The Science of the Total Environment, 4 (1975) 185-192 © Elsevier Scientific Publishing Company, Amsterdam - Printed in Belgium
TOXICITY AND POLLUTION POTENTIAL OF THALLIUM
V. ZITKO
Department of Environment, Biological Station, St. Andrews, New Brunswick, EOG 2XO (Canada) (Received February 13th, 1975)
ABSTRACT
Toxicity and pollution potential of thallium are reviewed. Thallium is slightly more acutely toxic to mammals than mercury, and as acutely toxic as copper to fish. Its present industrial uses are too limited to generate pollution, but thallium, discharged in wastes from mines, ore-processing, and coal-burning plants, is contaminating the environment.
INTRODUCTION
Thallium is a relatively obscure metal with limited industrial applications. The average concentration of thallium in the lithosphere is 0.1-1.0 pg/g (Lange and Forker, 1967; Hampel, 1968), and 0.01-0.02 #g/1 in sea water (Matthews and Riley, 1970; Gaskell, 1971). Thallium ores are rare and the metal is recovered during processing of sulfide ores of lead, copper, and zinc, containing thallium in levels of up to 10 mg/g (Robinson, 1973). Relatively high levels of thallium are also present in manganese nodules (Glasby, 1973). The world production of thallium is 10-12 t/year (Kogan, 1970). The amount of recoverable thallium is much higher and the pollution potential of thallium should be judged on the basis of the amount released into the environment in wastes rather than on the basis of production. According to the author's estimate, 48 t/year of thallium may be present in wastes from zinc production in Canada. In its compounds thallium is either mono-(I) or trivalent(III). Thallium(I) is more stable and in some properties resembles closely the alkali metal cations. The solubility of thallium(l) hydroxide in water is 259 g/1 (Lange and Forker, 1967). Many organic compounds of thallium(III) are known and dimethyl thallium salts are very stable. The preparation and properties of organothallium compounds and the stability of their complexes have been reviewed (Nesmeyanov and Sokolik, 1967; Beletskaya et al., 1973). Industrial uses of thallium include alloys, electronic devices, and special glass. Thallium compounds are useful in synthetic organic chemistry (for a review see Taylor and McKillop, 1970) and many thallium-containing catalysts have been patented for industrial organic reactions. 185
Very extensive literature, including a monograph (Korenman, 1963), is available on analytical chemistry of thallium. Sensitive methods for the determination of thallium include spectrophotometry of ion-association complexes of thallium(III) and basic dyes (Fogg et al., 1971, 1973), fluorometry (Kirkbright et al., 1965), anodic stripping voltammetry (Sinko and Gomiscek, 1972; Paolaggi et al., 1972), and atomic absorption spectrophotometry (Curry et al., 1969; Shkolnik and Bevill, 1973). TOXICITY Thallium and its compounds are highly toxic. Human toxicity of thallium was recently reviewed by Oehme (1972). Thallium is absorbed through skin and mucous membranes, is widely distributed throughout the body and accumulates in bones, renal medulla and, eventually, in the central nervous system. Thallium passes through the placenta, occurs in milk, and is excreted mainly in urine. The biological half-life of thallium in man is 3-8 days. Toxic doses or concentrations of thallium and some other metals are summarized in Tables 1 and 2. It can be seen that in mammals thallium is slightly more acutely toxic than mercury and its toxicity is exceeded only by that of methyl mercu~. To fish thallium is as acutely toxic as copper on a weight basis, and 3 to 4 times more toxic than copper on a molar basis. Thallium kills fish quite slowly (Zitko et al., 1975) and this may explain the much higher toxic concentrations reported by Nehring (1962). Species differences, however, cannot be excluded. Hardness of water, which affects strongly the toxicity of metals to fish (see for example Lloyd and Herbert, 1962), may not have much effect on the toxicity of thallium because of its low complexing ability. For the same reason, humic acid probably does not affect the toxicity of thallium. The acute toxicities of copper and thallium, and of zinc and thallium to fish are not additive (Zitko et al., 1975). Hypertension is one of the symptoms of thallium poisoning in humans (Merguet et al., 1968, 1969) and in fish (Nehring, 1962). Burger and Starke (1969) suggest that this effect may be caused by the oxidation of thallium(I) to thallium(III) which inhibits the ATPase of amine-storing granules, thus causing alterations in the catecholamine metabolism. The uptake of thallium by yeast mitochondria (Linglen, 1971) and the formation of thallium(III) oxide in these (Lindgren and Lindgreu, 1973) confirm that oxidation of thallium in vivo takes place. It is not known to what extent this process is responsible for thallium toxicity. Thallium(III) catalyzed in vitro the iodination of cytidine residues in a transfer RNA (Schmidt et al., 1973), but it is not clear whether a similar reaction could also occur in vivo. Thallium(I) is able to substitute monovalent cations, particularly potassium, in enzymatic reactions. Thallium is isomorphic with potassium, but has approximately 10 times higher affinity than potassium for the enzymes. The increased affinity may cause the toxic effects. Thallium activation was demonstrated in the case of several enzymes. Britten and Blank (1968), Inturrisi (1969a, b), Robinson (1970), Maslova et al. (1971), Nazarenko et al. (1972), Skul'skii et al. (1973), and Lishko et al. (1973) studied the 186
TABLE 1 TOXIC DOSE OR C O N C E N T R A T I O N O F T H A L L I U M
Species
Effective dose or concentration
Effect
Reference
