Assessment of haematological and histopathological effects of mixture toxicity of phenanthrene and benzo[a]pyrene in catfish

The effect of joint mixtures of phenanthrene and benzo[a]pyrene on selected haematological and histopathological parameters of the Clarias gariepinus was investigated. Healthy juvenile C. gariepinus (n = 90) weighing 19.7 ± 1.8 g were exposed to sublethal concentrations of joint mixtures of phenanthrene and benzo[a]pyrene for a subchronic period of 35 days. Acute toxicity studies showed that phenanthrene and benzo[a]pyrene had LC50 values of 1400 and 16 μg/L respectively while the safe limits of the chemicals varied in the ranges of 0.00016 to 1.6 μg/L and 0.014 to 140 μg/L for benzo[a]pyrene and phenanthrene respectively. The joint mixture significantly (p < 0.05) reduced growth rate in exposed fish. The joint mixtures also led to significant (p < 0.05) declines in the studied haematological parameters including blood cell count (RBC), haemoglobin (Hb) and haematocrit (Hct). The erythrocyte indices including mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) all showed significant (p < 0.05) declines in the presence of the joint toxicants. There were significant (p < 0.05) increases in white blood cells (WBC) count and platelet (PLT) count. Histopathological examination showed alterations in liver and gill sections of exposed fish