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: Incidence of solid tumours among pesticide applicators exposed to the organophosphate insecticide diazinon in the Agricultural Health Study : an updated analysis .
### Output Text:
Incidence of solid tumours among pesticide applicators exposed to the <span class="chemical">organophosphate</span> insecticide <span class="chemical">diazinon</span> in the Agricultural Health Study : an updated analysis . 