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: These findings suggest that it may be possible to identify a succimer treatment protocol that improves cognitive outcomes in Pb - exposed children .
### Output Text:
These findings suggest that it may be possible to identify a <span class="chemical">succimer</span> treatment protocol that improves cognitive outcomes in <span class="chemical">Pb</span> - exposed children . 