5935
In order to understand the toxic mechanisms of cardiovascular system injuries induced by ambient PM ( 2 . 5 ) and / or ozone , a subacute toxicological animal experiment was designed with exposure twice a week for 3 continuous weeks .
 Chemical: ozone
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: ozone