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 nursing staff , by reviewing the patient ' s health history with his family , discovered a history of polydipsia and long - standing lithium use .
### Output Text:
The nursing staff , by reviewing the patient ' s health history with his family , discovered a history of polydipsia and long - standing <span class="chemical">lithium</span> use . 