16637
While some histopathological changes detected in liver tissues in chlorpyrifos treated group , less histopathological changes were observed in catechin + chlorpyrifos and quercetin + chlorpyrifos treated groups at the end of the 4thweek .
 chlorpyrifos, catechin, chlorpyrifos, quercetin, chlorpyrifos
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 chlorpyrifos, catechin, chlorpyrifos, quercetin, chlorpyrifos