Due to the increasing levels of pollution and its effects on human health, heavy metal pollution has become a serious problem worldwide. Various contaminants are highly toxic and can accumulate in seafood. Thus, the fact that people can be easily exposed to these contaminants means that ultimately human health can also be at risk. When toxic elements are absorbed for a long period of time, they can be highly harmful even at low concentrations (Biswas et al. 2012). Industrial effluents, agricultural runoff, transport, burning of fossil fuels, animal and human excretion, geological weathering, and domestic waste cause pollution of water bodies with heavy metals (Olowu et al. 2010).
Various marine pollution monitoring programs have been initiated due to the fact that marine organisms accumulate contaminants such as metals from the environment (Linde et al. 1998; de Mora et al. 2004). Fish accumulate metals contained in water, their food, seabed sediments and some other particulate material. In many countries, industrial waste, geochemical structure and mining of metals are known to cause heavy metal pollution in the aquatic environment owing to their toxicity and accumulation behavior. Under certain environmental conditions, these heavy metals can accumulate up to toxic concentration levels and cause ecological damage (Sivaperumal et al. 2007).
It should be noted that the level and variety of heavy metals among different fish species depend on their feeding, habits, age, size (including length and weight) and habitats (Amudsen et al. 1997). Contamination caused by heavy metals in animal-based food is a severe threat to human health due to their toxicity, persistence, bioaccumulation, and biomagnification (Kannan et al. 2007; Chary et al. 2008).
Fish can accumulate high concentrations of metals in their tissues, especially in muscles, which makes them a major source of these metals in the human diet (Rose et al. 1999). In general, residents of our coastal areas are very poor and do not have a good sense of food security. It is therefore the responsibility of relevant authorities to focus on this aspect and ensure that food security objectives are incorporated into national poverty reduction strategies. This would have an impact at national, sub-national, household and individual levels, with a particular emphasis on reducing hunger and extreme poverty (FAO 1983).
A large number of commercial fisheries are located in the coastal waters of Balochistan. The fishing pressure on pelagic and demersal fisheries resources has been gradually increasing. However, information on fishing pressure and sustainable stock status is limited and little information on the population dynamics and the status of exploitation in the coastal waters of Pakistan is available. The mullet
The objective of this study was to determine concentrations of heavy metals (Fe, Zn, Cu, Mn, Cd and Pb) in the mullets
The carnivorous mullets
A 1–2 g aliquot of each dry sample was placed in a cylindrical Teflon vessel and digested with 3 ml of a 1:2 v/v mixture of H2O2 and HNO3 at 250°C. The organic part was discarded and the remaining part was diluted with demineralized water to 50 ml in a graduated flask (Bernhard 1976).
Concentrations of metals in
The length and weight (min.–max) of
Seasonal metrics of
Seasons | |||||||
---|---|---|---|---|---|---|---|
N | Length (cm) | Weight (g) | N | Length (cm) | Weight (g) | ||
northeast monsoon | mean | 10 | 13 | 30 | 10 | 17 | 46 |
SD | 23 | 82 | 20 | 66 | |||
min. | 16.60 | 46.40 | 18.60 | 56.60 | |||
max | 3.64 | 19.85 | 1.36 | 8.72 | |||
post-monsoon | mean | 12 | 14 | 34 | 12 | 13.50 | 31 |
SD | 19 | 58 | 18 | 42 | |||
min. | 16.79 | 42.25 | 14.92 | 35.58 | |||
