RED 2G Explanation This food colourant was evaluated by JECFA in 1977, and a temporary ADI for man of 0-0.006 mg/kg bw was established (WHO, 1978). Further work required included a multigeneration study, and studies on bone marrow to elucidate the toxic effects on erythropoiesis. In 1979 none of these studies had been completed and JECFA extended the previously established temporary ADI (WHO, 1980). Since the previous evaluations, additional data have become available and are included in this monograph. BIOLOGICAL DATA BIOCHEMICAL ASPECTS Rats were injected intravenously with Red 2G. Bile was collected for six hours and analysed. The recovery of the colour was on average 64% of the administered quantity (Priestly & O'Reilly, 1966). Biliary excretion of i.v. administered Red 2G was also reported by Ryan & Wright (1961). In another experiment 250 mg/kg bw of Red 2G was administered by gastric intubation to five male and five female rats. On average the males excreted 61.8% of the dose in the urine and the females 71.5%, 42.2% of the dose was excreted in the urine as p-aminophenol in 48 hours, 9.2% as aniline in 24 hours and 3% as unreduced dye in 24 hours. The corresponding faecal excretion was 6.3, 1.0 and 0.1%. For females urinary excretion amounted to 56.4% as p-aminophenol in 48 hours, 2% as aniline in 24 hours and 2.6% as unreduced dye in 24 hours. The corresponding faecal excretion was 8.6, 0.3 and 1.6% (Walker, 1971). The contents of a rat caecum were incubated at 37°C with a solution of Red 2G in isotonic saline. At one-hour intervals a sample of the incubate was filtered and Red 2G was estimated in the filtrate by measuring the optical density. Two metabolites of Red 2G were detected in the incubation mixture after separation by thin layer chromatography on silica plates. One was 2-amino-8-acetamido-1- naphtho-3,6-disulfonic acid, the other, aniline, was detected using two different solvent systems. When Red 2G was incubated at 37°C with liver homogenate the same two metabolites were detected (Jenkins et al., 1966). When a mixture of Red 2G and caecal contents were incubated at 37°C darkening at the surface was observed. This was attributed to oxidation of a metabolite of Red 2G, presumed to be a sulfur- containing compound. Two groups of 12 rats were fed purified diet and a purified diet containing 0.51% Red 2G respectively. Faeces were collected and it was calculated that 48.2% of the sulfur derived from Red 2G was excreted in the faeces (Unilever, 1974). When rabbits were fed 0.5 g/kg bw of the colour the following metabolites could be identified in urine over a period of 48 hours: total p-aminophenol, 46%; p-aminophenylglucuronide, 37%; aniline, 0.6% and o-aminophenol, 9%. The ratio of o-aminophenol to p-aminophenol was the same for rabbits fed Red 2G and rabbits fed aniline previously examined by Parke (1960) indicating that hydroxylation does not necessarily precede fission of the azolinkage. No binding of Red 2G to serum protein occurs (Jenkins et al., 1966a). TOXICOLOGICAL STUDIES Special studies on aniline Rat Aniline dissolved in isotonic saline was administered either intravenously to rats under anaesthesia or by stomach tube. Saline was administered to control animals. Blood samples from the tail were taken at 30-minute intervals at first and then at 60-minute intervals. The no-effect dose of aniline was 20 mg/kg bw orally and 10 mg/kg bw intravenously (Jenkins et al., 1972). Groups of six male and six female rats were fed diets containing 0.098% aniline and molecular equivalent levels of p-aminophenol and phenylhydroxylamine. Methaemoglobinaemia, Heinz bodies and splenic enlargement were noted in rats which received either aniline or phenylhydroxylamine. The no-effect single oral dose of aniline in rats was 20 mg/kg bw (Jenkins et al., 1972). Man Aniline was administered orally to a volunteer for five days. The dose was 10 mg on days 1 and 2 and 25 mg on days 3, 4 and 5. Urine samples were tested for urobilinogen, glucose and protein and blood tests included, haemoglobin, methaemoglobin, packed cell volume, serum transaminases, alkaline phosphatase, thymol turbidity, serum proteins, serum