KARACHI, Aug 18: A recent study has shown high levels of lead in fish samples collected from different parts of the city.

Lead exposure, according to experts, can damage the nervous system and cause brain disorders at a certain contact degree.

The research titled Determination of heavy metals pollution in 10 fish species of Arabian Sea: A case study of commercially available fish species of Karachi. Samples of the fish were collected from Shah Faisal Colony, Malir, Korangi, Saddar and Federal B Area and tested with the help of flame atomic absorption spectrophotometer.

Namra A. Khan, Nazish Kausar, Atta-ur-Rehman, Sajid Jahangir and Iftikhar Saeed conducted the research under the supervision of Dr Kousar Yasmeen at the Department of Chemistry of the Federal Urdu University of Arts, Science and Technology.

The study determined concentration of metals (lead, iron, copper, cadmium) in the heart, skin and fillet of fish species such as Epinephelus chlorostigma (Gisser), Pampus argenteus (Sufed Pamplet), Scomberomorus commerson (Surmai), Rachycentron canadum (Sangra), Labeo rohita (Rohu), Johnius belangerii (Mushka), Trachinotus blochii (Sonaf), Lutjanus argentimaculatus (Hira), Acanthopagrus berda (Dandya) and Pomadsys olivaceum (Dhotar).

“When concentration of metals in fish species were compared with the International Atomic Energy Agency (IAEA)-407, World Health Organisation (WHO) and Food and Agriculture Organisation (FAO) limits, we found that the concentration of lead in the skin of Epinephelus chlorostigma, Scomberomorus commerson, Lutjanus argentimaculatus, Acanthopagrus berda and fillets of Epinephelus chlorostigma, Johnius belangerii exceeded the IAEA-407 recommended values while lead levels in the heart and skin of Johnius belangerii exceeded the IAEA-407 and FAO recommended values,” the study says.

Copper, cadmium and iron levels, according to the study, were below the corresponding limits (IAEA-407, FAO and WHO).

According to the findings, the ranges for elements analysed were: cadmium (0.00 – 0.041mg/kg), copper (0.006 – 0.189mg/kg), iron (0.413 – 4.952mg/kg) and lead (0.00 –0.569mg/kg). Results showed that the heart of Trachinotus blochii had the highest accumulation of cadmium 0.041mg/kg. The element was not detected in the heart, skin and fillet of Lutjanus argentimaculatus.

The results of analysis indicated that the concentration of cadmium in the heart of all species was in the range of 0.00 – 0.041mg/kg; skin 0.00 – 0.037mg/kg and fillet 0.00 – 0.020mg/kg.

Varying concentration of copper was found in the heart, skin and muscles of all species. The fillet of Scomberomorus commerson (0.189mg/kg) contained high accumulation of copper.

Accumulation of iron was higher in the heart of Labeo rohita (3.931mg/kg), in the skin of Epinephelus chlorostigma (4.952mg/kg) and in the fillet of Scomberomorus commerson (3.098mg/kg). The maximum iron level permitted in fish is 100mg/kg (WHO, 1989).

Accumulation of lead was found high in the skin of Epinephelus chlorostigma (0.276mg/kg), Scomberomorus commerson (0.236mg/kg), Lutjanus argentimaculatus (0.147mg/kg), Acanthopagrus berda (0.131mg/kg); in fillet of Epinephelus chlorostigma (0.168mg/kg), Johnius belangerii (0.218mg/kg) and exceeded the IAEA-407 recommended value while heart (0.569mg/kg) and skin (0.529mg/kg) of Johnius belangerii exceeded the FAO recommended values.

(WHO, IAEA and FAO limits for lead is 2.0mg/kg, 0.120mg/kg and 0.50mg/kg).

The results of analysis indicated that the concentration of cadmium in the heart of all species was in the range of 0.00 – 0.041mg/kg; skin 0.00 – 0.037mg/kg and fillet 0.00 – 0.020 mg/kg.

On the health effects of these metals, the study examines the role of cadmium, lead, iron and copper in human body.

“Copper is essential for the proper functioning of different organs and metabolic processes. Its levels were found to be below the maximum permissible limit (30.0mg/kg) of WHO 1989 and FAO 1983. Copper contents in the reported data were 0.002mg/kg in fish species,” it says.

Cadmium, according to the study, is a non-essential and toxic element. It increases the formation of kidney stones and excretion of calcium in urine. Long term exposure to cadmium may also cause skeletal damage.”

It says the increased industrialization is increasing the risk of lead exposure to humans through different types of food chains. The exposure to lead can have negative effects on many organs especially the nervous system, kidneys and blood of a person, the study states. “Therefore, it is necessary to have regular biological monitoring of marine water and fish to ensure continuous safety of seafood especially fish which is important sea food containing high quality proteins, minerals and essential polyunsaturated fatty acids.

“It is also necessary that industrial effluent and domestic sewage are released into the sea after treatment,” it says.