Dioxin body burdens in operation ranch hand veterans: promotion blocking and cancer causation.

The cancer incidence data from the Operation Ranch Hand Study are plotted as a function of seven dioxin body burden classifications from zero through modest levels above background. The three significant cancer incidence peaks and three significant cancer incident troughs observed are used to test a model which specifies dioxin activity as both a promoter blocker and a cancer causation agent. There is a significant, 50% reduction in total cancers other than skin at the highest dioxin body burden level compared to background. There is a significant reduction in prostate cancers in Black veterans, but not in White, as a function of increasing dioxin body burden.