The maximum permissible concentrations in the U.S.S.R. for harmful substances in drinking water

Toxicology, 1 ( 1 9 7 3 ) 1 8 7 - 195 © Elsevier/North-Holland, Amsterdam - - Printed in The Netherlands

THE MAXIMUM PERMISSIBLE CONCENTRATIONS IN THE U.S.S.R. F O R H A R M F U L SUBSTANCES IN D R I N K I N G WATER*

D. S T O F E N 543 Montabaur, Westerwaldstrasse 1 (W. Germany) (Received May 15th, 1973)

SUMMARY

The paper lists the 294 maximum permissible concentrations in the U.S.S.R. for harmful substances in drinking water decreed in 1970. The list covers toxic substances, organoleptic substances~ and substances which impair the self-purification of water courses. It is supplemented by a short survey of the history of U.S.S.R. water hygiene and gives an example showing the practice of the Russian toxicologists in assessing the limits for toxic substances. Reflexologic tests are used. The few World Health Organization limits for harmful substances are compared with the corresponding Russian values. Mostly the limits do not show any considerable differences.

INTRODUCTION

It is known that the WHO has included some tentative limits for toxic and other substances in drinking water in its "European Standards for Drinking Water ( 1 9 7 0 ) " and in its "International Standards for Drinking Water (1971)". Less known is that the U.S.S.R. has already decreed 294 limits for harmful substances in the same medium. These limits cover: (1) toxic substances (Table III); (2) substances which influence smell, taste, and colouring (Table V); (3) substances which effect changes in the process of self-purification in watercourses (Table IV). It is n o t e w o r t h y that the Russian limits for drinking water mostly do not differ considerably from those proposed by the WHO, whereas the American and U.S.S.R. threshold limit values for atmospheric pollutants in industrial premises differ, on average, by a b o u t a factor of 10. The Russian list covers * Published with the permission of the Schriftleitung "Stadtehygiene", M.L. Verlag, Uelzen (W. Germany). Abbreviation: WHO, World Health Organization.

187

several organic metal compounds and biocides and contains provisions for the combined effects of several substances. A survey of the development of U.S.S.R. water hygiene has been supplied by Cherkinskii 1 . In 1944 and 1945 scientifically based criteria for the quality of drinking water have been published. At that time the microbiological aspects received priority consideration, but in the assessment of the limits for Pb and As reflexological investigations were used already then. In 1972 the actual principles and methods for the assessment of the permissible limits have been reported by Cherkinskii 1. The definitive limit list was decreed in 1970. Objections against the U.S.S.R. values are of course possible. That most values cannot be checked by epidemiological investigations, seems to be inevitable. Experience in animals may often not apply to humans. The threshold doses for the carcinogenic, teratogenic and other genetic effects remain open problems also in the U.S.S.R. But even the functional disturbances induced by poisons, though mostly having distinct threshold limits, appear to be uncertain, because the Russian toxicologists have failed, for instance, to take account of the special problems of infants and children associated with their higher metabolic rate and therefore higher intake of drinking water per kg body weight. It is known that in Western countries, and perhaps also partly in the U.S.S.R., the food of infants is mostly prepared from dry milk and drinking water. Williams 7 has calculated the oral lead intake of infants aged 1--2 months to average 14 pg/kg, if the water contains 0.1 mg/1 Pb corresponding to the WHO limit. Under the same conditions the oral lead intake of adults amounts to 6 or 7 pg/kg. Still more important seems to be the possibly considerably higher gastro-intestinal lead a b s o r p t i o n in infants. In the research of Kostial e t al. 4 infant rats absorbed up to 55 times as much Ca and Pb as adult rats (4 months of age}, lactating rats 3.5 times as much Ca and Pb as non-pregnant rats 5. A further example of the greater sensitivity of infants is presented by the nitrates and their effect on methaemoglobinaemia in infants. The way in which the Russian toxicologists assess the limits for harmful substances in drinking water may be illustrated by a summary of the paper of F o m e n k o 3, which covers the scientific basis for the limit of tetrachlorobenzene (4-ChB) in drinking water. After havmg determined that the upper limit of the solubility of 4-ChB in normal and distilled water lay between 0.16 and 0.36 mg/1, the odour threshold was found to be 0.006 and the taste threshold to be 0.0064 mg/1. As small and taste of 4-ChB are n o t specific and easily mingle with those of stale water, the practical organoleptic threshold was fixed at 0.013 mg/1. The stability of the poison was tested by tracing the constancy of the smell in tap water. Values between 0.08 and 0.16 mg/1 influence the biochemical oxygen utilization and the nitrification. The oral LDso was found to be 1500 mg/1 for rats and rabbits. In the acute toxicological experiment the investigator observed adynamia, damage of the sphincters, clinical jerks, vascular damage etc. The phenomena 188

