Organochlorine Pesticide Residues In Shellfishes And Finfishes From Lagos Lagoon

ABSTRACT

Organochlorine pesticides are persistent environmental contaminants which are lipophilicand hydrophobic, leading to their accumulation in biological tissues and the subsequent magnification of concentrations in organisms, progressing through to the food chain. Shellfishes, finfishes, microlayer water, mixed layer water, epipellic and benthic sediment samples were collected from the Lagos Lagoon and analysed for organochlorine pesticide residues. Sampling was conducted between December 2008 and September 2009 during the dry and wet seasons to study the effects of seasonal variation on the samples. The five sampling sites were Agboyi Creek, Oworonshoki, Ajara, Ogogoro and Tarkwa Bay. Water samples were subjected to liquid-liquid extraction using dichloromethane while sediment and fish samples were subjected to cold extraction with petroleum ether/acetone (1:1 v/v) mixture and clean-up on silica gel adsorbents. The shellfishes analysed were Ocypoda africanus, Penaeus notialis, and Procambarus clarkii while the finfishes included Tilapia guineensis, Sarothorodon melanotheron, Chrysichthys nigrodigitatus, Liza grandisquamis, Psettias sebae, Ethmalosa fimbriata, Epinephelus aeneus, Sphyraena guachancho, Pseudotolithus senegalensis, Pseudotolithus typus, Cynoglossus canariensis, Lutjanus goreensis, Sardinella maderensis, Caranx hipposandRegalecus glesne. The physicochemical properties of water, namely, temperature, pH, conductivity, total dissolved solids, salinity and turbidity were measured in situ. The dry season recorded higher mean values than the wet season for temperature, conductivity, total dissolved solids (TDS) and salinity.The fish, water and sediment samples were analysed for aldrin, dieldrin; endrin, DDT, heptachlor and their metabolites; HCH and endosulfan isomers; α, γ-chlordane and methoxychlor. The detection and determination of the pesticide residues were performed by gas chromatography. The total OCPs ranged from 18.26 ng/mL in Ogogoro mixed layer water to 89.82 ng/mL in microlayer water from Tarkwa Bay. Endrine ketone was not detected in all the water samples investigated. Total OCPs ranged from 35.97 ng/g to 17513.80 ng/g in the benthic sediments of Tarkwa Bay and Ogogoro respectively. The total detectable concentration of OCP residues (wet weight) of the muscle tissues of the finfishes ranged from 3.78 ng/g in C. nigrodigitatus to 6181.16 ng/g in R. glesne while in the shellfishes the range was from 6.47 ng/g to 4516.71 ng/g in P. clarkii. The order of accumulation of OCPs in the organs of the fishes was largely gills > livers > large intestines > small intestines > kidneys > muscles. Detection limits ranged from1.43 ng/g to 10.29 ng/g. Pesticide residues in the fishes were higher than residues in water and largely comparable to residues in the sediments. The residue levels were higher in the lagoon than in the creek while a higher concentration of the residues was observed during the dry season. In many of the fish species, the female fishes accumulated higher concentrations of OCP than the male fishes. or der·micadj.Of or relating to the skin or dermis.   abbr. American Society for Testing and Materials M. Araoud, W. Douki, A. Rhim, M.F. Najjar and N. Gazzah, Multiresidue analysis of pesticides in fruits and vegetables by gas chromatography–mass spectrometry, Journal of Environmental Science and Health B (2007), pp. 179–187. | | Cited By in Scopus (0)The estimated daily intakes of the pesticides were within the acceptable daily intakes. Levels of residues in the fishes were within the recommended maximum residues limits, suggesting that the fishes are safe for human consumption. Despite the positive risk assessment results obtained in this study, the potential health risk associated with fish consumption cannot be neglected, hence the need for continuous monitoring to ensure the long-term safety of consumers.