Ten samples were taken from the local markets in Jeddah―Saudi Arabia. The samples data of fish (i.e. Scientific Name, Common Name, Country of Origin, Type, Collection Time) are indicated in Table 1. The fish species were collected from random commercial market depending on the availability of the species for sale at April 2014. Samples obtained were cleaned, thawed on, cut to pieces and dried to constant weight at 110˚C. These samples were ground into powder and stored in polyethylene bags.

Half (0.5) gm of the fish samples were analyzed by Inductively coupled plasma optical emission spectrometry

(ICP-OES) (Perkin Elmer- Optima 8300 ICP-OES Spectrometer) to get the concentrations of toxic elements (Al, Hg, Cd, Pb, U, Th, and As) and essential elements (K, Sn, Ca, Ni, Cu, Fe, Co, and Mn) in fish samples. For radiometric analyses, each dried sample was weighed, put, and sealed in 640 cc polyethylene Marinelli beakers then stored for nearly 4 month under 27˚C to prevent the escape of Radon gas and to allow the attainment of radioactive secular equilibrium between ²³⁸U series and ²³²Th series. The radioactive nuclei concentrations in the samples were determined using High purity Germanium (HPGe) coaxial detector with relative efficiency of 25% and FWHM 2.0 keV at 1332 keV, of ⁶⁰Co. To reduce gamma ray background (HPGe) Detector was surrounded by lead shielding Genie 2000 basic spectroscopic software was installed in the computer for data acquisition and analysis. The system was calibrated for energy and absolute efficiency. The lowest limits of detection (LDL) were calculated tobe0.311, 0.312, 0.34, 1.66, and 0.45 Bq/Kg for ²³⁸U, ²²⁶Ra,²³²Th, ¹³⁷Cs, and ⁴⁰K respectively. To collect the background count rates, an empty polyethylene Marinelli beaker was placed in the detection system. The measurements were done for a counting time of 82,800 sec.

1) Assessments of heavy metals hazard index (HI) in fish samples:

A hazard index (HI) may be used to describe the risk from metals intake through ingestion. The hazard index (HI) was calculated by using the equation below [8] [9] :

It is the ratio of the estimated metal dose (EDI mg/Kg of body weight per day) and the reference dose (R_fD mg/kg/day). If HI > 1.0, then the EDI of a particular metal exceeds the R_fD, pointing out that there is a potential risk associated with that metal.

The estimated daily intake (EDI) was determined using the following equation [10] [11] :

where: C_metal is the metal concentration level of metals in fish; W represents the daily average consumption of fish is given as: 0.003, 0.025, and 0.068 kg/day for Infants, children and adults respectively [12] , m is the body weight of 10 kg for Infants, 30 kg for children and 70 kg for adults.

2) Activity concentrations:

The photon energies of63.29 and 92.57 keV were used to calculate ²³⁸U average concentration and the photon energies of 351.87 keV of ²¹⁴Pb and 609.31 and 1120.27 keV of ²¹⁴Bi were used to find the average concentration of ²²⁶Ra (since there is a secular radioactivity equilibrium between ²²⁶Ra progenies). The average concentration of ²³²Th, which it is in a secular radioactivity equilibrium with its short half-life daughters, was determined using the gamma lines of ²²⁸Ac (338.32, 911.16, and 968.97 keV) and of ²⁰⁸Tl (583.10 keV). The analysis of ⁴⁰K and ¹³⁷Cs concentrations was based on their peaks in the spectrum at energies 1460.80 and 661.66 keV respectively.

Determination of activity concentrations in Bq/kg dry weight was calculated using the flowing equation [13] :

where: C is the count per second of the net peak area of specific gamma ray energy. m is the mass of the samples in (kg). β is the transition probability of gamma-decay. ε is the detector absolute efficiency at the specific gamma-ray energy.

3) Annual effective dose:

Annual radionuclide intakes and effective doses for fish consumers age groups as (infant (≤5 Y), children (5 - 10 Y and 10 - 15 Y), and adults (≥17 Y)) were calculated using the equation [14] :

where: D is the effective dose by ingestion of the radionuclide (Sv/Y), A is the activity concentration of the radionuclides in the sample (Bq/kg), C is the internal dose conversion factor by ingestion of the radionuclides (Sv/Bq) which varies with both radioisotopes and the age of the individual were reported by (ICRP) [7] , R is the annual intake of fish (Kg/Y) which is calculated for different age groups of population. In our study the average mass of the fish consumed by the infants (age ≤ 5 y), children (age 5 - 10 y and 10 - 15 y) and adults (age from 17 y and above) were 1 kg/y, 5 kg/y, 10 kg/y and 25 kg/y, respectively .

Table 2 shows the corresponding concentrations of toxic and essential elements in mg/Kg of analyzed fish samples namely (Seagan, Bagha, Tilapia, Sardine, Herring, Catfish, Shrimp, Tuna) using inductively coupled plasma optical emission (ICP-OES) spectrometry.

Toxic elements:

Aluminum (Al) is a trace element in fish. The results obtained shows that Al concentrations were not detected (ND) in the fish samples from 1 to 8, samples 9 and 10 (Tuna) were lower than detection limits (LDL^*).

Mercury (Hg) is a heavy element in fish, the existing of this element in food such as fish may cause risk on human health. Table 2 represents the Hg for all fish species were (ND).

Cadmium (Cd) highest concentrations mg/Kg were in fresh Seagan, frozen Tilapia, and fresh Sardine (0.015, 0.019, 0.022) respectively. On the other hand, the lowest Cd concentrations mg/kg were in frozen Herring, Shrimp, and canned Tuna (0.001, 0.002, 0.002, 0.03). For the rest of samples analyzed, cadmium concentrations were low or not detected.

Lead (Pb) is heavy element and can be found in fish directly from seawater and sediments and exists in the fish consumers’ tissues. It is harmful to human health at high concentrations, the allowed limit is 0.2 mg/kg [15] . In this study, Pb was not detection (ND), so there is no risk to fish consumers.

Uranium (U) is a radioactive metal, but Uranium's toxic hazard resides not only in its radiation effects but in its chemical effects [16] . Results show that highest U concentrations mg/kg were in fresh Bagha and Tilapia (3.086, 4.906, 5.075). For all samples, the concentrations mg/Kg ranged from 0.519 to 5.075.

Thorium (Th) is a naturally-occurring, radioactive metal. Since Thorium is found almost everywhere, all people absorb some through food, drinking water, and in air. Th concentrations of fish species ranged from ND to 0.032 mg/kg. The concentration in frozen Tilapia was LDL.

Arsenic (As) presents in fish consumed by human. It is a toxic and trace element and inorganic arsenic is found at very low concentrations in fish and other seafood products, some types of fish have high concentrations. In this work, values for As ranged from ND for canned Tuna to 0.752 mg/kg for fresh Sardine. All the samples analyzed were below the maximum allowed limit put by Brazilian legislation (1 mg/kg).

Essential element

Potassium (K): All fish contain potassium. It is necessary for human health, but deficiency or increase in potassium intake is a risk for human, the recommended daily dietary intake of potassium (in Australia) for adults is 2.0 - 5.5 g). The lowest k concentration determined in fish species was found as 21.017 mg/kg in frozen shrimp and the highest 176.571 mg/kg in frozen Herring.