5054
Down - regulated MSH gene activities reaching about 50 % of control were also induced in embryos exposed to paraquat , a reactive oxygen species ( ROS ) - generating herbicide , or hydrogen peroxide at 200 mu M .
 Chemical: paraquat; Chemical: oxygen; Chemical: hydrogen peroxide
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: paraquat, oxygen, hydrogen peroxide 
Answer:
 Chemical: paraquat; Chemical: oxygen; Chemical: hydrogen peroxide