21209
As the relative amount of selenium increases compared to mercury , risk may be lowered , but it is unclear how much excess selenium is required .
 Chemical: selenium; Chemical: mercury; Chemical: selenium
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: selenium; Chemical: mercury; Chemical: selenium