Gulp.

THE BLUE DEATH

Disease, Disaster, and the Water We Drink

By Robert D. Morris

HarperCollins. 310 pp. $24.95

POISONED NATION

Pollution, Greed, and the Rise of Deadly Epidemics

By Loretta Schwartz-Nobel

St. Martin's. 216 pp. $24.95

With all the recent talk about childhood obesity and juvenile diabetes, it is hard to remember that the modern public health movement began with the Great Sanitary Awakening of the mid-19th century. Reformers in England and elsewhere convincingly argued that the environment served as a major source of disease and needed to be cleaned up. Now two new books remind us that toxins and other waste products are producing new and frightening threats to public health. Like Al Gore's arguments about oil dependence and the ozone layer, these concerns are surely inconvenient. But are they also true?

The hero of Robert D. Morris's "The Blue Death" is John Snow, the British epidemiologist who proved in the 1850s that epidemic cholera was spread by waste products in drinking water. Snow reached his conclusions, which initially were mocked, decades before the discovery of the cholera bacillus. His work eventually led to the modern system of purifying tap water, which involves both filtering and treatment with chlorine.

But success has bred complacency, according to Morris. His book is full of examples of recent health problems traceable to inadequate supervision of our water supply. For instance, the majority of pipes that supply major urban centers -- including Washington -- are close to 100 years old and full of leaks that allow contamination. Morris puts into this broader context the now-familiar story of what happened in the District in 2004, when officials added phosphoric acid to the city's water system in an attempt to reduce lead levels and instead created a new headache by loosening a layer of slime and microorganisms, known as the biofilm, and flooding the system with bacteria. He also describes how a 1993 outbreak of diarrhea in Milwaukee was caused by cryptosporidium, an organism experts insisted could not be present.

Morris is no impartial observer. An epidemiologist who specializes in drinking water, he is the author of a controversial paper suggesting that chlorine might increase the rates of several cancers. Indeed, some of his narrative describes his David-like efforts to challenge the Goliaths of water, ranging from the Environmental Protection Agency to the drinking-water industry, which he suggests are cutting corners on water purification to save money.