This headline is not correct. The ruling was that a constitutional lawsuit was not successful, not that the the US government has carte blanche to poison its citizens drinking water…
So, the correct headline would be “safe drinking water ruled not to be covered by the US constitution”. There are other binding agreements and regulations than the constitution in the US.
Still not that simple:
> The Jackson plaintiffs alleged that their city government deliberately withheld information about the water’s toxicity, and exacerbated the problem through a series of boil-water notices - a practice that can eliminate some bacterial contamination, but also concentrates lead in water. Engelhardt stated there is no “constitutional right to truthful information from officials during a public health crisis”
The constitutional question (and note that state Constitutions, e.g. Massachusetts, may instead cover it) is just one piece of the mess.