Yenagoa — The National Oil Spills Detection and Response Agency (NOSDRA) Thursday said its investigation of the death of tonnes of fishes along the Atlantic Ocean coastline in Nigeria was caused by the discharge of toxic waste into the ocean.
The Director-General of NOSDRA, Mr. Idris Musa, said in a statement that the high toxicity of the dead fishes and water samples was caused by pollution from heavy metals from industrial and domestic wastes discharged from domestic and industrial sources on land.
NOSDRA had instituted a multi-agency investigation on April 22 to unravel the cause of the reported massive death of fishes along the Niger Delta coast stretching from Delta State through Bayelsa State to Rivers State.
The agencies are the Nigerian Maritime Administration and Safety Agency (NIMASA), Nigerian Institute of Oceanography and Marine Research (NIOMR), the National Environmental Standards and Regulations Enforcement Agency (NESREA) and the Federal Institute for Fisheries Research.
According to Musa, results of the tests conducted confirmed its preliminary findings that the death of the fishes were not linked to oil leakages as the levels of hydrocarbon in the samples tested were within regulatory limits.
Musa said: "In the course of the analyses, Total Petroleum Hydrocarbons (TPH), Polycyclic Aromatic Hydrocarbon (PAR), Benzene, Toluene Ethylene and Xylene (BTEX) were within regulatory standard limits in water, sediments and fish tissue analyses.
"However, there were some heavy metals such as cadmium, chromium copper, zinc and iron that exceeded regulatory standard limits in the coastlines of the three states of Delta, Bayelsa and Rivers.
"In the water samples taken at the coastline in Bayelsa State, the values of cadmium and iron were higher than the regulatory standards limit.
"The cadmium in the water was between 0.001 and 0.173 miligramme per litre (mg/l) with an average value of 0.064 mg/l. This is above the regulatory limit of 0.05 mg/l as well as the control sample value of 0.08 mg/l.
"Similarly, the value of the iron content in the water in the area ranged between 1.914 and 3.408 mg/l with a mean value of 2.503 mg/l. This is above the regulatory limit of 1.00 mg/l.
"The values of the parameters in sediments were substantially within regulatory limits. The values of chromium and copper in the sampled dead fishes' tissue were slightly higher than the European Union standards limits."
He noted that having ruled out oil pollution as the cause for the dead fishes, the causes could be other pollution activities that are land-based.
Musa added: "Most industrial and domestic wastes which contain heavy metals such as cadmium, iron, zinc, copper found their ways into drainages and onward transfer to the water bodies.
"Their harmful impact may be negative to aquatic species, other mammals and human beings. The main sources of these are batteries, galvanised pipes, fertilizers, sewage sludge and plastics.
"Such may be the case in the analyses of dead fishes found at the coastline in Delta and Bayelsa States where chromium was found in fish tissue.
"Copper was also found in the fish tissue sampled in Delta State but not in those of Bayelsa and Rivers State.