19652
The two key issues are the extent of exposure to ZnO - NP and the likely hazard after the application of ZnO - NP in sunscreen and cosmetic products to humans in vivo .
 ZnO, ZnO
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 ZnO, ZnO