Articles like these are frustrating because the mineralization of lead pipes (which prevents contact between water in the service line and the lead in the pipes) is actively managed by the Metropolitan Water Reclamation District, which is one of the most sophisticated water management agencies in (I think?) the world, and lead in pipes is not a major source of lead exposure in Chicago --- by far the biggest real culprit is paint.
If you want to map lead exposure, map home ages and renovations (and, unfortunately, the soil around the houses, which gets contaminated by the paint over time).
Ironically, for at least a short term after lead service lines are replaced, you're actually at higher risk of exposure --- the process disrupts the mineralization layer in the lines.
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