There is growing awareness and public concern about environmental impacts of waste management and disposal. Environmental policy instruments have been strengthened and associated governmental programmes have increased in recent years, resulting in high level strategies for waste management. Risk assessment is now an essential tool in the prioritisation of environmental and human health protection. However, regulators need to compare the full range of risks on a sound and consistent basis. Comparing risks from such diverse sources poses a significant challenge, and traditional hazard and risk assessments are no longer sufficient. Consideration now needs to be given to a much wider range of factors if risk assessment is to be used as an aid to more integrated decision-making process. For this purpose, baseline study - the foundation of risk assessment - can play a crucial role. To date limited research has been conducted on the need, parameters, requirements, and constituents of baseline study particularly in the context of how, why, and what information is to be collated in order to render risk assessments more appropriately integrated and complete. To establish the \'state-of-the-art\' of baseline study, this paper comprehensively reviews the literature regarding environmental risk assessment in general terms, and then proceeds to review work that is specifically related to landfills and landfill leachate, thereby identifying knowledge gaps and shortfall areas. This review concludes that a holistic baseline study procedure for waste disposal sites, which risk assessors could use for carrying out risk analyses specifically for landfill leachate, does not as yet exist.