pointed to a primary narcotic action of the poison. Accumulation was inferred because 50% of an animal group died after 5 applications of 1/5 of the LDso. In the subacute experiment (1/20 of the LD5o daily for 2 months} the whole metabolism, expressed as the 0 2 consumption, rapidly fell. The prothrombin index of the liver fell to 2/3 of the normal value. The cholinesterase activity increased. The number of the reticulocytes fell initially and later rose. At the end of the experiment an increase of macrocytic erythrocytes, some decrease in the K level of the blood, a reduction of the free SH-groups in the blood serum, h y p e r t r o p h y of the suprarenal glands and decrease of their content in ascorbic acid were to be noted. Pathological findings differed little from those of the controls. The experience of other investigators with similar substances (2-ChB, 3ChB, and 6-ChB) induced the author to use in the chronic experiment daily doses of 0.001, 0.002, and 0.005 mg/kg 4-ChB (corresponding to a b o u t 0.02, 0.04, and 0.1 mg/l water} for 8 months and to determine the changes in "conditioned reflexes" in white rats and the changes in b o d y weight, in the state of health, in the morphology of the white and red blood cells, in the serum content of SH-groups, in the protein and glycogen synthesis by the liver, in the cholinesterase activity in the blood, and in the weight coefficients of different organs in rabbits. All parameters were affected except the number of the reticulocytes and the haemoglobin values. In the final assessment 0.02 mg/1 4-ChB was proposed as maximum permissible limit. In Table III it is shown as 0.01 mg/1, a value which obviously

TABLE I WHO LIMITS FOR TOXIC SUBSTANCES IN PIPED WATER SUPPLIES COMPARED WITH THE CORRESPONDING U.S.S.R. VALUES IN mg/l WHO

limits

Substance

Lead (as Pb) Arsenic (as As) Selenium (as Se) Chromium (Cr 6) Chromium (Cr 3) Cadmium Cyanide (as CN) Mercury (as Hg)

U.S.S.R. values

European

International

0.1 a 0.05 0.01 0.05 -0.01 0.05 --

0.1 0.05 0.01

0.01 0.05 0.001

0.1 (TEL: nil) 0.05 (org. compounds excluded) 0.001 (SeO3) 0.1 (organol. limit) 0.5 (organol. limit) 0.01 b 0.1 (ferrocyanides excluded) 0.005 (inorg. compounds only}

a Where water undertakings still use lead piping, concentrations may be higher, but in no instances higher than 0.3 mg/1 after 16 h contact with the pipes. b In view of impairment of self-purification in watercourses.

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T A B L E II WHO LIMITS F O R S U B S T A N C E S A F F E C T I N G T H E ACCEPTABILITY O F W A T E R F O R D O M E S T I C P U R P O S E S C O M P A R E D WITH T H E C O R R E S P O N D I N G U.S.S.R. V A L U E S IN m g / l Substance

WHO limits European limit

U.S.S.R. limits International Limit

Desirable maximum

Phenolic c o m p o u n d s (as p h e n o l ) F l u o r i d e (as F) Nitrate (as NO3)

0.001

0.001

0.002

0.001

1.O--1.7 a 50---100

---

0.8--1.7 a --

Copper (as Cu) e Iron (as F e ) e Manganese (as Mn) Zinc (as Zn) Magnesium (as Mg)

0.05 0.1 0.05 5.0 30-125 b

0.05 0.1 0.05 5.0 30--125 b

1.5 1.0 0.5 15.0 150

1.5 (toxicol. limit) 10 (as N) (toxicol. limit) 0.1 0.5 -1.0 --

Sulfate (as SO4)

