Acute and long-term toxicity of water-soluble cationic polymers to rainbow trout (Oncorhynchus mykiss) and the modification of toxicity by humic acid

The toxicity of two classes of cationic polymers, epichlorhydrin/dimethylamine polyamines and quaternary amine copolymers, were investigated. Static bioassays of those polymers resulted in LC50 concentrations ranging from 271 μg/L to 1,733 μg/L. Under flow-through conditions the toxicity was 1.7 to 13.9 times greater, depending on the polymer used. Using a reference humic acid along with the polymers in toxicity studies, strong correlations were established between humic acid concentration and LC50. Even at a fairly low humic acid concentration (5 mg/L), the toxicity of the polymers was reduced 7- to 16-fold. At higher humic acid concentrations (50 mg/L), cationic polymer toxicity was reduced 33- to 75-fold.