What harmful compound is formed from increased levels of sulfur dioxide and how is it formed?

Answer 1

I assume you mean increased sulfur dioxide levels in the atmosphere? In this case, the sulfur dioxide created from processes such as the combustion of fossil fuels can dissolve in water in the atmosphere creating sulfuric acid, commonly know as acid rain

Answer 2

I have worked in the oil field in west Texas . The gas there has H2S or hydrogen sulfide very deadly so they burn it and it will produce SO2 . The plants are in a desert environment but the local plants do just fine the SO2 doesn't effect anything that I could see.