Since the mid-1980s, Battelle has been at the forefront of research into the most effective ways of measuring lead in residential environments and reducing the hazards of lead exposure. Battelle is nearing completion on two long-term programs that examine clearance testing, a way to determine if lead hazard control treatments and cleaning have made a contaminated dwelling safe.

Lead exposure has been linked to an array of ailments, from developmental disorders to hearing loss. Young children living in older homes or low-income areas are at the greatest risk and are most commonly exposed to lead through dust from lead-based paint. Environmental interventions can reduce or eliminate lead hazards. After intervention, clearance testing involves collection and analysis of dust samples for lead. The decision to clear a dwelling for either reoccupancy or further work by unprotected contractors is made by comparing the results of the sample analyses to government-established clearance criteria.

Dust-lead clearance standards of 200 micrograms of lead per square foot (µg/ft²) for bare floors, 500 for window sills, and 800 for window troughs were adopted by the U.S. Department of Housing and Urban Development (HUD) in 1990. HUD later lowered the standard for floors to 100 µg/ft². In January 2001, the U.S. Environmental Protection Agency (EPA) lowered the clearance standards for floors, interior window sills, and troughs to 40, 250, and 400 µg/ft², respectively.

Battelle provided technical support to EPA during its rulemaking on these standards, investigating clearance testing activities between 1989 and 1999. Collected data included more than 39,000 dust sample measurements taken on floors, window sills, and troughs from more than 4,500 housing units that had received lead-based paint abatement or other intervention. The range of dust-lead averages confirmed the presence of high, potentially hazardous concentrations of dust lead on window sills and troughs, which require relatively greater effort to clean when compared to bare floors.

For HUD, Battelle investigated the differences between individual dust-wipe samples and samples that have been combined or composited with other samples to save analytical effort and cost in clearance testing. In addition to composite sampling, Battelle examined the role of visual inspections and reduced-cost sampling schemes in clearance testing.

Battelle conducted statistical analyses on the results from both studies, in part to determine if different clearance standards for composite samples might offer residents and workers the same protection they get from clearance tests using individual samples. For example, if four individual samples are analyzed, three of which are below the clearance level and one of which is above the level, the dwelling should fail clearance. If those same four samples were composited, however, the single failing sample might be hidden among the three passing samples, and the dwelling would pass.

The pass/fail decision rule that appeared to be the best involved changing the standard for composite samples to twice the level used for clearance testing with individual samples, divided by the number of subsamples in the composite. EPA’s January 2001 rule has already adopted this standard for composite samples.

Reports on both the EPA and HUD investigations are in the final review stages. For more information, contact Warren Strauss at (614) 424-4275, strauss@battelle.org.