26986
Compared with the control group , the intracellular ROS levels were significantly increased ( 2 . 56 - fold ) by the combination of 19mg / L Fe3O4 NPs and 1 . 0mg / L As ( V ) .
 Fe3O4, As ( V )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Fe3O4, As ( V )