Safe water is the most fundamental prerequisite for health — the body is mostly water, and what that water carries matters enormously. Contamination with pathogens, heavy metals, agricultural runoff, and industrial chemicals causes documented disease across populations, and access to adequate safe water remains one of the great determinants of global health disparity. At the individual level, understanding your local water quality and choosing appropriate filtration is a practical health investment; at the collective level, water access and safety is a justice and governance issue of the first order.
Each step builds on the last.