Analysis and Human Health Risk Assessment of Arsenic, Cadmium, and Mercury in Manta Birostris (Manta Ray) Caught Along the Ghanaian Coastline

ABSTRACT

The Ghanaian marine water of the Atlantic Ocean could be said to be polluted with As and Hg. However, Cd levels do not appear to pose an environmental concern based on levels reported in tissue samples collected. Tissue samples from six Manta birostris (manta ray) used as a bioindicator were tested for these heavy metals because many people in Ghana eat this fish (aka “kako”). The pattern of bioaccumulation of these heavy metals found in the tissues of manta rays, which feed on phytoplankton, suggests that pollution has traveled deeper into the sea, which is an environmental concern and one that may require some urgent attention. Concentrations of As, Cd, and Hg were determined in kidney, liver, and muscle samples from six Manta birostris using the neutron activation analysis method. The results showed elevated levels of the metals in the manta rays. If these values are interpreted to represent daily human exposure estimates of possible human health cancer and non-cancer risks may be derived to conclude some potential risk for daily consumers of manta ray tissues. From the assessment, most of the hazard indexes for children were less than 1 except for arsenic, which was greater than 1. This means that there is for arsenic some hazard risk for children consumers of the manta ray. This is the first study to show the accumulation of heavy metals in manta ray; although the sources are not very clear, and may be due to the numerous mining activities, it needs to be investigated further. The presence of the heavy metals is very significant because the meat (muscle) is consumed in Ghana and hence there is possible accumulation in humans.

Key Words:

• Manta birostris
• “kako”
• Dixcove
• Fante
• NAA
• madai
• xenobiotic

ACKNOWLEDGMENTS

The author thanks the government of Ghana for financial assistance to complete this study. This work was also supported under a contract with the Ghana Atomic Energy commission Reactor 1 (GHAER 1) Accra Ghana. The author also thanks the technical assistance of the workers of the GHAER 1 and the staff and research team of the Chemistry Department University of Cape Coast for their financial support. The author also expresses his appreciation to HERA's Managing Editor, whose editorial work improved the manuscript.