Toxicological evaluation of some food additives including anticaking agents, antimicrobials, antioxidants, emulsifiers and thickening agents WHO FOOD ADDITIVES SERIES NO. 5 The evaluations contained in this publication were prepared by the Joint FAO/WHO Expert Committee on Food Additives which met in Geneva, 25 June - 4 July 19731 World Health Organization Geneva 1974 1 Seventeenth Report of the Joint FAO/WHO Expert Committee on Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 539; FAO Nutrition Meetings Report Series, 1974, No. 53. SULFUR DIOXIDE AND SULFITES Explanation These compounds have been evaluated for acceptable daily intake by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1, Refs No. 6, No. 7 and No. 13) in 1961, 1964 and 1965. Since the previous evaluation, additional data have become available and are summarized and discussed in the following monograph. The previously published monographs have been expanded and are reproduced in their entirety below. BIOLOGICAL DATA BIOCHEMICAL ASPECTS Sulfite is oxidized in the body to sulfate. Bisulfite reacts with aldehydes and ketones, including aldehydic sugars. This is a reversible reaction; the equilibrium concentrations depend on temperature. The acute effects of sulfite in foods are related to the amount and concentration of free sulfur dioxide and to the speed at which the additive compounds liberate the bound sulfur dioxide. Sulfite may also react reversibly with disulfide linkages in proteins. The disulfide is split into one part containing a thiol group and another part with an S-sulfonic acid group (Swan, 1957). Four rats given oral doses of sodium metabisulfite as a 0.2% solution eliminated 55% of the sulfur as sulfate in the urine within the first four hours (Bhagat & Lockett, 1960). A rapid and quantitative elimination of sulfites as sulfate was also observed in man and dog (Rost, 1933). Sulfite is a strong inhibitor of some dehydrogenases, e.g. lactate dehydrogenase (heart) and malate dehydrogenase; 50% inhibition by about 10-5M sulfite (Pfleiderer et al., 1956). Small amounts of sulfite are regularly formed in the intermediary metabolism of the body in the catabolism of cystine by the non- enzymatic decomposition of 8-sulfinyl pyruvic acid to pyruvic acid and SO2. The stationary concentration of sulfite in the cells is too small to be measured. However, 0.10-0.12 meq/100 ml was found in bull seminal fluid (Larson & Salisbury, 1953). Sulfur dioxide is strongly bound by plasma proteins in the form of - S - Sulfonates. These are gradually cleared from the blood but by what mechanism is at present not clear (Gunnison & Benton, 1971; Gunnison & Palmes, 1973). Sulfur dioxide can form complex additive compounds with other substances present in foods, for example aldehydes, ketones and sugars. The reaction is reversible, the equilibrium being influenced by temperature and pH. It also reacts reversibly with disulfide groups in proteins. In foods SO2 is therefore present in free and bound forms, the bound form predominating (Allen & Brook, 1970). Following oral administration of 10 or 50 mg SO2/kg (as Na HSO3 mixed with Na2 35SO3), 70 to 95% of the 35S was absorbed from the intestine and voided in the urine of mice, rats and monkeys within 24 hours. The majority of the remaining 35S was eliminated in the faeces, the rate being species-dependent. Only 2% or less of 35S remained in the carcass after one week. Free sulfite was not detected in rat urine even after a single oral dose of 400 mg SO2/kg. Neither could induction of liver sulfite oxidase be demonstrated either after single, or 30 daily doses of 200 mg SO2/kg/day (Gibson & Strong, 1972). Effects on DNA The possibility that SO2 might cause point mutations was put forward by Shapiro et al. (1970) who showed that sulfite can convert the nucleic acid base cytosine (which occurs in DNA and RNA) into uracil (which is found in RNA only). Hayatsu et al. (1970) confirmed the findings and showed that bisulfite binds to certain nuclectides. However, exposure of cells in tissue culture to various concentrations of SO2 in the medium showed that strain L cells could tolerate 5 ppm (0.0005%) SO2 for periods of eight hours provided a recovery period followed each exposure. At higher concentrations (500-2000 ppm (0.05%-0.5%)) of SO2 there was inhibition of growth; at the 500 ppm (0.05%) level the growth was comparable to control cultures. The addition of salts of SO2 caused stimulation of growth at lower levels and complete inhibition at 2000 ppm (0.5%) NaHSO3 (Thompson & Pace, 1962). Effects on thiamine Treatment of foods with sulfites reduced their thiamine content (Morgan et al., 