From cholera to cancer to cryptosporidiosis

The introduction of piped water to cities in the mid-19th century led to the spread of cholera and typhoid in the United States and the other industrialized countries. Filtration and then chlorination around the turn of the century virtually eliminated waterborne enteric disease in the industrialized world. The development of synthetic organic chemicals following World War II and the recognition that chlorine, which is so important for disinfection, reacts with natural and other organic precursors in the water, producing carcinogenic byproducts, shifted the major emphasis in water quality in the industrial world away from infectious disease to a concern for control of trace chemical contaminants. The recent emergence of waterborne giardiasis and cryptosporidiosis is shifting emphasis back to a concern for the control of enteric infectious disease. Particularly troublesome is that water meeting current microbiological standards has been demonstrated to be responsible for diarrheal disease. The principal conclusion to be drawn from these changes is the affirmation of the original principles for the protection of drinking water quality, that water intended; for potable purposes should be drawn from the highest quality sources available, that the sources should be protected, and that the treatment must be appropriate and reliable.