12039
For the relationship of childhood leukemia and parental exposure to PCP , three published studies suggested an increased risk of childhood leukemia because of their parental exposure to PCP at the preconception period .
 Chemical: PCP; Chemical: PCP
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: PCP; Chemical: PCP