ascertain how these data could assist in assessing human health risks from arsenic exposures. This volume recommends specific changes to improve the toxicity analyses and risk characterization. The implications of the changes for EPA's current MCL for arsenic are also described.

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