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 risk of bladder cancer doubled for every 10 g increment in cyclophosphamide ( OR = 2 . 0 , 95 % confidence interval ( CI ) 0 . 8 to 4 . 9 ) .
### Output Text:
The risk of bladder cancer doubled for every 10 g increment in <span class="chemical">cyclophosphamide</span> ( OR = 2 . 0 , 95 % confidence interval ( CI ) 0 . 8 to 4 . 9 ) . 