This study was carried out to investigate the toxicological effects of four brands of mosquito incense stick smoke (DR insecticide stick (AS-1987), Incense upgraded formula (BM-102), Fragrance (B3-254) and Citronella (A7-435) on selected biochemical and histological profile of male albino wistar rats.  Fifteen (15) wistar rats with mean weight (174.6 ±0.91g) were randomly divided into five (5) groups. Group I were considered as negative control while group II, III, IV and V were challenged with the brands of mosquito incense stick smoke for 8 hours daily by inhalation for 21 days. Laboratory investigations were carried out using standard protocols. It was observed that the activities of the liver enzymes (Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST) and Alkaline Phosphatase (ALP) increased significantly (p<0.05) in all the experimental rats when compared with the control. The histopathological alterations examined in the liver tissues of the experimental rats during the study period include mild necrosis, mild degeneration of hepatocytes and cellular infiltration from group III, IV and V respectively. Lung tissues of the challenged rats of group II, III and V revealed mild cellular infilterations around alveolar septa, hyperplasia and bronchiolar epithelial wall degeneration   respectively. Kidney tissues revealed glomeruli distortion, mild haemorrhage and renal damage from group III and IV respectively. The alterations examined in the liver, kidney and lung tissues of the experiment rats were period dependent but independent of mosquito sticks brands which inferred that continuous exposure to mosquito stick 

The study evaluated the acute toxicity of vehicle wastewater on African catfish (Clarias gariepinus). With a weight range of 250–275.5g and a mean length of 23.5-28.5cm, 150 post-juvenile catfish were purchased from Dalar Kifi Fish Farm BUK New site road, Kano State, and acclimated in a tank for 14 days. Fish were exposed to different vehicle wastewater concentrations of 0.0, 20, 40, 60, and 80% v/v with 5-level exposure concentrations during the acute test (96 hours) in a Completely Randomized Design (CRD) employing renewal bioassay. The acute bioassay showed that the LC50 for the wastewater was 56 percent by volume at 96 hours. Compared to the control, the exposed fish exhibited abnormal swimming, erratic opercular movement, reflex loss, mucus secretion, increased air gulping with an increase in wastewater concentration. Except for water temperature, Biochemical Oxygen Demand (BOD) and pH,  the remaining physicochemical parameters were not within the WHO/FAO recommended Standard The order of concentrations of the heavy metal in the wastewater was Cu > Pb > Cd > Cr > Ni. Antioxidant biomarker activities showed that Glutathione reductase (GSH) reduced in the same manner while Catalase (CAT) and Superoxide dismutase (SOD) activities rose considerably (P<0.05) in the liver and gill tissues. Histopathological changes observed in gill tissues were as follows: Hyperplasia, necrosis, primary and secondary lamellae distortion, and epithelial thickening distortion. Hepatic cell breakdown, fatty degeneration, cellular infiltration, localized fibrosis, and cellular necrosis were all visible in the liver tissues. It can be inferred that changes in the histology and activity of the oxidative stress enzymes in fish tissues after exposure to wastewater harmed the experimental fish. As a result of their effects on fish and other non-target aquatic biotas, it is advised that the competent authorities create initiatives to reduce the indiscriminate discharge of untreated vehicle wash wastewater.

Pharmaceutical effluents collected from Bompai industrial area, Kano State were assessed for their physiochemical parameters, heavy metals and effect on haematology and biochemical changes in Clarias gariepinus. Laboratory analyses were performed using standard methods in a Completely Randomized Design (CRD). Five test solutions of the effluents (0, 25, 50, 75, and 100% v/v) were prepared for LC50 96hr acute toxicity test. The LC50 for 96hr was 48.7% concentration of effluents by volume. Experimental fish were exposed to sublethal concentrations of 0.00% 2.43% (5/100 LC50), 12.17% (25/100 LC50), 24.35% (50/100 LC50) and 36.52% (75/100 LC50) for 28days.  Physicochemical parameters recorded were higher than WHO recommended Standard with the exception of water temperature. Heavy metals concentrations decreased in the order of Cr > Cu > Pd > Cd. Red blood Cells count, haemoglobin concentrations, packed cell volume, lymphocytes and monocytes of the experimental fish decline significantly (p<0.05) when exposed with 2.43, 12.17, 24.35, 36.52% effluents  compared to the control. White blood cell count, mean corpuscular haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentrations, neutrophils and eosinophils were significantly higher (P<0.05) than the control. However, a significant increase (P<0.05) in the activities of serum aspartate aminotransferase (AST), Alkaline Phosphatase (ALP) and alanine aminotransferase (ALT) were recorded as the exposure period continued when compared with control. It is concluded that the effluents induces haematological and biochemical alterations. It is therefore recommended that regulatory bodies should adopt holistic approach on the aquatic pollution abatement, bearing in mind the negative impact to non-target organisms.

Pesticides play  a significant role in improving food production through control against harmful pests with low labour and efforts while on the other hand are regarded as aquatic pollutants. These toxicants persist in aquatic environment and cause harmful effects to non- target organisms including fish.   The development of pesticide tolerant species led to the need and use of varieties of pesticides with the risk of exposure to many compartments including water. Many pesticides have been proscribed for agricultural purposes by the regulatory agencies such as WHO (2020). However, It is unfortunate that many of these are sold in Nigeria or donated by donor agencies.  The donated pesticides often become “obsolete” while in stock due to poor logistics and delays in receiving them at the point of need. The review on the classification, bioavailability, biotransformation, the direct and indirect effects of pesticides on freshwater fish was carried out. Biomarkers of pesticides toxicity that induce alterations in fish physiology were discussed; these include: behavioral changes such as erratic swimming, hyperactivity among other alterations. Other alterations include feeding behaviour, fluctuation in antioxidant enzyme activities, histology, haematology, growth performance and DNA damage.