Answer the following question given this paragraph: 

Secondary pollutants are formed when primary pollutants interact with sunlight, air, or each other. They do not directly cause pollution. However, when they interact with other parts of the air, they do cause pollution. For example, ozone is created when some pollutants interact with sunlight. High levels of ozone in the atmosphere can cause problems for humans.


Q: What  are formed when primary pollutants interact with sunlight, air, or each other?


A:
secondary pollutants