# Heavy metals (Pb, Cd, Hg)

Lead, cadmium, and inorganic mercury are the heavy metals most consistently linked to chronic low-level exposure and harm in human studies. Each has its own route in. Lead comes from aging water pipes and old paint. Cadmium builds up from cigarette smoke, contaminated soil, and certain foods. Methylmercury concentrates in big predatory fish as it moves up the food chain (bioaccumulation). Once inside you, these metals do damage in similar ways. They shove aside essential minerals, jam enzymes, generate reactive oxygen species, and alter your DNA methylation, an epigenetic effect tied to faster biological aging. NHANES studies of blood lead show a steady dose-response link between lead levels and death from all causes and from heart disease, even at levels once thought safe. That is part of why official 'safe' reference values keep getting revised downward.

## Sources

- Lanphear BP, Rauch S, Auinger P, Allen RW, Hornung RW. (2018). Low-level lead exposure and mortality in US adults: a population-based cohort study. Lancet Public Health. https://doi.org/10.1016/S2468-2667(18)30025-2

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