In California, lead-based paint is defined as paint or another surface coating containing lead at or above 1.0 milligram per square centimeter (mg/cm²) or 0.5% by weight. A concentration of 0.5% by weight is equivalent to 5,000 parts per million (ppm).
This threshold is important because a laboratory can detect lead at concentrations far below the legal definition of lead-based paint.
For example, paint containing 1,000 ppm lead contains detectable lead but is below the 5,000 ppm concentration threshold used in the lead-based-paint definition.
However, paint below the lead-based-paint threshold should not automatically be considered harmless. Different occupational, renovation, waste, and exposure requirements may use different criteria.