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We investigated whether prenatal exposure from the maternal diet to the toxicants polychlorinated biphenyls ( PCBs ) and dioxins is associated with the development of immune - related diseases in childhood .
 Chemical: polychlorinated biphenyls; Chemical: PCBs; Chemical: dioxins
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: polychlorinated biphenyls; Chemical: PCBs; Chemical: dioxins