250

200

400

--

H y d r o g e n sulfide (as H2S ) Chloride (as C1 )e Chlorine, free Anionic detergents

0.05

--

--

Sulfides: Nil c

200--600 -0.2

200 -0.2

600 -1.0

-Nil d Single det. in Table V

0.05 nil ----

--75 0.001 --

--200 0.002 --

2.0 (as N) --0.1 0.3

A m m o n i a (as NH4) Carbon dioxide, free Calcium (as Ca) Mineral oil Mineral oil with high S content a b c d e

D e p e n d i n g on temperature. Depending on SO 4 concentration. In view o f 0 2 regime u n d e r winter conditions. In view of C1 d e m a n d in the w a t e r of watercourses. Under certain circumstances higher levels.

a g r e e s b e t t e r w i t h t h e r e s u l t s o f t h e e x p e r i m e n t s ; i t is n o t e w o r t h y that this l i m i t is a l i t t l e h i g h e r t h a n t h e s m e l l a n d t a s t e t h r e s h o l d s . Finally it may be remarked that the (organoleptic) tolerance limit for c r u d e o i l ( 0 . 1 , r e s p e c t i v e l y 0 . 3 m g / 1 ) is c e r t a i n l y t o o h i g h , b u t i t is a b o u t t o b e r e c o n s i d e r e d 6. T h i s m a y a p p l y t o o t h e r l i m i t s t o o .

190

TABLE III TOXICOLOGIAL LIMITS IN THE U.S.S.R. IN mg/l No.

No. a Substance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

5 6 2 51 29 61 4 3 70 48 7 8 92 83 84 85 41 40 86 87 89 90 91 88 21 31 20 32

29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

33 35 36 37 34 22 23 24 25 26 27 28 30 93 94 95 79 290

47

291

48

292

49

293

50

289

Limit

Acetone cyanohydrin 0.001 Acetophenone 0.1 Acrylic acid 0.5 Acrylonitrile 2.0 Adipic acid dinitrile 0.1 A m m o n i u m perchlorate 5.0 Aniline 0.1 Anisol 0.05 Antimony 0.05 Arsenic (As3) h 0.05 Benzene 0.5 Beryllium (Be 2) 0.0002 Carbon tetrachloride 0.3 m-Chloraniline 0.2 p-Chloraniline 0.2 Chlorobenzene 0.02 Cobalt (Co 2) 1.0 Crotonitrile 0.1 Cyanides c 0.1 Cyclohexane 0.1 Cyclohexanol 0.5 Cyclohexanone 0.2 Cyclohexanone oxime 1.0 Cyclohexene 0.02 DDT 0.1 Dibutyl tin chloride 0.002 Dibutyl tin dilaurate 0.1 2,3-Dichloro-l,4-naphtho- 0.25 quinone Diethylamine 2.0 Diethyleneglycol 1.0 Diethyl ether maleate 1.0 Diethyl mercury 0.0001 Diethyl tin dicaprylate 0.01 Diisopropylamine 0.5 m-Diisopropylbenzene 0.05 p-Diisopropylbenzene 0.05 Dimethylamine 0.1 Dimethyldioxane 0.005 Dimethyldithiocarbamate 0.5 Dimethylphenylcarbinol 0.05 2,4-Dinitrophenol 0.03 Epichlorohydrin 0.01 Ethylene glycol 1.0 Ethylmercuric chloride 0.0001 Ferrocyanides 1.25 Flocculation agent VA-2 0.5 (polystyrene) Flocculation agent VA-2- 0.5 T (polyvinyl toluene) Flocculation agent 2.0 VA-102 d Flocculation agent 2.0 VA-212 d Flotation agent OPS-M d 0.5

a In the Russian original. b Organic compounds excluded.

i No.