1935; Williams et al., 1935). It has been suggested that the ingestion of SO2 in a beverage may effectively reduce the level of thiamine in the rest of the diet (Hötzel, 1962). Six rats were given a diet providing 40 mg thiamine daily. At weekly intervals an additional 160 mg thiamine was given and the urinary excretion of thiamine measured on the following two days. When the response, in terms of urinary output of thiamine, appeared to be constant, 160 mg thiamine was given together with 120 mg potassium metabisulfite. It was found that the addition of SO2 greatly reduced the urinary output of thiamine, especially on the day when both were given together (Causeret et al., 1965). In wine containing 400 ppm (0.04%) SO2, 50% of the thiamine was destroyed in one week. However, no loss of thiamine was observed in 48 hours. The small amounts of SO2 resulting from the recommended levels of usage in wine are therefore not likely to inactivate the thiamine in the diet during the relatively short period of digestion (Jaulmes, 1965). In a series of studies Hötzel and co-workers (1969) gave 400 mg/sulfite/person/day to a group of subjects who were fed on a thiamine deficient diet. The diet produced signs of vitamin deficiency in 50 days and the sulfite, dissolved in wine or grape juice was given between days 15-40. No effect on thiamine status was detected by measurement of blood thiamine levels, urinary thiamine excretion and by determination of thiamine-dependent enzyme activity. Clinical, neurophysiological and biochemical investigations produced no indication of adverse effects from sulfite. The work of Sharratt (1970) also supports the view that SO2 in beverages does not reduce the level of thiamine in the rest of the diet. Effects on calcium balance Interest in this aspect arises from the possibility that sulfate formed metabolically from sulfite may serve to increase loss of calcium in urine and faeces of man. Levels of 0.5 to 0.7% calcium carbonate in the diet caused increased faecal excretion and diminished urinary levels of Ca. Levels up to 0.2% had no effect on the excretion of Ca (Causeret & Hugot, 1960). In a further experiment, diets containing 0.5 and 1% calcium carbonate and 0.5 and 1% potassium metabisulfite (2885 and 5770 ppm (0.2885 and 0.5770%) SO2) were administered to young rats and the faecal and urinary excretion of Ca measured for 10 days. At the lower level of dietary Ca (0.5%) both levels of the metabisulfite caused a significant increase in the urinary excretion of Ca but had no effect on the faecal excretion. At the higher dietary Ca level (1%) the reverse was found. There was no difference between the effects of the two levels of metabisulfite. This was interpreted as being due to saturation of the body's capacity to convert sulfite to sulfate (Hugot et al., 1965). The levels of hepatic vitamin A were determined on both control and test rats receiving 1.2 g/l potassium metabisulfite in the drinking-water (700 mg/l as SO2). There was an insignificant decrease in the vitamin A level in the liver of test animals after 10 days. In another experiment, two groups of 40 rats each were kept for four months on a diet containing only traces of vitamin A. The drinking- water of one group contained 1.2 g/l potassium metabisulfite. Hepatic vitamin A levels were determined at the end of each month. A gradual reduction in the liver vitamin A levels was observed in both groups. The addition of SO2 to the drinking-water did not accentuate this reduction (Causeret et al., 1965). TOXICOLOGICAL STUDIES Special studies on reproduction Rat Six groups of 20 male and 20 female rats were mated (group matings) after 21 weeks on diets containing 0, 0.125, 0.25, 0.5, 1.0 or 2.0% Na2S2O5, 10 males and 10 females being remated at 34 weeks. Ten male and 10 female F1a rats were mated at 12 and 30 weeks old to give F2a and F2b offspring. Ten males and 15 females of the F2a generation were mated at 14 and 22 weeks to give F3a and F3b offspring. F1a parents and F2a parents were kept on diet for 104 and 30 weeks respectively. Incidence of pregnancy, birthweight, and postnatal survival were all normal. In the Fo first mating, body weight gain of offspring was decreased at 2%, and in F1 matings at 1 and 2%. The F2 first mating showed decreased weight gain of offspring in all test groups at weaning but little effect was seen in offspring of the second F2 mating. Litter size was significantly decreased at 0.5% and above in the first F2 mating only. Body weight of Fo adults was unaffected, whilst F1 females at 2% and F2 males and females at 2% both showed slight decreased body weight gain (Til et al., 1972b). Special