13391
PFOS , perfluorooctanoic acid ( PFOA ) and PFOSA induced a concentration dependent increase in ROS formation with EC ( 50 ) - values of 27 +/- 9 . 0 , 25 +/- 11 and 57 +/- 19 mu M respectively .
 Chemical: PFOS; Chemical: perfluorooctanoic acid; Chemical: PFOA; Chemical: PFOSA
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: PFOS; Chemical: perfluorooctanoic acid; Chemical: PFOA; Chemical: PFOSA