Results and discussions

Concentrations of HMs in the muscle of flathead grey mullet, sardine, and mackerel

The mean concentrations of Hg, As, Pb, and Cd in muscle tissues of the three fish species examined are shown in Fig. 3. Arsenic (As) showed the highest mean level across all species. In contrast, Cd revealed the lowest mean concentration. Furthermore, the flathead grey mullet exhibited the highest concentrations of Hg and As, whereas sardine had the highest Pb concentration, and mackerel showed the highest Cd concentration (Fig. 3). Variations in metal levels among fish species may be influenced by differences in water quality, ecological factors, fish size, and dietary habits. This is in accordance with Abd-Elghany et al., who attributed differences in Hg concentrations among fish species to variations in feeding habits, habitat preferences, geographical distribution, and seasonal changes25. However, in the present study, Spearman’s rank correlation analysis revealed no statistically significant correlations (P > 0.05) between fish size parameters (total length and body weight) and the concentrations of Hg, As, Pb, and Cd across all fish species examined.

Fig. 3: Mean concentrations of heavy metals (µg/g wet weight) in the muscle of flathead grey mullet, sardine, and mackerel. Columns with different letters for each metal indicate statistically significant differences at P < 0.05 or P < 0.01.

Concentrations of As

Mercury is a toxic HM that contaminates aquatic environments through industrial and agricultural discharges. Fish can accumulate Hg by consuming benthic organisms that ingest contaminated sediments. The Hg levels found in flathead grey mullet, sardine, and mackerel were in ranges of 0.01 to 0.66, 0.04 to 0.91, and 0.02 to 1.04 µg/g wet weight (Table 2), with mean values of 0.313 ± 0.02, 0.131 ± 0.04, and 0.196 ± 0.05 µg/g, respectively (Fig. 3A). Flathead grey mullet had a significantly (P < 0.05) higher mean Hg level, while sardine showed significantly lower mean Hg levels when compared with other species (Fig. 3A). In this context, Monier et al. mentioned that Mugil cephalus accumulates higher levels of HMs than other species because of their feeding habits, as they stay near sediment and feed on minute invertebrates, fish parts, algae, and detritus7. Our results are consistent with the study by El-Sherbiny and Sallam, who found that the mean Hg concentration in mackerel was significantly higher than that of sardine samples (0.413 µg/g versus 0.272 µg/g)6.

Fish species | Metal analyzed | Range of metal analyzed (µg/g) | MPL (µg/g wet weight) | The percentage and number of samples exceeded the MPL
Minimum level | Maximum level
Flathead grey mullet | Hg | 0.01 | 0.66 | 0.5 a, b | 20% (10/50)
As | 0.54 | 5.60 | 2.0 c | 56% (28/50)
Pb | 0.05 | 1.18 | 0.3 a, b | 20% (10/50)
Cd | 0.01 | 0.04 | 0.05 b | 0% (0/50)
Sardine | Hg | 0.04 | 0.91 | 0.5 a, b | 9% (9/100)
As | 0.35 | 4.19 | 2.0 c | 41% (41/100)
Pb | 0.07 | 1.19 | 0.3 a, b | 58% (58/100)
Cd | 0.01 | 0.07 | 0.10 b | 0% (0/100)
Mackerel | Hg | 0.02 | 1.04 | 0.5 a, b | 12% (12/100)
As | 0.22 | 3.23 | 2.0 c | 22% (22/100)
Pb | 0.03 | 1.25 | 0.3 a, b | 45% (45/100)
Cd | 0.01 | 0.1 | 0.10 b | 0% (0/100)

Concentrations of As

Arsenic displayed the highest mean level among all HMs analyzed (Fig. 3B). The As concentrations in flathead grey mullet, sardine, and mackerel ranged from 0.54 to 5.60, 0.35 to 4.19, and 0.22 to 3.23 µg/g wet weight (Table 2), with mean values of 2.13 ± 0.2, 1.65 ± 0.1, and 0.98 ± 0.06 µg/g, respectively (Fig. 3B). Flathead grey mullet exhibited significantly higher As concentrations compared to sardine (P < 0.05) and mackerel (P < 0.01) (Fig. 3B). This can be attributed to its benthic feeding habits, as the species primarily consumes detritus, sediments, algae, and organic matter that accumulate higher arsenic levels7. In contrast, sardine is a plankton-feeding fish that transfers energy and nutrients from planktonic organisms to larger pelagic species10. This behavior may explain why sardine samples contain higher arsenic levels than mackerel (1.65 µg/g versus 0.98 µg/g) (Fig. 3B). Similarly, Bordajandi et al. found that As concentration in sardine was higher than that in mackerel (2.65 µg/g versus 0.91 µg/g)41.

