ABSTRACT
All life on Earth requires water to survive. How - ever, water can also be harmful to life. Chemical and physical hazards can threaten the health of individuals, populations and even whole eco - systems through changes in water quality (the characteristics of freshwater that make it suitable to sustain life) and water quantity (the availability of freshwater resources). Physical hazards such as drought and flooding, along with chemical hazards such as saline intrusion or pollution events, impact on the health of many organisms including humans. It is also true that many patho genic organisms use water as a pathway to
infect host organisms; for human hosts, waterrelated diseases that result from such infection make sig nifi cant contributions to morbidity and mortality.
