PHOSPHORIC ACID AND PHOSPHATE SALTS Explanation These compounds have been evaluated for acceptable daily intake by the Joint FAO/WHO Expert Committee on Food Additives in 1961, 1963, 1964, 1965, 1969 and 1970 (see Annex I, Refs. 6, 7, 9, 13, 20 and 23). A toxicological monograph was published in 1974 (see Annex I, Ref. 33). Since the previous evaluation, additional data have become available and are summarized and discussed in the following monograph. The previously published monograph has been revised, and deals with the following compounds: phosphoric acid calcium phosphate (mono-, di-, and tri-basic) sodium phosphate (mono-, di-, and tri-basic) disodium diphosphate tetrasodium diphosphate pentapotassium triphosphate pentasodium triphosphate sodium polyphosphate (Graham's salt) sodium hexametaphosphate sodium potassium polyphosphate (Tammann's salt) Kurrol's salt (KPO3)n sodium tripolyphosphate disodium phosphate magnesium phosphate (mono-, di-, and tri-basic) potassium phosphate (mono-, di-, and tri-basic) bone phosphate ammonium phosphate, dibasic ammonium polyphosphate calcium polyphosphate calcium pyrophosphate potassium polyphosphate potassium pyrophosphate The toxicity of these phosphate compounds is in part due to separate problems arising from the various cations and to the phosphate anions in general. Most of the available toxicity data has been developed with sodium salts. However, it is unlikely that effects of the potassium and ammonium moieties of the salts, at the levels used in foods, would be of concern and the effect of these salts would not be significantly different from sodium salts. In the case of calcium and magnesium salts, these salts provide a source of calcium, magnesium and phosphate ions. Problems relating to calcium, magnesium and phosphate imbalances in the diet are of concern and are considered in this monograph. They are primarily due to excess phosphorus in the diet, and deficiencies in calcium and magnesium. Thus the present monograph is applicable to all the inorganic phosphates listed. A separate monograph has been prepared for aluminium phosphates. BIOLOGICAL DATA BIOCHEMICAL ASPECTS Several reviews of phosphate metabolism and toxicity are available (Ellinger, 1972; FASEB, 1975; FASEB, 1981; Roe, 1979). Phosphorus is an essential constituent of the human organism, not only in the bones and teeth, but also in many enzyme systems. Phosphorus compounds play an important role in carbohydrate, fat and protein metabolism. (a) Phosphoric acid, phosphates and orthophosphates Free orthophosphate is the major form in which phosphorus is absorbed from the diet. The amount and rate at which other phosphates are available for absorption depends on their enzymic hydrolysis to orthophosphates. The level of inorganic phosphate in the blood is stabilized by exchange with the mineral deposit in the skeleton through the action of parathyroid hormone. This hormone inhibits tubular reabsorption of phosphates by the kidney and brings about demineralization of bone tissue through the action of osteoclasts. The amount of parathyroid hormone that enters the circulation is probably regulated by the calcium level of the blood. Intestinal absorption depends on requirements and is therefore limited. Excretion takes place mainly in the faeces as calcium phosphate so that the continuous use of excessive amounts of sodium phosphate and phosphoric acid may cause a loss of calcium. As a result of physiological regulating mechanisms, man and animals can tolerate large variations in phosphate intake without the balance being upset. Some investigators have considered that the formation in the intestinal tract of insoluble salts of phosphate with calcium, iron and other metal ions might result in decreased absorption of such minerals. From studies dealing with this aspect (Lang, 1959; van Esch et al., 1957; Lauersen, 1953; van Genderen, 1961) it is concluded that moderate dose levels of phosphates do not impair absorption as shown by results from carcass analyses or haemoglobin determinations. Doses of 2-4 g of phosphate act as weak saline cathartics. Phosphate supplementation of the diet of rodents has been shown to lead to reduction in the incidence of dental caries and different phosphates have different powers in reducing the cariogenic potential of the carbohydrates in a diet (van Reen & Ostrom, 1962; Konig et al., 1961; McClure, 1960). Phosphate supplements seem to exert their cariostatic effect on the tooth surface either directly during eating or by excretion in the saliva (Anon., 1968a,b). Little specific toxicological information on potassium monophosphates is available. There is no reason to consider that the potassium salts, in the amounts that could be used as food additives, behave differently from the sodium salts and are therefore dealt with together. (b) Disodium phosphate and tetrasodium diphosphate In the animal body, diphosphate is formed from adenosyl triphosphate (ATP) in many enzymatic reactions. It is either utilized by entering phosphorolytic reactions, or it is hydrolysed by an inorganic diposphatase to monophosphate (Long, 1961). Ingested diphosphate is readily converted to monophosphate (Fourman, 1959; Mattenheimer, 1958); no diphosphate was found in faeces or urine of rats treated with diets containing up to 5% tetrasodium diphosphate. In these experiments diphosphate was almost completely absorbed by the gut and excreted as monophosphate in the urine. The pyrophosphates are formed by the loss of 1 molecule of water from 2 molecules of an orthophosphate. The pyrophosphates (e.g. Ca2P2O7) are readily absorbed intact but then are completely hydrolysed to orthophosphate (Schreier & Noller, 1955). Achlorhydria may have an effect on the metabolism and toxicity of the condensed phosphates. It has been estimated that the half-life for hydrolysis of pyrophosphate at pH 2 and 39°C (normal gastric conditions) is 400 hours (Mahoney & Hendricks, 1978). (c) Triphosphates and polyphosphates Several studies indicate that polyphosphates can be hydrolysed in vivo by enzymes with the formation of monophosphates. The localization of different polyphosphates in the nuclei of animal cells has been demonstrated (Grossmann & Lang, 1962). Injected hexametaphosphate is more slowly degraded than tripolyphosphate (Gosselin et al., 1952), and the higly polymerized Tammann's salt (KNa polyphosphate) is even more slowly eliminated from the blood after i.v. injection than is Graham's salt (Gotte, 1953). When administered parenterally a small part of these products may escape in the urine as oligophosphates (Gosselin et al., 1952; Gotte, 1953). The higher polyphosphates are probably not absorbed as such in the intestinal tract. After hydrolysis into smaller units, absorption takes place. The larger the molecule, the less the speed of hydrolysis and absorption, as shown by studies using P32-labelled polyphosphate (Ebel, 1958). After giving hexametaphosphate to rats and rabbits by stomach tube, no more than trace amounts of labile phosphate were found in the urine (Gosselin et al., 1952). The oral administration of radiolabelled Tammann's salt did not give rise to radioactivity in the blood (Gotte, 1953). With Graham's salt and Kurrol's salt,* 10-30% was absorbed as monophosphate and small amounts of oligophosphates were found in the urine (Lang et