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: RESULTS : Dermal exposure of rats to S - 53482 at 300 mg / kg produced patterns of developmental toxicity similar to those resulting from oral exposure .
### Output Text:
RESULTS : Dermal exposure of rats to <span class="chemical">S - 53482</span> at 300 mg / kg produced patterns of developmental toxicity similar to those resulting from oral exposure . 