Levels of PAHs and Potentially Toxic Metals in Three Species of Fresh and Smoked Fish Consumed in Lagos, Nigeria.

Abstract

Three samples of fish, Scomber japonica (titus), Sardinellaeba (sardine) and Merlucciuspolli (fresh stock fish) were collected from Ojo main market in Lagos. Two low molecular weight polycyclic aromatic hydrocarbons (naphthalene and anthracene) were determined using high performance liquid chromatography, (HPLC), after extraction with n-hexane by ultrasonication and clean up using SPE cartridges. Heavy metals were determined in the samples using atomic absorption spectrometer, (Perkin Elmer, Analyst 200) after digestion with aqua regia. The fat content was determined gravimetrically. The unsmoked samples had naphthalene range from 0.0788±0.0078 µg/g in Merlucciuspolli to 0.3845±0.0199 µg/g in Scomber japonica. Anthracene levels ranged from 0.4798± 0.0072 µg/g in unsmoked samples of Merlucciuspolli to 1.2254±0.0071 µg/g in Scomber japonica. The low fat containing specie (Merlucciuspolli) accumulated PAHs over the smoking periods, while a decrease was observed in the high fat containing species (Scomber japonica and Sardinellaeba). The highest concentration of Pb (8.65 µg/g), Cu (9.53 µg/g), Fe (201.80 µg/g) and Zn (122.15 µg/g) in the unsmoked fishes were found in unsmoked Scomber japonica while the highest concentration of Cr (13.68 µg/g) and Ni (5.88 µg/g) in the fishes were found in the unsmoked Merlucciuspolli. Cadmium was not detected in all the samples. The low fat containing specie showed increase in heavy metals over the smoking periods, while the high fat containing species also accumulated these heavy metals at 1 hour smoking period, but a decrease was noted over the 2 hours and 3 hours smoking periods. Smoking has effect on the level of these toxicants, as PAHs and heavy metals tend to accumulate on smoking. Smoking appeared to influence toxicants levels the fishes. Levels of the PAHs were higher than the regulatory permissible limits of the World Health Organization. Levels of the toxic metals were within the WHO set permissible limits except for Pb (in unsmoked Scomber japonica), Fe (in Sardinellaeba smoked for 1 and 2 hours, and in Merlucciuspolli smoked for 2 and 3 hours) and Cr (in all the samples). Keywords: Toxicants, smoked and unsmoked fish, ultrasonication, SPE, HPLC.