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: Despite these uncertainties , this initial evaluation of the direct cost of treating RIHA provides an estimate of the cost and management implications of this clinically important adverse effect .
### Output Text:
Despite these uncertainties , this initial evaluation of the direct cost of treating RIHA provides an estimate of the cost and management implications of this clinically important adverse effect . 