al., 1955; Lang, 1958). In experiments in rats with labelled tripolyphosphates and Graham's salts these polymers were not absorbed as such, but were taken up after hydrolysis into monophosphate and diphosphate. In a period of 18 hours only 40% of the dose of Graham's salt was hydrolysed and absorbed. The bacterial flora of the intestinal tract may contribute to the hydrolysis of the polyphosphates (Schreier & Noller, 1955). In other experiments, radiolabelled Kurrol's salt was given orally to rats. About half the radioactivity was recovered from the faeces, mainly as polymeric phosphate, and only a small percentage of the dose was found in the urine, in this case in the form of monophosphate. Ring as well as linear polyphosphates including sodium trimeta, sodium tetrameta, sodium tripoly and sodium hexametaphosphate (Graham's salt) were shown to be hydrolysed in in vitro rat and porcine small intestine, while incubation in simulated intestinal fluid gave only slight hydrolysis. Trimeta, tetrameta, tripoly and hexameta were reduced by 12-36%, 5%, 76-80% and 10%, respectively in in vitro rat intestine in 1 hour, by 9-11%, 4-5%, 30% and 10-19%, respectively in in vitro porcine intestine in 1 hour and by 0-4%, 0-1%, 17-19% and 2-3%, respectively in 12 hours in simulated intestinal fluid. The results indicate that simulated digestive juice contains little polyphosphatase activity. This enzyme is present in the intestinal lumen (Ivey & Shaver, 1975). It is noted that, for practical reasons, in the studies cited high dosages were given to the animals. The efficiency of hydrolysis and absorption may be greater at low-dose levels, such as were used in the short-term and long-term feeding experiments. In some of these (van Esch et al., 1957) the "monophosphate action", as demonstrated by the production of nephrocalcinosis, was not much smaller than when the same dose level was administered by the addition of monophosphate to the food. In another study, this applied only to tripolyphosphate, while Graham's salt had definitely less effect on the kidney (Hahn et al., 1958). * Kurrol's salt is a polymer of high molecular weight obtained by fusion of monopotassium monophosphates. The formula is (KPO3)n.H2O, where n = 400 to 5000. The possibility of the intermediate formation of small amounts of trimetaphosphate in the hydrolysis of polyphosphates has been considered (Mattenheimer, 1958). At present, the only known method of production of sodium polyphosphate is by the fusion process. In this process metaphosphates are also formed in amounts up to 8% and their presence is technically unavoidable. It is of interest to note that these metaphosphates (sodium trimetaphosphate and sodium tetrametaphosphate) have been tested in short-term experiments in rats and dogs in conjunction with polyphosphates (Hodge, 1956). The metaphosphates are also hydrolysed to monophosphates. No specific action of these metaphosphates different from that of the other phosphates has been observed, and it is concluded that the presence of these impuritites does not present a hazard. It is also noted that the preparation of sodium polyphosphates used in the toxicological studies mentioned always contained metaphosphates in amounts up to 8%. It has been considered by many authors that the ingestion of polyphosphate in the food may result in a loss of minerals (Ca, Fe, Cu, Mg) which are bound to the polyphosphate and are lost in the faeces with unhydrolysed polyphosphate. For this reason, in most of the toxicological studies cited, particular attention has been paid to the mineral composition of the carcass and to the possible development of anaemia. The experimental results available indicate that such an action, if it occurs at all, is not significant. Anaemia is not a characteristic feature of treatment with high-dose levels of polyphosphate and hexametaphosphate had no effect on iron utilization by rats (Chapman & Campbell, 1957). The use of polyphosphates for the prevention of scale formation in lead pipe water systems may lead to excessive lead levels in drinking-water (Buydens, 1957). (d) Calcium and magnesium phosphates Calcium phosphates are insoluble in water and constitute the following series: calcium phosphate (monobasic) which is used as acidulant and mineral supplement; calcium phosphate (dibasic) is used as dietary supplement in doses of 1 g orally; calcium phosphate (tribasic) is used as gastric antacid in doses of 1 g orally; and bone phosphate. Metabolically they behave as sources of calcium and phosphate ions. Magnesium phosphates are mostly insoluble in water and form the following series: magnesium phosphate (monobasic); magnesium phosphate (dibasic) which is used as laxative; magnesium phosphate (tribasic) is used as antacid in doses of 1 g orally. Metabolically they behave as sources of magnesium and phosphate ions. The phosphate moiety of these compounds need not be considered separately from other monophosphates from the toxicological point of view. TOXICOLOGICAL STUDIES Special studies on mutagenicity Monocalcium phosphate, monopotassium phosphate and monosodium phosphate were not mutagenic in an in vitro assay using Saccharomyces cerevisiae strain D4 and Salmonella typhimurium strains TA-1535, TA-1537 and TA-1538 with and without the addition of mammalian metabolic activation preparation (Litton Bionetics, Inc., 1975a,b,c). Sodium acid pyrophosphate was not mutagenic in a number of tests including: (1) host-mediated assay in mice using either Salmonella typhimurium TA-1530 or mitotic recombination frequency in Saccharomyces cerevisiae D3; (2) in an in vitro assay using S. typhimurium strains TA-1535, TA-1536 or TA-1537 and TA-1538, with and without the addition of mammalian metabolic activation preparations; (3) dominant lethal test in rats; and (4) translocation test in rats (Newell et al., 1974). Tetrasodium pyrophosphate was not mutagenic in an in vitro assay using S. cerevisiae strain D4, and S. typhimurium strains TA-1535, TA-1537 and TA-1538, with and without the addition of mammalian metabolic activation preparations (Food and Drug Research Lab., Inc., 1975d). Sodium tripolyphosphate was not mutagenic in a number of tests including: (1) host-mediated assay in mice using S. typhimurium strains TA-1530 and G-46 or mitotic recombination frequency in S. cerevisiae D3; (2) in an in vitro assay using S. typhimurium strains TA-1530 and G-46, and S. cerevisiae D3, with and without activation; (3) a cytogenetic study in vivo of rat bone marrow cells and in vitro of human lung cells in tissue culture; and (4) a dominant lethal study in rats (Litton Bionetics, Inc., 1974). Sodium hexametaphosphate was not mutagenic in an in vitro assay using S. typhimurium strains TA-1535, TA-1536 and TA-11537, with and without the addition of mammalian metabolic activation preparation (Litton Bionetics, 1975c). Special studies on teratogenicity and reproduction Verrett et al. (1980) reported that monocalcium phosphate, tricalcium phosphate, and monopotassium phosphate were not teratogenic in the developing chicken embryo. Monosodium phosphate, tetrasodium pyrophosphate, and sodium hexametaphosphate were found to produce teratogenic effects when injected during the period of rapid organogenesis in chicken embryos. Several different types of anomalies were observed, mostly structural. Teratology