studies on mutagenicity Using E. coli as an indicator, the frequency of mutation of the C gene of phage lambda was shown to be increased by a factor of 10 when compared with controls, by treatment with 3M NaHSO3 at pH 5.6 at 37°C for 1-1/2 hours (Hayatsu & Miura, 1970). Further studies indicated sodium bisulfite specifically induces mutations in only those mutants which have cytosine-guanine at the mutant site (Mukai et al., 1970). Acute toxicity Solution LD50 sodium Species Route conc. bisulfite Reference Rat i.p. 25% 498 Rabbit i.p. 25% 300 Dog i.p. 25% 244 Wilkins et al., 1968 Mouse i.p. 1.25% 675 Rat i.p. 5.00% 650 Rat i.p. 1.25% 740 In rabbits, the oral LD50 of sulfite, measured as SO2, was found to be between 600 and 700 mg/kg bw (Rost & Franz, 1913). LD50 (mg/kg bw) Animal Route Reference Sodium bisulfite Sodium sulfite Mouse i.v. 130 175 ) ) Rat i.v. 115 - ) ) Hoppe & Goble, ) 1951 Hamster i.v. 95 - ) ) - ) Rabbit i.v. 65 - Short-term studies Rat In thiamine-deficient rats, daily oral administration of fruit syrup containing 350 ppm (0.035%) of sulfur dioxide in a dose of 0.5 ml/150 g rat for eight weeks failed to influence growth (Locket, 1957). Groups of weanling raze numbering five per group were fed 0.6% sodium metabisulfite (not less than 3400 ppm (0.0340%) as SO2) for six weeks. The diets were either freshly sulfited or stored at room temperature before use. A reduction in growth occurred in rats receiving the fresh diet which was attributed to lack of thiamine. Rats fed the diet which had been stored for 75 days developed signs of thiamine deficiency and additional toxic effects including diarrhoea and stunting of growth which could not be reversed by the administration of thiamine (Bhagat & Locket, 1964). Three groups of 20 to 30 rats containing equal numbers of males and females received daily doses of sulfite dissolved in water or added to wine, and a control group received the same volume of water. The levels of sulfite in the two groups receiving wine were equivalent to 105 mg and 450 mg SO2 per litre respectively and the aqueous solution contained potassium metabisulfite equivalent to 450 mg SO2 per litre. The effect of this treatment was studied in four successive generations, the duration being four months in females and six months in males. Groups of animals from the second generation were treated for one year. No effect was observed on weight gain, efficiency of utilization of protein, biological value of the same protein or reproduction. There was also no effect on the macroscopic or microscopic appearance of organs or organ weights. The only effect observed was a slight diminution in the rate of tissue respiration by liver slices in vitro (Jaulmes, 1964). Rats were fed sulfite, as Na2S2O5 in stock or purified diet at levels from 0.125 to 6% for up to eight weeks. In the preliminary study increasing levels of sulfite (0.125 to 2.0% in diet) resulted in decreased urinary thiamine excretion. Supplementation of diet with 50 mg thiamine/kg diet prevented the thiamine deficiency as evidenced by reduction of offspring mortality, and weight loss to weaning at the 2% level of sulfite feeding. Toxic manifestations were noted at 1% and above (but not at 0.5%) comprising occult blood in the faeces (1% and over), reduced growth rate (2% purified diet, and 6% purified and stock diet), blood in the stomach and anaemia (2% and above), spleen enlargement, increased haematopoiesis and diarrhoea (4% and above), and increased white blood cells (6%). Histopathological changes in the stomach occurred at 1% and over (Til, 1970). Groups of 10 male and 10 female rats were fed on diets containing 0 to 8% sodium metabisulfite for 10-56 days. Vitamin deficiency was prevented by adding thiamine to the diet. Diets containing 6% and above depressed food intake and growth and glandular hyperplasia, haemorrhage, ulceration, necrosis and inflammation of the stomach occurred. Anaemia occurred in all animals receiving 2% and above and a leucocytosis in those receiving 6%. At 4% and above splenic haematopoiesis was found. The effects were reversible when sulfite was removed from the diet (Til et al., 1970). About 120 rats containing equal numbers of each sex were divided into two groups, one receiving potassium metabisulfite equivalent to 0.6% SO2 in the drinking-water, the other group serving as control. No effect was observed after treatment for three months on reproduction, mortality or blood count. The second and third generations were treated in the same way for three months, the only effect observed being a significant reduction in the size of the litters of treated mothers. No effect of sulfite on