4421
Following the transfer of crayfish to clean water for seven days , the concentration of insecticide residues were decreased in both the hepatopancreas and gills suggesting that these organs play an important role in elimination of ethion .
 Chemical: ethion
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: ethion