27503
This study aims to explore the effect of selenium in fluoride - induced renal cell apoptosis in rats and determine the optimal level of selenium in drinking water to prevent fluorosis .
 Chemical: selenium; Chemical: fluoride; 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: fluoride; Chemical: selenium