studies using rats, mice, rabbits or hamsters were performed on the following phosphates: monocalcium phosphate, sodium acid pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and tetrasodium phosphate. The dose levels reported were the maximum levels tested. For studies in mice, groups each of approximately 24 pregnant albino CD-1 mice were dosed by oral intubation with the test substance from day 6 through day 16 of gestation. Body weights were recorded on days 0, 6, 11, 15 and 17 of gestation. On day 17, all dams were subjected to caesarean section and the number of implantation sites, resorption sites and live and dead foetuses recorded. The body weight of the live pups was also taken. The urinogenital tract level of each dam was examined for abdominal abnormality. All foetuses were examined for the presence of external congenital abnormalities. One-third of the foetuses were examined for visceral abnormalities and the remaining two-thirds for skeletal abnormalities. For studies in rats, groups each of approximately 24 pregnant female albino rats (Wistar-derived stock) were dosed daily by oral intubation from day 6 of gestation through day 15. Body weights were recorded on days 0, 6, 11, 15 and 20. On day 20, all dams were subjected to caesarean section, and observations for dams and foetuses similar to those described in the mouse study were carried out. For studies in hamsters, groups each of approximately 22-25 pregnant female golden hamsters were dosed daily by oral intubation with the test compound from day 6 of gestation through day 10. Body weights were recorded on days 0, 6, 8, 10 and 14. On day 14, all animals were subjected to caesarean section, and observations for dams and foetuses, similar to those observed in the mouse study, were carried out. For studies in rabbits, groups each of approximately 20-22 pregnant Dutch-belted rabbits, were dosed by oral intubation with the test compound from day 6 through day 18. Body weights were recorded on days 0, 6, 12, 18 and 29 of gestation. On day 29, all does were subjected to caesarean section, and observations, similar to those described in the mouse study, were carried out. (a) Phosphoric acid, phosphates and orthophosphate Monosodium phosphate showed no maternal toxicity or teratogenic effects at dose levels up to 370 mg/kg bw in mice and 410 mg/kg bw in rats (Food and Drug Research Lab., Inc., 1975a). Monopotassium phosphate showed no maternal toxicity or teratogenic effects at dose levels up to 320 mg/kg bw in mice and 282 mg/kg bw in rats (Food and Drug Research Lab., Inc., 1975b). Sodium acid pyrophosphate showed no maternal toxicity or teratogenic effects at dose levels up to 335 mg/kg bw in mice, 169 mg/kg bw in rats, 166 mg/kg bw in hamsters and 128 mg/kg bw in rabbits (Food and Drug Research Lab., Inc., 1973a). (b) Tetrasodium diphosphate Tetrasodium diphosphate showed no maternal toxicity or teratogenic effects at dose levels up to 130 mg/kg bw in mice and 138 mg/kg bw in rats (Food and Drug Research Lab., Inc., 1975c). (c) Triphosphates and polyphosphates Sodium hexametaphosphate showed no maternal toxicity or teratogenic effects at dose levels up to 370 mg/kg bw in mice and 240 mg/kg bw in rats (Food and Drug Research Lab., Inc., 1975d). Sodium tripolyphosphates showed no maternal toxicity or teratogenic effects at dose levels up to 238 mg/kg bw in mice, 170 mg/kg bw in rats, 250 mg/kg bw in rabbits and 141 mg/kg bw in hamsters (Food and Drug Research Lab., Inc., 1973b). (d) Calcium phosphate Monocalcium phosphate showed no maternal toxicity or teratogenic effects at dose levels up to 465 mg/kg bw in mice and 410 mg/kg bw in rats (Food and Drug Research Lab., Inc., 1973c). Acute toxicity (a) Phosphoric acid, phosphates and orthophosphates Approx. Compound Animal Route LD50 Reference (mg/kg bw) NaH2PO4 Guinea-pig Oral 2 000 MLD Eichler, 1950 Monosodium phosphate Mouse Oral 3 700 Food and Drug Research Rat Oral 4 100 Lab., Inc., 1975a Monopotassium Mouse Oral 3 200 Food and Drug Research phosphate Rat Oral 2 820 Lab., Inc., 1975b Sodium acid Mouse Oral 3 350 Food and Drug Research pyrophosphate Rat Oral 1 690 Lab., Inc., 1975a Hamster Oral 1 660 (b) Tetrasodium diphosphate Approx. Compound Animal Route LD50 Reference (mg/kg bw) Na4P2O7 Mouse Oral 1 300 Food and Drug Research Rat Oral 1 380 Lab., Inc., 1975c (c) Triphosphates and polyphosphates Approx. Compound Animal Route LD50 Reference (mg/kg bw) Sodium triphosphate Mouse Oral 2 380 Food and Drug Research Rat Oral 1 700 Lab., Inc., 1973b Rabbit Oral 2 500 1/3 Kurrol's salt Rat Oral 4 000 van Esch et al., 1957 and 2/3 tetra- and disodium diphosphate (water soluble, Rat i.v. 18 van Esch et al., 1957 neutral) Sodium Mouse Oral 3 700 Food and Drug Research hexametaphosphate Rat Oral 2 400 Lab., Inc., 1975d (d) Calcium phosphate Approx. Compound Animal Route LD50 Reference (mg/kg bw) Monocalcium Mouse Oral 4 600 Food and Drug Research phosphate Rat Oral 2 170 Lab., Inc., 1973c Short-term studies (a) Phosphoric acid, phosphates and orthophosphates Rat There are many reports of short-term studies to determine the effects of the addition of monophosphates to the diet of rats (Maynard et al., 1957; Selye & Bois, 1956; MacKay & Oliver, 1935; Behrens & Seelkopf, 1932; McFarlane, 1941; van Esch et al., 1957; Sanderson, 1959). Pathological effects in the parathyroids, kidneys and bones have been observed in mature male rats fed a diet containing an excessively high level (8%) of sodium orthophosphate for 7 months or until the animal succumbed (Saxton & Ellis, 1941). Histological and histochemical changes in the kidneys have been found in rats fed for 24-72 hours on a diet containing an excess of inorganic phosphate (10% disodium acid phosphate)(Craig, 1957). Three groups of 12 rats each were fed diets containing added dibasic potassium phosphate so that the calcium and phosphorus concentrations in the experimental diets were as follows: Diet Calcium % Phosphorus % Control 0.56 0.42 "normal orthophosphate" 0.47 0.43 "high orthophosphate" 0.50 1.30 The experiment was conducted in 3 stages, with experimental observations made when animals had consumed the test diets for 50, 60 and 150 days. No adverse physiological effects were observed clinically at autopsy or on histological examination. All the data obtained from this study indicated that there was probably adequate absorption and utilization of calcium, phosphorus and iron with both high and normal levels of monophosphate (Dymsza et al., 1959). Reports of short-term studies do not provide for a differentiation between the action of the mono-, di- and trisodium or potassium salts; several authors have used "neutral mixtures", e.g. of mono- and disodium monophosphates. There is no reason to expect a specific action on the part of 1 of these 3 monophosphates, the relevant factor being the phosphate content and the acidity of the food mixture as a whole. On high-dose levels, hypertrophy of the parathyroid glands has been observed. A more important and more sensitive criterion for the deleterious action of phosphate overdosage is the appearance of calcification in soft tissues, especially in the kidney, stomach and aorta. Kidney calcification may be observed in a few weeks or months, depending on the dose level. The pathology of calcification and necrosis of the tubular epithelium in