Mouse Mouse Mouse Rat Rat
24--27 16-19 0.5-1 13-19 6.5
LD50 LD50 15 days, measurable effects LD50 6 times in 14 days, measurable effects Lethal 3-6 months, measurable effects LD50 Lethal Lethal Lethal Lethal Lethal Lethal Growth inhibition Growth inhibition Growth inhibition
Christensen, 1972 Tikhonova, 1967 Tikhonova, 1967 Christensen, 1972 Malachovskis, 1968
Dog Rabbit Atlantic salmon Rainbow trout Perch Roach Tadpole Daphnia Gammarus Azotobacter Proteus mirabilis Aspergillus niger
mg/kg mg/kg mg/kg mg/kg mg/kg
15 mg/kg 0.2 mg/kg 0.03 mg/l 10-15 rag/1 60 rag/1 40-60 rag/1 0.4 mg/l 2--4 mg/l 4 mg/l 20 rag/1 390 mg/l 200 mg/l
Christensen, 1972 Tikhonova, 1967 Zitko et al., 1975 Nehring, 1962 Nehring, 1962 Nehring, 1962 Dilling and Healey, 1926 Nehring, 1962 Nehring, 1962 DeJong and Roman, 1971 Watanabe et al., 1971 Scharrer, 1955
TABLE 2 TOXIC DOSE OR C O N C E N T R A T I O N O F SOME HEAVY METALS
Metal (chloride or acetate)
Species
LDSO or LCSO mg[kg
mmole/kg
Mercury Methyl mercury Cadmium Lead Copper Zinc
Rat Mouse Rat Rat Rat Rat
27 13 54 150 445 875
0.13 0.06 0.48 0.46 7 13.4
Mercury Ethyl mercury Cadmium Lead Copper Zinc
Stickleback Rainbow trout F a t h e a d minnow Rainbow trout Minnow, salmon Minnow, salmon
rng/l 0.2 0.09 1.4--19 0.8-1.3 0.05-0.5 0.6-10
mmole/l 0.001 0.0005 0.012-0.17
0.005-0.006 0.0008-0.008 0.009-0.15
Reference
Christensen, Christensen, Christensen, Christensen, Christensen, Christensen,
1972 1972 1972 1972 1972 1972
McKee and Wolf, 1963 Amend et al., 1969 Pickering and Gast, 1972 Lloyd and Herbert, 1962 Sprague, 1964; Mount, 1968 Sprague, 1964; Brungs, 1969
187
effect of thallium on various sodium-potassium-sensitive ATPases, Manners et al. (1970) on a vitamin B~2-dependent diol dehydratase, Kayne (1971) on pyruvate kinase, homoserine dehydrogenase, and AMP deaminase, and Antia et al. (1972) on L-threonine dehydratase. In frog skin, thallium was tightly bound in the membrane and could not substitute potassium in the sodium-potassium pump system (Natochin and Skul'skii, 1972). The relative rate of uptake of monovalent cations by goldfish intestinal mucosa decreased in the order thallium > potassium > rubidium > cesium > sodium > lithium (Ellory et al., 1973), and thallium restarted the activity of an isolated frog heart (Rusznyak et al., 1968). In chick embryos thallium induced achondroplasia (Hall, 1972), which was potentiated by cortisone acetate and prevented by vitamin C. Enlarged mitochondria were observed after exposure to thallium in the axons of peripheral nerve fibers in mice (Spencer et al., 1973). Thallium was not able to substitute for potassium in mice ribosomes in vitro and inhibited amino acid incorporation into protein both in vivo and in vitro (Hultin and N~islund, 1974). Thallium inhibited the development of Paracentrotus lividus eggs (Lallier, 1968). Thallium is toxic to bacteria, but quite high levels are generally required for measurable effects. Thallium inhibited the nitrification by Nitrobacter agilis (Tandon and Mishra, 1969), and the growth of Thiobacillus ferroxidans in a potassium-free medium (Tuovinen and Kelly, 1974). Staphylococcus aureus was approximately 15 times more resistant than S. epidermis (Kunze and Pramberger, 1972a) and, in general, Mycoplasmataceae were more resistent than Acholeplasmataceae (Kunze and Pramberger, 1972b). Thallium is toxic to plants and inhibits chlorophyll formation and seed germination (Scharrer, 1955). In Chlorellafusca the uptake of thallium was increased by illumination, and additional light-independent absorption of thallium was also observed (Solt et al., 1971). Similar results were obtained with Ulva lactuca (Skul'skii et al., 1972a). In contrast to potassium metabolism, sodium fluoride inhibited the uptake of thallium(I) (Skul'skii et al., 1972b). On the other hand, the uptake of thallium(III) was independent of temperature, light or sodium fluoride (Polikarpov, 1970). The accumulation coefficients of thallium(I) and (III) were approximately 20 and 50, respectively, and an equilibrium was reached within 20 h (Polikarpov, 1970). Thallium was not adsorbed by alginic acid (Lazorenko and Polikarpov, 1972). Little is known about the toxicity of organothallium compounds. Diphenyl thallium chloride and cyanate were toxic to a number of pathogenic fungi (Srivastava et al., 1973). Antidotes against acute thallium poisoning were reviewed by Munch (1968) and included activated charcoal, BAL, calcium salts, cystine, dithiocarb, dithizone, histamine, theophylline, potassium chloride, and thiosulfate. Prussian blue and other hexacyanoferrates(II) were recently recommended as antidotes (Dvorak, 1969; Kamerbeek et al., 1971). A 2% colloidal solution of ferrihexacyanoferrate(II) increased the urinary excretion of thallium by a factor of 2.8, but only if administered during the first 24 h (Guenther, 1971). Stevens et al. (1974) used this treatment success188
fully on 11 cases of thallium intoxication. The excretion of thallium was also increased by D-penicillamine (Slepicka et al., 1969), and a chronic intoxication was somewhat alleviated by vitamin B12 (Malachovskis, 1968). Data on the concentration of thallium in tissues and organs of acutely poisoned humans and animals were reviewed by Munch (1968). In the majority of human cases, the amount of thallium taken was not known. The concentration of thallium in kidney and liver was 2.7-42 and 10-34 pg/g, respectively. Three subjects died as a result of thallium acetate poisoning (6.9 mg/kg, as thallium), and the concentration of thallium in kidney and liver was 60-79 and 482-862 pg/g. Berman (1967) found a thallium concentration of 300 #g/1 in blood, and 30-1240 #g/1 in urine of acutely poisoned subjects. In cases of animal poisoning, the thallium concentrations were 12-135, 7-140, 3-103, and 3-120 ktg/g in kidney, liver, muscle, and spleen, respectively (Munch, 1968). The concentration of thallium in urine, hair and toenails is a useful indicator of sublethal poisoning. Toenails are preferred to hair because they contain thallium in higher concentration (Henke and Bohn, 1969). TABLE 3 ACCUMULATION OF SOME METALS IN FISH DURING LABORATORY EXPOSURE Metal
