21000
The present study suggests that nicotine may not be the major contributing factor for the previously reported synergistic toxic interaction between tobacco and arsenic .
 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