the kidneys (nephrocalcinosis) has been studied in detail (MacKay & Oliver, 1935; McFarlane, 1941; Sanderson, 1959; Fourman, 1959). It is difficult to indicate a border-line between those levels that do not produce nephrocalcinosis and those that produce early signs of such changes, because: (1) even on diets to which no phosphate has been added, rats, in apparently healthy condition, may have a few isolated areas of renal calcification; (2) the composition of the diet (amount of calcium, acid-base balance, vitamin D) has an important influence on the appearance of renal calcification. There are numerous reports of experimental phosphate-containing diets that do not produce kidney damage by excessive calcification, e.g. the Sherman diet (0.47-0.51%) (Lang, 1959; Hahn & Seifen, 1959; van Esch et al., 1957), the diet used by MacKay & Oliver (1935) (0.62% P) and the commerical "Purina A" diet (0.90% P) (Lang, 1959). Early calcification has been observed in rats on a Sherman diet to which 1% of a 2:3 mixture of NaH2PO4 and Na2HPO4 was added, bringing the P content to 0.71% (van Esch et al., 1957). Similar effects were observed with the addition of a phosphate mixture resulting in a P content of 0.89% (Hahn & Seifen, 1959), and with levels of phosphate in the diet corresponding to a P content varying from 1.25% to 2.85% (Lang, 1959; MacKay & Oliver, 1935; Eichler, 1950; McFarlane, 1941; van Esch et al., 1957; Haldi et al., 1939). In another study (Dymaza et al., 1959), however, a diet to which K2HPO4 had been added and containing 1.3% P and 0.5% Ca did not produce nephrocalcinosis in a group of mice within a period of 150 days, although the weight of the kidneys was increased. Also food and protein efficiency were diminished as compared with animals on the control diet. These effects may have resulted from the large amount of salts added to the diet in these experiments. Diets containing various levels of calcium, phosphorus and magnesium were reported to produce uroliths in female Wistar rats. The incidence and severity of calcium phosphate uroliths were reduced by increasing the magnesium concentration in the diet from 0.2% to 0.8% and by increasing the calcium-to-phosphorus ratio to greater than 1 (Chow et al., 1980). Diets containing 0.8% calcium and 0.9% phosphorus caused calcium phosphate deposits in the soft tissues of guinea-pigs (Hogan et al., 1950). When the phosphorus content of the diet was reduced to 0.5%, the number of animals with deposits was reduced from 90% to 10%. Further work (House & Hogan, 1955) demonstrated that with sufficient magnesium and potassium in the diet the calcium phosphate deposition could be significantly reduced. It has been pointed out that these 2 studies may explain the wide variations in the levels of phosphate reported to cause toxicological effects (Ellinger, 1972). Thus, "optimum ratios of calcium to phosphorus, or of magnesium and potassium to phosphorus most likely explain why the diets of some studies required higher levels of phosphates in order to demonstrate adverse physiological effects". Sheep Wether sheep (5 per treatment) were fed on a basal diet to which urea had been added as a nitrogen source. Comparisons were made between this diet and diets which in addition contained either 11 g of dicalcium phosphate or 6.25 g of ammonium polyphosphate per day. Addition of either form of supplementary P caused increased appetite, daily weight gain, and apparent N retention. These utilization experiments were conducted over 1-week periods and it was concluded that ammonium polyphosphate was a satisfactory form of dietary P for ruminants (Fishwick, 1974). (b) Disodium phosphate and tetrasodium diphosphate Rat In a series of successive experiments (Hahn & Seifen, 1959; Hahn at al., 1958), Na4P2O7 was added in concentrations of 1.8%, 3% and 5% to a modified Sherman diet and fed to groups of 34-36 young rats for 6 months. The studies also included control groups and groups receiving the same levels of sodium monophosphate. With 3% and 5% diphosphate diets growth was significantly decreased and at both these concentrations nephrocalcinosis appeared as the main toxic effect. The degree of damage to the kidneys was about the same as that observed in the corresponding monophosphate groups. With the 1.8% diphosphate and monophosphate diets, normal growth occurred, but a slight yet statistically significant increase in kidney weight was noted. Microscopic examination revealed kidney calcification in some of the animals, both in the diphosphate and monophosphate groups. This was more extensive than the calcification occasionally found in the control animals. In an additional experiment, 1.1% of diphosphate and of monophosphate were used (Hahn, 1961). There was a slight growth retardation in the first part of the experiment. After 39 weeks a slight degree of kidney calcification was noted and this was the same for both phosphates (Hahn, 1961). In a recent series of experiments (Datta et al., 1962), Sherman diets containing 1%, 2.5% and 5% Na4P2O7 were fed for 16 weeks to groups of 20 male and female rats weighing between 90 and 115 g; a similar group received a diet containing 5% monophosphate. In the sodium phosphate groups, growth was normal up to the 2.5% level; kidney weight was increased at the 2.5% level (females) and above; kidney function was (concentration test) decreased at the 2.5% level (males) and above. Kidney damage (calcification, degeneration and necrosis) was observed in a greater percentage of rats in the 1% group than in the controls. At the higher concentration of sodium diphosphate more severe kidney damage occurred and, in addition, some of the animals had hypertrophy and haemorrhages of the stomach. The latter abnormality was not found in the 5% monophosphate group. (c) Triphosphates and polyphosphates Rat Groups of 5 male rats were fed for a period of 1 month on diets containing 0.2%, 2% and 10% sodium hexametaphosphate or 0.2%, 2% and 10% sodium tripolyphosphate. Control groups were given the standard diet, or diets with the addition of 10% sodium chloride or 5% disodium phosphate (Hodge, 1956). With 10% of either of the polyphosphate preparations and also with 10% sodium chloride in the diet, growth retardation occurred, but none of the rats died. Increased kidney weights and tubular necrosis were, however, observed. With 2% of polyphosphate in the diet, growth was normal, but in the kidneys inflammatory changes were found which were different from the tubular necrosis observed in the 10% groups. With 0.2% of polyphosphate in the diet, normal kidneys were seen. In another series of experiments (Hahn & Seifen, 1959; Hahn et al., 1958; Hahn et al., 1956), 3% and 5% of sodium tripolyphosphate (pH 9.5 in 1% solution) and 1.8%, 3% and 5% of Graham's salt (pH 5) were added to a modified Sherman diet, which was fed during 24 weeks to groups of 36 male and 36 female rats. Growth retardation was exhibited by the rats in the 5% polyphosphate groups. With 3% of either preparation, a temporary growth inhibition was observed, and with 1.8% of Graham's salt (male animals) growth was normal. Nephrocalcinosis was observed in the 3% and 5% groups. It was noted that the degree of damage with Graham's salt was less than that in control groups treated with the same concentrations of orthophosphate; with