Why Blonde Hair Turns Green in the Pool

The Science Behind the Tint Blonde swimmers often return from the pool with an unexpected souvenir: a greenish tint to their hair. While it’s easy to blame chlorine, the real culprit is copper—its presence in pool water, combined with oxidation, leads to that telltale hue, especially in light or porous hair. Copper, Not Chlorine, Is to Blame Copper ions—from pennies turning green to the Statue of Liberty’s patina—oxidize when exposed to pool water and chlorine. As copper oxidizes, it leaches into the water and binds to the proteins in hair shafts, depositing green-tinted particles. How Copper Enters Pool Water Municipal or Well Water Sources Many well-water supplies naturally contain dissolved copper. Even some city water systems can have elevated copper levels, seeding pools with the metal. Copper-Based Algaecides Copper is a powerful algaecide, so many pool owners use copper-bearing treatments to prevent algae blooms. Overuse or improper dosing raises copper concentration...