Is serum selenium a risk factor for cancer?

A narrow band of counties extending along the southeastern Atlantic coast from Jacksonville, Florida to Charleston, South Carolina were found to have excessively high incidence rates for esophageal cancer in non-white males. White males in the same areas have a 30% higher incidence rate for lung cancer but only average incidence rates were found for non-white males. Selenium is considered to decrease cancer risk in the animal model. In this coastal region, a study of 130 cancer patients who developed a malignancy 2-12 years after baseline examination showed no dose response relationship between baseline serum selenium levels and risk of subsequent cancer.