3665
Both UGT2A2 and UGT2A3 exhibited no detectable activity against complex PAH proximate carcinogens , tobacco - specific nitrosamines , or heterocyclic amines .
 PAH, nitrosamines, heterocyclic amines
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PAH, nitrosamines, heterocyclic amines