To assess the radiological hazard of the concerning samples, it is useful to use the radium equivalent activity (R_eq) in Bq∙Kg⁻¹ [5] :

where A_Th, A_Ra and A_K represent the activity concentrations of ²³²Th, ²²⁶Ra and ⁴⁰K in Bq∙kg^?1 respectively. R_eq is defined according to the estimation that 1 Bq∙kg^?1 of ²²⁶Ra, 0.7 Bq∙kg^?1 of ²³²Th and 13 Bq∙kg⁻¹ of ⁴⁰K produce the same gamma-ray dose [6] the permissible dose limit for the public is 1.5 mSvy⁻¹ [7] .

The absorbed gamma dose scale in air 1mabove the ground surface for the uniform distribution of radionuclides (²³²Th, ²³⁸U, and ⁴⁰K) were computed by guidelines provided by [5] :

where A_Th, A_Ra and A_K represent the activity concentrations of ²³²Th, ²²⁶Ra and ⁴⁰K in Bq∙Kg^?1 respectively.

The annual effective dose equivalent received by a member has been calculated from the absorbed dose rate by applying dose conversion factor of 0.7 Sv/Gy and the occupancy factor for outdoor and indoor as 0.2 and 0.8, respectively, [5] , using the following equations:

Excess Lifetime Cancer Risk (ELCR) was calculated by the equation below [4] [5] :

where D_eff (outdoor), D_L and RF are the outdoor annual effective dose equivalent, the duration of life (70 years) and the risk factor (Sv^?1), fatal cancer risk per Sievert. For detriment-adjusted cancer risk of 5.52 × 10⁻² Sv^?1 for the whole population [5] .

The results of ²²⁶Ra, ²³²Th and ⁴⁰K concentrations in the waste samples were summarized in Table 1. From this Table, All samples under investigation, the average values of ²²⁶Ra ranged from 2.6329 Bq∙Kg⁻¹ in (Copper) to 173.29 Bq∙Kg⁻¹ in (Iron). ²³²Th average values ranged from 0.60 Bq∙Kg⁻¹ in (Copper) to 141.99 Bq∙Kg⁻¹ in (Iron) while the average values of ⁴⁰K ranged from 29.99 Bq∙Kg⁻¹ in (Copper) to 41.99 Bq∙Kg⁻¹ in (Aluminum). Iron waste recorded the highest average values concentration of ²²⁶Ra and ²³²Th, and are much higher than the world average values 30, 35 Bq∙Kg⁻¹ for ²²⁶Ra and ²³²Th respectively, as reported by [5] , which can be explained by adsorption on weathered ferromagnetic

minerals, also iron scrap were used in high percentage [8] . For all the studied samples, the average values of K were lower than the world average values of 400 Bq/kg [5] . Different concentrations of radioactive nuclei in the samples refer to the sources and environmental acting on these samples. The average activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the waste samples under study are given in Figure 1.

The calculated average values of radium equivalent activity (R_eq), absorbed Gamma Dose Rate (D) and the Annual Effective Dose Equivalent (D_eff), for all waste sample types and the total average values are shown in Table 2. The radiological hazards were compared with the recommended values by UNSCEAR 2000. From this table, we can establish the following:

1) Radium equivalent activity (R_eq)

The minimum average value of R_eq activity was 1.12 Bq∙Kg⁻¹ for Copper waste while the maximum average value was 378.86 Bq∙Kg⁻¹ for Iron waste, which is higher than the recommended maximum value of 370 Bq∙Kg⁻¹ [5] . The highest value in Iron is attributed to the high activity concentration level of ²²⁶Ra and ²³²Th in Iron waste samples. The total average value of R_eq for all samples was 95.87 Bq∙Kg⁻¹, this value is lower than 370 Bq∙Kg⁻¹.

2) Absorbed gamma dose rate (D)

As shown in Table 2, the average value of the absorbed dose of all types of waste samples ranged from 2.79 nGyyh⁻¹ (Copper) to 163.86 nGyyh⁻¹ (Iron) with total average value 44.56 nGyyh⁻¹. UNSCEAR 2000 reported that the world wild average value in an air of outdoor absorbed dose 55 nGyh⁻¹ with at y-pical range from 10 to 200 nGyh⁻¹. The average values for Copper, Aluminuim and Wood and the total average are lower than the recommended values by [5] . Table 2 shows that only for Iron waste samples, its absorbed average value is 3 times higher than the world average value. Figure 2 shows a comparison between the

average and total average values of radium equivalent (in Bq∙Kg) and absorbed dose (in nGyyh⁻¹) for the waste samples under investigation and the recommended values by UNSCEAR 2000.

3) The annual effective dose equivalent

The average annual effective dose of indoor and outdoor for all samples ranged from 0.012 mSvy⁻¹ (Copper) to 0.73 mSvy⁻¹ (Iron) and from 0.003 mSvy⁻¹ (Copper) to 0.18 mSvy⁻¹ (Iron) with the corresponding total average values of 0.20 mSvy⁻¹ and 0.05 mSvy⁻¹, respectively. These average values are less than the world average annual effective dose indoor 0.42 mSvy⁻¹ and outdoor 0.07 mSvy⁻¹ as reported by [5] . The maximum average values for outdoor and indoor effective doses were observed in Iron are higher than the world average effective dose for outdoor and indoor. This indicates that there is a significant effect for the workers in Iron workshops.

4) Excess lifetime cancer risk (ELCR)

The average values of ELCR ranged from 0.04 × 10⁻³ in Copper to 2.54 × 10⁻³ in Iron, with a total average value of 0.69 × 10⁻³. The average values of ELCR for all waste types are less than the world average (0.29 × 10⁻³) reported by [5] . The ELCR for Iron exceeded this value; this indicates that there is no risk to the general public and the workers in the industrial workshops which produce wastes of Copper, Aluminium and Woods and the workplace are still in zone of normal radiation, but there is a threat to the workers' health in Iron workshops.