Concentrations of lead

Lead is a highly toxic HM that poses significant risks to human health, making its accumulation in fish muscle an important concern for food safety. The Pb levels ranged from 0.05 to 1.18, 0.07 to 1.19, and 0.03 to 1.25 µg/g (Table 2), with mean levels of 0.194, 0.472, and 0.37 µg/g in the muscle of flathead grey mullet, sardine, and mackerel, respectively (Fig. 3C). The contamination level of Pb in fish species in the present study was in the following order: sardine > mackerel > flathead grey mullet (Fig. 3C). Sardine exhibited significantly higher Pb concentrations compared with mackerel (P < 0.05) and flathead grey mullet (P < 0.01) (Fig. 3C). These differences in metal concentrations among the three fish species examined might be related to the pollution level at the catching sites, feeding habits, the size of the caught fish, or complex interactions among biological and ecological factors6.

Concentrations of Cd

Cadmium residues were detected in the muscle of flathead grey mullet, sardine, and mackerel at ranges of 0.01 to 0.04, 0.01 to 0.07, and 0.01 to 0.1 µg/g with mean ± SE levels of 0.018 ± 0.003, 0.021 ± 0.002, and 0.025 ± 0.004 µg/g, respectively (Fig. 3D). The level of Cd contamination in fish species examined was in the following order: mackerel > sardine > flathead grey mullet (Fig. 3D). These variations in Cd concentrations may be due to their differences in detoxification capacity42. Flathead grey mullet and sardine likely sequester Cd more efficiently, via higher metallothionein activity, resulting in lower muscle concentrations. In contrast, mackerel appears to have comparatively lower detoxification efficiency with higher feeding intensity, leading to greater Cd retention. Cadmium had the lowest mean level among all HMs analyzed in our study (Fig. 3D). This may be attributed to its accumulation potential in the liver and kidney rather than in muscle tissues42.

Comparison of HMs detected in fish muscles with their maximum permissible limit (MPL)

HM concentrations in muscle samples were compared with their MPLs to assess the safety and acceptability of the fish species examined. For Hg, 20% (10/50), 9% (9/100), and 12% (12/100) of flathead grey mullet, sardine, and mackerel samples analyzed, respectively, exceeded the MPL of 0.5 µg/g proposed by FAO43 and Egyptian Organization for Standardization and Quality (EOS)44 (Table 2; Fig. 4). Meanwhile, 56% (28/50), 41% (41/100), and 22% (22/100) of flathead grey mullet, sardine, and mackerel samples tested, respectively, exceeded the MPL of 2.0 µg/g established by Food Standards Australia New Zealand (FSANZ) for As45 (Table 2; Fig. 4). Likewise, 40% of sardine samples from four coastal Egyptian governorates exceeded the Egyptian permissible limit of 2 µg/g for As in fish3. Furthermore, 12% and 26% of raw sardine and mackerel samples, respectively, exceeded the MPL for Hg6. Meanwhile, only 3.4% (2/60) of Flathead grey mullet from Manzala Lake, Egypt25, and 0.16% of 1245 mackerel samples from northern European waters46 exceeded the MPL for Hg. Conversely, the majority (80%, 48/60) of the examined Flathead grey mullet had As levels above the maximum recommended levels25. On the other hand, all sardine and mackerel samples from retail markets in Bosnia and Herzegovina47 and flathead grey mullet from Croatia48 contained Hg at concentrations below the MPL, whereas sardine samples from various fish sale markets in Giza, Egypt, were within the MPL for As49.

Fig. 4: Percentage of fish samples exceeding or within the maximum permissible limits (MPLs) of Hg, As, Pb, and Cd in the muscle of flathead grey mullet, sardine, and mackerel.

