2.2 Evaluating Friction, Impact, and Chewable Surface Hazards

2.2 Evaluating Friction, Impact, and Chewable Surface Hazards

Mechanical Surface Wear and Lead Hazard Genesis

While general paint deterioration (such as peeling, flaking, or cracking) is commonly caused by moisture breakdown and substrate decay, physical mechanical wear represents a distinct vector for lead dust generation and lead ingestion. Residential building components subject to daily physical movement, impact force, or childhood biting can generate hazardous levels of fine lead dust or loose paint chips even when the surrounding paint film appears superficially stable.

Under 40 CFR § 745.65 and Chapter 5 of the HUD Guidelines, environmental risk assessors must systematically evaluate three specific categories of mechanical surface hazards:

1. Friction Surfaces
2. Impact Surfaces
3. Chewable Surfaces

Distinguishing these mechanical hazards from general paint deterioration is vital because their remediation requires targeted mechanical controls—such as window re-alignment, threshold planing, vinyl sash installation, or impact-resistant capping—rather than simple repainting.

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Evaluating Friction Surface Hazards

A friction surface is defined as any interior or exterior painted surface that is subject to abrasion, rubbing, or sliding contact with another surface during normal operation.

Common Friction Components

• Double-hung and Single-hung Windows: Sash guides, side jambs, blind stops, parting beads, window troughs/wells, and top/bottom sash meeting rails.
• Doors and Frames: Door hinge edges, latch stiles, header jambs, side jambs, door stops, and threshold contact points.
• Stairways: Stair treads (where footwear abrades nose edges), risers, and runner tracks.
• Cabinetry: Sliding cabinet doors, drawer guides, and cabinet frame face-plates.

Regulatory Standard for a Friction Hazard

Under 40 CFR § 745.65(a)(4), a lead-containing friction surface is NOT automatically classified as a lead-based paint hazard simply because it rubs. To be designated as an actionable friction surface hazard, the surface must satisfy a strict two-part legal test:

1. Lead Content: The paint on the friction surface must be confirmed or presumed to be lead-based paint (>= 1.0 mg/cm² by XRF or >= 0.5% by weight).
2. Evidence of Abrasion AND Dust Contamination: The surface displays visible evidence of friction-induced wear (such as binding marks, paint powdering, or bare wood scraping) AND dust wipe samples collected on the nearest adjacent horizontal surface (e.g., window stool, window trough, or adjacent floor) exceed federal lead dust hazard standards.

If a window jamb contains lead paint and shows abrasion wear, but dust wipe samples on the adjacent window sill and trough are below EPA clearance/hazard standards, the friction surface is not an actionable hazard at the time of assessment. However, if dust levels exceed standards, the friction wear is confirmed as an active dust generator and classified as a lead-based paint hazard.

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Evaluating Impact Surface Hazards

An impact surface is an interior or exterior painted surface subject to repeated damage from mechanical impacts, force, or contact with moving objects.

Common Impact Components

• Door Stop & Frame Components: Areas struck by swinging doors or door handles.
• Baseboards and Chair Rails: Lower wall trim impacted by vacuum cleaners, furniture, toys, or shoe heels.
• Wall Corners & Plaster Trim: Outside wall corners in high-traffic hallways and door openings.
• Stair Risers: Surfaces repeatedly kicked by footwear during climbing.

Regulatory Standard for an Impact Hazard

Under 40 CFR § 745.65(a)(3), an impact surface is classified as an actionable impact surface hazard when ALL THREE of the following conditions are met:

1. Lead Content: The painted surface contains lead at or above regulatory thresholds (>= 1.0 mg/cm² or >= 0.5% by weight).
2. Physical Damage: The paint displays visible chipping, flaking, cracking, denting, or gouging caused by physical impact.
3. Ongoing Impact Exposure: The component is located in an area where repeated mechanical impact is likely to recur (e.g., baseboard behind a door without a doorstop).

Intact lead paint on a baseboard or wall corner is not an impact hazard. Physical damage must be present alongside a high likelihood of continued mechanical impact.

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Evaluating Chewable Surface Hazards

A chewable surface (also referred to as a biteable surface) is an accessible, protruding painted surface that can be chewed or mouthed by young children.

Common Chewable Components

• Window Stools (Sills): Especially low sills accessible to crawling infants or toddlers.
• Stair Railings & Balusters: Handrails, guardrails, spindles, and newel posts along stairways or porches.
• Porch Deck Trim & Guardrails: Low exterior balustrades accessible to young children during outdoor play.
• Doors and Low Trim: Exposed lower edges of doors, protruding baseboard corners, or low interior trim.

Accessible Dimensions and Childhood Behavior

To be considered accessible for chewing, the component must generally feature a protruding edge extending at least 0.5 inches that a child can grip with teeth, located within child height—typically <= 5 feet (60 inches) from the finished floor or ground surface.

Regulatory Standard for a Chewable Hazard

Under 40 CFR § 745.65(a)(2), an accessible, protruding surface containing lead-based paint is classified as an actionable chewable surface hazard ONLY IF it displays distinct visual evidence of teeth marks, mouthing wear, or childhood chewing damage.

An intact lead-painted window sill located 24 inches off the floor is an accessible chewable surface, but it is NOT an actionable chewable hazard unless visible bite marks or chewing degradation are present. If teeth marks are observed on lead-painted trim, it is immediately classified as a chewable hazard requiring interim controls (such as installing protective plastic guards or stripping paint) or abatement (component replacement).

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Summary Comparison of Mechanical Surface Hazards

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Risk Assessor Field Strategy and Diagnostic Integration

During the walk-through, the risk assessor must physically operate representative windows and doors to detect binding and friction powdering. When chewable or impact surfaces are noted, the assessor must cross-reference physical observations with occupant questionnaire responses—specifically asking whether children under 6 years of age reside in or visit the home and whether pica or mouthing behaviors have been observed. Synthesizing physical damage evidence, dust lead concentrations, and occupant demographics ensures a precise, defensible hazard evaluation.