20993
Predominant occurrence of both these chemicals and ease of their human exposure led us to investigate the effect of nicotine , a major tobacco alkaloid , on arsenic toxicity .
 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