No. a Substance

51 52 53 54 55 56 57 58 59 60 61 62 63

81 80 82 18 19 14 12 13 15 16 38 39 17

64 65 66

67 42 66

67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101

43 44 45 46 47 49 50 55 56 52 53 54 57 60 58 78 62 294 64 63 59 68 1 69 71 72 74 73 65 75 76 11 77 9 10

Limit

Fluorine e 1.5 Formaldehyde 0.5 Furan 0.2 Heptachlor 0.05 Heptyl alcohol 0.005 Hexochlorobenzene 0.05 Hexamethylene diamine 0.01 Hexanate 5.0 Hexogen 0.1 Hydrazine 0.01 Isocrotonitrile 0.1 Isopropylamine 2.0 Isopropylbenzene 0.5 hydroperoxide Lead (Pb 2) (see TEL) 0.1 2,5-Lutidine 0.05 Mercury (Hg2)-inorg. 0.005 comp. Meta-acrylamide 0.1 Methyl acetate 0.1 Methylol meta-acrvlamide 0.1 Molybdenum (Mo 6) 0.5 Monomethylamine 1.0 ~-Naphthol 0.4 Nitrates (as N) 10.0 Nitrochlorobenzene 0.05 Nitrocyclohexane 0.1 m-Nitrophenol 0.06 o-Nitrophenol 0.06 p-Nitrophenol 0.02 Nonyl alcohol 0.01 Pentanate 2.5 p-Phenylenediamine 0.1 Phenylhydrazine 0.01 ~-Picoline 0.05 Polyacrylamide 2.0 Polychloropinene 0.2 Pyridme 0.2 p-Quinone dioxime 0.1 Selenium (SeO 2 ) 0.001 Sodium adipate 1.0 Strontium (stable) 2.0 Tellurium (Te 2) 0.01 Tetrachlorobenzene 0.01 Tetraethyl lead Nil Tetraethyl tin 0.0002 Thiocyanates 0.1 Triethylamine 2.0 Trifluorochloropropane 0.1 Tungsten 0.1 Urotropin 0.5 Vanadium (V 5) 0.1 Vinyl acetate 0.2

c Except ferrocyanides. d Not identified by the author. e Compounds included.

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TABLE IV LIMITS F OR SUBSTANCES WHICH A F F E C T THE SELF-PURIFICATION OF WATER COURSES IN mg]l No.

No. a Substance

102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117

131 97 96 98 99 109 107 108 133 113 101 102 103 104 105 120

118 119 120 121

115 119 288 112

Acetic acid b Acetone b A m m o n i a ( a s N) Benzoic acid Butyl acetate Butyric acid b Cadmium (Cd 2) Caprolactam Chlorine, free Copper (Cu 2) Dibutyl phthalate Dimethyl formamide Dinitrothiocyanobenzene Dioctylphthalate Diphenylguanidine Diphenyl guanidine chloride Ethyleneglycol ethyl ether Fatty acids, synthetic b Flotation agent OPS-B d Formic acid b

Limit

2.0 0.1 0.01 1.0 Nil c 0.1 0.2 10.0 0.5 1.0 1.0 1.0 1.0 _ 2.0

No.

No. a Substance

Limit

122

100

1.0

123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141

106 111 110 114 116 117 132 118 129 121 123 124 122 125 126 127 128 130 134

Hexamethylene diamine adipate (nylon salt) Isobutyl alcohol Lactic acid b Methanol Methyl pyrrolidone Nickel (Ni 2) Norsulfazole Phthalic acid Propylene glycol b Sodium trichloracetate Streptocide Sulfides e Sulfodimezine Sulgin Terephthalic acid Tetrahydrofuryl alcohol Titanium (Ti) Trinitrotoluene Triethyleneglycol b Zinc (Zn 2)

1.0

0.5 0.1 0.1 0.5 5.0 0.5 Nil 1.0 0.01 0.1 0.5 0.1 0.5 1.0

a In the Russian original. b Within the limits for content of organic substances in the water of water courses and on the basis o f the biological 02 demand and O 2 utilization. c In view of the Cl demand of the water in water courses. d Not identified by the author. e In view o f the 02 regime under winter conditions.

192

TABLE V ORGANOLEPTIC LIMITS IN THE U.S.S.R. IN mg/l No.

No. a Substance

Limit

No.

