11266
One - fifth of UO 2 nanoparticles were rapidly cleared from lung ( T ( (1/2) ) = 2 . 4 h ) and translocated to extrathoracic organs .
 UO 2
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 UO 2