21001
Nicotine pre - exposure in arsenic - exposed animals revealed interesting toxicokinetics and oxidative stress modulating interactions in the brain and liver of rats , which requires further exploration .
 Chemical: Nicotine; Chemical: arsenic
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Nicotine; Chemical: arsenic