Journal of Research in Environmental Science and Toxicology (ISSN: 2315-5698) Vol. 6(1) pp. 001-007,  May 2017. DOI: http:/ Copyright © 2017 International Research Journals


Full Length Research Paper

Residual levels of the organophosphate malathion in water, sediment and a threatened fish from Ethiope River, Delta State, Nigeria

1Erewa O. and 2Ikpesu T.O

1Department of Animal and Environmental Biology, University of Benin, Nigeria

2Department of Biological Sciences, Federal University Otuoke, Nigeria

Corresponding author’s E-mail:

Received February 10, 2017;  Accepted March 15, 2017



The organophosphate pesticide malathion, was observed and measured in water, sediment and fish (Tilapia mariae) from Ethiope River. This study was made from three stations, Amukpe, Igun watershed and Owah-Abe, all along the River during the dry (January-April) and wet seasons (May-August). The physicochemical and microbiological characteristics of surface water were also taken on a monthly basis. Analysis of the pesticide was done using High Performance Liquid Chromatography (HPLC model CECIL 1010) to elucidate its distribution in the different environmental compartments. The concentration of the pesticide residue in the matrices ranged from 0.01μg/l – 2.24μg/l (water), 0.03ug/gdw – 2.46ug/gdw (sediment) and 0.16ug/gdw – 5.10ug/gdw (Tilapia mariae) during the dry and wet seasons. Results from the study showed that sediment and Tilapia mariae were higher in malathion residue than water, that is, concentrations of malathion increased in the order of water, sediment, fish samples. Spatial variations occurred with downstream stations having statistically higher concentrations in all matrices at p < 0.05. There was seasonal variation with higher concentrations of malathion residues observed in the dry season for water, while sediment and fish had higher concentrations during the wet season. The physicochemical parameters analysed were within the recommended limit accepted by the regulatory body in Nigeria. The observed residual levels of malathion were above the ecological bench mark (0.01ug/l) stipulated by the Federal Ministry of Environment, an observation that calls for proper monitoring of the Niger Delta water bodies in Nigeria so as to prevent contamination that could be detrimental to human health. 

Keywords: Surface water; Sediment;  Ethiope River; Amukpe; Igun ; Owah Abe.


The present study investigated the polycyclic aromatic hydrocarbon (PAH) contents of farm soils and three commonly consumed vegetables grown in farmlands in two communities- Alakahia and Eleme, Rivers state, Nigeria and their potential impacts on human health. The total PAH concentrations in vegetables and soil ranged from 1.34 to 9.51 and 51.02 to 93.14 µg/kg, respectively. Samples from the Eleme community had higher PAH concentration than samples from Alakahia community. Pyrene and Fluoranthene were the predominant PAH in the farm soil samples from Alakahia and Eleme respectively. The profile of PAH in the vegetable samples were dissimilar at both communities when compared to the farm soil samples. The Low molecular weight PAH to High molecular weight PAH ratio (LMW-PAH/HMW-PAH) showed that the high molecular PAH were predominant in the Alakahia farm soil while the low molecular PAH dominated the Eleme soil sample. The carcinogenic Potency equivalent concentration (µg/kg) were estimated to be 0.31- 1.51 and 0.37 - 0.97 for vegetablescollected from Alakahia and Eleme communities respectively. These values exceeded the screening value (0.23) for vegetables, thus indicating that the consumption of such vegetables is risky for the exposed population.


Keywords: PAH, Vegetables, Rivers state, Health risk, Carcinogenic.