This chapter outlines the specific exposure pathways and health risks through drinking-water, recreation and occupational use of water containing cyanobacteria and/or their toxins dissolved in water, food, renal dialysis and dietary supplements. A number of studies have concluded that cyanotoxins in drinking-water were the possible cause of documented cases of human illness. The chapter presents Alert Level Frameworks to guide short-term interventions if cyanotoxins or cyanobacterial biomass is present in a waterbody in concentrations that may become or may already be relevant to human health. Easing possible concerns of the public may be very important during phases with cyanobacterial biomass or toxin concentrations between the lifetime and short-term guideline values. Several epidemiological studies investigating acute illness following recreational exposure to freshwater cyanobacteria have been conducted between 1990 and 2011. These studies utilised various retrospective and prospective designs capable of detecting relative differences in commonly reported symptoms between exposed and unexposed groups.