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In 2007 , the authors measured serum concentrations of polybrominated diphenyl ethers ( PBDEs ) in Laizhou Bay residents .
 Chemical: polybrominated diphenyl ethers; Chemical: PBDEs
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: polybrominated diphenyl ethers, PBDEs 
Answer:
 Chemical: polybrominated diphenyl ethers; Chemical: PBDEs