Does require hard water. * Boiling hard water that’s rich with minerals — such as calcium or magnesium — creates a chalk-like residue known as limescale, or ca

Does require hard water. * Boiling hard water that’s rich with minerals — such as calcium or magnesium — creates a chalk-like residue known as limescale, or calcium carbonate (CaCO3), which can trap the plastics. That solid, chalky residue then had to be separated and removed from the water with a standard coffee filter or stainless steel filter, thereby removing NMPs. The team found that the impact was greatest in harder water: In samples that had 300 milligrams of CaCO3, for example, nearly 90% of NMPs were removed. In softer water samples with less than 60 mg of CaCO3, roughly 25% of NMPs were removed.* Tough for city people and those who bought water softeners. Go figure.