ABSTRACT
Humans may be at risk of negative health effects resulting from unexpected heavy metals exposures. Studies show that, Pb has the ability to induce multiple organ dysfunctions. This study was therefore designed to investigate the current levels of metallic pollutants in Warri River and evaluate the biochemical, haematological and histopathological effects of the identified heavy metal pollutants upon consumption of water containing established concentrations of the metals present, in the river and feed formulated with fish (Clarias gariepinus) maintained in water containing the same levels of the metals for 90 days. Since the principal identified heavy metal which is of serious environmental concern was Pb, it became the focus of the study.
A total of 110 albino rats (Wistar strain), weighing on average 150.00 ± 9 g were used for this study. They were divided into two major groups of 55 rats each, the drinking water-exposed and the feed-exposed groups. Each of the two groups was sub-divided into 11 groups of 5 rats each. Groups I and II of the rats exposed to the metals via drinking water were maintained on deionized water (DW) and non-deionized water (NDW) respectively. Groups III-X rats were exposed to Pb only, Pb + Fe, Pb + Ca, Pb + Cu, Pb + Mn, Pb + Mg, Pb + Zn and Pb +(Fe+ Ca+ Cu+ Mn+ Mg and Zn) salt solution while group XI rats were provided with the river water. Groups I and II exposed to the metal via feed were maintained on diets formulated with milled Clarias spp fishes, maintained first for 90 days in distilled water (DW) and non-distilled water (NDW) water respectively. Groups III-X rats were maintained on diets formulated with milled catfish, first maintained for 90 days in Pb only, Pb + Fe, Pb + Ca, Pb + Cu, Pb + Mn, Pb + Mg, Pb + Zn and Pb + (Fe + Ca + Cu + Mn + Mg+ Zn) salt contaminated water respectively while group XI rats in this category were maintained on diet formulated with milled fish caught from the river. The effects of the treatments on organ-body weight ratios as well as urea levels were investigated. Also investigated were their effects on plasma alkaline phosphatase, L-alanine amino transferase, L-aspartate amino transferase activities and malondialdehyde (MDA) levels. Liver alkaline phosphatase, liver and kidney catalase, superoxide dismutase activities and MDA levels were also examined. Liver and kidney Pb load, haematological and histopathological examinations were also done in the contaminated drinking water and contaminated feed-exposed rats.
The findings revealed the presence of lead (Pb), copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg), manganese (Mn) and iron (Fe) in the dry and rainy season water samples and in diets formulated with fish maintained in water containing the same levels of the metals for 90 days. Relative to the controls, there were significant (p≤ 0.05) decreases in the body weights, liver, kidney, bone and brain index weight ratios of rats exposed to drinking water contaminated with or exposed to feed formulated with catfish exposed to Warri River levels of Pb only, Pb + Cu, Pb + Mn and occasionally Pb + Fe or Pb + Zn. Relative to the controls also, there were significant (p≤ 0.05) increases in kidney, liver and plasma ALT, L-AST, ALP, acid phosphatases (ACP), SOD and CAT activities as well as plasma bilirubin, glucose, phosphorus and total protein levels in the groups of rats exposed to water and feed contaminated with Pb only, Pb + Cu, Pb + Mn and occasionally Pb + Fe. Relative to the controls, there were significant (p≤ 0.05) increases in WBC count and decreases in haemoglobin and platelet indices in rats caused by Pb only and Pb + Cu exposure via drinking water and feed. In the presence of Fe, Ca, Mn, Mg and Zn singly or as a whole, these Pb-associated changes in the water-exposed and feed- exposed rats were reversed. Residue of Pb metal accumulated significantly (P≤ 0.05) in the liver and kidney of rats exposed to Pb only, Pb + Cu, Pb + all metallic co-pollutants (AMP) and main river water (RW). The accumulation was more in liver which accumulated an average of 0.06 ppm and 0.05 ppm in rats exposed to water and feed contaminated with Pb only. The liver of rats exposed to Pb + Cu contaminated water or feed accumulated 0.11 ppm and 0.09 ppm respectively. Histopathological examinations revealed the presence of fatty deposits in liver and focal tubular necrosis in the kidney of rats exposed to Pb only milled fish formulated diet. These ultra-structural changes caused by Warri River Pb level were reversed when it was administered to rats along with Warri river Ca level. The findings from this study suggest that some of the metallic-co pollutants have the capacity to enhance Pb toxicity whereas some like Ca reversed its effects in the rat.
