Q: Which is safer: a reusable metal water bottle or a reusable plastic one? I've been using a metal bottle to avoid the chemicals in plastic, but now I've noticed an odd buildup in my metal bottle.
A: A reusable aluminum or stainless steel bottle or a hard plastic bottle are both good options. Metal bottles used to be the safer choice, to avoid the chemical BPA, which was commonly used in hard plastic water bottles and has been linked to many adverse health effects. But manufacturers have largely stopped using BPA. And some metal bottles contain plastic lining, to prevent a metallic taste; so using a metal bottle doesn't necessarily mean you're avoiding plastic.
Minuscule amounts of nickel, aluminum, or iron may leach from unlined metal bottles into the fluid within. This happens with cookware too and should not be a concern. The link between aluminum and Alzheimer’s disease has never been proved. “Studies have failed to confirm any role for aluminum in causing Alzheimer’s,” according to the Alzheimer’s Association.
Some users of metal water bottles may notice a crusty build-up in the bottle. This could simply come from hard water or from the contents of the bottle, and isn't cause for concern. Try washing it with a brush and soapy water. Or let it soak in a vinegar solution overnight and then rinse with warm water and baking soda. Wide-mouthed bottles are easier to clean, and most can go in the dishwasher. Follow the manufacturer’s instructions.