bilirubin and the staining for Heinz bodies. None of these tests revealed an effect due to the ingestion of aniline, nor could Red 2G be detected in the urine (Jenkins et al., 1972). Single oral doses of 5 and 15 mg aniline had no effect in 20 human subjects; doses ranging from 25 to 65 mg significantly increased the blood level of methaemoglobin to 2.46% but no Heinz bodies were observed. Although human subjects are more sensitive to aniline in vivo than rats, the methaemoglobin content of rat blood exposed to phenylhydroxylamine in vitro exceeded that of human blood exposed to phenylhydroxylamine in vitro. Glucose promoted the production of methaemoglobin (Jenkins et al., 1972). Special studies on haemotoxicity and haemopoiesis Rats were fed 1-1.5 g/kg per day Red 2G for 75 days. The mean peak Heinz body level was 80% falling to a maintained level of 30%. Internal changes included a moderate though well controlled anaemia, pronounced reticulocytosis, and splenomegaly (Rofe, 1957). Methaemoglobin and Heinz bodies have been observed in acute human aniline poisoning by a number of investigators (Freifield et al., 1937; Hughes & Treon, 1954; Rodek & Westhaus, 1952). Methaemoglobin formation occurred first followed by Heinz body appearance, the latter being an irreversible process, Heinz bodies are formed most in vivo but can be studied also in vitro. It has been shown that phenylhydroxylamine is the N-hydroxylated metabolite which produces most of the methaemoglobin observed in the dog after injection of aniline. The reaction probably proceeds by oxidation of phenylhydroxylamine to nitrosobenzene by O2 and Hb with conversion of Hb to methaemoglobin (Kiese, 1959). Since the rat is less susceptible to Heinz body producing agents than the cat and possibly man, a procedure was devised which increased the sensitivity of the rat to these agents by pretreating rats with p-aminopropiophenone, 15 mg/kg bw subcutaneously (Unilever, 1974). Methaemoglobinaemia is a reversible response to toxic injury and depends on the integrity of the erythrocyte in vivo. Reduction of methaemoglobin occurs through an NADH-dependent diaphorase system which is deficient in subjects with hereditary mathaemoglobinaemia or in young infants. The effects of feeding aniline, para-aminophenol and phenylhydroxylamine at a level of 0.1% in the diet of rats were compared for 13 days. The results indicated that compared with a control group, para-aminophenol had no effect on spleen weight, aniline increased mean relative spleen weight by about 60% and phenylhydroxylamine increased mean relative spleen weight by about 500%. Examination of the blood after feeding phenylhydroxylamine for 11 days revealed a high incidence of Heinz bodies. Therefore, the toxic effects of feeding aniline can be attributed to phenylhydroxylamine which is a metabolite of aniline (Gellatly & Burrough, 1966; Jenkins et al., 1966b). Three groups of six four-week old female rats were fed in their diet 0, 0.5% Red 2G or 0.093% aniline. All rats were fed ad libitum for 19 days. The faeces of rats fed Red 2G were almost black; the faeces of rats fed aniline were a normal colour. Both Red 2G and aniline caused a similar increase in spleen weight, accelerated erythropoiesis and haemosiderin content. For rats fed purified diets containing 0. 1, 0.2 and 0.3% Red 2G for two weeks there was a linear relationship between intake of Red 2G and relative spleen weight. For rats fed purified diets containing 0.004, 0.006 and 0.012% phenylhydroxylamine for two weeks there was a linear relationship between intake of phenylhydroxylamine and relative spleen weight (Jenkins et al., 1967; Gellatly & Burrough, 1967). For individual samples of rat blood and human blood the amount of oxidation of haemoglobin to methaemoglobin was linearly related to the logarithm of phenylhydroxylamine concentration. From the dose-response curve it has been estimated that for rat blood the no-effect dose is between 0.5 and 1 µg phenylhydroxylamine/ml blood. The response of human blood to phenylhydroxylamine was more variable than the response of rat blood. The no-effect concentration of phenylhydroxylamine in vitro for human