For Pb, 20% (10/50) of flathead grey mullet, 58% (58/100) of sardine, and 45% (45/100) of mackerel samples surpassed the MPL of 0.3 µg/g set by FAO43 (Table 2; Fig. 4). The Cd levels in the three fish species studied were lower than the MPL of 0.05 µg/g for Cd in flathead grey mullet and of 0.10 for Cd in sardine and mackerel set by EOS44 (Table 2; Fig. 4). Likewise, all sardine and mackerel samples from retail markets in Bosnia and Herzegovina contained Cd concentrations below their MPLs47. Furthermore, Cd concentrations were lowest in all fish muscles tested, with only five flathead grey mullet muscle samples exceeding the Cd limits set by Croatia, Germany, and Russia48. In contrast, all sardine samples obtained from several fish markets in Giza, Egypt, were higher than the MPL for Cd49. Conversely, Abd-Elghany et al. found that 66.6% of flathead grey mullet exceeded the Egyptian MPL for Pb, while 63.4% surpassed the MPL for Cd25, whereas Embaby et al.3 found that 44% and 50% of sardine samples from four coastal Egyptian governorates exceeded the MPL for Pb and Cd. However, only 10% and 6% of sardine samples and 14% and 10% of mackerel samples exceeded the MPLs for Pb and Cd, respectively6. Furthermore, only 0.24% of 1245 mackerel samples from northern European waters exceeded the permissible limits for Cd46.

Comparison of heavy metal concentrations with previous studies

A comparison of the heavy metal concentrations detected in the current study with those previously reported for similar fish species from Egypt and worldwide is presented in Table 3. This comparison highlights the variability in contamination levels across studies, which may be influenced by factors such as geographical locations, fish size and diet, water quality, and other ecological factors.

Fish species | Heavy metals concentrations (µg/g) | Country | References
Hg | As | Pb | Cd
Flathead grey mullet | 0.313 | 2.13 | 0.194 | 0.018 | Egypt | The current study
Sardine | 0.131 | 1.65 | 0.472 | 0.021 | Egypt | The current study
Mackerel | 0.196 | 0.98 | 0.37 | 0.025 | Egypt | The current study
Flathead grey mullet | 0.198 | 0.309 | 0.106 | 0.052 | Croatia | Has-Schön et al.48
Flathead grey mullet | 0.15 | 4.25 | 0.87 | 0.12 | Egypt | Abd-Elghany et al.25
Sardine | 0.0467 | 2.645 | 0.217 | 0.0125 | Spain | Bordajandi et al.41
Sardine | 0.62 | – | 2.13 | 0.55 | Algeria | Mehouel et al.50
Sardine | 0.272 | – | 0.194 | 0.0471 | Egypt | El-Sherbiny and Sallam 6
Sardine | 0.089 | 0.514 | 0.012 | 0.020 | Bosnia and Herzegovina | Hajrić et al.47
Sardine | 0.015 | 6.95 | 0.008 | 0.172 | Beni-Ensar, Morocco | Kasmi et al.55
Sardine | 0.068 | 1.810 | 0.329 | 0.03 | Egypt | Sabala et al.7
Sardine | ND | 0.43 | 0.14 | 0.34 | Egypt | Malak et al.49
Mackerel | 0.1 | 0.907 | 0.0151 | 0.0126 | Spain | Bordajandi et al.41
Mackerel | – | 3.669 | 0.003 | 0.0013 | Italy | Copat et al.53
Mackerel | 0.413 | – | 0.252 | 0.0392 | Egypt | El-Sherbiny and Sallam 6
Mackerel | 0.075 | 0.116 | 0.005 | 0.016 | Bosnia and Herzegovina | Hajrić et al.47
Mackerel | 0.046 | 2.20 | ND | 0.015 | Norway | Frantzen et al.46
Guidelines | Hg | As | Pb | Cd | References
Egyptian Organization for Standardization and Quality (EOS) | 0.50 | – | 0.30 | 0.05 excluding sardine and Mackerel (0.10) | EOS (No 7136/2010)44
European Commission Regulation (EC) | 0.50 | – | 0.30 | 0.05 excluding sardine (0.25) and Mackerel (0.10) | EU (No 915/2023)57
FAO | 0.50 | – | 0.30 | – | FAO (2018)43
FSANZ | 0.50 | 2.00 | 0.50 | – | FSANZ (2025)45

