Some rocks are simply packed with arsenic. We’re talking about volcanic rocks, shales, and certain sulfide minerals. If your local aquifer flows through a layer of these, congratulations: you’ve hit the rock lottery—just not the winning ticket.
Imagine if your kitchen faucet was connected to a rock tumbler filled with gravel and rusty nails. That’s basically what happens when water moves through arsenic-rich soil. The water picks up the element like a dog picks up mud at the park—accidentally and with no shame.
This is why wells in places like the western U.S., parts of India, and Bangladesh can have sky-high levels. It’s not because someone dumped a barrel of poison; it’s because they built a well in a geologically gifted spot.