blood ranged from 0.46 to 4.1 µg/ml (blood). At all levels of Red 2G fed to rats the proportion of Red 2G metabolized to phenylhydroxylamine was constant (Unilever, 1974). In vitro studies were conducted on samples of mouse, rat and human blood with 100 and 200 mg% concentration of Red 2G and acetylphenylhydrazine as a positive control. No Heinz bodies were seen with Red 2G (BIBRA, 1965). Red 2G was fed to male and female Colworth-Wistar rats at dietary levels of 0 or 0.5% for two weeks. Some rats from each group were bled by cardiac puncture (2 ml from males; 1 ml from females) to stimulate erythropoiesis two weeks after administration of Red 2G had ceased. At weekly intervals before, during and after feeding Red 2G, three to five rats from each group were killed, liver, spleen and kidneys were weighed and fixed for microscopic examination. Bone marrow samples were taken for differential cell counts and blood samples were examined for haemoglobin, methaemoglobin, red cell count, white cell count, differential white cell count and PCV. In rats fed Red 2G, methaemoglobinaemia, Heinz bodies, reticulocytosis, decreased haemoglobin, PCV and red 3 cell count and increased spleen weight were observed. In liver, spleen and bone marrow there was an increase in erythropoiesis. Rats previously dosed with Red 2G responded to bleeding in a similar manner to controls with increased erythropoiesis observed in bone marrow. The results indicated that liver, spleen and bone marrow respond to Red 2G with an increase in erythropoiesis but there was no evidence that Red 2G had a toxic effect on erythropoiesis (Jenkins et al., 1980). Special studies on mutagenicity In a series of microbial mutagenicity assays, food grade samples of Red 2G were shown to possess weak mutagenic activity, inducing repairable DNA damage and base-substitution mutations, only after metabolic activation with rat-liver microsomes. The products of reducing the azo group in Red 2G were non-mutagenic (Haveland-Smith et al., 1979; Haveland-Smith & Combes, 1980, 1980a). Special studies on reproduction Two groups of 46 male and 46 female rats were fed 0.2% Red 2G in their diet for 18 weeks and then mated for 10 days. The progeny were weaned on the same diet and mated at 16 weeks and the F2 generation was also weaned onto the same diet. No adverse effects were seen on litter size, litter weight and weaning weight nor were there any abnormalities at autopsy (Unilever, 1974). Special studies on teratogenicity Four groups of 20 female Colworth-Wistar rats were fed diets containing 0, 40, 200 or 2000 ppm (0, 0.004, 0.02 or 0.2%) Red 2G on days 0-19 of pregnancy (equal to 0, 3.5, 12.9 or 187.5 mg/kg bw per day). Fifteen rats from each group were subjected to Caesarian section on day 21 of gestation and the foetuses examined for visceral and skeletal malformations; dams were examined for corpora lutea, implantations and intrauterine deaths. Maternal blood, liver and spleen, and foetel bone marrow and spleen were examined histologically. Five rats from each group were allowed to litter normally and to suckle the pups to weaning at 21 days, when the pups were subjected to examination for malformations. There was no evidence that Red 2G possessed foeto-toxic or teratogenic potential at any of the dose levels studied. Treatment did not affect normal parturition or postnatal development to weaning. The only significant effect was the expected increase in the spleen weight and erythropoietic activity in dams at the top dose level; no effects on foetal spleen were observed (Cambridge et al., 1980). Acute toxicity LD50 Animal Route (g/kg bw) Reference Mouse Oral 7.35 Unilever, 1974 i.p. 4.76 (4.13-5.85) Unilever, 1974 i.p. 3.0-4.0 BIBRA, 1965 Rat i.p. 6.35 (5.62-7.17) Unilever, 1965 Oral >5.0 Unilever, 1974 Guinea-pig Oral 4.81 (3.16-7.35) Unilever, 1974 i.p. 3.0 (1.83-4.91) Unilever, 1974 Rabbit Oral >5.0 Unilever, 1974 Chicken Oral >10.0 Unilever, 1974 No deaths occurred in six weanling rats following administration of 5 g/kg bw (Unilever, 1974). A dose of 5 g/kg bw was administered on each of two successive days to a rabbit weighing 3.8 kg and a dose of 25 g/kg bw was