3141
We have previously shown that WC - Co specifically induces a burst of reactive oxygen species ( ROS ) and in vitro mutagenic / apoptogenic effects in human peripheral blood mononucleated cells ( PBMC ) used as a validated experimental model .
 WC, Co, oxygen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 WC, Co, oxygen