Species
Tissue
Accumulation coefficient*
Reference
Thallium
Atlantic salmon
Muscle Liver Gills Kidney Gills Whole fish Gills Liver Muscle Gut, gill Muscle Gut, gill Whole fish
130 170 480 9,000 5-8 19-65 17 65 2 13 8 100 10
Zitko et al., 1975 Zitko et al., 1975 Zitko et al., 1975 Giblin and Massaro, 1973 Mount and Stephan, 1967 Kariya et al., 1967 Brungs et al., 1973 Brungs et al., 1973 Mount, 1964 Mount, 1964 Lebedeva and Kuznetsova, 1969 Lebedeva and Kuznetsova, 1969 Hoss, 1964
Methyl mercury Pike Cadmium Bluegill Copper Carp Brown bullhead Zinc
Bluegill Carp Flounder
* Accumulation coefficient = tissue concentration /tg/g wet weight/water concentration /zg/ml. Little is known about the chronic toxicity of thallium and the tissue levels of thallium, resulting f r o m a chronic exposure. In fish exposed to metals in the laboratory, the accumulation factors of thallium are somewhat higher than those of other metals (Table 3). It can be seen that with the exception of methylmercury the accumulation coefficients are relatively low. N o data are available on the accumulation of thallium in shellfish, which are known to accumulate some heavy metals to a high degree. 189
POLLUTION POTENTIAL Bowen (1966) lists thallium together with silver, gold, cadmium, chromium, copper, mercury, lead, antimony, tin, and zinc as metals with a very high pollution potential. The rating is based on the ratio between the amount mined and the amount lost from the ocean per year. For all the above metals, with the exception of tin, this ratio is higher than 10. In the case of thallium it is 6,000 because of the very long residence time of thallium in the ocean (2.6 x 109 years). As in the case of other metals, human activity cannot change the concentration of thallium on the global scale, but localized pollution incidents, in which thallium contaminates the environment either intentionally or unintentionally, are possible. The intentional contamination includes the use of thallium compounds as rodenticides, which dates back to about 1920 (Munch, 1968). The high toxicity of these compounds resulted in the cancellation of their use against mammalian predators in the U.S.A. (Federal Register, 1972). Many countries, however, still use thallium compounds for this purpose. Saito and Masaharu (1972) reported that broadcast application of thallium sulfate did not cause water pollution. The rodenticidal application of thallium compounds may lead to accidental poisonings but is not likely to cause a major pollution problem and, in any case, will probably be phased out. The present industrial uses of thallium are limited and almost certainly do not generate pollution problems. This situation, however, could change, were the applications of thallium expanded. Thallium pollution may be a problem in the mining industry. As mentioned earlier, thallium is usually not recovered because of the limited market. In addition, the currently used wastewater treatment in the mining industry, aimed at the removal of heavy metals such as copper and zinc, and based on liming, would not remove thallium(I). Hawley (1972) suggested that metals such as gold, silver, selenium, thallium, indium, gallium, antimony, and arsenic may be present in effluents from base-metal mining operations. Zitko et al. (1975) reported thallium concentrations of 1-80/~g/l in two rivers draining base-metal mining properties in New Brunswick, Canada. Algae and moss from these rivers contained thallium in concentrations ranging from 9.5 to 162/~g/g dry weight. Thallium pollution may also be generated in the vicinity of smelters, particularly when thallium is not recovered. Mining of minerals other than sulfides, for example potash and silicates, may also release thallium into the environment. Coalfired power plants emit thallium in fly ash and the concentration of thallium increases from 5--45 #g/g in larger particles to 29-76 #g/g in airborne fly ash (Davison et al., 1974; Natusch et al., 1974). ACKNOWLEDGMENTS I thank Mrs. Madelyn M. Irwin for the efficient assistance in literature documentation, Miss M. Beryl Stinson and Mrs. Linda L. Morris for skillful librarian help. Mrs. Madelyn M. Irwin typed the manuscript. 190
REFERENCES Amend, D. F., W. T. Yasutake and R. Morgan, Trans. Amer. Fish. Soc., 98 (1969) 419. Antia, N. J., R. S. Kripps and I. D. Desai, Arch. Mikrobiol., 85 (1972) 341. Beletskaya, 1. P., K. P. Butin, A. N. Ryabtsev and O. A. Reutov, J. Organometal. Chem., 59 (1973) 1. Berman, E., At. Absorption Newslett., 6 (1967) 57. Bowen, H. J. M., Trace Elements in Biochemistry, Academic Press, New York, 1966. Britten, J. S. and M. Blank, Biochim. Biophys. Acta, 159 (1968) 160. Brungs, W. A., Jr., Trans. Amer. Fish. Soc., 98 (1969) 272. Brungs, W. A., Jr., E. N. Leonard and J. M. McKim, J. Fish. Res. Board Can., 30 (1973) 583. Burger, A. and K. Starke, Experientia, 25 (1969) 578. Christensen, H. E., N T I S PB-213 613, U.S. Dept. Commerce, Springfield, Va. 22151, 1972. Curry~ A. J., I. F. Reed and A. R. Knorr, Analyst, 94 (1969) 744. Davison, R. L., D. F. S. Natusch, J. R. Wallace and C. A. Evans, Jr., Environ. Sci. TechnoL, 8 (1974) 1107. De Jong, L, E. and W. B. Roman, Antonie van Leeuwenhoek J. Microbiol. SeroL, 37 (1971) 119. Dilling, W. J. and C. W. Healey, Ann. Appl. Biol., 13 (1926) 177. Dvorak, P., Z. Gesamte