tripolyphosphate, however, kidney damage was practically identical with that exhibited by the animals in the orthophosphate group. In the animals on a diet containing 1.8% Graham's salt, calcification in the kidneys was slight or absent and the kidney weights were normal (Hahn & Seifen, 1959). In a further group of experiments (van Esch et al., 1957; van Genderen, 1958), Kurrol's salt was used in a commercial preparation consisting of 1/3 Kurrol's salt and 2/3 of a mixture of disodium and tetrasodium diphosphate (Na2H2P2O7 and Na4P2O7). Kurrol's salt is practically insoluble in water, but the mixture with diphosphate can be dissolved and a 1% solution had a pH of 7.6. Groups of 10 male and 10 female rats were fed for a period of 12 weeks on a Sherman diet to which 0.5%, 1%, 2.5% and 5% of the preparation had been added. Normal growth was observed in the groups treated with the 0.5%, 1% and 2.5% concentrations of the polyphosphate mixture, but in those receiving the 5% concentrations, growth retardation was exhibited. Kidney weights were normal in the 0.5% group, slightly increased (males significantly) in the 1% group and further increased in the 2.5% and 5% groups. The histopathological examination revealed that in the kidneys of the animals of the 5% group, definite nephrocalcinosis had occurred, with extensive damage to the tubular tissue. Calcification was also observed in other tissues. In the 2.5% group, a less extensive nephrocalcification with lymphocyte infiltrations were found. In the 0.5% group, kidney structure was normal. The results obtained with this polyphosphate preparation were practically identical, qualitatively and quantitatively, with the results of a similar experiment made with a neutral mixture of NaH2PO4 and Na2HPO4 carried out at a later date in the same laboratory (Hahn et al., 1958; Gotte, 1953). In other experiments, groups of 12 male rats were treated with diets to which 0.9% and 3.5% sodium hexametaphosphate had been added (corresponding to 0.46% and 1.20% P). Other groups received the control diet alone (0.4% P and 0.5% Ca), or with addition of potassium monophosphate. To the experimental diets different amounts of salts were added to replace cornstarch in order to equalize the levels of major minerals; this resulted in a rather high salt concentration. The duration of treatment was up to 150 days. With 3.5% added hexametaphosphate growth and food and protein efficiency were poorest. The kidneys of the animals fed the high level of hexametaphosphate were significantly heavier than those of the control rats. This was perhaps a manifestation of the high salt load on the kidneys. No histopathological abnormalities were observed in kidney sections from animals taken from any of the groups (Dymsza et al., 1959). Dog Sodium tripolyphosphate (Na5P3O10) and sodium hexameta- phosphate were fed to 1 dog each in a dose of 0.1 g/kg/day for 1 month; 2 other dogs received daily doses which increased from 1.0 g/kg at the beginning to 4.0 g/kg at the end of a 5-month period. The dog treated with the starting dose of 10 g/kg/day of hexametaphosphate began to lose weight when the daily dose reached 2.5 g/kg, while the one receiving gradually increasing doses of tripolyphosphate lost weight only when its diet contained 4.0 g/kg/day. In other respects (urinalysis, haematology, organ weights) the animals were normal, with the exception of an enlarged heart, due to hypertrophy of the left ventricle, in the dog receiving gradually increasing doses of sodium tripolyphosphate. In addition, tubular damage to the kidneys was observed in both dogs on the higher dose regime. In the tissues of the dogs fed 0.1 g/kg/day no changes were found that could be attributed to the treatment (Hodge, 1956). Other species Ammonium polyphosphate, when substituted for 50% or 100% of the phosphorus supplied by defluorinated rock phosphate in corn-soybean meal diets for growing-finishing pigs, was found not to influence daily feed intake, rate of gain, or feed:gain ratio over a 13-week period when compared with controls (Clawson & Armstrong, 1981). Similar results were observed by Kornegay (1972) in pigs, by Jensen & Edwards (1980) in chickens, and by Fishwick (1974) in wether sheep. (d) Calcium and magnesium phosphates Groups of weanling Sprague-Dawley rats were fed 0.06% or 0.10% magnesium during phosphate depletion for 14 days. It was found that: (1) the hypomagnesaemia of phosphate depletion depends on the intake of magnesium; (2) the hypercalcaemia and hypercalciuria of phosphate depletion are not caused by changes in magnesium homeostasis; (3) low dietary magnesium during phosphate depletion may cause a defect in soft tissue utilization of P in the growing rat. Animals at the higher magnesium level had a significantly lower soft tissue content of P compared to those at the lower level (Brautbar et al., 1979). Groups of 3-week-old male Sprague-Dawley rats were maintained on diets containing either 0.03% or 0.44% phosphorus for periods up to 8 weeks. Mg balance became negative during the first day of phosphate depletion. Mg absorption increased by the third week but Mg balance remained negative throughout the 8 weeks. Mg levels in muscle, kidney, and liver tissues were not affected but Mg was lost from bone. Bone calcium content was not affected (Kreusser et al., 1978). Long-term studies (a) Phosphoric acid, phosphates and orthophosphates Rat Ellinger (1972) cited work done by Bonting in 1952 where over 700 rats were fed diets containing up to 0.75% phosphoric acid. Effects on reproduction were looked for through 3 generations; no adverse effects were observed. The study was reported to include examination of the blood, tissues, mineral balance, nitrogen retention, and the acidic conditions of the digestive tract. Three successive generations of rats were fed diets containing 0.4% and 0.75% of phosphoric acid for 90 weeks. No harmful effects on growth or reproduction could be observed. No significant differences were noted in the blood picture in comparison with control rats and there was no other pathological finding which could be attributed to the diets. There was no acidosis or any changes in the calcium metabolism. The dental attrition was somewhat more marked than that in the control rats (Lang, 1959). No other long-term studies on monophosphates have been found in the literature. (b) Disodium phosphate and tetrasodium diphosphate Rat No specific studies with diphosphates have been made, but in 1 series of experiments a mixed preparation was used which consisted of 2/3 Na2H2P2O7 and 1/3 Kurrol's salt. Concentrations of 0.5%, 1% and 5% were added to a Sherman diet and given to groups of 10 male and 10 female rats. From these animals a second and third generation were produced, during which the treatment with phosphates was continued. Growth and fertility and average life span were normal and the life span was not significantly reduced up to the 2.5% level. Nephrocalcinosis occurred at the 1% level and above. At 0.5% no abnormalities were observed that were not also present in control animals. At none of the concentrations did tumours appear with higher frequency than in the controls (van Esch et al., 1957). (c) Triphosphates and polyphosphates Rat To a Sherman diet containing 0.47% P, a mixture of 1/3 Kurrol's salt and 2/3 diphosphate was added in concentrations