digestive enzymes in vitro was observed at a level equivalent to 360 mg SO2 per gram of protein. No effect on the incidence of dental caries in the rat was produced by 0.5% potassium metabisulfite in the dietary regime. Work is in progress on the effects of sulfite on the metabolism of thiamine, vitamin A and calcium (Causeret, 1964). Groups of 20 Wistar rats (10 of each sex) were fed diets containing 0.125, 0.25, 0.5, 1.0 and 2.0% of sodium hydrogen sulfite (770-12 300 ppm (0.077-0.43%) as SO2) for 17 weeks. A group of 20 rats on untreated diet served as controls. Immediately after preparation, all diets were stored at -18°C in closed glazed earthenware containers, for not longer than two weeks. Measurements of loss of SO2 on keeping each diet in air for 24 hours at room temperature revealed losses amounting to 12.5. 10.0, 14.3, 8.2 and 2.5% of the sulfite present in the diets as listed above, i.e. with increasing SO2 content a decreasing proportion was lost. After 124 days there was no effect on the growth of male rats. In females, the 2.0% group grew as well as the controls; both these female groups were used for fertility studies, had given birth to litters during the course of the test, and had raised their young. The other female groups on lower levels of dietary sulfite were not mated and showed significant depression of growth (as compared with controls that had been mated). Haematological measurements at 7-8 weeks (all groups) and at 13 weeks (2% and controls) revealed no effect of sulfite. In the diet containing 2% sulfite, thiamine could not be measured after 14 days at -18°C; at 1.0% and 0.25% sulfite there was some loss of thiamine but this cannot be assessed precisely since the initial values are not quoted. Measurements of urinary thiamine excretion revealed substantial reduction at one week and particularly at 13 weeks in all groups receiving more than 0.125% sulfite in the diet. Urine concentration tests were not carried out on a sufficient number of animals to permit any firm conclusion to be drawn. Males and females of the control and 2% groups were mated with rats drawn from the main colony. The only untoward findings, with females of the 2% group, were lower weight of the offspring at seven and 21 days of life and 44.3% mortality as compared with mortalities of 0, 2.8 and 3.8% in the other groups of young rats. It is claimed that no changes were found in relative organ weight (liver, heart, spleen, kidneys, adrenalin, testes) nor in microscopical appearance (above organs, stomach, intestine, uterus, teeth and eyes). Since no measure of dispersion is quoted, it is impossible to say whether the apparent severe reduction in relative liver weight at the 0.125, 0.25, 0.5 and 1.0% levels is significant (Centraal Instituut voor Voedingsonderzoek (T.N.O., 1965)). Rabbit One rabbit given 3 g of sodium sulfite by stomach tube each day for 185 days lost weight, but all organs were normal post mortem. Two rabbits given 1.08 g daily for 127 days gained weight. Autopsy showed haemorrhages in the stomach. Three rabbits given 1.8 g daily for between 46 and 171 days lost weight and autopsy showed stomach haemorrhages (Rost & Franz, 1913). Dog A dose of 3 g of sodium sulfite daily was given by stomach tube to a dog weighing 17 kg for 23 days. Another weighing 34 kg was given 6-16 g of sodium sulfite daily for 20 days (total dose 235 g). No abnormalities were observed on autopsy in the first dog, but the second dog had haemorrhages in several organs. Sodium sulfite was given by stomach tube to 16 growing dogs in daily doses of 0.2-4.8 g for 43-419 days; no damage was observed in any of the dogs. Sodium bisulfite was given to two dogs by the same method and for the same length of time as in the preceding experiment in daily doses of 1.08-2.51 g. Examination of heart, lungs, liver, kidney and intestine showed no damage. A total of 91-265 g of sodium sulfite fed to five pregnant dogs over a period of 60 days had no effect on the weight of the mothers or on the weight gain of the litters (Rost & Franz, 1913). Pig Groups of 20 castrated male, and 20 female weanling Dutch Landrace pigs were placed on diets supplemented with 50 mg/kg thiamine, and containing 0, 0.06, 0.16, 0.35, 0.83 or 1.72% Na2S2O5. Fourteen males and 14 females/group were sacrificed at 15-19 weeks and the remainder at 48-51 weeks. In addition a paired feeding study on 15 male and 15 female weanling pigs/group was performed for 18 weeks at 0 and 1.72% Na2S2O5. Food intake and weight gain was reduced at the 1.72% level, but the pair feeding study indicated growth and food conversion were not affected when intake was controlled. Mortality