23765
In the present study , we investigated the in vitro oxidative metabolism of 2 , 2 ' , 4 , 4 ' - tetrabromodiphenyl ether ( BDE - 47 ) , a major PBDE detected in human tissue and environmental samples .
 Chemical: 2 , 2 ' , 4 , 4 ' - tetrabromodiphenyl ether; Chemical: BDE - 47; Chemical: PBDE
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
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Answer:
 Chemical: 2 , 2 ' , 4 , 4 ' - tetrabromodiphenyl ether; Chemical: BDE - 47; Chemical: PBDE