CDPH Lead Inspector/Assessor California State Practice Exam

What is the meaning of 1 mg/kg in terms of ppm?

1. 1 ppm

2. 10 ppm

3. 100 ppm

4. 0.1 ppm

The correct answer is: 1 ppm

To understand why 1 mg/kg is equivalent to 1 ppm (parts per million), it's essential to know how ppm is defined and calculated. PPM is a unit that expresses the concentration of a substance in a solution or mixture. Specifically, 1 ppm means that there is one part of the substance in one million parts of the whole. When dealing with solids or solutions, 1 ppm can be equated to 1 mg of substance per kg of total mass. In this case, 1 mg of a substance in 1 kg (which equals 1,000,000 mg) results in a ppm concentration calculated as: 1 mg / 1,000,000 mg = 1 ppm. Thus, when referring to a concentration of 1 mg/kg, it directly translates to a concentration of 1 ppm in terms of how concentrations are standardized in environmental, health, and safety regulations. Understanding this relationship is crucial when assessing lead levels and other contaminants, as it provides a clear and standard way to express very small concentrations in practical terms.