Effects of anionic polyacrylamide products on gill histopathology in juvenile rainbow trout (Oncorhynchus mykiss)

Abstract

Anionic polyacrylamide (PAM) products are commonly used to remove suspended materials from turbid waters and to help mitigate soil erosion. In the present study, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to 3 mg/L to 300 mg/L of 10 commercially available PAM products (Clearflow Water Lynx Polymer Log and Clearflow Soil Lynx Granular Polymer; Clearflow Enviro Systems Group), and gill histological parameters were measured following either 7 d or 30 d of polymer exposure. A cationic polymer product (≤0.38 mg/L MagnaFloc 368; Ciba Specialty Chemical) was also tested for comparison. Mild gill lesions were observed in fish exposed to polymer products. Lamellar fusion, interlamellar hyperplasia, epithelial lifting, mucous cell metaplasia, and cell counts of epithelial swelling and necrosis/apoptosis were minimal in fish exposed to environmentally relevant concentrations of anionic polymer (≤30 mg/L). Gill morphology was largely unaffected by exposure to concentrations up to 300 mg/L of many PAM products. Several anionic polymer products noticeably affected gill tissue by increasing epithelial hypertrophy, interlamellar hyperplasia, mucous cell metaplasia, and the frequency of necrotic cells. The severity of the lesions lessened with time, suggesting that fish may have experienced a short-term irritant effect. Similar levels of gill pathology were frequently observed in fish exposed to cationic polymer MagnaFloc 368 despite the concentration being 1000-fold lower than that of the PAM products. These observations highlight the increased toxicity of cationic polymers to aquatic life compared with anionic PAMs.

Fabricating an anionic polyacrylamide (APAM) with an anionic block structure for high turbidity water separation and purification

“…14,15 Up to now, a series of anionic polyacrylamide with high occulation performance have been developed and applied in the waste water treatment. 16,17 However, the defect of the APAM, namely, the disordered and random distribution of anionic units in the polymer chain, seriously restricts the further enhancement of the solidwater separation ability. In addition to the molecular weight (MW) and the density of the anionic monomer, the congura-tion and the distribution of anionic units also affect the nal occulation performance.…”

pH Dependence of Acrylate-Derivative Polyelectrolyte Properties

“…Testing of poly(acrylamide) interaction with the gill tissues of several aquatic species including fish [66,73,[75][76][77], crustaceans [66,73,77], algae [66,77] and insects [77] have been carried out. In many studies of adult fish, the anionic and non-ionic form of the poly(acrylamide) cause only low levels of damage to the fish, with effects increasing at higher concentrations [75]. However, sustained exposure of organisms over a 40 day period has shown that low levels of these polymers are intrinsically toxic to almost all aquatic fauna [73].…”

“…Even in tests where fish survival was not impacted, the general activity and swimming behaviour of the fish were sub normal [76]. Conversely the cationic form of the polymer is known to be far more toxic, causing pathological issues at sub mg ml −1 concentrations, as the polymer builds up on negatively charged gill surfaces [75,77]. Reduced gill functionality impairs oxygen uptake in the fish and results in death.…”

“…It has been observed that addition of combinations of both anionic and cationic polymer can reduce toxicity [77] and several patents have been issued suggesting that anionic polymers can be used to detoxify cationic polyelectrolytes [78,79]. In conclusion, the discrepancy between anionic and cationic polymers in regard to aquatic toxicity must be considered in the application of these polymers [75,77]. The cationic form of the polymer is regarded as generally more toxic but the anionic form has also been shown to cause chronic, sub-lethal responses even at low concentrations [66].…”

Measuring poly(acrylamide) flocculants in fresh water using inter-polymer complex formation

“…The polymers are added to wastewater to improve the settling and the subsequent removal of suspended particles, either by direct flocculation or by neutralising the suspended particles surface charge 18,21 . Both polymers are toxic at very low concentrations to aquatic lifeforms 5 , and whilst it is accepted that the cationic variant of the polymer is substantially more toxic than the anionic polymer both present a risk to the aquatic fauna 22 .…”