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BULLETIN OF BUREAU OF FISHERIES 
sufficient data to give a definite idea of the relative lethality of the substance in 
question under conditions which may be encountered in the streams of the United 
States. Only fresh-water fishes and fresh-water organisms have been considered. 
It is hoped that these summaries will prove helpful in evaluating specific pollution 
conditions when used in conjunction with the data presented in preceding sections. 
However, as has been pointed out repeatedly in this paper, arbitrary application of 
lethality data to specific pollution problems is absolutely impossible owing to the 
many limiting factors, various of which have been discussed in previous sections. 
Any student of the toxicity of the components of industrial and municipal efflu- 
ents to fishes and other aquatic life will find the pioneer work of Penny and Adams 
(1863) and of Weigelt, Saare, and Schwab (1885) starting points for the investigations 
of the commoner substances. However, much progress has been made in the study 
of the factors limiting the action of many pollutants, since these experiments and the 
lethality values given by these earlier observers have been quoted too often without 
regard to more recent findings. 
Important advances have been made in the measurement of stream-pollution 
hazards of particular effluents through the isolation from these effluents of various 
compounds of highly toxic nature, which compounds were formerly overlooked or 
disregarded because the actual amounts of these substances present in the effluent 
were quite small. These highly toxic compounds, some of which are volatile or may 
otherwise disappear from the effluent after a time, have been responsible for the wide 
discrepancies in lethality of the waste as a whole as reported by different observers 
working on the same type of effluent. 
In the present list of substances which may be participants in stream-pollution 
problems, several compounds have been included which are little known except to 
the professional chemist, although the harmful properties of these substances have 
been demonstrated in connection with certain industrial effluents. The list of these 
less familiar compounds will undoubtedly grow, both as investigations of particular 
effluents are completed and as chemical engineering produces new commercial proc- 
esses. The long series of dyes, many of which are highly toxic to aquatic life, used 
in industries and arts have not been included in this list of possible stream pollutants 
because the dye wastes are largely mordant, bleach and processing liquors containing 
only traces of the dyestuffs themselves which industry has found too costly to waste. 
The conservation of these expensive dye compounds by the manufacturing concerns 
has been very apparent to the writer in several recent investigations of plants dyeing 
fabric, paper, and leather. 
Acetic acid, CH 3 -COOH. Vinegar acid 
Beet-sugar pulp waste; some winery wastes; soured fruit wastes; and vinegar works. Penny 
and Adams (1863), 114 p. p. m. killed minnows in 20 hours, but 286 p. p. m. not fatal to goldfish; 
M. M. E., 100 p. p. m. in hard w’ater killed some goldfish, Carassius auratus, and 125 p. p. m. killed 
cladocerans, Daphnia magna, in 24-72 hours. 
Acetone, (CH 3 ) 2 CO 
Gas and coal-tar wastes; paint and chemical industries. Shelford (1917), 14,250-15,050 
p. p. m. in tap water killed orange-spotted sunfish, Lepomis humilis. 
