Further observations on the human maximum safe dietary selenium intake in a seleniferous area of China.

This report is a summarization of preliminary results from a study of dietary Se intake in a seleniferous area in order to determine safe levels. All patients have symptoms of toxicity: broken hair strands or various levels of nail damage. Finger-nail signs were the first symptoms used for diagnosis of selenosis in this work. Based upon the lowest blood-Se level of five subjects with persistent overt finger-nail signs of selenosis, it was found in 1986 that the individual marginal toxic blood Se level (LOAEL) and the corresponding Se intake were 1054 micrograms/L and 910 micrograms/d, respectively. To re-examine the clinical signs and blood Se levels of the five individuals and to see how the two are correlated, a study was conducted in July 1992 at the same location in the seleniferous area. The results showed that along with the absence of clinical signs, the average blood Se level had decreased from 1346 to 968 micrograms/L. The corresponding safe Se intake per day would be 819 +/- 126 micrograms (15 micrograms/kg B.W. or approximately 800 micrograms per day, which is suggested as the mean No Adverse Effect Level (NOAEL), and the lower limit of the 95% confidence interval, 600 micrograms per day would approximately the maximum individual safe Se intake. For safety, 400 micrograms is again proposed as the Maximum Safe Daily Dietary Se Intake. Problems inherent in this estimation have been discussed.