In comparison, Has-Schön et al. found a lower mean Hg level of 0.198 ± 0.04 µg/g in the muscles of flathead grey mullet from Croatia48, while Bordajandi et al. detected low mean Hg concentrations of 46.73 ng/g (0.0467 µg/g) in sardine and 100 ng/g (0.1 µg/g) in mackerel samples from Huelva, Spain41. Similarly, Hajrić et al. found slightly lower Hg levels of 0.075 and 0.089 µg/g in mackerel and sardine samples obtained from the retail market in Bosnia and Herzegovina47. Moreover, Abd-Elghany et al. reported lower Hg concentrations in the muscle of flathead grey mullet from Manzala Lake, Egypt, ranging from 0.04 to 0.40 µg/g, with a mean value of 0.15 ± 0.03 µg/g25. In contrast, sardine samples from the Algerian coast contained Hg concentrations of 0.620 µg/g50, approximately five times higher than that observed in the present study. Conversely, Embaby et al. did not detect Hg in sardine samples collected between 2019 and 2021 from 4 coastal governorates in Egypt (Alexandria, Kafr El-Sheikh, Damietta, and Port Said)3.

The current results are comparable to those reported by Sabala et al., who found that the mean As level in raw sardine was 1.810 ± 0.071 µg/g8. On the other hand, the highest mean As level in sardines from four Egyptian coastal governorates was 0.475 µg/g3, which is lower than those obtained in the present study. Likewise, Has-Schön et al. reported low As levels of 0.309 ± 0.048 µg/g in the muscles of flathead grey mullet from Croatia48, while Hajrić et al. observed low As concentrations of 0.116 and 0.514 µg/g in mackerel and sardine, respectively, from retail markets in Bosnia and Herzegovina47. In contrast, Abd-Elghany et al. reported higher As levels in the muscles of flathead grey mullet from Manzala Lake, Egypt, ranging from 0.15 to 9.36 µg/g, with a mean value of 4.25 ± 0.47 µg/g25. Furthermore, Frantzen et al. analyzed 1245 mackerel (Scomber scombrus) samples from northern European waters during 2007–2016 and found that the As concentrations varied between 0.43 and 6.9 µg/g, with a mean value of 2.2 µg/g46, which is markedly higher than the mean value of 0.98 µg/g observed in the present study (Fig. 3B).

Our findings agree with those obtained by Embaby et al., who reported mean Pb levels of 0.442 ± 0.016 and 0.482 ± 0.017 µg/g in sardine samples obtained from the Mediterranean coasts of Alexandria and Damietta, respectively, during the winter of 20193. In contrast, Monier et al. obtained a substantially higher Pb concentration of 1.48 ± 0.39 in flathead grey mullet samples obtained from the Damietta fishing port and its surrounding environment in the Mediterranean Sea during winter7, while Abd-Elghany et al. detected higher Pb levels in the range of 0.02 to 2.90 with mean values of 0.87 ± 0.15 µg/g in flathead grey mullet from Manzala Lake, Egypt25. Conversely, Has-Schön et al. reported slightly lower Pb concentrations of 0.106 ± 0.006 µg/g in the muscle of flathead grey mullet from Croatia48. Additionally, El-Sherbiny and Sallam found low mean Pb concentrations of 0.194 ± 0.011 and 0.252 ± 0.025 µg/g in sardine and mackerel samples from the Mediterranean Sea Coast, Egypt6, while Hajrić et al. reported very low Pb levels of 0.005 and 0.012 µg/g in mackerel and sardine from retail markets in Bosnia and Herzegovina47.

Our findings for Cd were comparable to those reported by Hajrić et al., who found Cd concentrations of 0.020 µg/g in sardine samples from Bosnia and Herzegovina47. Meanwhile, Bordajandi et al. found slightly lower mean Cd levels of 12.6 ng/g (0.0126 µg/g) in sardine and 12.5 ng/g (0.0125 µg/g) in mackerel samples from Huelva, Spain41. Likewise, Frantzen et al. found that Cd concentration in mackerel samples from northern European waters was 0.015 µg/g46. On the other hand, El-Sherbiny and Sallam reported slightly higher mean Cd values of 0.0471 ± 0.003 µg/g and 0.0392 ± 0.003 µg/g in sardine and mackerel, respectively6. Furthermore, Has-Schön et al. observed a higher Cd level of 0.052 ± 0.03 µg/g in the muscle tissues of flathead grey mullet from Croatia48, while Abd-Elghany et al. observed substantially higher Cd concentrations of 0.12 ± 0.02 µg/g in the muscles of flathead grey mullet from Manzala Lake, Egypt25. In contrast, Monier et al. found markedly higher Cd concentrations in flathead grey mullet samples (0.64 ± 0.01 µg/g) and sardine (0.21 ± 0.11 µg/g) collected from the Damietta fishing harbor during the winter season7. Similarly, sardine from the Algerian coastline showed considerably higher Cd content of 0.55 µg/g50.

