frequently pH, temperature, and other water quality parameters have been 

 omitted, making it difficult to reconstruct reported test conditions. 



Much of the literature on ammonia toxicity to fishes has recently been 

 reviewed in the EPA "Red Book" (U.S. EPA 1977) and the American Fisheries 

 Society "Red Book Review" (Thurston et al_. 1979). Reported acute toxicity 

 values in tests from 1 to 4 days duration on salmonids range from 0.25 to 

 0.85 mg/liter NH3; values for comparable tests on non-salmonids range be- 

 tween 0.4 and 4 mg/liter NH3. 



Published reports on chronic toxicity of ammonia do not include any 

 life-cycle mortality data, but effects of ammonia on both warm- and cold- 

 water fishes at sublethal concentrations of ammonia for periods of time 

 ranging from 1 week to 3 months have been reported by several researchers. 

 Within the concentration range of 0.06 to 0.4 mg/liter NH3, these reported 

 effects include swelling and diminishing of number of red blood cells, ir- 

 reversible blood damage, inflammation and degeneration of gills and other 

 tissues, and lessening of resistance to disease (Reichenbach-Klinke 1967; 

 Flis 1968; Smart 1976). Within the range 0.05 to 0.15 mg/liter NH3, re- 

 duced food uptake and assimilation and growth inhibition have been reported 

 (Ministry of Technology 1972; Robinette 1976; Schulze-Wiehenbrauck 1976; 

 Burkhalter and Kaya 1977). In a test of 6 months duration on rainbow trout 

 ( Salmo gairdneri ) it has been reported that concentrations as low as 0.01 

 mg/liter NH3 caused not only reduced growth rates, but pathological changes 

 to gills and livers (Smith and Piper 1975). Ball (1967) indicated that al- 

 though it may appear that different species of fishes exhibit dissimilar 

 susceptibilities to ammonia toxicity under acute exposure conditions, such 

 is not the case under long-term exposures. He theorized that trout and 

 carp, given time to react, may be equally susceptible to ammonia, and that 

 although acute responses are different, the ultimate response by both 

 fishes to a given concentration of ammonia may be the same. 



In sunmary, reported acute toxicity ammonia values for a variety of 

 species of fishes range between 0.25 and 4 mg/liter NH3, and other mani- 

 festations of the effects of ammonia have been reported at concentrations 

 as low as 0.01 mg/liter NH3. There is some evidence that differences in am- 

 monia tolerance among fish species may be less under chronic conditions than 

 under acute conditions. Based on the published literature, the European 

 Inland Fisheries Advisory Commission (EIFAC 1970) has recommended a crite- 

 rion of 0.025 mg/liter NH3 as being the maximum which can be tolerated by 

 fishes for an extended period of time, and the United States Environmental 

 Protection Agency (1977) has published a criterion of 0.02 mg/liter NH3, 

 just slightly more restrictive than that recommended by EIFAC. 



Mery possibly these criteria are "safe" for most water bodies which sup- 

 port aquatic life, but some questions remain unanswered as to whether they 

 are reasonable for all waters at all times under all conditions. Tabata 

 (1962) has attributed some toxicity to NH4"'", concluding that it may be 

 l/50th as toxic as NH3 to Daphnia pulex . Robinson-Wilson and Seim (1975), 

 testing coho salmon ( Oncorhynchus kisutch ), have demonstrated correlation 

 between pH and the acute toxicity of ammonia expressed as NH3. More re- 

 cently Armstrong et aj_. (1978), in tests on larvae of the prawn Macrobra- 



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