Evaluating the Effects of Full and Partial Lead Service Line Replacement on Lead Levels in Drinking Water.

Lead service line replacement (LSLR) is an important strategy for reducing lead exposure via drinking water, but jurisdictional issues can sometimes interfere with full replacement of the lead line. The effects of full and partial LSLR on lead levels were assessed using 5 × 1-L sample profiles collected at more than 100 single-unit residences. Profiles comprised four sequential standing samples (L1-L4) and a free-flowing sample (L5) drawn after a 5 min flush of the outlet. At 45 sites with full lead service lines, 90th percentile lead levels in standing samples ranged from 16.4 to 44.5 μg L(-1) (L1 and L4, respectively). In the free-flowing sample (L5), 90th percentile lead was 9.8 μg L(-1). Within 3 days, full LSLR had reduced L3-L5 lead levels by more than 50%, and within 1 month, lead levels were significantly lower in every liter of the sample profile. Conversely, partial LSLR more than doubled premises plumbing (L1, L2) lead release in the short term and did not reduce L1, L2 lead release in the long term. Even 6 months after partial LSLR, 27% of first-draw lead levels were greater than 15 μg L(-1) (the U.S. EPA action level), compared with 13% pre-replacement.