was not related to sulfite ingestion. Urinary and liver thiamine levels decreased with increasing dose, but only at 1.72% were they reduced below the levels found in pigs on basal diet alone. Haematology and faecal occult blood determinations were comparable in all groups. Organ/body weight ratios were elevated at 0.83 and 1.72% for heart, kidney and spleen, and at 1.72% for liver. The pair feeding study showed liver and kidney weight ratios to be increased at 1.72%. Gross pathology comprised mucosal folds in the stomach and black colouration of the caecal mucosa in the top two dose levels. At 0.83 and 1.72%, histopathological examination showed hyperplasia of mucosal glands and surface epithelium in the pyloric and cardiac regions. In the pars oesophagea, intra-epithelial microabscesses, epithelial hyperplasia and accumulations of neutrophilic leucocytes in papillae tips were observed. In the caecal mucosa, macrophages laden with pigment granules (PAS positive containing Ci and Fe) were observed at all dose levels, including controls. Incidence was markedly increased at 0.83% and above. At 1.72%, fat-containing Kupffer cells were present in usually high numbers in the liver (Til et al., 1972a). Long-term studies Rat Groups of rats numbering from 18 to 24 per group were fed sodium bisulfite in dosages of 0.0125, 0.025, 0.05, 0.1, 0.25, 0.5, 1 or 2% of the diet for periods ranging from one to two years. The rats fed 0.05% sodium bisulfite (307 ppm (0.0307%) as SO2) for two years showed no toxic symptoms. Sulfite in concentrations of 0.1% (615 ppm (0.0615%) as SO2), or more, in the diet inhibited the growth of the rats, probably through destruction of thiamine in the diet (Fitzhugh et al., 1946). Three groups of weanling rats containing 18, 13 and 19 animals received drinking-water containing sodium metabisulfite at levels of 0 ppm (0%) SO2, 350 ppm (0.035%) SO2 and 750 ppm (0.075%) SO2. Prior interaction of the sulfite with dietary constituents was thus prevented. The experiment lasted 2-1/2 years and extended over three generations of rats. No effects were observed on food consumption, fluid intake, faecal output, reproduction, lactation or the incidence of tumours (Locket & Natoff, 1960). A solution containing 1.2 g of potassium metabisulfite per litre of water (700 ppm (0.07%) SO2) was administered to 80 weanling rats (40 of each sex) over a period of 20 months. A group of 80 rats given distilled water served as controls. It was shown that the intake of fluid by the test group was the same as that of the controls (but no study appears to have been made of SO2 loss from the metabisulfite solution). The intake of SO2 calculated from the consumption of water was 30-60 mg/kg bw per day for males and 40-80 mg/kg bw per day for females. The following criteria provided no evidence of toxic effect: growth rate, food intake, clinical condition, haematological indices of blood and bone marrow (except peripheral leucocyte count, which was increased in males), organ weights (except spleen weight, which was heavier in females), micropathological examination of a large number of tissues and mortality rate. Fatty change in the liver was mostly slight or absent, with a similar incidence and severity in test and control groups. Reproduction studies over two generations revealed no effect except for a slightly smaller number of young in each litter from test animals and smaller proportion of males in each of these litters. Growth of the offspring up to three months was almost identical in test and control groups (Cluzan et al., 1965). Four groups of 20 rats (10 of each sex on standard diet) were given daily doses (30 ml/kg bw) of red wine containing 100 and 450 ppm (0.01% and 0.045%) SO2, an aqueous solution of potassium metabisulfite (450 ppm (0.045%) SO2) and pure water by oral intubation on six days each week for four successive generations. The females were treated for four and the males for six months; the second generation was treated for one year. The only effect seen was a slight reduction in hepatic cellular respiration. All other parameters examined: weight gain, weight and macroscopic or histological appearance of various organs, appearance and behaviour, proportion of parturient females, litter size and weight, biological value of a protein sample, showed no changes attributable to SO2 (Lanteaume et al., 1965). Groups of 20 male and 20 female rats were fed 0, 0.125, 0.25, 0.5, 1.0 or 2.0% Na2S2O5 in a diet enriched with 50 ppm (0.005%) thiamine for two years. Animals were stressed by breeding at 21 weeks, and again for half of each group at 34 weeks. Percentage loss of sulfite from the