23687
This study aimed to evaluate the relationship between blood lead and serum creatinine and blood lead and serum urea nitrogen levels as biomarkers of lead exposure from subjects living in a historic polymetallic mining area in China .
 Chemical: creatinine; Chemical: urea; Chemical: nitrogen
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: creatinine; Chemical: urea; Chemical: nitrogen