Lead contamination in Washington, D.C., drinking water, first discovered in 2001, left thousands of children with lifelong health risks, and led to a re-evaluation of the use of monochloramine in public drinking-water systems. Professor Marc Edwards, an expert in plumbing corrosion, discovered lead levels at least 83 times higher than the accepted safe limit while performing research into premature pipe corrosion for the District of Columbia Water and Sewer Authority (WASA). He found that the decision to change from chlorine to chloramine as a treatment chemical had caused the spike in lead levels.