Global Journal of Environmental Research 3 (3): 135-140, 2009 ISSN 1990-925X © IDOSI Publications, 2009 Corresponding Author: C.G. Alimba, Department of Cell Biology and Genetics, University of Lagos, Akoka, Lagos State, Nigeria E-mail: chivoptera@yahoo.com 135 Effects of Municipal Solid Waste Leachate on Leucocyte and Differential Counts in Rats Chibuisi G. Alimba, Adekunle A. Bakare and Olatubosun G. Arinola 1,2 1 3 Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Nigeria 1 Department of Cell Biology and Genetics, University of Lagos, Akoka, Lagos, Nigeria 2 Immunology Unit, Department of Chemical Pathology, University of Ibadan, Ibadan, Nigeria 3 Abstract: This study investigated the immunotoxic potentials of raw and simulated leachates from Olushosun municipal solid waste landfill in rat using quantitative leucocyte and differential counts. Blood samples of rats intraperitoneally exposed to 1 – 25 % concentrations of each of the leachate samples for 48 hours were examined post treatment for leukocyte and differential counts. Compared to the negative control, there was concentration dependent and statistical significant decrease in leucocyte (P < 0.05) and lymphocyte (P < 0.001) count and increase in neutrophil count (P < 0.001). There was statistically insignificant decrease in basophil and monocyte count and increase in eosinophil count. The constituents of the tested leachate samples were believed to provoke the observed changes in leucocyte and differential count. This finding suggests that municipal solid waste leachate induced a non-specific immunotoxic effects in rats and may be of public health importance as there is continuous residential and occupational exposure of human population to hazardous substances from solid wastes landfill. Key words: Differential counts Immunotoxicity Leucocyte Municipal solid wastes Landfill leachate Rat INTRODUCTION chemical substances in leachate through ingestion, Nigeria, with an estimated 140 million population [1], potential adverse effects of leachates on public health and generates an annual estimation of 29.78 x 10 kg municipal the environment led to several studies on leachate 9 solid waste [2]. This will continue to increase due to induced toxicity on microalgae, bacteria, Daphnia population growth, accelerated industrial development and fish [5-8], cytotoxicity, mutagenicity and genotoxicity and high urbanization rate. The common methods of [9-16]. Ecotoxicological studies have resulted in harmful disposing these wastes are incineration, landfilling and or effects been observed in rodent and aquatic species but open dumps at the nearest available space. Wastes the extrapolation of these model systems to human decompose in these landfills/dumpsites through a population requires multidisciplinary consideration complex and highly variable processes that lead to [8, 15,17,18]. leachate and landfill gas production. Leachate contains Amongst these reports, information on the potential organic and inorganic chemicals and many unidentified adverse effects of solid waste leachate on the immune toxicants known as non-conventional pollutants (NCPs) system is limited. This is despite that the immune system [3]. These compounds may pose serious risks to the is one of the most sensitive targets for chemical induced ecosystems and human health if contamination and toxicity [19]. The potential for chemicals to cause damage exposure occur. to the immune system is of considerable public health Report from the United Nations Children’s Fund significance and alterations to immune functions may lead showed that about 52 % of the Nigerian population makes to incidence of hypersensitivity disorders, autoimmune use of unprotected underground and surface water for and infectious diseases or neoplasia [20]. Quantitative their domestic and commercial activities [4]. This indicates and morphologic investigations of non-specific that individuals around landfills/dumpsites who make immune cells, like total leukocyte counts and differentials use of unprotected underground and surface water for formed the basic investigations mostly included in domestic and commercial activities may be exposed to immunotoxicity studies [21]. Total leukocyte and inhalation and or dermal contact. Concern about the