Effectiveness of Walk-Off Mats in Reducing Interior Dust Lead

Project Funder: U.S. Department of Housing and Urban Development

Project Partner: Community Development Department, City of Cambridge, MA, Lead-Safe Cambridge Program

Project Contact: Jill Breysse, jbreysse@nchh.org, 443-539-4155

What we studied: Determine whether walk-off mats provided to tenants after lead hazard control treatment reduce the amount of lead dust within homes.

Why it matters: Walk-off mats may reduce hazards posed by dust tracked into dwellings from exterior sources of lead, including lead-contaminated soil and dust from lead-contaminated paint on untreated porches.

What we found: One-year post-remediation results indicated the Lead-Safe Cambridge program was effective in treating homes. Results for the initial post-remediation visit often exceeded clearance standards, even though clearance testing had been performed approximately one month prior. The postponement of cleaning common areas until after all units in these multifamily buildings were treated may have contributed to high results. One-year post-intervention results indicated mats may help reduce interior dust lead loadings at least slightly. Because mats are inexpensive and may aid in preventing track-in, programs should consider distributing mats after lead remediation, educating tenants about maintenance and periodic replacement to prevent mats from becoming exposure sources themselves.

Project Description

Using funds from the HUD Lead Hazard Control Grant Program, units in multifamily buildings were remediated then randomly assigned to appropriate groups. Of 65 enrolled units, 23 had complete study data: six “no mat” units, seven “program mat” units, six “tenant mat” units, and four “gain mat” units (units that had no mats at initial visit but had mats at the one-year visit). Four dust wipe samples were collected from each unit at an initial visit within one month post-remediation and again one year later: (1) just inside the primary door into the unit; (2) just outside this door; (3) five feet inside the unit in the direction tenants were expected to walk routinely upon entry; and (4) on the opposite side of the room.

Resources

Cambridge Walk-Off Mat Study Report [Final Report]: