12990
In this study , we conducted a 24h intermittent exposure ( 5 min on and 10 min off ) of a mouse spermatocyte - derived GC - 2 cell line to 1800 MHz Global System for Mobile Communication ( GSM ) signals in GSM - Talk mode at specific absorption rates ( SAR ) of 1 W / kg , 2 W / kg or 4 W / kg .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None