Exp. Med., 151 (1969) 89. Ellory, J. C., J. Nibelle and M. W. Smith, J. Physiol. (London), 231 (1973) 105. Federal Register, Fed. Regist., 37 (1972) 5718. Fogg, A. G., C. Burgess and D. T. Burns, Talanta, 18 (1971) 1175. Fogg, A. G., C. Burgess and D. T. Burns, Analyst, 98 (1973) 347. Gaskell, T. F., Chem. Ind. (London), (1971) 1149. Giblin, F. J. and E. J. Massaro, Toxicol. Appl. PharmacoL, 24 (1973) 81. Glasby, G. P., Marine Chem., 1 (1973) 105. Guenther, M., Arch. Toxikol., 28 (1971) 39. Hail, B. K., Can. J. Zool., 50 (1972) 1527. Hampel, C. A., The Encyclopedia of Chemical Elements, Reinhold, New York, 1968. Hawley, J. R., The Problems of Acid Mine Drainage in the Province of Ontario, Ont. Ministry of the Environment, Toronto, 1972. Henke, G. and G. Bohn, Arch. ToxicoL, 25 (1969) 48. Hoss, D. E., Trans. Amer. Fish. Soc., 93 (1964) 364. Hultin, T. and P. H. N~islund, Chem.-Biol. Interactions, 8 (1974) 315. Inturrisi, C. E., Biochim. Biophys. Acta, 173 (1969a) 567. Inturrisi, C. E. Biochim. Biophys. Acta, 178 (1969b) 630. Kamerbeek, H. H., A. G. Rauws, M. Ten Ham and A. N. P. Van Heijst, Acta Med. Scand., 189 (1971) 321. Kariya, T., Y. Haga, H. Haga and T. Tsuda, Nippon Suisan Gakkaishi, 33 (1967) 818. Kayne, F. J., Arch. Biochem. Biophys., 143 (1971) 232. Kirkbright, G. F., T. S. West and C. Woodward, Talanta, 12 (1965) 517. Kogan, B. I., Redk. Elem. (Rare Elements), 5 (1970) 27. Korenman, I. M., Analytical Chemistry of Thallium, Oldbourne Press, London, 1963. Kunz¢, M. and I. Pramberger, Zentralbl. Bakteriol. Parasitenk., lnfektionskr. Hyg., Abt. 1 (Orig., Reihe A), 222 (1972a) 548. Kunze, M. and I. Pramberger, Zentralbl. Bakteriol. Parasitenk., Infektionskr. Hyg., Abt. 1 (Orig., Reihe A), 222 (1972b) 535. Lallier, R., C.R. Acad. Sci. (Paris), Ser. D, 267 (1968) 962. Lange, N. A. and G. M. Forker, Handbook of Chemistry, McGraw-Hill, New York, 10th ed., 1967. Lazorenko, G. E. and G. G. Polikarpov, Radiats. Khim. Ekol. Gidrobiontov, (1972) 105. Lebedeva, G. D. and G. A. Kuznetsova, Gig. Sanit., 34 (1969) 119. Lindegren, C. C., J. Biol. Psychol., 13 (1971) 3. Lindegren, C. C. and G. Lindegren, J. Microbiol. Serol., 39 (1973) 351. Lishko, V. K., L. I. Kolchinskaya and N. T. Parkhomenko, Ukr. Biochim. Zh., 45 (1973) 42. Lloyd, R. and D. W. M. Herbert, J. Inst. Pub. Health Eng., (1962) 132. Malaehovskis, A., Liet. TSR Aukst. Mokyklu Mokslo Darb., Biol., 8 (1968) 23. Manners, J. P., K. G. Morallee and R. J. P. Williams, J. Chem. Soc. D, (1970) 965. Maslova, M. N., Yu. V. Natochin and I. A. Skul'skii, Biokhimiya, 36 (1971) 867. Matthews, A. D. and J. P. Riley, Chem. GeoL, 6 (1970) 149. 191
McKee, J. E. and H. W. Wolf, The Resources Agency of California, State Water Quality Control Board, Publication No. 3-A (1963). Merguet, P., H. J. Schuemann, T. Murata, J. G. Rausch-Stroomann, K. D. Bock and E. Schroeder Verh. Deut. Ges. Inn. Med., 74 (1968) 429. Merguet, P., H. Schuemann, T. Murata, J. G. Rausch-Stroomann, E. Schroeder, D. Paar and K. D. Bock, Arch. Klin. Med., 216 (1969) 1. Mount, D. I., Trans. Amer. Fish. Soc., 93 (1964) 174. Mount, D. I., Water Res., 2 (1968) 215. Mount, D. I. and C. E. Stephan, J. Wildl. Manag., 31 (1967) 168. Munch, J. C., in W. B. Duchmann (Ed.), Pesticide Symp., 1968-1970, p. 239. Natochin, Yu. V. and I. A. Skul'skii, Dokl. Akad. Nauk SSSR, 203 (1972) 1437. Natusch, D. F. S., J. R. Wallace and C. A. Evans, Jr., Science, 183 (1974) 202. Nazarenko, V. I., A. V. Palladin and V. K. Lishko, Ukr. Biokhim. Zh., 44 (1972) 139. Nehring, D., Z. Fisch., 11 (1962) 557. Nesmeyanov, A. N. and R. A. Sokolik, Methods of Elemento-Organic Chemistry Vol. 1, North Holland, Amsterdam, 1967. Oehme, F. W., Clin. Toxicol., 5 (1972) 151. Paolaggi, F., B. Lancon, C. Dreux and M. L. Girard, Ann. Biol. Clin. (Paris), 30 (1972) 279. Pickering, Q. H. and M. H. Gast, J. Fish. Res. Board Can., 29 (1972) 1099. Polikarpov, G. G., Proc. Syrup. Hydrogeochem. Biogeochem., 1 (1970) (Publ. 1973) 356. Robinson, K., in D. A. Brobst and W. P. Pratt (Eds.), U. S. Mineral Resources, Geological Survey Professional Paper 820; U.S. Government Printing Office, Washington, 1973, p. 631. Robinson, J. D., Arch. Biochem. Biophys., 139 (1970) 17. Rusznyak, I., L. Gyorgy, S. Ormai and T, Millner, Experientia, 24 (1968) 809. Saito, M. and K. Masaharu, Hokkaidoritsu Eisei Kenkyushoho, 22 (1972) 92. Scharrer, K., Biochemie der Spurenelemente, Parey, Berlin, 1955, Schmidt, F. J., D. R. Omilianowski and R. M. Bock, Biochemistry, 12 (1973) 4980. Sinko, I. and S. Gomiscek, Microchim. Acta, (1972) 163. Skul'skii, I. A., V. V. Glazunov, A. Ya Zesenko and A. A. Lyubimov, Tsitologiya, 14 (1972a) 849. Skul'skii, I. A., V. V. Giazunov, A. Ya Zesenko and A. A. Lyubimov, Biofizika, 17 (1972b) 824. Skul'skii, I. A., V. Manninen and J. Jarnefelt, Biochim. Biophys. Acta, 298 (1973) 702. Slepicka, J., V. Boschetty and J. Dluhos, Prac. Lek., 21 (1967) 67. Solt, J., H. Paschinger and E. Broda, Planta, 101 (1971) 242. Spencer, P. S., E. R. Peterson, R. A. Madrid and C. S. Raine, J. Cell Biol., 58 (1973) 79. Sprague, J. B., ~r. Fish. Res. Board Can., 21 (1964) 17. Srivastava, T. N., K. K. Bajpai and K. Singh, Indian J. Agr. Sci.~ 43 (1973) 88. Stevens, W., C. van Peteghem, A. Heyndrickx and F. Barbier, Int. J. Clin. Pharmacol., 10 (1974) 1. Tandon, S. P. and M. M. Mishra, Proc. Nat. Acad. Sci., lndia, Sect. A, 39 (Pt. 2) (1969) 209. Taylor, E. C. and A. McKillop, Accounts Chem. Res., 3 (1970) 338. Tikhonova, T. S., Nov. Dannye Toksikol. Redk. Metal. lkh. Soedin., (1967) 24. Tuovinen, O. H. and D. P. Kelly, Arch. Microbiol., 98 (1974) 167. Watanabe, T., O. Fujita and T. Horikawa, Bull. Tokyo Med. Dent. Univ., 18 (1971) 311. Zitko, V., W. V. Carson and W. G. Carson, Bull. Environ. Contam. Toxicol., 13 (1975) 23.