Health risk assessment

The accumulation of HMs in fish muscles may pose a serious health risk to consumers. Previous studies in Egypt7,25, China27, and Pakistan51,52 have evaluated the potential health risks associated with HM consumption by estimating EDI, THQ, TTHQ, and CR.

The EDI of HMs detected in fish muscle compared with their PTDI or BMDL values

The EDIs of HMs detected in the muscle of flathead grey mullet, sardine, and mackerel were estimated for both the general population and high-fish consumers and compared to their PTDIs or BMDLs set by regulatory organizations, such as JECFA and EFSA, to assess if the HM concentrations detected in fish samples fall within the safe limit for consumption in humans (Tables 4 and 5). The EDI was calculated based on the average metal concentration in fish muscle and the daily fish consumption rate of 57.09 g/day for the general population2and 200 g/day for high-fish consumers33 by a 70-kg Egyptian consumer. The EDIs for the general population were lower than PTDIs or BMDLs for the four metals analyzed across all fish species examined, except for Hg in flathead grey mullet, which slightly exceeded the safety threshold (111%) (Table 4). For high-fish-consumption groups, the EDI of Hg in all species, As in flathead grey mullet and sardine, and Pb in sardine and mackerel, exceeded their corresponding PTDI/BMDL values, indicating a potential health concern (Table 5).

Heavy metals | PTDI/BMDLmg/kg.bw/day | Mean concentration (µg/g) | EDI* (mg of metal /70-kg BW person/day) compared with PTDI or BMDL
Flathead grey mullet | Sardine | Mackerel | Flathead grey mullet | Sardine | Mackerel
EDImg/person/d | %EDI/PTDIor BMDL | EDImg/person/d | %EDI/PTDIor BMDL | EDImg/person/d | %EDI/PTDIor BMDL
Hg | 2.30E−04a | 0.313 | 0.131 | 0.196 | 2.55E−04 | 111% | 1.07E−04 | 46.5% | 1.59E−04 | 69.1%
As | 3.00E−03a | 2.13 | 1.65 | 0.98 | 1.74E−03 | 58% | 1.35E−03 | 45% | 7.99E−04 | 26.6%
Pb | 6.30E−04b | 0.194 | 0.472 | 0.37 | 1.58E−04 | 25.1% | 3.85E−04 | 61.1% | 3.02E−04 | 47.9%
Cd | 8.30E−04c | 0.018 | 0.021 | 0.025 | 1.47E−05 | 1.77% | 1.71E−05 | 2.06% | 2.04E−05 | 2.46%

Heavy metals | PTDI/BMDLmg/kg.bw/day | Mean concentration (µg/g) | EDI* (mg of metal /70-kg BW person/day) compared with PTDI or BMDL
Flathead grey mullet | Sardine | Mackerel | Flathead grey mullet | Sardine | Mackerel
EDImg/person/d | %EDI/PTDIor BMDL | EDImg/person/d | %EDI/PTDIor BMDL | EDImg/person/d | %EDI/PTDIor BMDL
Hg | 2.30E−04a | 0.313 | 0.131 | 0.196 | 8.94E−04 | 388.7% | 3.74E−04 | 162.6% | 5.60E−04 | 243.5%
As | 3.00E−03a | 2.13 | 1.65 | 0.98 | 6.09E−03 | 203% | 4.71E−03 | 157% | 2.80E−03 | 93.3%
Pb | 6.30E−04b | 0.194 | 0.472 | 0.37 | 5.54E−04 | 87.9% | 1.35E−03 | 214.3% | 1.057E−03 | 167.8%
Cd | 8.30E−04c | 0.018 | 0.021 | 0.025 | 5.14E−05 | 6.19% | 6.00E−05 | 7.23% | 7.14E−05 | 8.60%

