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: Risk of renal failure , Injury to the kidney , Failure of kidney function , Loss of kidney function , and End - stage renal damage ( RIFLE criteria ) were used to define CIN and its incidence in the study population .
### Output Text:
Risk of renal failure , Injury to the kidney , Failure of kidney function , Loss of kidney function , and End - stage renal damage ( RIFLE criteria ) were used to define CIN and its incidence in the study population . 