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 suggestion of an association between metolachlor and liver cancer among pesticide applicators is a novel finding and echoes observation of increased liver neoplasms in some animal studies .
### Output Text:
This suggestion of an association between <span class="chemical">metolachlor</span> and liver cancer among pesticide applicators is a novel finding and echoes observation of increased liver neoplasms in some animal studies . 