and social, so that there are many overlaps with environmental impact assessment and social impact assessment. Levels of HIA Three forms of HIA exist: Desk-based HIA, which takes 2–6 weeks for one assessor to complete and provides a broad overview of potential health impacts; Rapid HIA, which takes approximately 12 weeks for one assessor to complete and provides more detailed information on potential health impacts; and Comprehensive HIA, which takes approximately 6 months for one assessor and provides a in-depth assessment of potential health impacts. It has been suggested that HIAs can be prospective (done before a proposal is implemented), concurrent (done while the proposal is being implemented) or retrospective (done after a proposal has been implemented) . This remains controversial, however, with a number of HIA practitioners suggesting that concurrent HIA is better regarded as a monitoring activity and that retrospective HIA is more akin to evaluation with a health focus, rather than being assessment per se . Prospective HIA is preferred as it allows the maximum practical opportunity to influence decision-making and subsequent health impacts. HIA practitioners HIA practitioners can be found in the private and public sectors, but are relatively few in number. There are no universally accepted competency frameworks or certification processes. It is suggested that a lead practitioner should have extensive education and training in a health related field, experience of participating in HIAs, and have attended an HIA training course. It has been suggested and widely accepted that merely having a medical or health degree should not be regarded as an indication of competency. The International Association for Impact Assessment has an active health section. A HIA People Directory can be found on the HIA GATEWAY. HIA worldwide HIA used around the world, most notably in Europe, North America, Australia, New Zealand, Africa and Thailand . The safeguard policies and standards of the International Finance Corporation (IFC), part of the World Bank, were established in 2006. These contain a requirement for health impact assessment in large projects. The standards have been accepted by most of the leading lending banks who are parties to the Equator Principles. Health impact assessments are becoming routine in many large development projects in both public and private sectors of developing countries. There is also a long history of health impact assessment in the water resource development sector - large dams and irrigation systems. See also Impact Assessment Environmental impact