For the general population, only the EDI of Hg through consumption of flathead grey mullet exceeded its corresponding PTDI, reaching 111% of the recommended limit. In contrast, the EDIs of As, Pb, and Cd remained below their respective PTDI/BMDL values (Table 4). The current findings align with Monier et al., who reported that the EDIs for Cd and Pb in flathead grey mullet and sardine muscles from the Damietta fishing harbor were lower than the recommended safety thresholds7. In contrast, Abd-Elghany et al. reported a lower EDI of 1.3 × 10−4 µg/g /d for Hg but higher EDIs of 3.8 × 10−3, 7.9 × 10−4, and 1 × 10−4 µg/g/d for As, Pb, and Cd, respectively, in flathead grey mullet samples25. Furthermore, Mehouel et al. estimated the EDIs of Pb and Cd in sardine from Algerian coasts at 1.6 × 10−5 and 1.6 × 10−6 µg/g bw, respectively50, and Copat et al. reported lower EDI values for Pb (1 × 10−5 µg/g bw) and Cd (4 × 10−6 µg/g bw) in Atlantic mackerel from the Gulf of Catania, Italy53, which are considerably lower than the values reported in our study for the general population.

For high-fish consumers, EDIs increased markedly across all fish species. The EDI of Hg exceeded the corresponding PTDI in flathead grey mullet (388.7%), sardine (162.6%), and mackerel (243.5%). Likewise, As exceeded its corresponding BMDL in flathead grey mullet (203%) and sardine (157%), whereas Pb exceeded the recommended limit in sardine (214.3%) and mackerel (167.8%) (Table 5), indicating a potential health concern for high-fish consumers, especially for Hg, As, and Pb. Similarly, the non-carcinogenic EDIs of Hg and As from consuming flathead grey mullet by high fish consumers exceeded their respective PTDIs and BMDLs by 186.33% and 404.76%, respectively25. Overall, the higher EDIs of HMs analyzed across fish species examined for both general and high-fish consumers pose a significant public health issue; thus, monitoring fish consumption and adopting strict contamination control measures are crucial to protect public health.

THQ and TTHQ

THQ or TTHQ assesses the potential non-carcinogenic health risk linked to exposure to HMs in food7,25,27. Values exceeding 1.0 indicate potential non-carcinogenic health risks, whereas values between 0.1 and 1.0 suggest a low health risk, and those < 0.1 denote negligible risk54. THQ values for Hg and As in flathead grey mullet, sardine, and mackerel exceeded 1.0 for both the general population and high-fish consumers, indicating a potential non-carcinogenic health concern (Table 6). Whereas values for Pb and Cd were below 1.0 across all fish species, suggesting negligible health risks. Interestingly, THQ values were extremely high among high-fish consumers (Table 6). Overall, the TTHQ values for flathead grey mullet, sardine, and mackerel were 8.4, 5.7, and 4.35 for the general population and 29.43, 19.84, and 15.26 for high-fish consumers, respectively (Table 6).

Consumers | Heavy metals | RfD (mg/kg /day) | Flathead grey mullet | Sardine | Mackerel
EDImg/kg BW/day | THQ | EDImg/kg BW/day | THQ | EDImg/kg BW/day | THQ
General population | Hg | 1E−04a | 2.55E−04 | 2.55 | 1.07E−04 | 1.07 | 1.59E−04 | 1.59
As | 3E−04a | 1.74E−03 | 5.8 | 1.35E−03 | 4.5 | 7.99E−04 | 2.66
Pb | 4E−03b | 1.58E−04 | 0.04 | 3.85E−04 | 0.09 | 3.02E−04 | 0.08
Cd | 1E−03c | 1.47E−05 | 0.015 | 1.71E−05 | 0.017 | 2.04E−05 | 0.02
Σ HI or TTHQ d | 8.4 |  | 5.7 |  | 4.35
High-fish consumers | Hg | 1E−04a | 8.94E−04 | 8.94 | 3.74E−04 | 3.74 | 5.60E−04 | 5.60
As | 3E−04a | 6.09E−03 | 20.3 | 4.71E−03 | 15.7 | 2.80E−03 | 9.33
Pb | 4E−03b | 5.54E−04 | 0.14 | 1.35E−03 | 0.34 | 1.057E−03 | 0.26
Cd | 1E−03c | 5.14E−05 | 0.05 | 6.00E−05 | 0.06 | 7.14E−05 | 0.07
Σ HI or TTHQ d | 29.43 |  | 19.84 |  | 15.26

