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: This study is the first to demonstrate that impairment of hepatocyte TJs occurs heterogenously in the liver lobule after BDL and suggests that BDL and EE treatments produce different lobular distributions of increased paracellular permeability .
### Output Text:
This study is the first to demonstrate that impairment of hepatocyte TJs occurs heterogenously in the liver lobule after BDL and suggests that BDL and <span class="chemical">EE</span> treatments produce different lobular distributions of increased paracellular permeability . 