Urban stormwater runoff contains many chemicals, but just because they exceed water quality standards doesn't mean they harm aquatic life. Most of these chemicals are stuck to particles and don't affect water quality. There isn't enough evidence to show that stormwater runoff actually harms water quality. The current standards for water quality might not be the best way to assess stormwater pollution. Controlling contaminants in stormwater might not be necessary and could be a waste of money.