No. a Substance

142 143 144

142 143 136

0.2 0.03 0.002

145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166

137 138 139 281 282 283 140 141 135 144 145 146 149 147 148 194 191 236 192 274 262 270

189 190 191 192 193

177 178 181 182 183

194

160

195 196 197 198

185 162 158 159

199

221

200 201 202 203 204 205 206

161 164 166 165 170 167 284

167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188

271 269 264 267 266 265 268 272 273 168 215 216 275 157 171 172 173 174 175 179 180 176

207 208 209 210 211 212 213 214 215 216 217 218 219

169 280 276 278 277 285 286 287 261 151 152 153 154

220 221 222 223 224 225

155 156 186 187 188 190

226

189

227 228

193 196

Acetaldehyde Acetophos Aldrin Aliphatic amines: C7--C 9 C10--C16 C16--C20 Alkyl benzenesulfonates Alkyl sulfates Alkyl sulfonates o-Aminophenol p-Aminophenol Avadex Barium Benzine Butyl acrylate Butyl alcohol Butyl benzene Butylene Butyl xanthate Carbine Carbon disulfide Carbophos Celatox Chloranil "Khlorendikovyi angridid"b Chlorocyclohexane Chloroheptanoic acid Chloronitrocyclohexane Chlorononanoic acid Chlorophos Chloroprene Chloroundecanoic acid Chromium (Cr 6) C h r o m i u m ( C r 3) Cresyl dithiophosphate Crude oil, high S content Other crude oil Cyanuric acid Dalapon 3,4-Dichloraniline 2,5-Dichloraniline o-Dichlorbenzene p-Dichlorbenzene Dichlorobutene Dichlorocyclohexane Dichloroethane Dichlorohydrin

0.1 0.04 0.03 0.5 0.5 0.5 0.01 0.05 0.03 4.0 0.1 0.015 1.0 0.1 0.2 0.001 0.03 1.0 0.05 0.5 0.01 1.0 0.05 0.05 0.005 0.3 0.05 0.1 0.1 0.1 0.5 0.001 0.1 0.3 6.0 2.0 0.05 0.05 0.002 0.002 0.05 0.02 2.0 1.0

Limit

Dichloromethane 7.5 Dichlorophenol 0.002 Dicyanodiamide 10.0 Diethanolamine 0.8 Diethyl phosphorodithioic acid 0.2 Dichlorovinyl dimethyl phosphate 1.0 Diethyl ether 0.3 Diisobutylamine 0.07 Dikotex 0.25 Dimethyldithiophosphoric acid 0.1 o-Dimethyl-s-ethylmercaptodithiophosphate (M-81) 0.001 Dimethyl terephthalate 1.5 Dinitrobenzene 0.5 Dinitrochlorobenzene 0.5 Dinitronaphthalene 1.0 Diphenylolpropane 0.01 Dipropylamine 0.5 Disodium monoalkylsulfosuccinate 0.5 Diuron 1.0 Ether sulfonate 0.2 Ethyl acrylate 0.005 Ethyl benzene 0.01 Ethylene 0.5 Flotation agent APN b 0.05 Flotation agent OP-7 b 0.4 Flotation agent OP-10 b 1.5 Furfurol 1.0 Hexachlorane 0.02 Hexachlorobutadiene 0.01 Hexachlorobutane 0.01 Hexachlorocyclopentadiene 0.001 Hexachlorethane 0.01 Hydroquinone 0.2 Iron (Fe 2) 0.5 Isobutylene 0.5 Isoprene 0.005 Isopropylchlorophenylcarbamate 1.0 Isopropylphenylcarbamate 0.2 Kerosine 0.1 Maleic acid 1.0

193

TABLE V (continued) No.

No. a Substance

229 230 231 232 233

197 198 199 200 201

234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258

259 260

Limit

No.

No. a Substance

5-Mercaptodiethylamine 0.1 Mercaptophos 0.01 Metaphos 0.02 Methyl acrylate 0.02 Methyl dithiocarbamate (carbathione) 0.02 206 Methyl ethyl ketone 1.0 202 Methylnitrophos 0.25 204 Methylsystox 0.01 205 ~-Methylstyrene 0.1 209 Monochlorohydrin 0.7 210 Monoethylamine 0.5 208 Monopropylamine 0.5 207 Monosodiumcyanurate 25.0 211 Monuron 5.0 214 ~-Naphthol 0.1 213 Naphthonic acids 0.3 220 Nitroform 0.01 219 p-Nitrophenylacetylaminoethanol 1.0 217 p-Nitrophenylaminoethanol (oxyamine) 0.5 218 p-Nitrophenylchloromethylcarbinol 0.2 222 Pentachlorobutane 0.02 223 Pentachlorophenol 0.3 257 Phenol c (carbolic acid) 0.001 258 Phosbutyl 0.03 259 Phosphamide 0.03 260 Phthalophos 0.2 225 Picric acid 0.5 228 Polyethylhydrosiloxane (HOB-94) 10.0 229 Polyethylsiloxane 10.0 227 Polymethyldichlorophenylhydrosiloxane (ChS-2-1) 10.0 226 Polymethylhydrosiloxane (HOB-94M) 2.0 184 Potassium diethylphosphorodithioate 0.5