of 0.5%, 1%, 2.5% and 5% and fed to groups of 30 male and 10 female rats from weaning to end of their life span (van Esch et al., 1957). Two successive generations of offspring were produced on these diets. Significant growth inhibition was observed in the 5% group of both first and second generations. In other groups, growth was normal. Fertility was normal in the 0.5%, 1% and 2.5% groups, but much decreased in the 5% group. Haematology of the 0.5%, 1% and 2.5% groups showed a decreased number of erythrocytes in the 2.5% group, second generation only. In the 0.5% group, no kidney damage attributable to the polyphosphate treatment was observed, but in the groups having higher intakes renal calcification occurred in a degree increasing with the dose level. In another series of feeding studies (Hodge, 1960a), diets containing 0.05%, 0.5% and 5% sodium tripolyphosphates were given for 2 years to groups of 50 male and 50 female weanling rats. Only when 5% polyphosphate was added to the diet was growth reduced; the reduction was significant in males but slight and delayed in females. A smaller number of rats survived in the 5% groups than in the other groups. A low grade of anaemia was sometimes observed in the 5% groups only. Increased kidney weights were noted in the 5% group; pathological changes which could be ascribed to treatment were not observed in the 0.5% and 0.05% groups. In the control groups and the 0.5% tripolyphosphate group, reproduction studies were carried out over 3 generations involving the production of 2 litters in each generation. Reproduction was normal and no changes in the offspring were observed. A long-term study (Hodge, 1960b) of the same design was made with sodium hexametaphosphate also at concentrations of 0.05%, 0.5% and 5% in the diet. Growth retardation occurred only in the 5% groups. Mortality was high in all groups but had no relation to the amount of hexametaphosphate in the diet. Periodic blood examination gave haematological values. Kidney weights were increased in the 5% group and calcification was present. Rats given the 0.5% diet did not have significant changes in the kidneys. Reproduction studies for 3 generations in the 0.5% group revealed normal performance in every respect. Special studies on calcium and phosphorus metabolism with reference to calcium and phosphorus and magnesium ratios in the diet Diets containing various levels of calcium, phosphorus and magnesium were reported to produce uroliths in female Wistar rats. The incidence and severity of calcium phosphate uroliths were reduced by increasing the magnesium concentration in the diet from 0.2% to 0.8% and by increasing the calcium-to-phosphorus ratio to greater than 1 (Chow et al., 1980). Diets containing 0.8% calcium and 0.9% phosphorus caused calcium phosphate deposits in the soft tissues of guinea-pigs (Hogan et al., 1950). When the phosphorus content of the diet was reduced to 0.5%, the number of animals with deposits was reduced from 90% to 10%. Further work (House & Hogan, 1955) demonstrated that with sufficient magnesium and potassium in the diet, the calcium phosphate deposition could be significantly reduced. Groups of weanling Sprague-Dawley rats were fed 0.06% or 0.10% magnesium during phosphate depletion for 14 days. It was found that: (1) the hypomagnesaemia of phosphate depletion depends on the intake of magnesium; (2) the hypercalcaemia and hypercalciuria of phosphate depletion are not caused by changes in magnesium homeostasis; (3) low dietary magnesium during phosphate depletion may cause a defect in soft tissue utilization of P in the growing rats. Animals at the highest magnesium level had a significantly lower soft tissue content of P compared to those at the lower level (Brautbar et al., 1979). Groups of 3-week-old male Sprague-Dawley rats were maintained on diets containing either 0.03% or 0.44% phosphorus for periods up to 8 weeks. Mg balance became negative during the first day of phosphate depletion. Mg absorption increased by the third week but Mg balance remained negative throughout the 8 weeks. Mg levels in muscle, kidney, and liver tissues were not affected (Kreusser et al., 1978). Although many studies on Ca/P metabolism have been carried out with rats, the pig was selected by DeLuca et al. (1976) as a more appropriate animal model. Groups of adult pigs were fed diets containing 0.65% Ca and 1, 2 or 3 times this amount of P for 6 months. Ca:P ratios of 1:2 or 1:3 resulted in decreased weight gain, slight hypocalcaemia, significant hyperphosphataemia, increased PTH, and an increased rate of bone turnover. At the 1:3 ratio, total kidney calcium and phosphorus were increased; rib ash and femoral bone formation were decreased. Wild-caught cinnamon ringtail monkeys were maintained for up to 88 months on high phosphorus-containing diets (Ca:P ratios of up to 1:4). Only minor bone changes were observable with a microscope; these changes were not detectable by conventional means (Anderson et al., 1977). This finding prompted the authors to suggest that primates may tolerate a greater phosphate load than lower species without incurring bone loss. They also suggested that findings in lower species must be re-evaluated with respect to the hypothesis that high dietary phosphate levels are a significant etiological factor in human senile osteoporosis. High phosphate intakes result in reduced urinary excretion of calcium (FASEB, 1981); however, Spencer et al. (1975) demonstrated that 47Ca absorption in humans was not influenced by high phosphate intakes. Bell et al. (1977) fed 8 adult volunteers a diet containing 0.7 g Ca and 2.1 g P per day for 4 weeks after a 1-month control period. Intestinal distress, soft stools, or mild diarrhoea resulted. These symptoms subsided in 6 but occurred intermittently throughout the 4 weeks in the other 2 subjects. The high phosphorus diet increased serum and urinary P and decreased serum and urinary Ca. Parfitt & Kleerekoper (1980) reported that the dietary intake of phosphate by human adults is rarely great enough to raise plasma phosphate levels appreciably. FASEB (1981) reviewed the literature but could not reach any conclusion on the optimal Ca:P ratio or whether this ratio is of any dietary significance in man: "High phosphorus intakes in some animal species result in bone loss even with normally adequate intakes of calcium. The Ca:P ratio at which bone loss occurs varies with the absolute intakes of the individual elements; a ratio of 1:2 prevents bone loss when calcium intakes are low, whereas bone loss occurs even at a ratio of 2:1 when intakes are high. Various expert groups have recommended a Ca:P ratio of 1:1 to 2:1 for man, but there is insufficient evidence at present to support the establishment of a firm ratio." It was noted that the Ca:P ratio in bone is about 2:1 and that self-selection of phosphorus in animals approaches this ratio (1.8:1) during rapid growth and favours phosphorus in adulthood (1:1.2). Thus, children would be more susceptible to excessive dietary phosphate intakes. OBSERVATIONS IN MAN Studies on 15 students, who drank 2000-4000 mg of phosphoric acid in fruit juices every day for 10 days, and on 2 males who received 3900 mg of phosphoric acid every day for 14 days, revealed no observable change in urine composition indicative of a disturbed metabolism (Lauersen, 