The assessment of the impacts and risks to health is possible through studies on health (and environmental conditions) before and after the installation of dams. This condition allows the construction of causal relations in timescale and the transformation of data and information on scientific knowledge and public policy. In this article, it is analyzed the issues regarding the attribution of causality in the emergency (or decrease) of the diseases or injuries, taking as examples the relationship between migration and workers' diseases (brought or acquired), cases of syphilis in pregnant women, deaths due to violence (such as homicide) and traffic accidents in the context of the construction of the Belo Monte hydroelectric dam. It is analyzed the challenges for the construction of a complex network of causal relations, that incorporate the bio-physiological causes with other causes derived from human actions and political decisions (or omissions), in this specific context.192287304