By comparison, none of the THQ or TTHQ values for Cd and Pb in flathead grey mullet or sardine muscles exceeded 1.07. On the other hand, TTHQ values for sardine from the Kafr El-Sheikh governorate surpassed 1.03. Furthermore, the THQ of Hg and the TTHQ values of both Hg and Cd in flathead grey mullet exceeded 1.0 for both the general population and high-fish consumers, indicating a potential non-carcinogenic health risk25. Additionally, the THQ values for Cd in Atlantic mackerel from the eastern Mediterranean Sea were below 1.0, while values for As were above 1.0, for a consumption rate of more than 1 meal/week, particularly among children53. Meanwhile, THQ values for Hg and Cd in sardine and mackerel from Italian supermarkets were < 1.0, indicating a negligible risk. Collectively, TTHQ values for the three fish species examined in the current study exceeded 1, indicating that cumulative exposure poses a substantial non-carcinogenic health concern, primarily due to higher THQ values for both As and Hg (Table 6).

Cancer Risk (CR)

CR values between 1 × 10−6 (one additional case per 1,000,000 individuals) and 1 × 10−4 (one additional case per 10,000 individuals) are not of concern, whereas values exceeding 10−4 reveal a potential carcinogenic risk26. Arsenic (As) exhibited the highest CR values among the analyzed metals, exceeding 1.0 × 10−4 for both the general population and high-fish consumers. CR values for As were 2.61E−03, 2.03E−03, and 1.20E−03 for flathead grey mullet, sardine, and mackerel, respectively, in the general population, while higher values of 9.14E−03, 7.07E−03, and 4.20E−03 were observed for the same fish species in high-fish consumers (Table 7). Meanwhile, CR values of Pb and Cd from consuming flathead grey mullet, sardine, and mackerel were < 1.0 × 10−4 for the general population and high fish consumers, indicating a lack of potential carcinogenic risk (Table 7).

Heavy metals | CSF(mg/kg/day) | Flathead grey mullet | Sardine | Mackerel
General population | High-fish consumers | General population | High-fish consumers | General population | High-fish consumers
CR | CR | CR | CR | CR | CR
Hg
As | 1.5a | 2.61E−03 | 9.14E−03 | 2.03E−03 | 7.07E−03 | 1.20E−03 | 4.20E−03
Pb | 0.0085b | 1.34E−06 | 4.71E−06 | 3.27E−06 | 1.15E−05 | 2.57E−06 | 8.98E−06
Cd | 0.38b | 5.59E−06 | 1.95E−05 | 6.49E−06 | 2.28E−05 | 7.75E−06 | 2.71E−05

Similar findings were reported by Abd-Elghany et al., who revealed that CR values of As through consuming flathead grey mullet by both the general population and high-fish consumers were above 1.0 × 10−4; in contrast, Pb and Cd values fell within the acceptable thresholds25. Likewise, arsenic displayed the highest carcinogenic risk, with a value of 2.5 × 10⁻³ associated with the consumption of sardine samples8. Furthermore, Kasmi et al. found that the CR values for As and Cd associated with Sardina pilchardus consumption from the Moroccan Mediterranean coast exceeded acceptable limits55. Also, CR values for As in most fish species collected from the eastern Mediterranean Sea were above the acceptable lifetime risk threshold53. Conversely, Malak et al. found lower CR values of 3.57E−05, 9.44E−07, and 1.02E−04 for As, Pb, and Cd, respectively, in sardine samples from markets in Giza, Egypt49.

Overall, the current findings revealed considerable concern regarding As contamination, as CR values of As were above 1.0 × 10−4, signifying a potential carcinogenic risk linked to consuming fish contaminated with HMs, especially among high fish consumers. Therefore, it is necessary to monitor HM contamination in fish to ensure food safety and protect public health.

This study has a few limitations that should be considered when interpreting the health risk assessment. First, evaluating health risks based on heavy metal concentrations in raw muscle tissue may overestimate actual human exposure, because cooking processes, such as frying or grilling, can alter metal concentrations through moisture loss and volatilization56. Future studies should consider the effects of commonly used cooking methods to improve the accuracy of health risk assessments. Second, chemical speciation of arsenic was not performed, and only total arsenic concentrations were determined. Because marine fish predominantly accumulate less toxic organic arsenic species, such as arsenobetaine, whereas inorganic arsenic represents the primary carcinogenic form, the use of total arsenic concentrations for cancer risk assessment may substantially overestimate the actual carcinogenic risk. Future studies should include arsenic speciation to provide a more accurate assessment of its health risks.