13923
During the latter exposure , fish were monitored for survival till all fish had died , and ( during the first 8h of this exposure ) for changes in whole - body Na levels and lipid peroxidation ( LPO ) .
 Na
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Na