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Therefore , biofilms were grown in channels for 38 days and then exposed to different concentrations ( 0 - 150 mu gL ( - 1 ) ) of the herbicide oxyfluorfen for 5 more weeks .
 oxyfluorfen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 oxyfluorfen