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: A significant increase in the myocardial t1 / 2 of the I - 131 HA was observed only at a higher cumulative dose , 10 mg / kg .
### Output Text:
A significant increase in the myocardial t1 / 2 of the <span class="chemical">I - 131 HA</span> was observed only at a higher cumulative dose , 10 mg / kg . 