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: Overexpression of copper / zinc - superoxide dismutase protects from kanamycin - induced hearing loss .
### Output Text:
Overexpression of <span class="chemical">copper</span> / <span class="chemical">zinc</span> - <span class="chemical">superoxide</span> dismutase protects from <span class="chemical">kanamycin</span> - induced hearing loss . 