192
TOXICITY AND POLLUTION POTENTIAL OF THALLIUM
V. ZITKO
Department of Environment, Biological Station, St. Andrews, New Brunswick, EOG 2XO (Canada) (Received February 13th, 1975)
ABSTRACT
Toxicity and pollution potential of thallium are reviewed. Thallium is slightly more acutely toxic to mammals than mercury, and as acutely toxic as copper to fish. Its present industrial uses are too limited to generate pollution, but thallium, discharged in wastes from mines, ore-processing, and coal-burning plants, is contaminating the environment.
INTRODUCTION
Thallium is a relatively obscure metal with limited industrial applications. The average concentration of thallium in the lithosphere is 0.1-1.0 pg/g (Lange and Forker, 1967; Hampel, 1968), and 0.01-0.02 #g/1 in sea water (Matthews and Riley, 1970; Gaskell, 1971). Thallium ores are rare and the metal is recovered during processing of sulfide ores of lead, copper, and zinc, containing thallium in levels of up to 10 mg/g (Robinson, 1973). Relatively high levels of thallium are also present in manganese nodules (Glasby, 1973). The world production of thallium is 10-12 t/year (Kogan, 1970). The amount of recoverable thallium is much higher and the pollution potential of thallium should be judged on the basis of the amount released into the environment in wastes rather than on the basis of production. According to the author's estimate, 48 t/year of thallium may be present in wastes from zinc production in Canada. In its compounds thallium is either mono-(I) or trivalent(III). Thallium(I) is more stable and in some properties resembles closely the alkali metal cations. The solubility of thallium(l) hydroxide in water is 259 g/1 (Lange and Forker, 1967). Many organic compounds of thallium(III) are known and dimethyl thallium salts are very stable. The preparation and properties of organothallium compounds and the stability of their complexes have been reviewed (Nesmeyanov and Sokolik, 1967; Beletskaya et al., 1973). Industrial uses of thallium include alloys, electronic devices, and special glass. Thallium compounds are useful in synthetic organic chemistry (for a review see Taylor and McKillop, 1970) and many thallium-containing catalysts have been patented for industrial organic reactions. 185
Very extensive literature, including a monograph (Korenman, 1963), is available on analytical chemistry of thallium. Sensitive methods for the determination of thallium include spectrophotometry of ion-association complexes of thallium(III) and basic dyes (Fogg et al., 1971, 1973), fluorometry (Kirkbright et al., 1965), anodic stripping voltammetry (Sinko and Gomiscek, 1972; Paolaggi et al., 1972), and atomic absorption spectrophotometry (Curry et al., 1969; Shkolnik and Bevill, 1973). TOXICITY Thallium and its compounds are highly toxic. Human toxicity of thallium was recently reviewed by Oehme (1972). Thallium is absorbed through skin and mucous membranes, is widely distributed throughout the body and accumulates in bones, renal medulla and, eventually, in the central nervous system. Thallium passes through the placenta, occurs in milk, and is excreted mainly in urine. The biological half-life of thallium in man is 3-8 days. Toxic doses or concentrations of thallium and some other metals are summarized in Tables 1 and 2. It can be seen that in mammals thallium is slightly more acutely toxic than mercury and its toxicity is exceeded only by that of methyl mercu~. To fish thallium is as acutely toxic as copper on a weight basis, and 3 to 4 times more toxic than copper on a molar basis. Thallium kills fish quite slowly (Zitko et al., 1975) and this may explain the much higher toxic concentrations reported by Nehring (1962). Species differences, however, cannot be excluded. Hardness of water, which affects strongly the toxicity of metals to fish (see for example Lloyd and Herbert, 1962), may not have much effect on the toxicity of thallium because of its low complexing ability. For the same reason, humic acid probably does not affect the toxicity of thallium. The acute toxicities of copper and thallium, and of zinc and thallium to fish are not additive (Zitko et al., 1975). Hypertension is one of the symptoms of thallium poisoning in humans (Merguet et al., 1968, 1969) and in fish (Nehring, 1962). Burger and Starke (1969) suggest that this effect may be caused by the oxidation of thallium(I) to thallium(III) which inhibits the ATPase of amine-storing granules, thus causing alterations in the catecholamine metabolism. The uptake of thallium by yeast mitochondria (Linglen, 1971) and the formation of thallium(III) oxide in these (Lindgren and Lindgreu, 1973) confirm that oxidation of thallium in vivo takes place. It is not known to what extent this process is responsible for thallium toxicity. Thallium(III) catalyzed in vitro the iodination of cytidine residues in a transfer RNA (Schmidt et al., 1973), but it is not clear whether a similar reaction could also occur in vivo. Thallium(I) is able to substitute monovalent cations, particularly potassium, in enzymatic reactions. Thallium is isomorphic with potassium, but has approximately 10 times higher affinity than potassium for the enzymes. The increased affinity may cause the toxic effects. Thallium activation was demonstrated in the case of several enzymes. Britten and Blank (1968), Inturrisi (1969a, b), Robinson (1970), Maslova et al. (1971), Nazarenko et al. (1972), Skul'skii et al. (1973), and Lishko et al. (1973) studied the 186
TABLE 1 TOXIC DOSE OR C O N C E N T R A T I O N O F T H A L L I U M
Species
Effective dose or concentration
Effect
Reference
Mouse Mouse Mouse Rat Rat
24--27 16-19 0.5-1 13-19 6.5
