Units: Parts-per-billion (ppb) are the same as micro-grams-per-liter (µg/L)
The EPA action threshold is 15 ppb (adopted in 1991).
The international guideline is 10 ppb (adopted by the WHO, EU, Canada, and China).
Does this mean lead levels below 10ppb or 15ppb are safe? No. According to Joel Beauvias, the deputy assistant administrator for the EPA’s Office of Water, “the 15 parts per billion action level isn’t meant to be a threshold for public health.” The EPA maximum contaminant level goal for lead is 0, because there is no safe level of lead in drinking water.