In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The estimated attributable risk of ototoxicity from exposure to the drug is 8 . 4 % ( 95 % confidence interval , - 2 . 0 % to 18 . 8 % ; P = 0 . 12 ) .
### Output Text:
The estimated attributable risk of ototoxicity from exposure to the drug is 8 . 4 % ( 95 % confidence interval , - 2 . 0 % to 18 . 8 % ; P = 0 . 12 ) . 