Instructions: In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 
Input: Chemicals like sulfur dioxide and nitrogen are released into the air. These substances rise into the high atmosphere. They react with water and oxygen. This creates a more acidic rain. The rain with the high acid content falls. 
Output:
sulfur dioxide ,nitrogen ,acidic rain ,water ,oxygen 