Cytogenotoxicity and Hematological Alterations Induced by the Environmentally Relevant Concentration of Low-Density Polyethylene Microplastics and Nickel Oxide Nanoparticles in Cirrhinus mrigala (Ham.).

The omnipresence of microplastics and metal nanoparticles in aquatic ecosystems has become an escalating threat to the health of fish and consumers. Keeping this in mind, this study envisaged the assessment of hematological alterations and cytogenotoxicity in Cirrhinus mrigala during an exposure and a recovery period (60 days each) due to environmentally relevant concentration (50 μg/L) of 150-250 μm (M1) and < 150 μm (M2) low-density polyethylene microplastics and predicted no-effect concentration (2.95 mg/L: 1/100 96 h LC₅₀) of nickel oxide nanoparticles (N) and their combination (M1N and M2N). Cell viability, frequency of nucleo-cellular abnormalities, hemoglobin content, hematocrit, MCHC, and count of RBCs, WBCs, and platelets decreased (p < 0.001), but tail length, % tail DNA, tail moment, and olive tail moment increased (p < 0.001) over control throughout the experiment. The MPs and NPs showed synergism, and the order of toxicity was M2N > M1N > M2 > M1 > N. Necrotic cell frequency was higher than apoptotic cells. In comparison to M2 and N, M2N showed lower frequency of viable cells (49.1 and 56.11%, respectively), but a higher frequency of nucleo-cellular abnormalities (98 and 238.66%, respectively) and DNA damage (tail moment: 267 and 577.94%, respectively). Hb, RBC count, and Hct of M2N were 2.6, 2.2, and 1.3 times less than N. More increase in monocytes and neutrophils indicates an extreme inflammatory impact of co-existing MPs and NPs. Therefore, there is a dire need to regulate levels of MPs and NPs in aquatic ecosystems to maintain the health and well-being of organisms, especially fish.