Air-conditioning. Heat is deadly and we don't respect it enough. A Chicago heat wave killed more than 700 people in one week in 1995. The National Weather Service issues heat alerts, and cities have started to offer air-conditioned cooling centers for people who would overheat at home. A recent study shows that air conditioning has cut the death rate on hot days by 80 percent since 1960.
The residents of Framingham, Mass. In 1948, researchers signed up more than 5,000 adults for a long-term study of heart disease. Nobody anticipated just how long-term the study would be — it's still going strong and now includes the children and grandchildren of the original cohort. It taught us much of what we know about heart disease. Before the study, high blood pressure was thought to be a sign of good health; now it's recognized as a risk factor for heart attacks and strokes. Thanks to the generosity and commitment of volunteers in Framingham and other studies, we know the dangers of high cholesterol, obesity, inactivity and smoking.
Pasteurization. This should be an obvious lifesaver, right up there with hand-washing and proper nutrition. But the rise of the raw milk movement suggests that a lot of people take safe dairy products for granted. Contaminated milk was one of the major killers of children, transmitting typhoid fever, scarlet fever, diphtheria, tuberculosis and other diseases. One of the most successful public health campaigns of the late 19th and early 20th centuries was for pure and pasteurized milk — so successful that we don't really remember how deadly milk can be.
Shoes. Hookworms are parasites that enter the human body through bare feet — often by biting into the soft skin between the toes. The disease was common in the Southeast, spread when people walked barefoot across ground that was contaminated with feces of people who were already infected. Education initiatives at the beginning of the 20th century encouraged people to build sanitary outhouses and wear shoes.