16905
In order to determine a time course of Pb elimination after oral exposure to two different forms of this heavy metal ( lead acetate vs . phyto - bound Pb ) , a feeding study was carried out in experimental rats using the Pb phyto - hyperaccumulator Pistia stratiotes as a model diet .
 Chemical: Pb; Chemical: lead acetate; Chemical: Pb; Chemical: Pb
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: lead acetate; Chemical: Pb; Chemical: Pb