Stormwater can be reused for irrigation and other purposes, but it contains pollutants that need to be removed first. A study looked at pollutants in stormwater over three years and found that most pollutants are washed off early in a rainfall event, known as the first flush. UV spectroscopy can help identify when the first flush ends for certain pollutants. The study also found that organic pollutants and heavy metals in stormwater are expected to increase due to urbanization.