Summary and Assessment of Published Information on Determining Lead Exposures and Mitigating Lead Hazards Associated with Dust and Soil in Residential Carpets, Furniture, and Forced Air Ducts

December 1997, EPA 747-S-97-001

EXECUTIVE SUMMARY

This report presents the findings of a literature review on information concerning lead in dust within residential carpets, furniture (including upholstery and window treatments), and forced air ducts. Research areas include: 1) determining amounts of lead in dust within these surfaces (including dust collection techniques), 2) characterizing the association between lead contamination of dust within these surfaces and children's blood-lead concentration, and 3) mitigating lead-contaminated dust within these surfaces that pose a potential lead exposure to residents, especially children. This review is in support of research by the U.S. Environmental Protection Agency (EPA) in their efforts to address Congressional mandates within Title X (specifically, Section 1051).

While 59 documents provided information on dust and lead exposure associated with residential carpet, only 11 documents provided information relative to residential furniture, upholstery, and window treatments, and only eight documents provided information relative to residential air ducts. This information was typically a small part of the total information presented in these documents and was often insufficient to answer the questions addressed in this report. In addition, the studies referenced in these documents did not necessarily address the specific objectives of this report. Therefore, considerable research is necessary to adequately characterize lead exposures associated with these lead sources, as well as to mitigate such exposures.

Among the main findings of the literature review are the following (according to lead source):

Carpets

• Over time, carpets can become a reservoir of dust and exterior soil introduced to a residence.

• Different methods used to collect dust from carpets (and other surfaces) may collect different types of dust, thereby affecting how dust-lead is characterized.

• As carpets can hold large amounts of dust and soil and provide less particle movement relative to hard surfaces, carpet dust-lead loading can be high, while dust-lead concentration tends to be low except in high-traffic areas.

• Carpets that are easily able to trap dust within their fibers, such as clean carpets, may act as a short-term mitigator of lead exposure associated with floor dust.

• Behavioral techniques that limit the amount of exterior contamination, such as removing shoes prior to entry and use of walk-off mats, have been found to significantly reduce the likelihood of lead contamination of carpets.

• When sampling dust from carpets, factors significantly associated with reduced collection efficiency from vacuum methods include shag carpets, low relative humidity, low vacuum particle lifting velocity, fine dust particles, and no agitator bar present on the vacuum.

• Lead levels in carpet dust tend to have a significant positive association with children's blood-lead concentration, with dust-lead loading having a higher correlation than dust-lead concentration.

• Repeated vacuuming of old, contaminated carpets may increase lead-loading in surface dust if deeply-embedded dust cannot be removed in its entirety. For such carpets, it may be better to remove them than to decontaminate them. Carpet removal may be preferable if the carpet is a shag carpet, or if it has been highly contaminated by remodeling, peeling paint, paint removal, or being near a lead source, such as a lead or copper smelter, secondary smelter, etc.

• Use of wet methods to decontaminate carpets was generally found to be ineffective. However, use of detergent-based solutions that reduce the electrostatic interaction between carpet and lead-dust (such as sodium hexa-metaphosphate solutions, whose phosphate or polyphosphate groups coat the dust particles) has been effective, reducing dust-lead concentrations on average from 30% to 50% and dust-lead loadings by 60%.

• Effective cleaning of carpets, furniture, bare floors, and bare surfaces has been documented to reduce lead exposure in the home. A plush carpet is more popular than level loop or flat carpets, yet they are more difficult to clean. Old shag rugs are the hardest type of carpet to clean effectively.

Furniture

• While the same dust collection methods tend to be used to sample dust from carpets and furniture, one method (the High Volume Furniture Sampler, a modification of the HVS3) was developed specifically for sampling dust from upholstered surfaces. However, no field study has been encountered which used this dust sampler.

• Average dust-lead loadings on furniture, upholstery, and window treatments are generally lower than for other surfaces, such as floors, windows, and air ducts.

• A significantly positive correlation coefficient between blood-lead concentration and (pre-intervention) dust-lead levels in upholstery was observed within the Baltimore R&M study. However, positive correlation coefficients imply only statistical association, and not a causal relationship.

• Foreign-made, vinyl mini-blinds can be a direct source of dust-lead, as documented by the Consumer Product Safety Commission (CPSC).

• While several procedures were used to mitigate dust-lead in furniture, upholstery, and window treatments, available data were limited and inconclusive.

Air Ducts

• Lead loadings in air ducts are generally very high, especially when the ducts contain large amounts of dust, or when ductwork is old.

• It is not certain how lead in air ducts may be bioavailable to humans, especially in the absence of renovation or cleaning.

• One study reported that, on average, lead in dust within air ducts represented nearly one-third of lead in household dust (only floor-dust represented more).

• In the Baltimore R&M study, the correlation coefficient between blood-lead concentration and (pre-intervention) dust-lead levels in air ducts was not significant at the 0.05 level. However, this analysis was based on a small sample size and did not adjust for the effects of other exposure variables such as lead in floor dust and soil. Lead levels in air ducts were found to be significantly correlated with lead levels on certain surfaces, such as floors.

While one study detailed a protocol used to mitigate dust in air ducts, available data to evaluate mitigation procedures were virtually non-existent.