LD50 LD50 15 days, measurable effects LD50 6 times in 14 days, measurable effects Lethal 3-6 months, measurable effects LD50 Lethal Lethal Lethal Lethal Lethal Lethal Growth inhibition Growth inhibition Growth inhibition
Christensen, 1972 Tikhonova, 1967 Tikhonova, 1967 Christensen, 1972 Malachovskis, 1968
Dog Rabbit Atlantic salmon Rainbow trout Perch Roach Tadpole Daphnia Gammarus Azotobacter Proteus mirabilis Aspergillus niger
mg/kg mg/kg mg/kg mg/kg mg/kg
15 mg/kg 0.2 mg/kg 0.03 mg/l 10-15 rag/1 60 rag/1 40-60 rag/1 0.4 mg/l 2--4 mg/l 4 mg/l 20 rag/1 390 mg/l 200 mg/l
Christensen, 1972 Tikhonova, 1967 Zitko et al., 1975 Nehring, 1962 Nehring, 1962 Nehring, 1962 Dilling and Healey, 1926 Nehring, 1962 Nehring, 1962 DeJong and Roman, 1971 Watanabe et al., 1971 Scharrer, 1955
TABLE 2 TOXIC DOSE OR C O N C E N T R A T I O N O F SOME HEAVY METALS
Metal (chloride or acetate)
Species
LDSO or LCSO mg[kg
mmole/kg
Mercury Methyl mercury Cadmium Lead Copper Zinc
Rat Mouse Rat Rat Rat Rat
27 13 54 150 445 875
0.13 0.06 0.48 0.46 7 13.4
Mercury Ethyl mercury Cadmium Lead Copper Zinc
Stickleback Rainbow trout F a t h e a d minnow Rainbow trout Minnow, salmon Minnow, salmon
rng/l 0.2 0.09 1.4--19 0.8-1.3 0.05-0.5 0.6-10
mmole/l 0.001 0.0005 0.012-0.17
0.005-0.006 0.0008-0.008 0.009-0.15
Reference
Christensen, Christensen, Christensen, Christensen, Christensen, Christensen,
1972 1972 1972 1972 1972 1972
McKee and Wolf, 1963 Amend et al., 1969 Pickering and Gast, 1972 Lloyd and Herbert, 1962 Sprague, 1964; Mount, 1968 Sprague, 1964; Brungs, 1969
187
effect of thallium on various sodium-potassium-sensitive ATPases, Manners et al. (1970) on a vitamin B~2-dependent diol dehydratase, Kayne (1971) on pyruvate kinase, homoserine dehydrogenase, and AMP deaminase, and Antia et al. (1972) on L-threonine dehydratase. In frog skin, thallium was tightly bound in the membrane and could not substitute potassium in the sodium-potassium pump system (Natochin and Skul'skii, 1972). The relative rate of uptake of monovalent cations by goldfish intestinal mucosa decreased in the order thallium > potassium > rubidium > cesium > sodium > lithium (Ellory et al., 1973), and thallium restarted the activity of an isolated frog heart (Rusznyak et al., 1968). In chick embryos thallium induced achondroplasia (Hall, 1972), which was potentiated by cortisone acetate and prevented by vitamin C. Enlarged mitochondria were observed after exposure to thallium in the axons of peripheral nerve fibers in mice (Spencer et al., 1973). Thallium was not able to substitute for potassium in mice ribosomes in vitro and inhibited amino acid incorporation into protein both in vivo and in vitro (Hultin and N~islund, 1974). Thallium inhibited the development of Paracentrotus lividus eggs (Lallier, 1968). Thallium is toxic to bacteria, but quite high levels are generally required for measurable effects. Thallium inhibited the nitrification by Nitrobacter agilis (Tandon and Mishra, 1969), and the growth of Thiobacillus ferroxidans in a potassium-free medium (Tuovinen and Kelly, 1974). Staphylococcus aureus was approximately 15 times more resistant than S. epidermis (Kunze and Pramberger, 1972a) and, in general, Mycoplasmataceae were more resistent than Acholeplasmataceae (Kunze and Pramberger, 1972b). Thallium is toxic to plants and inhibits chlorophyll formation and seed germination (Scharrer, 1955). In Chlorellafusca the uptake of thallium was increased by illumination, and additional light-independent absorption of thallium was also observed (Solt et al., 1971). Similar results were obtained with Ulva lactuca (Skul'skii et al., 1972a). In contrast to potassium metabolism, sodium fluoride inhibited the uptake of thallium(I) (Skul'skii et al., 1972b). On the other hand, the uptake of thallium(III) was independent of temperature, light or sodium fluoride (Polikarpov, 1970). The accumulation coefficients of thallium(I) and (III) were approximately 20 and 50, respectively, and an equilibrium was reached within 20 h (Polikarpov, 1970). Thallium was not adsorbed by alginic acid (Lazorenko and Polikarpov, 1972). Little is known about the toxicity of organothallium compounds. Diphenyl thallium chloride and cyanate were toxic to a number of pathogenic fungi (Srivastava et al., 1973). Antidotes against acute thallium poisoning were reviewed by Munch (1968) and included activated charcoal, BAL, calcium salts, cystine, dithiocarb, dithizone, histamine, theophylline, potassium chloride, and thiosulfate. Prussian blue and other hexacyanoferrates(II) were recently recommended as antidotes (Dvorak, 1969; Kamerbeek et al., 1971). A 2% colloidal solution of ferrihexacyanoferrate(II) increased the urinary excretion of thallium by a factor of 2.8, but only if administered during the first 24 h (Guenther, 1971). Stevens et al. (1974) used this treatment success188
fully on 11 cases of thallium intoxication. The excretion of thallium was also increased by D-penicillamine (Slepicka et al., 1969), and a chronic intoxication was somewhat alleviated by vitamin B12 (Malachovskis, 1968). Data on the concentration of thallium in tissues and organs of acutely poisoned humans and animals were reviewed by Munch (1968). In the majority of human cases, the amount of thallium taken was not known. The concentration of thallium in kidney and liver was 2.7-42 and 10-34 pg/g, respectively. Three subjects died as a result of thallium acetate poisoning (6.9 mg/kg, as thallium), and the concentration of thallium in kidney and liver was 60-79 and 482-862 pg/g. Berman (1967) found a thallium concentration of 300 #g/1 in blood, and 30-1240 #g/1 in urine of acutely poisoned subjects. In cases of animal poisoning, the thallium concentrations were 12-135, 7-140, 3-103, and 3-120 ktg/g in kidney, liver, muscle, and spleen, respectively (Munch, 1968). The concentration of thallium in urine, hair and toenails is a useful indicator of sublethal poisoning. Toenails are preferred to hair because they contain thallium in higher concentration (Henke and Bohn, 1969). TABLE 3 ACCUMULATION OF SOME METALS IN FISH DURING LABORATORY EXPOSURE Metal