1953). The long-continued daily intake of 5000-7000 mg of NaH2PO4 (corresponding to 1500 mg of P) did not produce adverse effects (Lang, 1959). Similarly a daily intake of 6000 mg of NaH2PO4.2H2O was tolerated for 15 days without difficulty (Lauersen, 1953). Thomas (1972) administered orthophosphates to some 37 renal calculi patients for periods of up to 8 years with usually favourable results. Two groups of anionic inhibitors of mineralization were found in the urine and the more potent of these was found to be present at a lower concentration in the urine of affected patients when compared with normal controls. Alkaline phosphate (K2HPO4) was found to cause increased concentrations of these mineralization inhibitors in urine (acidic and neutral phosphates increased only the less potent inhibitor). In a study in which the daily basal diet of 4 men contained 450 mg calcium and 1400 mg phosphorus, supplementation with 750 mg phosphorus as phosphoric acid for 1 week resulted in a slight decrease in urinary excretion of calcium. When the treatment was continued for 12 weeks, there was a further decrease in urinary calcium excretion (Malm, 1953). In another study, groups of 6 women previously on a basal diet containing 300 mg calcium and 800 mg phosphorus, received a diet containing 1500 mg calcium and 1400 mg phosphorus, or 1500 mg calcium and 800 mg phosphorus. The high level of phosphorus in the first diet resulted in decreased calcium utilization when compared to the second group (Leichsenring et al., 1951). Comments Metabolically, the phosphate salts provide a source of the various cations and the phosphate ion. Of greatest concern is the toxicity arising from calcium, magnesium and phosphate imbalance in the diet. Phosphate salts were not mutagenic in a number of test systems. Teratogenic effects have not been observed in mammalian test systems. Numerous animal studies have shown that excessive dietary phosphorus causes an increase of plasma phosphorus and a decrease in serum calcium. The resulting hypocalcaemia stimulates secretion of PTH which in turn increases the rate of bone resorption and decreases calcium excretion. These homeostatic adjustments to high dietary phosphorus may result in bone loss and calcification of soft tissues in animals. The dose levels of phosphate producing nephrocalcinosis were not consistent among the various rat feeding studies. However, the rat is exquisitely susceptible to calcification and hydronephrosis upon exposure to acids forming calcium chelates or complexes. The lowest dose levels that produce nephrocalcinosis overlap the higher dose levels failing to do so. However, this may be related to other dietary imbalances, such as the level of magnesium in the diet. There is still uncertainty on the optimal Ca:P ratio and whether this ratio is of any dietary significance in man. The lowest level of phosphate that produced nephrocalcinosis in the rat (1% P in the diet) is used as the basis for the evaluation and, by extrapolation based on the daily food intake of 2800 calories, this gives a dose level of 6600 mg P per day as the best estimate of the lowest level that might conceivably cause nephrocalcinosis in man. The usual calculation for provision of a margin of safety is probably not suitable for food additives that are also nutrients. Ingested phosphates from natural sources should be considered together with that from food additives sources. Since phosphorus (as phosphates) is an essential nutrient and an unavoidable constituent of food, it is not feasible or appropriate to give a range of values from zero to a maximum. EVALUATION Estimate of maximum tolerable daily intake for man 70 mg/kg bw.* * This figure represents the maximum tolerable daily intake (MTDI) of phosphates. It is not an ADI. The MTDI is expressed as phosphorus and it applies to the sum of phosphates naturally present in food and the additives listed below. It also applies to diets that are nutritionally adequate in respect of calcium. However, if the calcium intake were high, the intake of phosphate could be proportionately higher, and the reverse relationship would also apply. Phosphates and polyphosphates evaluated for food additive use (see WHO Technical Report Series, No. 683, 1982): phosphoric acid; ammonium phosphate, dibasic; bone phosphate; calcium phosphate (mono-, di- and tri-basic); magnesium phosphate (mono-, di- and tri-basic); sodium phosphate (mono-, di- and tri-basic); sodium aluminium phosphate, basic; sodium aluminium phosphate, acidic; disodium dihydrogen diphosphate; tetrasodium diphosphate; pentasodium triphosphate; pentapotassium triphosphate; sodium hexametaphosphate; ammonium polyphosphate; calcium polyphosphate; potassium polyphosphate; sodium polyphosphate; sodium potassium polyphosphate; sodium tripolyphosphate; calcium pyrophosphate; tetrapotassium pyrophosphate. REFERENCES Anderson, M. P. et al. (1977) Long-term effect of low dietary calcium:phosphate ratio on the skeletons of Cebus albifrons monkeys, J. Nutr., 107, 834-839 Anon. (1968a) Phosphates and caries, Lancet, 1, 1187 Anon. (1968b) Phosphates to prevent dental caries, Brit. Med. J., 1, 267 Behrens, B. & Seelkopf, K. (1932) Arch. exp. Path., 169, 238 Bell, R. R. et al. (1977) Physiological responses of human adults to foods containing phosphate additives, J. Nutr., 197, 42-50 Buydens, M. R. (1957) Du danger de saturnisme par l'addition de phosphates condensés aux eaux de distribution incrustantes, Bull. Acad. Roy. Med. Bulg., 22, 293-318 Brautbar, N. et al. (1979) Influence of dietary magnesium in experimental phosphate depletion: bone and soft tissue mineral changes, Am. J. Physiol., 237, E152-7 Chapman, D. G. & Campbell, J. A. (1957) Effects of calcium and phosphorus salts on the utilization of iron by anaemic rats, Brit. J. Nutr., 11, 127-133 Chow, F. H. et al. (1980) Effect of dietary calcium, magnesium, and phosphorus on phosphate urolithiasis in rats, Invest. Urol., 17, 273-276 Clawson, A. J. & Armstrong, W. D. (1981) Ammonium polyphosphate as a source of phosphorus and nonprotein nitrogen for monogastrics, J. Anim. Sci., 52, 1-7 Craig, J. M. (1957) Histological and histochemical changes in the kidneys of rats fed a diet with an excess of inorganic phosphate, Amer. J. Path., 33, 621 Datta, P. K. et al. (1962) Biological effects of food additives. II. Sodium pyrophosphate, J. Sci. Food Agric., 13, 556-566 DeLuca, H. F. et al. (1976) Studies on high phosphate diets, Food Research Institute Annual Reports, University of Wisconsin, Madison, pp. 394-398 Dymsza, H. A., Reussner, G., Jr & Thiessen, R., Jr (1959) Effect of normal and high intakes of orthophosphate and metaphosphate in rats, J. Nutr., 69, 419-428 Ebel, J. P. (1958) Action physiologique et toxicologique des phosphates condenses, Ann. Nutr. Alim., 12(1), 57-97 Eichler, O. (1950) Handbuch der experimentellen Pharmakologie. Bd 10, Berlin, 363 Ellinger, R. H. (1972) Phosphates as food ingredients, The Chemical Rubber Co. Press, Cleveland, Ohio, pp. 19-25 van Each, G. J., Vinke, H. H., Wit, S. J. & van Genderen H. (1957) Die physiologische Winkung von Polyphosphaten, Arzneimittel-Forsch., 7, 172-175 FASEB (1975) Evaluation of the health aspects of phosphates as food ingredients (SCOGS-32), Federation of American Societies for Experimental Biology, Bethesda, Maryland, 37 pp. FASEB (1981) Effects of dietary factors on skeletal integrity in adults: calcium, phosphorus, vitamin D, and protein, Federation of American Societies for Experimental Biology, Bethesda, Maryland, 75 pp. Fishwick, G. (1974) Proceedings: Utilization of dietary ammonium polyphosphate by growing wether lambs, Proc. Nutr. Soc., 33, 46A-47A Food and Drug Research Laboratories, Inc. (1973a) Teratologic evaluation of FDA 71-61 (sodium acid pyrophosphate) in mice, rats, hamsters and rabbits. