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: On average , age - specific mortality rates were slightly higher for the 101 patients whose paracetamol - induced liver injury had caused an acute liver failure ( adjusted mortality rate ratio = 1 . 70 , 95 % CI 1 . 02 - 2 . 85 ) , but the association was age - dependent , and no survivors of acute liver failure died of liver disease , whereas suicides were frequent in both groups .
### Output Text:
On average , age - specific mortality rates were slightly higher for the 101 patients whose <span class="chemical">paracetamol</span> - induced liver injury had caused an acute liver failure ( adjusted mortality rate ratio = 1 . 70 , 95 % CI 1 . 02 - 2 . 85 ) , but the association was age - dependent , and no survivors of acute liver failure died of liver disease , whereas suicides were frequent in both groups . 