Dr. Stevens has been working for a long time trying to help figure out why people get cancer. One of his major interests has been in the possible role of iron overload. Largely on the basis of his work, published in the Journal of National Cancer Institute and the New England Journal of Medicine, the Swedish food industry decided to cease iron fortification of flour in the early 1990s. A perplexing challenge, which Stevens began to engage in the late 1970s, is the confounding mystery of why breast cancer risk rises so dramatically as societies industrialize. He proposed in 1987 a radical new theory that use of electric lighting, resulting in lighted nights, might produce "circadian disruption" causing changes in the hormones relevant to breast cancer risk. Accumulating evidence has generally supported the idea, and it has received wide scientific and public attention. For example, his work has been featured on the covers of the popular weekly Science News (October 17, 1998) and the scientific journal Cancer Research (July 15, 1996). As well as more recent stuff, like now.