Environmental Protection Agency (EPA) Model Lead Based Paint Risk Assessor Practice Test

For XRF results below 4.0 mg/cm², which materials require substrate correction?

1. Wood and Metal

2. Brick, Concrete, Drywall, and Plaster

3. Glass and Ceramics

4. None; correction is not needed

The correct answer is: Brick, Concrete, Drywall, and Plaster

In the context of X-Ray Fluorescence (XRF) lead testing, substrate correction is important because the substrate material can influence the readings obtained. When XRF results show lead levels below 4.0 mg/cm², it becomes critical to consider which materials may require correction to ensure accurate assessments. Brick, concrete, drywall, and plaster are porous materials that can absorb some energy from the XRF beam, potentially leading to underreporting of lead levels. If the XRF instrument does not account for the substrate's properties, the readings can misrepresent the actual lead concentration present. Correcting for these substrates ensures that the lead levels indicated by the XRF measurements accurately reflect the environmental risks. In contrast, materials like wood and metal, glass, and ceramics do not typically require substrate correction because they do not significantly absorb the XRF signal in a way that skews the measurement. Therefore, the focus on brick, concrete, drywall, and plaster for substrate correction aligns with the need for precise assessment of lead risks in environments where these materials are prevalent.