The aim of this study was to evaluate the effect of long-term exposure to cadmium in the death rate from cancer. The observed cohort totaled American Indians from Arizona, Oklahoma, North and South Dakota, and the time of observation cohort was 20 years old. The study found that prolonged exposure cadmium increases the risk of mortality from cancer in a 1.30-fold (95% Ci 1,09-1,55), and the death rate from lung cancer - 2.27 times (95% Ci 1 , 58-3,27). What is the design of the study conducted