13542
Stratified analysis found that the association between OGG1 polymorphism and sperm 8 - OHdG levels was only observed among smokers with pack - years >= 5 but not among those subjects with pack - years < 5 ( pack - years = packs smoked per day x years as a smoker ) .
 Chemical: 8 - OHdG
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: 8 - OHdG