11054
We also observed a significant increase in BAL total antioxidant capacity following O 3 exposure , suggesting development of protective mechanisms for oxidative stress damage from O 3 .
 O 3, O 3
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 O 3, O 3