The CDC says that.
MMWR Morb Mortal Wkly Rep. Nov 29;62(47) Very high blood lead levels among adults - United States, Centers for Disease Control.
Most states require reporting all BLLs, elevated or not. Reporting all Reference blood lead level for adults An elevated BLL is defined as a BLL ≥5 µg/dL.
CDC has designated 10 µg/dL as the reference BLL for adults; levels ≥10 µg/dL are considered elevated (2). CDC's Adult Blood Lead.
Blood lead level (BLL), is a measure of the amount of lead in the blood. Lead is a toxic heavy metal and can cause neurological damage, especially among children, at any detectable level. High lead levels cause decreased vitamin D and haemoglobin synthesis as . An adult might only retain 10% of the lead in that water.