25985
The pattern was similar in human hepatocytes , although PFDA and PFOS showed higher activity than previously observed while PFOA showed somewhat less activity .
 PFDA, PFOS, PFOA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PFDA, PFOS, PFOA