Species
Tissue
Accumulation coefficient*
Reference
Thallium
Atlantic salmon
Muscle Liver Gills Kidney Gills Whole fish Gills Liver Muscle Gut, gill Muscle Gut, gill Whole fish
130 170 480 9,000 5-8 19-65 17 65 2 13 8 100 10
Zitko et al., 1975 Zitko et al., 1975 Zitko et al., 1975 Giblin and Massaro, 1973 Mount and Stephan, 1967 Kariya et al., 1967 Brungs et al., 1973 Brungs et al., 1973 Mount, 1964 Mount, 1964 Lebedeva and Kuznetsova, 1969 Lebedeva and Kuznetsova, 1969 Hoss, 1964
Methyl mercury Pike Cadmium Bluegill Copper Carp Brown bullhead Zinc
Bluegill Carp Flounder
* Accumulation coefficient = tissue concentration /tg/g wet weight/water concentration /zg/ml. Little is known about the chronic toxicity of thallium and the tissue levels of thallium, resulting f r o m a chronic exposure. In fish exposed to metals in the laboratory, the accumulation factors of thallium are somewhat higher than those of other metals (Table 3). It can be seen that with the exception of methylmercury the accumulation coefficients are relatively low. N o data are available on the accumulation of thallium in shellfish, which are known to accumulate some heavy metals to a high degree. 189
POLLUTION POTENTIAL Bowen (1966) lists thallium together with silver, gold, cadmium, chromium, copper, mercury, lead, antimony, tin, and zinc as metals with a very high pollution potential. The rating is based on the ratio between the amount mined and the amount lost from the ocean per year. For all the above metals, with the exception of tin, this ratio is higher than 10. In the case of thallium it is 6,000 because of the very long residence time of thallium in the ocean (2.6 x 109 years). As in the case of other metals, human activity cannot change the concentration of thallium on the global scale, but localized pollution incidents, in which thallium contaminates the environment either intentionally or unintentionally, are possible. The intentional contamination includes the use of thallium compounds as rodenticides, which dates back to about 1920 (Munch, 1968). The high toxicity of these compounds resulted in the cancellation of their use against mammalian predators in the U.S.A. (Federal Register, 1972). Many countries, however, still use thallium compounds for this purpose. Saito and Masaharu (1972) reported that broadcast application of thallium sulfate did not cause water pollution. The rodenticidal application of thallium compounds may lead to accidental poisonings but is not likely to cause a major pollution problem and, in any case, will probably be phased out. The present industrial uses of thallium are limited and almost certainly do not generate pollution problems. This situation, however, could change, were the applications of thallium expanded. Thallium pollution may be a problem in the mining industry. As mentioned earlier, thallium is usually not recovered because of the limited market. In addition, the currently used wastewater treatment in the mining industry, aimed at the removal of heavy metals such as copper and zinc, and based on liming, would not remove thallium(I). Hawley (1972) suggested that metals such as gold, silver, selenium, thallium, indium, gallium, antimony, and arsenic may be present in effluents from base-metal mining operations. Zitko et al. (1975) reported thallium concentrations of 1-80/~g/l in two rivers draining base-metal mining properties in New Brunswick, Canada. Algae and moss from these rivers contained thallium in concentrations ranging from 9.5 to 162/~g/g dry weight. Thallium pollution may also be generated in the vicinity of smelters, particularly when thallium is not recovered. Mining of minerals other than sulfides, for example potash and silicates, may also release thallium into the environment. Coalfired power plants emit thallium in fly ash and the concentration of thallium increases from 5--45 #g/g in larger particles to 29-76 #g/g in airborne fly ash (Davison et al., 1974; Natusch et al., 1974). ACKNOWLEDGMENTS I thank Mrs. Madelyn M. Irwin for the efficient assistance in literature documentation, Miss M. Beryl Stinson and Mrs. Linda L. Morris for skillful librarian help. Mrs. Madelyn M. Irwin typed the manuscript. 190
REFERENCES Amend, D. F., W. T. Yasutake and R. Morgan, Trans. Amer. Fish. Soc., 98 (1969) 419. Antia, N. J., R. S. Kripps and I. D. Desai, Arch. Mikrobiol., 85 (1972) 341. Beletskaya, 1. P., K. P. Butin, A. N. Ryabtsev and O. A. Reutov, J. Organometal. Chem., 59 (1973) 1. Berman, E., At. Absorption Newslett., 6 (1967) 57. Bowen, H. J. M., Trace Elements in Biochemistry, Academic Press, New York, 1966. Britten, J. S. and M. Blank, Biochim. Biophys. Acta, 159 (1968) 160. Brungs, W. A., Jr., Trans. Amer. Fish. Soc., 98 (1969) 272. Brungs, W. A., Jr., E. N. Leonard and J. M. McKim, J. Fish. Res. Board Can., 30 (1973) 583. Burger, A. and K. Starke, Experientia, 25 (1969) 578. Christensen, H. E., N T I S PB-213 613, U.S. Dept. Commerce, Springfield, Va. 22151, 1972. Curry~ A. J., I. F. Reed and A. R. Knorr, Analyst, 94 (1969) 744. Davison, R. L., D. F. S. Natusch, J. R. Wallace and C. A. Evans, Jr., Environ. Sci. TechnoL, 8 (1974) 1107. De Jong, L, E. and W. B. Roman, Antonie van Leeuwenhoek J. Microbiol. SeroL, 37 (1971) 119. Dilling, W. J. and C. W. Healey, Ann. Appl. Biol., 13 (1926) 177. Dvorak, P., Z. Gesamte Exp. Med., 151 (1969) 89. Ellory, J. C., J. Nibelle and M. W. Smith, J. Physiol. (London), 231 (1973) 105. Federal Register, Fed. Regist., 37 (1972) 5718. Fogg, A. G., C. Burgess and D. T. Burns, Talanta, 18 (1971) 1175. Fogg, A. G., C. Burgess and D. T. Burns, Analyst, 98 (1973) 347. Gaskell, T. F., Chem. Ind. (London), (1971) 1149. Giblin, F. J. and E. J. Massaro, Toxicol. Appl. PharmacoL, 24 (1973) 81. Glasby, G. P., Marine Chem., 1 (1973) 105. Guenther, M., Arch. Toxikol., 28 (1971) 39. Hail, B. K., Can. J. Zool., 50 (1972) 1527. Hampel, C. A., The Encyclopedia of Chemical Elements, Reinhold, New York, 1968. Hawley, J. R., The Problems of Acid Mine Drainage in the Province of Ontario, Ont. Ministry of the Environment, Toronto, 1972. Henke, G. and G. Bohn, Arch. ToxicoL, 25 (1969) 48. Hoss, D. E., Trans. Amer. Fish. Soc., 93 (1964) 364. Hultin, T. and P. H. N~islund, Chem.