Human dietary exposure to heavy metals through consumption of fish in Nakuru town, Kenya

Abstract

Heavy metal pollution in the environment is a problem experienced all over the world. Whereas heavy metals exist naturally in the environment, heavy metal pollution is associated withn anthropogenic activities. Pollution studies reveal that the aquatic ecosystems in Kenya and the fish that inhabit these ecosystems are contaminated with heavy metals. Literature also reveals that exposure to levels of heavy metals above the recommended doses may possibly cause various adverse health effects. This study assessed human exposure to lead, cadmium and copper through consumption of fish in Nakuru town, Kenya. Three hundred and eighty five (385) fish consumers who buy and consume fish from the markets in Nakuru town were randomly selected to participate in a cross-sectional survey, to establish the consumption patterns of the widely consumed fish species in Nakuru town. Composite samples of the widely consumed fish species were bought and transferred to Egerton university laboratory for heavy metal analysis using flame atomic absorption spectrophotometer. Data was analyzed using both descriptive and inferential statistical tools. In addition, estimated weekly intake (EWI), target hazard quotient (THQ) and hazard index (HI) of lead, copper and cadmium were computed in order to assess if human exposure to these three heavy metals in fish is above the recommended standards. The findings revealed that Tilapia, Silver sardine, Nile perch and Lungfish were the widely consumed fish species in Nakuru town. The pooled averages of lead, copper and cadmium in the widely consumed fish species were 7.0898±2.6889, 1.9977±1.0577 and 0.4498±0.3394 mg/kg respectively. Computed estimated weekly intake (EWI) of lead, copper and cadmium for the consumers of the widely consumed fish species were within FAO/WHO recommended safe limits. Computed THQ values of cadmium for high consumers of large Tilapia from Ponda Mali market and small Tilapia from the Main municipal market indicated possible health risk for the consumers of these fish. Fish fillets were the safest forms of fish in the market as far as exposure to the three heavy metals is concerned. The findings of this study can be used by food safety and quality control entities in Kenya as a premise upon which to prescribe the amount of fish that is safe for consumption with minimal health risks over a life time.