max | 2.03 | 7.47 | 1.79 | 3.90 | |||
pre-monsoon | mean | 10 | 11 | 24 | 10 | 16 | 39 |
SD | 23 | 82 | 24 | 86 | |||
min. | 15.80 | 41.45 | 18.15 | 52.60 | |||
max | 3.28 | 16.33 | 2.03 | 12.61 | |||
southwest monsoon | mean | 12 | 16 | 33 | 12 | 14 | 34 |
SD | 21 | 74 | 26.50 | 106 | |||
min. | 17.71 | 46.67 | 18.58 | 57.42 | |||
max | 1.97 | 14.78 | 5.63 | 31.58 | |||
average | mean | 44 | 11 | 24 | 44 | 13.50 | 31 |
SD | 23 | 82 | 26.50 | 106 | |||
min. | 16.59 | 43.09 | 17.39 | 49.27 | |||
max | 2.73 | 13.89 | 3.62 | 20.13 |
Std. Deviation – SD
Seasonal concentrations in
Fe | Zn | Cu | Mn | Cd | Pb | Fe | Zn | Cu | Mn | Cd | Pb | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
northeast monsoon | mean | 19.44 | 12.04 | 1.91 | 0.26 | 0.05 | 0.20 | 31.31 | 15.28 | 2.20 | 0.32 | 0.25 | 0.30 |
SD | 7.92 | 3.54 | 0.91 | 0.07 | 0.05 | 0.07 | 10.24 | 2.88 | 0.92 | 0.12 | 0.11 | 0.13 | |
min. | 12.36 | 7.08 | 1.23 | 0.16 | 0.00 | 0.05 | 15.56 | 11.98 | 1.33 | 0.16 | 0.03 | 0.16 | |
max | 42.41 | 17.65 | 4.56 | 0.41 | 0.14 | 0.34 | 46.35 | 20.49 | 3.91 | 0.52 | 0.42 | 0.61 | |
post-monsoon | mean | 26.07 | 13.68 | 1.91 | 0.22 | 0.03 | 0.11 | 31.27 | 16.89 | 2.41 | 0.38 | 0.28 | 0.29 |
SD | 8.47 | 4.29 | 0.79 | 0.13 | 0.03 | 0.07 | 8.63 | 5.37 | 0.71 | 0.22 | 0.13 | 0.12 | |
min. | 17.46 | 7.08 | 0.36 | 0.08 | 0.00 | 0.01 | 21.56 | 10.39 | 1.46 | 0.24 | 0.04 | 0.16 | |
max | 38.75 | 19.32 | 3.14 | 0.45 | 0.08 | 0.23 | 48.41 | 26.16 | 3.68 | 0.93 | 0.51 | 0.56 | |
pre-monsoon | mean | 39.59 | 12.75 | 1.81 | 0.26 | 0.14 | 0.35 | 30.39 | 24.28 | 2.37 | 0.32 | 0.29 | 0.31 |
SD | 9.72 | 5.63 | 0.96 | 0.06 | 0.10 | 0.15 | 13.29 | 6.038 | 1.42 | 0.08 | 0.10 | 0.13 | |
min. | 26.03 | 3.62 | 1.06 | 0.16 | 0.02 | 0.09 | 10.72 | 13.59 | 0.88 | 0.22 | 0.18 | 0.14 | |
max | 51.68 | 21.16 | 3.98 | 0.34 | 0.34 | 0.56 | 58.66 | 32.66 | 5.85 | 0.51 | 0.42 | 0.51 | |
southwest monsoon | mean | 23.75 | 16.61 | 1.09 | 0.24 | 0.03 | 0.04 | 24.58 | 19.55 | 1.82 | 0.30 | 0.21 | 0.30 |
SD | 9.93 | 3.87 | 0.44 | 0.13 | 0.03 | 0.04 | 7.85 | 6.90 | 0.89 | 0.10 | 0.11 | 0.10 | |
min. | 14.67 | 10.84 | 0.19 | 0.05 | 0.00 | 0.01 | 10.58 | 8.12 | 0.36 | 0.18 | 0.02 | 0.12 | |
max | 45.79 | 24.16 | 1.63 | 0.46 | 0.08 | 0.16 | 38.08 | 28.76 | 3.10 | 0.46 | 0.41 | 0.48 | |
average | mean | 26.70 | 13.82 | 1.66 | 0.24 | 0.06 | 0.17 | 29.26 | 18.85 | 2.18 | 0.32 | 0.25 | 0.30 |
SD | 11.49 | 4.56 | 0.84 | 0.10 | 0.07 | 0.14 | 10.18 | 6.278 | 1.01 | 0.14 | 0.11 | 0.12 | |
min. | 12.36 | 3.62 | 0.19 | 0.05 | 0.00 | 0.01 | 10.58 | 8.12 | 0.36 | 0.16 | 0.02 | 0.12 | |
max | 51.68 | 24.16 | 4.56 | 0.46 | 0.34 | 0.56 | 58.66 | 32.66 | 5.85 | 0.93 | 0.51 | 0.61 |
Std. Deviation – SD
The accumulation of the metals in the muscles of
The highest accumulation of Fe and Pb in
In the northeast, post-monsoon and southwest monsoon seasons, the concentration of all elements was higher in
The accumulation of Fe found in the muscles is lower than that reported by Al-Najare (2012) for
Comparison of concentrations in fish tissues reported in the literature
Location | Fish | Metal concentrati on (μg g−1 d.w.) | Reference | |||||
---|---|---|---|---|---|---|---|---|
Fe | Zn | Cu | Mn | Cd | Pb | |||
Arabian Gulf | 10.7 | 7.0 | 3.7 | 3.55 | 0.09 | 1.36 | Al-Khafajy et al. 1997 | |
Manila Bay | - | - | - | - | 0.0170 | 0.0382 | Sai Su et al. 2009 | |
Oeshm Island | - | - | - | - | 0.16 | 0.11 | Norouzi et al. 2012 | |
Iraqi Marine | 57 | 9.5 | 6.72 | 5.9 | - | Al-Najare 2012 | ||
Coastal regions of Karachi | - | 0.160 | 0.180 | - | 0.160 | 0.007 | Ali et al. 2013 | |
Indian Sunderbans S1 | - | 124.12 | 75.91 | - | 4.01 | 19.89 | Mitra & Ghosh 2014 | |
Indian Sunderbans S2 | - | 94.63 | 54.39 | - | BDL | 15.16 | ||
