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: CONCLUSION : We suggest that the increased risk of venous thromboembolism due to raloxifene treatment may be related to increased tPA levels , but not TAFI levels .
### Output Text:
CONCLUSION : We suggest that the increased risk of venous thromboembolism due to <span class="chemical">raloxifene</span> treatment may be related to increased tPA levels , but not TAFI levels . 