Estimation of metal residues in Oreochromis niloticus and Mugil cephalus intended for human consumption in Egypt: a health risk assessment study with some reduction trials

Tetracycline residues in tilapia and catfish tissue and the effect of different cooking methods on oxytetracycline and doxycycline residues

Fish such as tilapia (Oreochromis niloticus) and catfish (Clarias gariepinus) is an important source of high biological value animal protein. Fish can be exposed to antimicrobials in intensive aquaculture systems or exposed to remnants of the antimicrobials released to various water bodies via drainage systems. This study aimed at screening for antimicrobial residues in two major fish species commonly consumed in Egypt, namely, tilapia, and catfish, either in wild or cultured fish using a microbial inhibition assay. Besides, quantitative estimation of tetracycline (oxytetracycline and doxycycline) residues in the edible fish muscles was carried out using the solid phase extraction (SPE) technique and high-performance liquid chromatography with photodiode-array detection (HPLC-PAD). In addition, the effects of different cooking methods (pan-frying, grilling, and microwaving) on oxytetracycline and doxycycline residues in tilapia and catfish were investigated. The microbiological inhibition assay revealed that 2, 24, 18, and 32% of the examined wild tilapia, cultured tilapia, wild catfish, and cultured catfish, respectively, contained antibiotic residues. Cultured tilapia, wild catfish, and cultured catfish had mean concentrations of oxytetracycline residues of 0.147 ± 0.067, 0.106 ± 0.046, and 0.313 ± 0.044 µg/g. 3 (6%), 4 (8%), and 9 (18%) of the sampled cultured tilapia, wild catfish, and cultured catfish exceeded the established maximum permissible limits (MPL) of tetracycline (0.100 ng/g). The mean concentrations of doxycycline residues were 0.276 ± 0.045, 0.026 ± 0.004, and 0.070 ± 0.010 µg/g in cultured tilapia, wild catfish, and cultured catfish, respectively, with 2 (4%) of the cultured tilapia exceeding the MPL of doxycycline. Consumption of fish with high residual levels of tetracyclines might pose potential health risks to consumers. In an experimental trial, heat treatment of tilapia and catfish could significantly reduce both oxytetracycline and doxycycline residues, particularly grilling had the highest reduction rates.

Heavy Metal Concentrations in Fish from River Tano in Ghana and the Health Risks Posed to Consumers

Appreciable levels of trace metals have been reported in the Tano basin, but data on the corresponding levels in fish and the risk they pose to consumers are limited. The levels of 7 trace metals in 18 fish muscles were assessed between November 2016 and October 2017 using acid digestion and PerkinElmer (PinAACle 900T) Atomic Absorption Spectrophotometry. Apart from Cu, all the metals studied were detected in all fish samples. The levels of Cr, As, and Hg were higher than the acceptable levels of fish muscles. Cr concentration ranged from 16.10 ± 0.2 mg/kg in Clarias gariepinus to 57.9 ± 4.2 mg/kg in Sarotherodon galilaeus. The levels of As ranged from 1.01 ± 0.08 in Clarias gariepinus to 3.00 ± 0.01 mg/kg in Mormyrus rume. Hg level was 0.58 ± 0.69 mg/kg in Oreochromis niloticus and 2.52 ± 0.70 mg/kg in Ctenopoma kingsleyae. However, Pb, Zn, and Cd concentrations were below the Food and Agriculture Organization limits with low target hazard quotients in all fish samples, suggesting no possible noncarcinogenic risks to adult consumers. Possible noncarcinogenic and carcinogenic health risks were recorded for As, Hg, and Cr in all fish species. Strong associations were observed between Hg, As, Zn, and Cr and between Pb and Cd suggesting a possible common source. Mormyrus rume fish species was under stress in the river, but the remaining species were in good condition. Periodic monitoring of trace metal concentrations in fish and enforcement of the buffer zone policy are recommended.

Health Risk Assessment of Metals (Cu, Pb, Zn, Cr, Cd, As, Hg, Se) in Angling Fish with Different Lengths Collected from Liuzhou, China

Wild fish caught by anglers (WFAs) were confirmed to be usually contaminated with metals, and the contamination status is radically affected by the growth and length of the fish. To determine the contamination levels of metals and health risks in WFAs with different length ranges of fish, this study ascertained the concentration of eight metals, including Cu, Pb, Zn, Cr, Cd, As, Hg and Se, in 171 wild fishes collected from the watershed of Liujiang River. The assessment of metal pollution and health risks from the consumption of these fishes with seven length ranges were accomplished. The obtained results implied a relatively high concentration of Zn, Cr, and Cd up to 109.294 mg/kg, 4.226 mg/kg, and 0.196 mg/kg (wet weight), respectively, which exceed the corresponding Maximum Residue Limit (MRL). The negative correlation between Cu, Zn, Cr, and Cd was observed to be significant with fish length, signifying a possible occurrence of biological dilution on these metals. The WFAs were mostly contaminated with Cr and Cd irrespective of the length ranges of fish, which were denoted by the average pollution index (Pi) of Cr and Cd and were commonly found to be beyond 0.2. Based on the results of health risk assessment analysis, most of the target hazard quotient (THQ) values of Cr were below 1, implying that the consumption of wild fish for adults has insignificant health risk. For children, the total target hazard quotient (TTHQ) values of beyond 1 were found in fishes with the length range of <25 cm, particularly a TTHQ value 1.627 in the range of 10–15 cm, indicating that children are being prone to serious health risks owing to the consumption of WFAs. The weekly recommended consumption of WFAs with the length range of 10–15 cm for adults and children was 0.298 kg/week and 0.149 kg/week, respectively. These are substantially lower than the current rate of fish consumption (0.42 kg/week), and therefore, the wild fish with the length range of 10–15 cm should be avoided for consumption.