THE CHRONIC ORAL TOXICITY OF SELENIUM

¹ From the Division of Pharmacology, Food and Drug Administration, Federal Security Agency, Washington, D. C.

Rats fed selenium in a grain diet at concentrations of 3, 5, 7, 10, 20 and 40 parts per million showed toxic effects at all levels of selenium.

Selenium at the concentration of 10 parts per million, or more, with the exception of the 10 parts per million from the selenide, killed most of the animals within the first eight weeks. Lower concentrations of selenium produced chronic symptoms which included a decreased growth rate, a restriction of food consumption, and slight to severe pathological lesions.

Selenium at the concentration of 10 parts per million from the selenide was about half as toxic as the same concentration from wheat and corn.

The outstanding pathological lesion was cirrhosis of the liver, seen in over 70 per cent of the rats surviving more than three months. Among 43 cirrhotic rats surviving 18 months or longer, hepatic cell tumors developed in 11 and marked adenomatoid hyperplasia in four others. Rats dying during the first three months showed a subacute type of liver damage. Lesions in viscera other than the liver were not characteristic or extensive.

Female rats were more susceptible to selenium than male rats.

Rats from different litters on the same dosage of selenium showed a significant difference in growth rates.