Toxicologie environnementale et analytique

Assessment of Organochlorine Pesticides in Water, Sediment, African Cat fish and Nile tilapia, Consumer Exposure and Human Health Implications, Volta Lake, Ghana

Abstract

Gustav Gbeddy, Eric Glover, Israel Doyi, Samuel Frimpong and Louis Doa

The levels of organochlorine pesticides (OCPs) in water, sediment, Nile Tilapia and African Catfishes were assessed to estimate possible consumer exposures and potential health implications from the Volta Lake, Ghana using gas chromatography equipped with 63Ni electron-capture detector. In agreement with their lipophilic nature, higher levels of OCPs were measured in fish samples than water and sediment samples. Heptachlor was the highest level of OCP measured with concentration of 37.75 ng/g in tilapia gill followed by δ-HCH in tilapia muscle and catfish muscle respectively. All OCP residues in tilapia muscle and catfish muscle did not differ significantly (p<0.05). The highest total OCP load of 66.70 ng/g was measured in tilapia muscle, followed by 63.44 ng/g for tilapia gill. This observation however, contradicts the lipophilic nature of OCPs since the fat content of tilapia gill (14.49%) was five times that of muscle tissues (2.80%). Gill tissues however, may be serving as channels to absorb and distribute OCPs to various fatty tissues in the anatomy and physiology of fish. In water a sample δ-HCH was the highest OCP determined with concentration of 0.669 μg/L. DDT was not detected in both water and sediment samples but was however measured in fish samples. This could be attributed to historical use since DDD and DDE were measured in higher concentrations. From the consumer exposure analysis, the water from the lake is relatively safe for domestic, agricultural and ranching since the acute risk ratio for all detected OCP residues were less than one. The Nile tilapia and African catfishes from this lake are also comparatively safe for human consumption because the estimated dietary intakes from this study are far below the corresponding acceptable dietary intakes for various OCPs. This study therefore shows a declining trend on the environmental burden of OCPs in the middle section of the Volta Lake.