Environmental justice debate

Parallel case (not today's prompt): An older apartment building draws its tap water through lead service lines installed decades ago, while a newer building across the street was plumbed with copper. Water testing shows the older building has a much higher lead level at the tap. Who bears responsibility for the residents' exposure, and what does the data actually prove?\n\nClaim: Because the older building's tap water carries lead well above the level considered safe while the newer building's water does not, the utility that owns the service lines and the property owner who left them in place share responsibility for reducing the exposure, since the data shows the risk comes from the pipes, not from anything the residents did.\n\nEvidence: The water samples show the older building averaged roughly 20 parts per billion of lead at the tap, above the 15 parts per billion action level, while the newer building measured near zero. Both buildings receive water from the same treatment plant and the same source, so the treated water entering each building started out the same. The only measured difference between the two water paths is the metal in the pipes, lead in the older lines and copper in the newer ones.\n\nReasoning: Lead does not appear in water on its own, it dissolves into the water as it sits in contact with lead pipes, so a higher reading at the tap points to the plumbing the water traveled through rather than to the residents' habits or choices. Because both buildings share the same source and treatment, that shared starting point rules out the treatment plant as the cause and isolates the service lines as the variable that changed the outcome. The residents cannot see, choose, or replace the buried lines they rent water through, so the burden of an exposure they did not create falls on the parties who control those lines, the utility that owns them and the owner responsible for the building's plumbing. The data proves where the lead is coming from, and that source is on the responsible parties' side of the tap.