administered on each of two successive days to a rabbit weighing 4.3 kg. No signs of toxicity were observed and their red cells contained no Heinz bodies (Unilever, 1974). Histological studies in rats, rabbits and guinea-pigs doses as given above showed extensive renal necrosis. In mice dosed orally with Red 2G there was gross leptomeningeal vascular engorgement and focal subarachnoid haemorrhage (Unilever, 1974). No deaths occurred in three-week old and nine-week old chickens following administration of 10 g/kg bw. There was no evidence of renal necrosis (Unilever, 1974). Short-term studies Mouse Five groups of 15 male and 15 female mice were given diets containing 0.0, 0.01, 0.1, 1.0 and 2.0% Red 2G. Five mice of each sex at each dose level were killed at 26, 55 and 96 days, when a full autopsy and haematological investigation was carried out on each animal. No adverse effect on growth or food consumption was evident in any animal given Red 2G in the diet. Heinz bodies were seen at all levels, the incidence being related to dose and duration of treatment. The maximal effect was seen on day 26 and day 55 at a level of 0.1% and below and on day 26 at 1.0 and 2.0%. Splenomegaly was seen at 2.0% in both sexes and at 1.0% in females. Increased relative liver weights were found in females at 2.0% throughout the tests and at 1.0% after 26 days treatment. The only pathological finding attributable to the administration of Red 2G was increased haemosiderin in the Kupffer cells of the liver at 2.0 and 1.0%. Haemosiderin was also present in the spleen at 2.0% throughout the test; at 1.0, 0.1 and 0.01% the incidence of haemosiderin increased with the duration and treatment (BIBRA, 1965). In another study Red 2G was fed for six weeks to five groups of 10 mice at dietary levels of 0, 0.02, 0.1, 0.5 and 1.0%. The toxic effects observed were development of Heinz bodies, methaemoglobinaemia, splenic enlargement, accelerated splenic macrophages. No toxic effects were observed in mice fed the diet containing 0.02% (Unilever, 1974). Rat Six groups of five male and five female rats were given diets containing 0.0, 0.05, 0.1, 0.5, 1.0 and 2.0% Red 2G for three weeks. A further four groups of 10 male and 10 female rats were given diets containing 0.0, 0.01, 0.05 and 0.1% Red 2G for two months. Retarded growth associated with reduced food consumption was seen at 5.0 and 2.5% after nine days, with an initial retardation at 2.0%. No effect on growth or food consumption was seen at lower levels of administration. Macrocytosis, reticulocytosis and polychromasia were evident at 5.0% with circulating normoblasts and a normoblastic marrow. Heinz bodies were present in animals at 1.0% and above after nine days and 1.0 and 0.5% after three weeks exposure. Signs indicative of increased erythropoiesis could be seen in animals at all levels down to 0.1%. Significant splenomegaly was evident at all levels above 0.5% with scattered non-significant increases in spleen weight at 1.0 and 0.05% after two months. Increased kidney weight was also seen at 0.1% and above. On histological examination the only change attributable to Red 2G was the increased haemosiderin seen in the Kupffer cells of the liver, renal tubule cells and spleen in all animals at 2.0% and in some at 1.0 and 0.5%. Blood samples were taken from the tail of the rats. By nine days a definite haemolytic anaemia with Heinz body formation was present at all levels from 0.5 to 2.0% (BIBRA, 1965). Three groups of 12 rats received Red 2G in the drinking-water at levels of 0, 0.1 and 0.5% for 100 days. Heinz bodies were seen after 10 days in the red cells of rats fed 0.5% Red 2G in the drinking- water, fewer were seen after 18 days and none or very few on later occasions. A few Heinz bodies were occasionally seen in the red cells of some of the rats fed 0.1% Red 2G in the drinking-water. The spleens of rats fed 0.1% Red 2G were slightly larger than controls and the spleen of rats fed 0.5% Red 2G were very much larger than controls. Histological examination of livers of rats fed 0.5% Red 2G revealed an increase in haemosiderin present in Kupffer cells and increased erythropoietic activity. Histological