Evaluation of Sampling Methods for Determining Dust Lead Loading on Residential Carpet Surfaces Zhipeng Bai, Junfeng Zhang, George G. Rhoads, Paul J. Lioy, David Q. Rich, John L. Adgate, Stella M. Tsai, Lih- ming Yiin, and Peter J. Ashley* Environmental and Occupational Health Sciences Institute (EOHSI), University of Medicine and Dentistry of New Jersey (UMDNJ) * Office of Lead Hazard Control, the US Department of Housing and Urban Development
House dust is a major pathway by which children are exposed to lead. Carpets are commonly used in residential buildings. Therefore, it is important to obtain measures that are representative of lead exposures resulting from lead-contaminated dust embedded in carpets. Introduction
Study Design and Strategy Between May and November 1998, 33 houses were recruited from homes with children having elevated blood lead levels in Northern New Jersey. Five sampling methods were compared to measure dust lead loading ( g/m 2 ) on carpet surfaces. Lead loading on surfaces is the metric most strongly correlated with elevated blood lead levels in children.
The Five Sampling Methods HUD Wipe Method EOHSI Vacuum Method Technician Hand Rinse Method Adhesive Label Method C18 Method (Simulated Skin)
Digestion Procedure Samples are microwave digested (CEM Corporation, MDS-2000) in an acid solution: a. 20% (v/v) nitric acid (trace metal grade, Pb <0.1ppb) for C18, Vacuum, and Technician Hand Rinse samples. b. Concentrated nitric acid for Adhesive Label and HUD Wipe samples.
Analysis Adhesive label, C18, and Technician hand rinse samples were analyzed using graphite furnace atomic absorption spectrophotometer (GFAA) (Perkin-Elmer Zeeman 5100). HUD wipe samples and EOHSI vacuum samples were analyzed using flame atomic absorption spectrometer (FAA) (Perkin-Elmer Model 3100) or using GFAA if the lead levels were below the FAA detection limit.
QA: Correlation (r) between Duplicate Measurements Results within Each Method Adhesive Label:0.612 C18:0.324 Hud Wipe:0.653 Hand Rinse:0.213 EOHSI Vacuum:0.707
Methods Comparison HUD wipe results were used to normalize values. Ratios were generated for each of the four methods to assess the collection efficiency.
Results The descriptive statistical results showed that the vacuum sampling method yielded higher lead loading from carpet surfaces than the HUD wipe did. A total of 90.3% of the vacuum samples had the ratio higher than 1. The median ratios of vacuum, technician hand rinse, adhesive label, and C18 were 6.07, 0.52, 0.46, and 0.27, respectively.
Conclusions General linear model methods were applied to log- transformed lead loading results. The results showed that not all five sampling methods yielded the same level of lead loading (p < 0.001). Multiple comparison results showed that the technician hand rinse, adhesive label, and EOHSI vacuum methods were significantly correlated with the HUD wipe method.
Acknowledgement We are grateful to the families who participated in the study and to Richard Madison and Chen Zhang of the Development and Testing of Lead Exposure Metrics: New Jersey Assessment of Cleaning Techniques (NJACT) Study.Development and Testing of Lead Exposure Metrics: This study was Funded by the Office of Lead Hazard Control, the US Department of Housing and Urban Development through a grant to UMDNJ (Grant # NJLH0023-97).