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From gestation day ( GD ) 0 until postnatal day ( PND ) 20 , dams were fed daily with a cookie laced with corn oil ( control ) or a chemical mixture ( M ) [ polychlorinated biphenyls ( PCBs ) , organochlorine pesticides , and methylmercury ] at 0 . 5 or 1 . 0mg / kg / day ( 0 . 5M , and M ) .
 polychlorinated biphenyls, PCBs, organochlorine, methylmercury
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 polychlorinated biphenyls, PCBs, organochlorine, methylmercury