Indian Sunderbans S3 | - | 61.21 | 28.12 | - | BDL | 14.85 | ||
Indian Sunderbans S4 | - | 27.67 | 21.01 | - | BDL | 13.92 | ||
Indian Sunderbans S1 | - | 103.45 | 43.89 | - | 1.95 | 15.77 | Mitra & Ghosh 2014 | |
Indian Sunderbans S2 | - | 91.25 | 50.38 | - | BDL | 13.51 | ||
Indian Sunderbans S3 | - | 53.98 | 27.91 | - | BDL | 15.79 | ||
Indian Sunderbans S4 | - | 25.45 | 18.65 | - | BDL | 11.65 | ||
Gangetic Delta Reg. S1 | - | 102.78 | 70.11 | - | - | 13 | Chakraborty et al. 2016 | |
Gangetic Delta Reg. S2 | - | 80.16 | 49.99 | - | - | 11.64 | ||
Gangetic Delta Reg. S3 | - | 56.12 | 28.46 | - | - | 9.21 | ||
Gangetic Delta Reg. S4 | - | 34.66 | 19.50 | - | - | 8.43 | ||
Gangetic Delta Reg. S1 | - | 96.41 | 52,60 | - | - | 11.23 | Chakraborty et al. 2016 | |
Gangetic Delta Reg. S2 | - | 72.33 | 42 | - | - | 10.44 | ||
Gangetic Delta Reg. S3 | - | 49.87 | 25.26 | - | - | 7.4 | ||
Gangetic Delta Reg. S4 | - | 24.89 | 15.9 | - | - | 6 | ||
Balochistan | 26.70 | 13.82 | 1.66 | 0.24 | 0.06 | 017 | This study | |
29.26 | 18.85 | 2.18 | 0.32 | 0.25 | 0.30 | |||
International limits | 100 | 50 | - | 1.00 | 1.00 | 2.00 | WHO (1989) | |
- | 40 | 10–100 | - | 0.50 | 0.50 | FAO (1983) |
There is no difference (
Table 4 demonstrates that there is no high correlation between the metals for
Pearson correlation coefficients between metal concentrations in the muscle tissue of
Metal | Fe | Zn | Cu | Mn | Cd | Pb |
---|---|---|---|---|---|---|
Fe | 1.000 | |||||
Zn | −0.058 | 1.000 | ||||
Cu | −0.027 | −0.122 | 1.000 | |||
Mn | 0.105 | 0.003 | 0.094 | 1.000 | ||
Cd | 0.380 indicates a significance level of |
−0.004 indicates a significance level of |
−0.021 | −0.184 | 1.000 | |
Pb | 0.385 indicates a significance level of |
−0.315 indicates a significance level of |
0.106 | 0.191 | 0.499 indicates a significance level of |
1.000 |
Fe | 1.000 | |||||
Zn | −0.025 | 1.000 | ||||
Cu | −0.088 | −0.034 | 1.000 | |||
Mn | −0.144 | −0.108 | −0.178 | 1.000 | ||
Cd | 0.133 | 0.031 | −0.034 | 0.229 | 1.000 | |
Pb | 0.079 | −0.022 | 0.09 | 0.011 | −0.180 | 1.000 |
Concentrations of Fe, Zn, Cu, Mn, Cd and Pb found in daily fish consumption per capita are calculated to assess a potential health risk to Pakistanis. The average daily fish consumption by Pakistanis is 33 g per capita (Chughtai & Mahmood 2012). The Provisional Permissible Tolerable Weekly Intake (PTWI) of Fe, Zn, Cu, Mn, Cd and Pb (for a 60 kg adult person; g/week/60 kg body weight) was 5600, 7000, 3500, 980, 7 and 25, respectively, expressed in g/week/60 kg body weight (FAO/WHO 2004). The heavy metal accumulation in the muscles of
Estimated daily and weekly intakes for the economically significant fish species consumed by adults in Pakistan
Metal | PTWI Provisional Permissible Tolerable Weekly Intake (PTWI) in g/week/kg body weight |
PTWI PTWI – permissible tolerable weekly intake (g/day/60 kg body weight) |
PTDI PTDI – permissible tolerable daily intake (g/day/60 kg body weight) |
EWI – estimated weekly intake in g/week/60 kg body weight EDI – estimated daily intake in g/day/60 kg body weight |
EWI – estimated weekly intake in g/week/60 kg body weight EDI – estimated daily intake in g/day/60 kg body weight |
---|---|---|---|---|---|
Fe | 5600 | 336000 | 48000.00 | 881.10 (125.87) | 965.58 (137.94) |
Zn | 7000 | 420000 | 60000.00 | 456.06 (65.15) | 622.05 (88.86) |
Cu | 3500 | 210000 | 30000.00 | 54.78 (7.82) | 71.94 (10.28) |
Mn | 980 | 58800 | 8400.00 | 7.92 (1.13) | 10.56 (1.51) |
Cd | 7 | 420 | 60.00 | 1.98 (0.28) | 8.25 (1.18) |
Pb | 25 | 1500 | 214.29 | 5.61 (0.80) | 9.90 (1.41) |
The accumulation of Fe, Zn, Cu, Mn, Cd and Pd in the muscles of
The results of this study show that the accumulation of Fe, Zn, Cu, Mn, Cd and Pd in