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The relation between lead ( Pb ) and iron ( Fe ) becomes increasingly concerned because they are both divalent metals that are absorbed by the same intestinal mechanism , and Pb exposure and Fe deficiency in the developmental brain , as well as Fe overload in the aged brain , can cause cognitive deficits .
 Chemical: Pb; Chemical: iron; Chemical: Fe; Chemical: Pb; Chemical: Fe; Chemical: Fe
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: Pb; Chemical: iron; Chemical: Fe; Chemical: Pb; Chemical: Fe; Chemical: Fe