**1. Introduction**

The progressive growth in industrialization and population caused severe environmental problems worldwide, these problems need to be analyzed, monitored, controlled and mitigated when appropriate to ensure the quality and sustainability of life [1]. Currently, there is growing international recognition for these problems and in particular environmental pollution is receiving considerable attention either on the international, regional, national and individual scales. To help controlling the existing pollution sources and preventing new pollution sources/areas, strengthen regulations have been issued and human and natural resources have been allocated all over the world [1]. The results of these efforts will be very helpful in supporting various sustainable development goals that were identified in the United Nation 2030 agenda [2]. Among these goals, the achievement of good health and well-being (Goal 2), clean water and sanitation (Goal 4), affordable and clean energy (Goal 5), industry, innovation and infrastructure (Goal 9), sustainable cities and communities (Goal 11), responsible consumption and production (Goal 12), climate action (Goal 13), life below the water and on land (Goals 14 and 15, respectively) are affected by the efforts to prevent and control the environmental pollution.

To ensure effective pollution prevention and control, there is a need to prove that each planned/operated human activity will not impose negative impacts on the human society and the environment. This situation is stressful for the decision makers, e.g. policy makers, designers, regulators, where the decisions must balance the benefits from this activity to the society and its potential negative impacts on the environment, their probabilities, and their consequences. Different assessment methodologies were ratified more than 5 decades ago and are used as tools to support the decision making process. These assessments aim to provide systematic procedures to study the impacts/risks of the human activities on their societies and on the environment. These assessments include life cycle assessment (LCA), life cycle sustainability assessments (LCSA), environmental impact assessment (EIA), strategic environmental assessments (SEA), and risk assessments (RA) [3, 4]. LCA is used to assess the environmental impacts associated with the life cycle stages of a product or service supply chain, e.g. raw material extraction processes, manufacturing and processing, transportation, usage and disposal. It includes goal definition and scoping, inventory assessment, impact assessment, and interpretation. LCSA aims to evaluate the impacts of a product or service on the environment (LCA), social life (social life cycle assessment S-LCA) and society's economic (life cycle costing, LCC) towards more sustainable products throughout their life cycle [5, 6]. EIAs are widely used for regulating human activities worldwide. EIAs focus on the evaluation of the impacts of specified project over its different life phases, i.e. construction, operation, and closure, on the ecological components of the environment. EIA performed by identifying the baseline project, assessing and mitigating the impacts, and monitoring planning. SEA aims to evaluate the environmental impacts of alternative visions and development intentions incorporated in policy, planning or program initiative [7, 8]. Finally, RA used to assess health risk assessment (HRA), hazard risk assessment (HZRA), and environmental (ecological) risk assessment (ERA).

To build confidence in these assessment's results and subsequently in the decisions to be taken based on them, there is a need to identify, present, and describe the uncertainties associated with data collection and analysis, scenario developments, and expert judgment. In this chapter, uncertainty management to support regulatory decision making process to prevent and control pollution will be presented. In this respect, it should be noted that basic elements for regulatory decision making process include clear identification of the applied laws, regulations and acceptance criteria, assessment of the safety significance, verification of collected data and information, assigning priorities, and clarification of the analysis/ assessment to be performed [3]. Based on the safety significance of the activity, it might require a simple qualitative assessment, i.e. for activities of low safety significance, or it might need in-depth quantitative assessment, i.e. for activities of high safety significance. Depending on the existing regulations, this assessment can cover impacts (e.g. EIA) and/or risks (e.g. RA) to human, property, or/and the environment, and the results of the assessment are used to manage these impacts and/or risks, i.e. prioritize the efforts to minimize or mitigate the impacts and/or risk. The rest of this chapter is devoted to introduce the uncertainty management. This will be achieved by introducing the applications of risk assessment to support the regulatory decision making process, then elements of the uncertainty management will be overviewed.
