Data on occupational illness and disease are more difficult to tie down than those on accidents because the links are often harder to document in an authoritative way. However, U.S. government estimates suggest that as many as 100,000 people a year die as a result of work-related illnesses. It is estimated that anywhere between 23 and 38 percent of cancer deaths may be work related. To put the figures in perspective, the number of people killed by occupational diseases and accidents each year exceeds the number of American lives lost in the duration of the Vietnam War.