pH, carbon dioxide and dissolved 

 oxygen concentrations. Toxicity 

 of ammonia (undissoclated) in- 

 creases as oxygen concentration 

 decreases. Carbon dioxide in low 

 concentrations (up to 30 p. p.m.) 

 reduces the toxicity of ammonia 

 by lowering the pH value and thus 

 increasing the ionization of 

 coBnonia. 



b. Trout may be killed in the pre- 

 sence of 15 to 60 p. p.m. of cop 

 if the concentration of dissolved 

 oxygen is lees than about 30 per- 

 cent of the saturation value. 



c. An anionic detergent equivalent 

 to 1.26 p. p.m. of sodium lauryl 

 sulphate, produced a 50-percent 

 mortality to rainbow trout after 

 about 12 weeks exposure. When 

 the concentration was k p. p.m., 

 the median period of survival of 

 the trout was about 7 days. 



Doudoroff and Katz made a critical 

 review of the literature on the toxicity of 

 industrial wastes and their components to 

 fish (10, 11). A summary of this review 

 follows : 



a. gH - under otherwise favorable 

 conditions, pH values between 5-0 

 and 9-0 are not lethal for most 

 fully developed fresh-water 

 fishes . 



b. Strong alkalies , such NaOH, 

 Ca(0H)2j and KOH, 8u:« not lethal 

 to fully developed fish In fresh 

 water when their concentration 

 does not raise the pH value above 

 9.0. 



c. Ammonia , ammonium hydroxide , and 

 ammonium salts can be very toxic 

 to fish. Nonlonic ammonia is 

 most toxic and its concentration 

 Increases as the pH increases. 

 1.2 to 3 p. p.m. of nonlonic ammo- 

 nia (as NH^) has been reported as 

 being toxic to hardy species of 

 fish. 



d. Strong mineral acids , such as 

 HgSOi^, HCl, and ENO3, and some 

 moderately weak organic acids can 

 be lethal to fully developed fish 



in natural fresh water only when they 

 reduce the pH to below 5.0. 



e. WesUt inorganic and organic acids , 

 such as hydrosulfuric , hypochlorous , 

 hydrocyanic, carbonic, chromic, tan- 

 nic, and boric acids, and probably 

 also Bulfurous, benzoic, acetic, and 

 propionic acids, csm Impart pro- 

 nounced toxicity to seme waters for 

 fresh-water fish without lowering 

 the pH to a value as low as 5.0. 



f . Carbon dioxide - fish differ greatly 

 in their susceptibility. Sensitive 

 fresh-water species may succumb 

 rapidly under concentrations of be- 

 tween 100 and 200 p. p.m. of free CO2 

 with high dissolved oxygen concen- 

 trations. Low CO2 concentrations 

 are lethal when the dissolved oxygen 

 concentration is low. 



g. Solutions of hydrogen sulfide , free 

 chlorine , chloramine , cysmogen chlo - 

 ride , carbon monoxide, ozone , phos - 

 phlne , and sulfur dioxide , are all 

 extremely toxic to fish. These 

 inorganic gases may be lethal to 

 sensitive fish in concentrations of 

 1.0 p. p.m. (and in some cases less 

 than 0.1 p.p.m. ) and less. 



h. Silver , mercury , copper , lead, 

 cadmium , aluminum , zinc , nickel, 

 tin, iron , gold, cerium , platinum , 

 thorium , and palladium , can be 

 classified as metals of high toxicity 

 to fish. The salts of some of these 

 metals are ccmparatlvely harmless in 

 highly mineralized waters, because of 

 precipitation or because of insoluble 

 compounds and antagonism. Some of 

 the highly toxic metals are strongly 

 synergistic, such as zinc and copper. 

 Calcium tends to counteract the 

 toxicity of seme of the heavy meteLLs. 

 Cupric, mercuric, and silver salts 

 have, in soft water, been toxic at 

 metal concentrations as low as 0.02 

 to O.OOl*- p.p.m. In soft water, zinc, 

 cadmiimi, lead and aluminum have 

 proved injurious to fish at concen- 

 trations between 0.1 and O.5 p.p.m. 

 Nickel and chromium (and peiiiaps iron) 

 have not been observed to cause 

 toxicity much below concentrations of 

 1.0 p.p.m. 



12 



