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: RESULTS : We observed positive associations of Parkinson ' s disease with ozone ( odds ratio = 1 . 39 ; 95 % CI : 0 . 98 to 1 . 98 ) and fine particulate matter ( odds ratio = 1 . 34 ; 95 % CI : 0 . 93 to 1 . 93 ) in North Carolina but not in Iowa .
### Output Text:
RESULTS : We observed positive associations of Parkinson ' s disease with <span class="chemical">ozone</span> ( odds ratio = 1 . 39 ; 95 % CI : 0 . 98 to 1 . 98 ) and fine <span class="chemical">particulate matter</span> ( odds ratio = 1 . 34 ; 95 % CI : 0 . 93 to 1 . 93 ) in North Carolina but not in Iowa . 