Lead is one of the most dangerous contaminants found in tap water. Lead is a powerful neurotoxin that is especially harmful for infants and children. Lead is often leached into water supplies after it has left the treatment facility. Lead enters drinking water primarily through the corrosion of pipes, fixtures, solder and service lines. Homes built before 1986 are more likely to have lead plumbing, and an estimated 6 to 10 million lead service lines are still in use today.