**2.8 Risk assessment and leaching in POC utilization**

Heavy metal leaching from waste depends on the matrix's bonding energy and perhaps even the leaching state. In terms of POC, the concentration of heavy metals present depends on the palm oil mill boiler burning condition and geological condition of the location where palm oil tree grew [8]. POC solubility relies on different bonding energy in solid matrix. If the hydration energy exceeds existing bonding strength of POC matrix, POC dissolves into the solution; otherwise, the metals of POC are deposited as residue at the bottom of the vessel. Under normal environmental condition, heavy metals do not leach from solid matrix of POC, because the leaching values of heavy metals are well below the standard limit of risk. With POC acid soluble fraction in the range of 0.0–9.27%, risk assessment code (RAC) analysis by [8] confirms the safe incorporation of POC in cement-based applications because RAC values are <1%. Therefore, there is no potential threat to environment and health safety [8].

It's crucial to understand human exposure to ionizing radiation because radiation from natural sources can cause cancer and genetic mutations that influence future generations. Knowing the radiological health hazards caused by the incorporation of POC in building elements is very important. The radioactivity levels were measured by [9] and the activity concentration in POC was found to be less than 50 Bq kg-1 world average values for building materials. To evaluate the potential radiological hazards, radiological parameters and hazard indices, such as absorbed dose rate, radium equivalent activity, and annual effective dose were determined. Obtained results were within the recommended standard limit, precisely less than unity. This implies that POC is safe to be used in concrete construction.