examination of the spleens of rats fed 0.5% Red 2G also revealed increased erythropoiesis and red pulp engorgement. There was no effect of Red 2G on urine specific gravity (Jenkins et al., 1966c; Gellatly et al., 1966). Four groups of 24 male and 24 female rats were fed at dietary levels of Red 2G which would ensure intakes of 100 x and 600 x the assumed average daily dietary intake of Red 2G. This was achieved by feeding sausage meat, containing 0, 30 and 180 ppm (0, 0.003 and 0.018%) Red 2G respectively in the diet at a level of 80%. The diets containing Red 2G in sausage meat had no effect on growth, organ function or organ weights. Blood tests also revealed no evidence of toxicity. Histological examination revealed that, in the spleens of rats fed sausage meat containing 180 ppm (0.018%) Red 2G, there was increased erythropoiesis, increased splenic red pulp haemosiderin and increased red pulp reticular impregnation with iron. No-effects on spleen were seen in rats fed sausage meat containing 30 ppm (0.003%) of Red 2G. Red 2G at 30 ppm (0.003%) and at 180 ppm (0.018%) in sausage meat had no detectable histological effect on liver (Jenkins et al., 1966d). Long-term studies Mouse Five groups of 40 male and 40 female mice were fed diets containing 0, 0.005, 0.025, 0.125 and 0.625% for 20 months. Splenic enlargement and darkening were seen in mice fed dietary levels of 0.125 and 0.625% of Red 2G; in these animals there was accelerated formation of red blood cells in the spleen and increased deposition of iron in spleen and kidneys. There was no evidence of carcinogenicity attributable to the feeding of Red 2G to mice. More than three- quarters of the animals in each group survived for two years (Unilever, 1974). Rat Five groups of 40 male and 40 female rats were fed at dietary levels of 0.004, 0.016, 0.064 and 0.16% Red 2G. Rats fed diets containing 0.064 and 0.16% of Red 2G showed splenic enlargement and darkening attributable to increased storage of iron resulting from haemolysis of red blood cells. Necrosis of splenic elastica was also identified, this lesion being a sequel to prolonged splenic enlargement. There was no evidence of carcinogenicity attributable to the feeding of dietary levels of Red 2G up to 0.16% for two years. Over half of each group of rats survived for two years (Unilever, 1974). Two groups of 30 male and 30 female rats were fed a diet containing 0 or 0.5% Red 2G. At the 0.5% level there was enlargement and darkening of the spleen, attributable to accelerated splenic erythropoiesis, increases splenic haemosiderin deposition and extensive degeneration of splenic elastica. Biochemical studies of blood and urine revealed no adverse effects on liver and kidneys which could be attributed to feeding 0.5% Red 2G in the diet. More than half the animals in the test group survived for two years (Unilever, 1974). Comments In the in vitro bacterial mutagenicity studies Red 2G only induced mutations at very high concentrations of 10 mg/ml; no activity was detectable at 1 mg/ml. Microsomal activation was required for mutagenic activity and the reduction products of Red 2G were inactive. Since Red 2G is substantially reduced by the gut microflora prior to absorption (Walker, 1971) the concentrations of the dye reaching the tissues (other than the intestinal mucosa) is likely to be very small and considerably lower than that required to induce mutations in the bacterial studies. The teratology study and the study on the effects on erythropoiesis were in response to the work required in the previous evaluation by JECFA (WHO, 1980). EVALUATION Level causing no toxicological effect Mouse: 0.025% in the diet, equal to 43-26 mg/kg/day for 80 weeks. Rat: 0.016% in the diet, equivalent to 8 mg/kg/day for two years. Estimate of acceptable daily intake for man 0-0.1 mg/kg bw. FURTHER WORK OR INFORMATION Desirable Further studies on the mutagenicity of Red 2G and its major subsidiary components in a range of test systems in vitro. REFERENCES BIBRA (1965) Acute and short-term feeding studies on Red 2G with associated haematological investigations, British Industrial Biological Research Association, Research Report 3/1965. Unpublished report submitted to WHO Cambridge, G. W. et al. (1980) Teratology study on Red 2G in the Colworth Wistar Rat. