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: Because intensity of alcohol consumption is associated with poorer fetal outcomes , separate analyses were conducted for the heavy ( average of > or = 5 drinks per drinking day ) alcohol consumers .
### Output Text:
Because intensity of <span class="chemical">alcohol</span> consumption is associated with poorer fetal outcomes , separate analyses were conducted for the heavy ( average of > or = 5 drinks per drinking day ) <span class="chemical">alcohol</span> consumers . 