17637
Levels of PAH - DNA adducts were lower in the NTD group ( 8 . 12 per 10 ( 8 ) nucleotides ) compared to controls ( 9 . 92 per 10 ( 8 ) nucleotides ) .
 PAH, nucleotides, nucleotides
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PAH, nucleotides, nucleotides