261

163

262 263 264 265 266 267 268 269

230 231 232 233 234 235 237 238

270 271

263 212

272

279

273

203

274

224

275

150

276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294

240 248 243 244 245 246 247 241 242 249 250 251 252 255 253 256 254 239 195

Potassmm diisopropyldithiophosphate 0.02 Prometrine 3.0 Propazine 1.0 Propylbenzene 0.2 Propylene 0.5 Saponin 0.2 Sevin 0.1 Simazine (undissolved) Nil Simazine, 2-oxyderivative (undissolved) Nil Sodium chlorate 20.0 Sodium dichlorophenoxyacetate (Na-2,4D) 1.0 Sodium ethylsiliconate (HOB-10) 2.0 Sodium methylsiliconate (HOB-11) 2.0 Sodium pentachlorophenolate 5.0 Sodium vinylsiliconate (HOB-12) 2.0 Styrene 0.1 Tetrachlorethane 0.2 Tetrachloroheptane 0.0025 Tetrachlorononane 0.003 Tetrachloropentane 0.005 Tetrachloropropane 0.01 Tetrachloroundecane 0.007 Tetrahydroquinone 0.05 Tetranitromethane 0.5 Thiophene 2.0 Thiophos 0.003 Toluene 0.5 Tributyl phosphate 0.01 Trichlorethylene 0.5 Trichlorometaphos-3 0.4 Trichlorophenol 0.0004 Triethanolamine 1.4 Turpentine 0.2 Xylene 0.05

a In the Russian original. b Not identified by the author. c When water in water courses is used for domestic drinking water.

194

Limit

NB.

When the water in water courses used for domestic purposes is polluted by a combination of different substances which belong to the same category of harmfulness -- organoleptic properties (smell, taste, colouring); impairment of self-purification; toxicological quality -- the m a x i m u m permissible concentrations in the table for the single substances must be adopted under one of these provisions: (a) In carrying out prophylactic sanitary inspection, the m a x i m u m permissible concentration for each substance forming the combination must be reduced as m a n y times as the number of harmful substances with the same category of harmfulness which are supposed to be discharged with waste water or are contained in the water reservoirs. (b) In carrying out routine sanitary inspection, the sum of the concentrations of all the substances expressed as a percentage of the corresponding m a x i m u m permissible concentrations for each substance separately must n o t exceed 100%. The list of m a x i m u m permissible concentrations in the water of water reservoirs used for domestic and hygienic purposes No. 662/67 of January 12th, 1967 is hereby superseded. REFERENCES 1 S.N. Cherkinskli, Gig. i. San.,32 (1967) 11,28. 2. S.N. Cherkinskii, Printsipi i m e t o d y gigienicheskogo normirovaniya khimicheskikh veshchestv v interesakh samtarnoi okhrany vodoemov, in S.N. Cherkinskii (Ed.), Nauchnye Osnovy Ustanovleniya P D K v Vodnoi Srede ~ Sarnoochishchenw Poverk h n y k h Vod, Moscow, 1972, pp. 3--7. 3 V.N. Fomenko, Gig. i. San.,30 (1965) 1, 9 4 K. Kostial, I. Simonovic and M. Pisonic, Nature, 233 (1971) 564. 5 K. Kostial and B. Mom~ilovi6, Health Phys., 23 (1972) 383. 6 N.D. Mazmanidi, K voprosu ob opredelenii PDK nefti, in S.N. Cherkinskii (Ed.) Nauchnye Osnovy Ustanovlemya PDK v Vodnoi Srede i Samoochishchenie Poverkhnykh Vod, Moscow, 1972, pp. 26--29. 7 H.A. Williams, R o y Soc. Health J., 5 (1972) 225.

195