Pyrex measuring cup glass

There is no safe amount of lead. This number is a starting point, not a verdict on your safety. What matters is whether the lead can actually reach a person. Think of tacks: a box of them in a drawer is fine, the same tacks loose on the kitchen floor are not. Lead locked in a stable fired glaze is mostly in the drawer. The same ppm in something a child can mouth, chew, or swallow, like paint dust, play sand, or a worn or chipped surface, is on the floor. Food is its own category: if the lead is in something you eat or drink there is no "might reach you," you are guaranteed to take the dose. Dose is what counts: 1 gram of a 90 ppm material is about 90 micrograms of lead, roughly 40 times the 2.2 micrograms per day the FDA uses as a child reference level. A reading that looks low can still matter in the wrong form, and a high reading on intact glaze may never reach anyone. Do not trust the number alone. Test the actual item, and when in doubt keep it away from kids and food.