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Freifield, H., Schilowa, A. & Ludwinowsky, R. (1937) Heinz bodies and methaemoglobin formation in poisoning by compounds containing amino and nitro groups, Folia Haematol., 56, 333-342 Gellatly, J. B. M. & Burrough, R. (1966) Effects of diets containing aniline and metabolites of aniline on spleen weights; pathology. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd Gellatly, J. B. M. & Burrough, R. (1967) Pathology of Red 2G and phenylhydroxylamine in fat diets. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Gellatly, J. B. M., Salmond, G. & Burrough, R. (1966) Sub-acute toxicity of Red 2G; pathology. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Haveland-Smith, R. B., Combes, R. D. & Bridges, B. A. (1979) Methodology for the testing of food dyes for genotoxic activity: Experiments with Red 2G (C.I. 18050), Mut. Res., 64, 241-248 Haveland-Smith, R. B. & Combes, R. D. (1980) Screening of food dyes for genotoxic activity, Fd. Cosmet. Toxicol., 18, 215-221 Haveland-Smith, R. B. & Combes, R. D. (1980) Genotoxicity of the food colours Red 2G and Brown FK in bacterial systems. Use of structurally-related dyes and azo-reduction, Fd. Cosmet. Toxicol., 18, 223-228 Hughes, J. P. & Treon, J. F. (1954) Erythrocytic inclusion bodies in the blood of chemical workers, Arch. Hyg. occup. Med., 10, 192-202 Jenkins, E. P. et al. (1966) Metabolism of Red 2G by rat liver homogenate. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Jenkins, F. P. (1966a) Metabolism of Red 2G (protein binding capacity). Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Jenkins, F. P. at al. (1966b) Effects of diets containing aniline and metabolites of aniline on spleen weights. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Jenkins, F. P. et al. (1966c) Sub-acute toxicity of Red 2G. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Jenkins, F. P., Salmond, G. & Gellatly, J. B. M. (1966d) Sub-acute toxicity of Red 2G in sausage meat. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Jenkins, F. P. et al. (1967) Effect of Red 2G and phenylhydroxylamine on spleen weight. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Jenkins, F. P. et al. (1972) The no-effect dose of aniline in human subjects and a comparison of aniline toxicity in man and rat, Fd. Cosmet. Toxicol., 10, 671-679 Jenkins, F. P., Kennedy, S. & Williams, T. C. (1980) Erythropoiesis in the Colworth Wistar rat fed Red 2G. Unpublished report from Unilever Research Laboratories, submitted to WHO by Unilever Ltd. Kiese, M. (1959) Significance of the oxidation of aniline to nitrosobenzene for the formation of methemoglobin after absorption of aniline into the organism, Arch. exp. Path. Pharmak., 235, 360-364 Parke, D. V. (1960) Studies in detoxication 84. The metabolism of 14C aniline in the rabbit and other animals, Biochem. J., 77, 493-503 Priestley, G. & O'Reilly, W. J. (1966) Protein binding and the secretion of some azo dyes in rat bile, J. Pharm. Pharmacol., 18, 41-45 Rodek, H. & Westhaus, H. (1952) Aniline poisoning in nurslings from ink and labeling dyes, Arch. Kinderh., 145, 77-90 Rofe, P. (1957) Azo dyes and Heinz bodies, Brit. J. ind. Med., 14, 275-280 Ryan, A. J. & Wright, S. E. (1961) The excretion of some azo dyes in rat bile, J. Pharm. Pharmacol., 13, 492-495 Unilever (1974) Unpublished review of the biological effects of food colour Red 2G dated November 1974. Submitted to WHO by Unilever Ltd. Walker, R. (1971) Personal communication to E. M. den Tonkelaar, National Institute of Public Health, Bilthoven, Netherlands World Health Organization (1978) Twenty-first report of the Joint FAO/WHO Expert Committee on Food Additives, Wld Hlth Org. techn. Rep. Ser., No. 617, 94-102 World Health Organization (1980) Twenty-third report of the Joint FAO/WHO Expert Committee on Food Additives, Wld Hlth Org. techn. Rep. Ser., No. 648, 84-92
See Also: Toxicological Abbreviations Red 2G (WHO Food Additives Series 12) Red 2G (WHO Food Additives Series 14) RED 2G (JECFA Evaluation)