assessing the toxicity of benzalkonium chloride on common carp (cyprinus carpio): impacts on blood cells, gills, intestines, and liver

The use of benzalkonium chloride and other alternative disinfectants increased during the covid-19 pandemic. therefore, it is crucial to consider their environmental effects. this study aims to investigate the toxicity potential of different concentrations of benzalkonium chloride on the blood cells, gills, intestines, and liver of common carp. for this purpose, 50 fish were divided into 5 groups of 10 (including one control group) and exposed to bac concentrations of 0.10, 0.32, 0.58, and 0.75 mg/l for 28 days. the results showed that the rbc count (millions/mm³) in all exposed groups (group b: 9.6 ± 1.07; group c: 8.7 ± 0.78; group d: 7.4 ± 0.96; group e: 6.9 ± 0.55) was significantly lower (p<0.05) than in the control group (13.9 ± 1.25). the cholesterol, triglyceride, protein, and albumin levels (mg/dl) in all experimental groups were lower than those in the control group. conversely, the ast levels in all exposed groups were significantly higher (p<0.05) compared to the control group. gill damage included lamellar fusion, curvature, edema, and necrosis. in the liver, histological damage consisted of hepatocyte degeneration, central vein wall rupture, melano-macrophage aggregation, and blood vessel dilation. the results indicate that as benzalkonium chloride concentration increases from 0.10 to 0.78 mg/l, its toxicity effects on common carp also intensify. therefore, before incorporating benzalkonium chloride into commercial products like cosmetics, its toxic effects should be thoroughly assessed to mitigate environmental harm.