19409
The remaining four groups received same concentrations of Mn and were also exposed to ELF - MF ( 1 . 5 mT ; 50 Hz ) for 4 h for 5 days a week during 45 days .
 Mn
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Mn