What are the EPA clearance standards for lead dust on interior windowsills and troughs?

• A. < 50 µg/ft²
• B. < 100 µg/ft²
• C. < 5 µg/ft²
• D. < 200 µg/ft²

Answer: (B)

The key idea is knowing the specific clearance level the EPA uses for lead dust on interior windowsills and troughs after cleaning or abatement. For these surfaces, the standard is a lead loading of less than 100 micrograms per square foot. That means a wipe sample from a windowsill or trough must show under 100 µg of lead per ft² to meet clearance.

This threshold is chosen because dust accumulates differently on window sills and troughs than on floors, and the EPA sets surface-specific targets to ensure safety. Other numbers don’t match this surface-specific standard. For example, interior floors have a different clearance value, typically lower, so they’re governed by a separate requirement.