diet decreased with increasing dietary concentration, but increased with increasing time. Thiamine loss increased with increasing sulfite concentration. Body weight, food consumption, kidney function, and organ weights were all unaffected. Thiamine content of urine and liver showed a dose-related decrease commencing at 0.125 and 0.25% respectively. However, thiamine levels at 2% were comparable to levels in control rats. Marginally reduced haemoglobin levels were noted on three occasions in females at 2%, and occult blood was noted in faeces at 1% and above. In 10% of the females at 0.25%, and in 10% of the males at 0.5% sulfite slight indications of intestinal blood loss were noted at week 32 only. Pathological changes were limited to the stomach (either hyperplasia or inflammation) and occurred at 1% and above. Incidence of neoplasms was not increased above normal levels at any site at any dose (Til et al., 1972b). OBSERVATIONS IN MAN In man, a single oral dose of 4 g of sodium sulfite caused toxic symptoms in six of seven persons. In another subject, 5.8 g caused severe irritation of the stomach and intestine (Rost & Franz, 1913). The vomiting reflex in man appeared regularly with doses of sulfite equivalent to less than 250 mg SO2, i.e. 3.5 mg SO2 per kg bw (Lafontaine & Goblet, 1955). (See also under: effects on thiamine). Comments: Long-term and 3-generation studies on rats using metabisulfite in a diet with added thiamine showed a no-effect level of 0.215% metabisulfite (equivalent to 72 mg/kg bw per day SO2). This level is higher than that indicated by the earlier studies involving metabisulfite administration to rats in drinking-water (equivalent to 35 mg/kg bw per day SO2). The effect of sulfite on food components needs further study since the earlier observations of toxicity from the feeding of stored sulfited foods point to the formation of some toxic addition compound. Human studies over short periods showed that 400 mg/day produced no effect on thiamine excretion. While it has been shown that sodium bisulfite reacts with DNA and produces mutation in bacteria, the, relevance of these observations to man is highly questionable. The mutagenicity of bisulfite in bacteria is manifest only at low pH. It has been shown that maximal mutagenic activity of bisulfite occurs at pH 5.0 while at pH. 7 and 8 no induction of mutants was observed. Further, studies in Drosophila reveal no elevation of mutation frequency at two levels of exposure including one which killed a sizeable proportion of flies. Based on these observations, it can be assumed that bisulfite poses no threat to genetic material at physiological pH. However, confirmation of this claim utilizing mammalian cell in culture is recommended. Any one of several mammalian cell mutational assay systems might be applied for this purpose. EVALUATION Level causing no toxicological effect Rat: 0.215% metabisulfite in the diet equivalent to 70 mg/kg bw per day calculated as SO2. Estimate of acceptable daily intake for man 0-0.7* mg/kg bw FURTHER WORK OR INFORMATION Desirable: Additional mutagenic studies in a mammalian system. Studies over longer periods in man. REFERENCES Allen, R. J. L. & Brook, M. (1970) Third International Congress of Food Science & Technology, Washington Bhagat, B. & Locket, M. F. (1960) J. Pharm. Pharmacol., 12, 690 Bhagat, B. & Locket, M. F. (1964) Food Cosmet. Toxicol., 2, 1 Causeret, J. (1964) Unpublished report of work in progress submitted to WHO Causeret, J. et al. (1965) Fruits, 20, 109 Causeret, J. & Hugot, D. (1960) C.R. hebd. Séanc. Acad. Sci., Paris, 250, 401 * As SO2. 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(1970) Third International Congress of Food Science & Technology, Washington Swan, J. M. (1957) Nature (Lond.), 180, 643 Thompson, J. R. & Pace, D. M. (1962) Canad. J. Biochem. Physiol., 40, 207 Til, H. P. (1970) Toxicologisch Onderzoek Naar de Werking van Sulfiet bij Ratten, Varkens en Kwartels. Thesis - Rijksuniversiteit te Utrecht, March Til, H. P., Feron, V. J. & de Groot, A. P. (1972a) The toxicity of sulfite. II. Short and long-term feeding studies in pigs. Fd. Cosmet. Toxicol., 10, 463 Til, H. P., Feron, V. J. & de Groot, A. P. (1972b) The toxicity of sulfite. I. Long-term feeding and multigeneration studies in rats. Fd. Cosmet. Toxicol., 10, 291-310 Wilkins, J. W. jr, Greene, J. A. jr & Weller, J. M. (1968) Toxicity of intraperitoneal bisulfite, Clin. Pharmac. Ther., 9, 328 Williams, R. R. et al. (1935) J. Amer. chem. Soc., 57, 536
See Also: Toxicological Abbreviations Sulfur dioxide and sulfites (WHO Food Additives Series 18) Sulfur dioxide and sulfites (WHO Food Additives Series 21)