GENETICS:Questions about SNPS (Single Nucleotide Polymorphisms)

Any info helps!

Are SNPS in ANY away environmental? Can they be caused by your environment such as chemicals or changes from addiction, etc.? I know they are genetic.

What percentage of the population has SNPS? Is there a certain part of the population that are more likely to have SNPS (race ethnicity etc)?

Do SNPS make you vulnerable to more diseases?

TIA

~AX