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Food and Drug Research Laboratories, Inc. (1973b) Teratologic evaluation of FDA 71-46 (sodium tripolyphosphate; anhydrous) in rabbits, mice, rats and hamsters. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Food and Drug Research Laboratories, Inc. (1973c) Teratologic evaluation of FDA 71-81 (monocalcium phosphate; monohydrate) in mice and rats. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Food and Drug Research Laboratories, Inc. (1975a) Teratologic evaluation of FDA 73-2 (monocalcium phosphate; anhydrous) in mice and rats. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Food and Drug Research Laboratories, Inc. (1975b) Teratologic evaluation of FDA 73-65 (monopotassium phosphate) in mice and rats. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Food and Drug Research Laboratories, Inc. (1975c) Teratologic evaluation of FDA 73-1 (tetrasodium pyrophosphate, anhydrous) in mice and rats. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Food and Drug Research Laboratories, Inc. (1975d) Teratologic evaluation of FDA 73-3 (sodium hexametaphosphate) in rats and mice. Unpublished report from Food and Drug Research Laboratories, Inc., Waverly, NY, USA. Submitted to the World Health Organization by the US Food and Drug Administration Fourman, J. (1959) Two distinct forms of experimental nephrocalcinosis in the rat, Brit. J. Exp. Path., 40, 464-473 van Genderen, H. (1958) In: Kondensierte Phosphate in Lebensmitteln, Berlin, Springer van Genderen, H. (1961) Phosphatbedarf und grenzen der phosphatzufukn, Z. Ernahrungsw., Suppl. 1, pp. 32-44 Gosselin, R. E. et al. (1952) The hydrolysis and excretion of polymeric phosphate, J. Pharmacol. Exp. Ther., 106, 180-192 Gotte, H. (1953) Untersuchungen mit hochpolymeren radioaktiv mankierten phosphaten im saugetierorganismus, Z. Naturforsch., 86, 173-176 Grossman, D. & Lang, K. (1962) Anorganische Poly-und metaphosphatasen sowic polyphosphate im tierischen zellkern, Biochem. Z., 336, 351-370 Hahn, F. (1961) Toxikologie der polyphosphate, Z. Ernahrungsw., Suppl. 1, p. 55 Hahn, F., Jacobi, H. & Rummel, W. (1956) Chronische futterungsuensuchi mit polyphosphaten, Naturwissenschaften, 43, 539-540 Hahn, F., Jacobi, H. & Seifen, E. (1958) Do ortho- and polyphosphates show variable compatibilities on chronic feeding? Naturwissenschaften, 8, 286-289 Hahn, F. & Seifen, E. (1959) Arzneimittel-Forsch, Naturwissenschaften, 9, 501-503 Haldi, J. et al. (1939) The effects produced by an increase in the calcium and phosphorus content of the diet on the calcium and phosphorus balance and on various bodily constituents of the rat, J. Nutr., 18, 399-409 Hodge, H. C. (1956) Short-term oral toxicity tests of condensed phosphates in rats and dogs, Unpublished report Hodge, H. C. (1960a) Chronic oral toxicity studies in rats of sodium tripolyphosphate, Unpublished report Hodge, H. C. (1960b) Chronic oral toxicity studies in rats of sodium hexametaphosphate, Unpublished report Hogan, A. G., Regan, W. O. & House, W. B. (1950) Calcium phosphate deposits in guinea pigs and the phosphorus content of the diet, J. Nutr., 41, 203-213 House, W. B. & Hogan, A. G. (1955) Injury to guinea pigs that follows a high intake of phosphates, J. Nutr., 55, 507-517 Ivey, F. J. & Shaver, K. J. (1975) Polyphosphate hydrolysis in the gastrointestinal tract. Monsanto Industrial Chemical Co., St Louis, MO 63166. Unpublished report submitted to the US Food and Drug Administration Jensen, L. S. & Edwards, H. M., Jr (1980) Availability of phosphorus from ammonium polyphosphate for growing chickens, Poult. Sci., 59, 1280-1283 Konig, K. G., Marthaler, T. M. & Muhlemann, H. R. (1961) Effects of some phosphates in a short-period rat caries experiment, Arch. Oral Biol., 3, 258-270 Kornegay, E. T. (1972) Supplementation of lysine, ammonium polyphosphate and urea in diets for growing-finishing pigs, J. Anim. Sci., 34, 55-63 Kreusser, W. J. et al. (1978) Effect of phosphate depletion on magnesium homeostatis in rats, J. Clin. Invest., 61, 573-581 Lang, K. et al. (1955) Der stoffinechsel von polyphosphaten, Biochem. Z., 327, 118-125 Lang, K. (1958) In: Kondensierte Phosphate in Lebensmitteln, Berlin, Springer Lang, K. 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(1978) Some effects of different phosphate compounds on iron and calcium absorption, J. Fd. Sci., 43, 1473-1476 Malm, O. J. (1953) On phosphates and phosphoric acid as dietary factors in the calcium balance of man, Scand. J. Clin. Lab. Invest., 5, 75-84 Mattenheimer, H. (1958) In: Kondensierte Phosphate in Lebensmitteln, Berlin, Springer Maynard, L. A. et al. (1957) Dietary mineral interrelations as a cause of soft tissue calcification in guinea pigs, J. Nutr., 64, 85-97 McClure, F. J. (1960) The cariostatic effect in white rats of phosphorus and calcium supplements added to the flour of bread formulas and to bread diets, J. Nutr., 72, 131-136 McFarlane, D. (1941) Experimental phosphate nephritis in the rat, J. Path. Bact., 52, 17-24 Newell, G. W., Jorgenson, T. A. & Simmon, V. F. (1974) Study of mutagenic effects of sodium acid pyrophosphate (compound FDA 71-61). Unpublished report from Stanford Research Institute, Menlo Park, Calif., USA. Submitted to the World Health Organization by the US Food and Drug Administration Parfitt, A. M. & Kleerekoper, M. (1980) Clinical disorders of calcium, phosphorus, and magnesium metabolism. In: Maxwell, M. H. & Kleeman, C. R., eds, Clinical disorders of fluid and electrolyte metabolism, 3rd ed., New York, McGraw Hill Book Co., pp. 269-398 Roe, F. J. E. (1979) Mineral deposition in the renal pelvis: A brief review, Unpublished report, submitted to WHO Sanderson, P. H. (1959) Functional aspects of renal calcification in rats, Clin. Sci., 18, 67-79 Saxton, J. A., Jr & Ellis, G. H. (1941) Effects of long-continued ingestion of sodium phosphate upon the parathyroids, kidneys and bones of mature rats, Amer. J. Path., 17, 590 Schreier, K. & Noller, H. G. (1955) Stoffmechselversuche mit venschiedenen markierten Polyphosphaten, Naunyn-Schmiedeberg's Arch. Exp. Path. Pharmak., 227, 199-209 Selye, H. & Bois, P. (1956) Effect of corticoids on the resistance of the kidney to an excess of phosphates, Amer. J. Physiol., 187, 41-44 Spencer, H., Kramer, L. & Norris, C. (1975) Calcium absorption and balances during high phosphorus intake in man, Proc. Fed. Am. Soc. Exptl. Biol., 34, 888 Thomas, W. C. (1972) Effectiveness and mode of action of orthophosphates in patients with calcareous renal calculi, Trans. Am. Clin. Climatol. Assoc., 83, 113-124 van Reen, R. & Ostrom, C. A. (1962) Effect of dietary phosphate supplements on dental caries in the rat, J. Dent. Res., 41, 875-882 Verrett, M. et al. (1980) Toxicity and teratogenicity of food additive chemicals in the developing chicken embryo, Toxicol. Appl. Pharmacol., 56, 265-273
See Also: Toxicological Abbreviations