-Biol. Interactions, 8 (1974) 315. Inturrisi, C. E., Biochim. Biophys. Acta, 173 (1969a) 567. Inturrisi, C. E. Biochim. Biophys. Acta, 178 (1969b) 630. Kamerbeek, H. H., A. G. Rauws, M. Ten Ham and A. N. P. Van Heijst, Acta Med. Scand., 189 (1971) 321. Kariya, T., Y. Haga, H. Haga and T. Tsuda, Nippon Suisan Gakkaishi, 33 (1967) 818. Kayne, F. J., Arch. Biochem. Biophys., 143 (1971) 232. Kirkbright, G. F., T. S. West and C. Woodward, Talanta, 12 (1965) 517. Kogan, B. I., Redk. Elem. (Rare Elements), 5 (1970) 27. Korenman, I. M., Analytical Chemistry of Thallium, Oldbourne Press, London, 1963. Kunz¢, M. and I. Pramberger, Zentralbl. Bakteriol. Parasitenk., lnfektionskr. Hyg., Abt. 1 (Orig., Reihe A), 222 (1972a) 548. Kunze, M. and I. Pramberger, Zentralbl. Bakteriol. Parasitenk., Infektionskr. Hyg., Abt. 1 (Orig., Reihe A), 222 (1972b) 535. Lallier, R., C.R. Acad. Sci. (Paris), Ser. D, 267 (1968) 962. Lange, N. A. and G. M. Forker, Handbook of Chemistry, McGraw-Hill, New York, 10th ed., 1967. Lazorenko, G. E. and G. G. Polikarpov, Radiats. Khim. Ekol. Gidrobiontov, (1972) 105. Lebedeva, G. D. and G. A. Kuznetsova, Gig. Sanit., 34 (1969) 119. Lindegren, C. C., J. Biol. Psychol., 13 (1971) 3. Lindegren, C. C. and G. Lindegren, J. Microbiol. Serol., 39 (1973) 351. Lishko, V. K., L. I. Kolchinskaya and N. T. Parkhomenko, Ukr. Biochim. Zh., 45 (1973) 42. Lloyd, R. and D. W. M. Herbert, J. Inst. Pub. Health Eng., (1962) 132. Malaehovskis, A., Liet. TSR Aukst. Mokyklu Mokslo Darb., Biol., 8 (1968) 23. Manners, J. P., K. G. Morallee and R. J. P. Williams, J. Chem. Soc. D, (1970) 965. Maslova, M. N., Yu. V. Natochin and I. A. Skul'skii, Biokhimiya, 36 (1971) 867. Matthews, A. D. and J. P. Riley, Chem. GeoL, 6 (1970) 149. 191
McKee, J. E. and H. W. Wolf, The Resources Agency of California, State Water Quality Control Board, Publication No. 3-A (1963). Merguet, P., H. J. Schuemann, T. Murata, J. G. Rausch-Stroomann, K. D. Bock and E. Schroeder Verh. Deut. Ges. Inn. Med., 74 (1968) 429. Merguet, P., H. Schuemann, T. Murata, J. G. Rausch-Stroomann, E. Schroeder, D. Paar and K. D. Bock, Arch. Klin. Med., 216 (1969) 1. Mount, D. I., Trans. Amer. Fish. Soc., 93 (1964) 174. Mount, D. I., Water Res., 2 (1968) 215. Mount, D. I. and C. E. Stephan, J. Wildl. Manag., 31 (1967) 168. Munch, J. C., in W. B. Duchmann (Ed.), Pesticide Symp., 1968-1970, p. 239. Natochin, Yu. V. and I. A. Skul'skii, Dokl. Akad. Nauk SSSR, 203 (1972) 1437. Natusch, D. F. S., J. R. Wallace and C. A. Evans, Jr., Science, 183 (1974) 202. Nazarenko, V. I., A. V. Palladin and V. K. Lishko, Ukr. Biokhim. Zh., 44 (1972) 139. Nehring, D., Z. Fisch., 11 (1962) 557. Nesmeyanov, A. N. and R. A. Sokolik, Methods of Elemento-Organic Chemistry Vol. 1, North Holland, Amsterdam, 1967. Oehme, F. W., Clin. Toxicol., 5 (1972) 151. Paolaggi, F., B. Lancon, C. Dreux and M. L. Girard, Ann. Biol. Clin. (Paris), 30 (1972) 279. Pickering, Q. H. and M. H. Gast, J. Fish. Res. Board Can., 29 (1972) 1099. Polikarpov, G. G., Proc. Syrup. Hydrogeochem. Biogeochem., 1 (1970) (Publ. 1973) 356. Robinson, K., in D. A. Brobst and W. P. Pratt (Eds.), U. S. Mineral Resources, Geological Survey Professional Paper 820; U.S. Government Printing Office, Washington, 1973, p. 631. Robinson, J. D., Arch. Biochem. Biophys., 139 (1970) 17. Rusznyak, I., L. Gyorgy, S. Ormai and T, Millner, Experientia, 24 (1968) 809. Saito, M. and K. Masaharu, Hokkaidoritsu Eisei Kenkyushoho, 22 (1972) 92. Scharrer, K., Biochemie der Spurenelemente, Parey, Berlin, 1955, Schmidt, F. J., D. R. Omilianowski and R. M. Bock, Biochemistry, 12 (1973) 4980. Sinko, I. and S. Gomiscek, Microchim. Acta, (1972) 163. Skul'skii, I. A., V. V. Glazunov, A. Ya Zesenko and A. A. Lyubimov, Tsitologiya, 14 (1972a) 849. Skul'skii, I. A., V. V. Giazunov, A. Ya Zesenko and A. A. Lyubimov, Biofizika, 17 (1972b) 824. Skul'skii, I. A., V. Manninen and J. Jarnefelt, Biochim. Biophys. Acta, 298 (1973) 702. Slepicka, J., V. Boschetty and J. Dluhos, Prac. Lek., 21 (1967) 67. Solt, J., H. Paschinger and E. Broda, Planta, 101 (1971) 242. Spencer, P. S., E. R. Peterson, R. A. Madrid and C. S. Raine, J. Cell Biol., 58 (1973) 79. Sprague, J. B., ~r. Fish. Res. Board Can., 21 (1964) 17. Srivastava, T. N., K. K. Bajpai and K. Singh, Indian J. Agr. Sci.~ 43 (1973) 88. Stevens, W., C. van Peteghem, A. Heyndrickx and F. Barbier, Int. J. Clin. Pharmacol., 10 (1974) 1. Tandon, S. P. and M. M. Mishra, Proc. Nat. Acad. Sci., lndia, Sect. A, 39 (Pt. 2) (1969) 209. Taylor, E. C. and A. McKillop, Accounts Chem. Res., 3 (1970) 338. Tikhonova, T. S., Nov. Dannye Toksikol. Redk. Metal. lkh. Soedin., (1967) 24. Tuovinen, O. H. and D. P. Kelly, Arch. Microbiol., 98 (1974) 167. Watanabe, T., O. Fujita and T. Horikawa, Bull. Tokyo Med. Dent. Univ., 18 (1971) 311. Zitko, V., W. V. Carson and W. G. Carson, Bull. Environ. Contam. Toxicol., 13 (1975) 23.
192
