Grantee Research Project Results
Final Report: Rapid Immunochromatographic Strip Tests Detecting Lead-Based Paint
EPA Contract Number: EPD06056Title: Rapid Immunochromatographic Strip Tests Detecting Lead-Based Paint
Investigators: Geisberg, Mark
Small Business: Silver Lake Research Corporation
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2006 through August 31, 2006
Project Amount: $69,990
RFA: Small Business Innovation Research (SBIR) - Phase I (2006) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Lead Paint Detection and Removal , Small Business Innovation Research (SBIR)
Description:
Exposure to lead-based paint (LBP) is the major source of potentially dangerous levels of lead in children and adults in the United States. Assay technology for the detection of lead in paint is central to both monitoring and effective remediation of lead contamination. “Gold standard” laboratory methods involve significant costs in sample collection, transportation, and analysis, as well as the associated time delays in obtaining a result. On-site instrumental methods such as X-ray fluorescence also require technical expertise and may be too costly for many users. Several vendors sell non-instrumental test kits for lead in paint, based on the color-producing reaction of lead with sodium sulfide or sodium rhodizonate. These methods have been judged too inaccurate for widespread use.
Recent proposed rule changes by the U.S. Environmental Protection Agency and other agencies have prompted new efforts in the development of rapid, on-site test kits (Lead: Renovation, Repair, and Painting Program; Proposed Rule, 71 FR 1587-1 636, January 10, 2006). The goal of this research project was to develop a simple, inexpensive, and rapid on-site test kit for the detection of harmful levels of lead (Pb) in paint. The proposed test kit will be calibrated to determine both the presence and absence of LBP, will require no user training or instrumentation, and will resemble a home pregnancy test. The test kit will be designed to meet the proposed federal performance specifications of less than 5 percent false positive and false negative rates, on-site results in less than 1 hour, and at a cost not to exceed $2 per test. The proposed kit will be based on Silver Lake Research Corporation’s (SLRC’s) existing immunoassay strip test for lead in water, the Watersafe® Lead Test. The planned development of the proposed test kit includes development of an extraction step to produce a lead-containing extractant for analysis by the immunoassay test strip.
The overall goal of this Phase I project was to demonstrate a proof-of-principle extraction procedure by which a liquid extractant could be produced from LBP and non-LBP samples; the lead content in such extractants could be analyzed by an immunoassay to determine the LBP or non-LBP nature of the original sample. Specific research objectives included: (1) obtain LBP samples and non-LBP samples, characterized by lead content; (2) develop extraction solvents and process; (3) test each extraction solvent for efficiency of lead extraction from LBP samples; (4) determine extraction kinetics and reproducibility for selected extractants; and (5) develop an immunoassay procedure for determination of lead concentration in extractant, including a method of conditioning the extractant for use in immunoassay.
SLRC has completed this Phase I project and accomplished the five research objectives.
Summary/Accomplishments (Outputs/Outcomes):
SLRC quickly found that obtaining sufficient numbers of characterized samples of LBP from third-party sources, both governmental and commercial, proved impossible. To complete the first research objective and enable further work, SLRC developed a process for obtaining real-world paint samples and preparing a collection of characterized replicates. A major achievement in the Phase I work was the development of a process for collecting and characterizing replicate samples of paint, representing both LBP and non-LBP paints according to the federal definition of LBP by both the surface area standard (1 mg Pb/cm2) and the weight percent standard (0.5% Pb by weight). SLRC created a collection of more than 500 paint samples, each with a known lead content and many with a known weight/surface area relationship. These samples included more than 20 sets of 20+ replicates of essentially identical lead content, an invaluable resource for subsequent experiments on reproducibility and kinetics. Lead content of these samples ranged from non-LBP to barely above the LBP limit to significantly higher than the LBP limit (0.01%-26% Pb by weight). The benefits of this system will be the basis of much of the work in the further development of the proposed test kit, and also can be applied to broader research, development, and validation efforts in this field.
SLRC also developed an extraction process that could generate lead-containing extractants from paint samples in less than 10 minutes. Many solvents were tested for extraction efficiency, and two were selected for their ability to produce an extractant in which the concentration of lead reflected the lead content of the paint. These solvents, solvent A and solvent B, are substances that have low toxicity, present minimal packaging and safety issues, and are easily adaptable for compatibility with a follow-on immunoassay detection step (as demonstrated by experiments analyzing paint extractants by a laboratory immunoassay). The combination of timing, extraction volume, and mildness of solvent produced an extraction procedure that is well matched to proposed on-site use as part of a rapid test kit.
Extraction experiments using solvents A and B showed that, despite significant inconsistencies in extraction from multiple replicate samples, all extractants from LBP samples were in a different concentration range than extractants from non-LBP samples. This finding is key to the next stages of development of the proposed test kit. Although many other test kits use detection methods that are quantitative in nature, the SLRC immunoassay test strips are semiquantitative—they produce a positive/negative result with a pre-set analyte concentration. To produce an immunoassay test strip in the SLRC format for the detection of lead in solvents A or B, the positive/negative cutoff can be calibrated to the middle of the range identified, and the positive/negative result will reflect faithfully the LBP/non-LBP nature of the original paint sample. The identification of this cutoff for both solvent A and solvent B is the proof-of-principle for the development of the proposed test kit.
Conclusions:
SLRC has demonstrated proof-of-principle for an extraction/immunoassay procedure to determine the presence or absence of LBP in real-world paint samples. The results indicate that this procedure, when combined with an immunochromatographic test strip in the Watersafe® Lead Test format, could be used to determine whether a particular paint sample is LBP or non-LBP, according to regulatory definitions of LBP. Based on the results of this Phase I effort, SLRC plans to submit a Phase II proposal for the continuation of the development of the proposed test kit. The objectives of this proposal will be to: (1) develop a paint sampling procedure to use on-site to produce paint samples similar to those produced by SLRC in this Phase I project; (2) develop an immunoassay test strip designed to analyze extractants; (3) combine sampling, extraction, and test strip procedures into a single test kit; (4) calibrate, optimize, and validate the final test kit; and (5) verify performance by an external testing organization. At the successful conclusion of Phase II, SLRC will have demonstrated a rapid, accurate, on-site LBP test kit matching the federal criteria for accuracy, ease-of use, and cost.
SLRC has a long-standing track record of successfully developing, manufacturing, and marketing rapid immunoassay test kits under the Watersafe® brand and other product families. The company perhaps is unique in its combination of strong scientific and technical development, process development, manufacturing, and marketing teams, with specific experience in rapid immunoassay test kits. SLRC has existing manufacturing facilities in California, dedicated expertise in the production of immunochromatographic test kits, and existing distribution channels; these factors will be invaluable to SLRC on the path to commercialization of the proposed LBP test kit.
Supplemental Keywords:
small business, SBIR, lead-based paint, LBP, lead paint, lead paint remediation, lead poisoning, childhood lead poisoning, renovation, remodeling, monitoring, test kits, environmental testing, antibodies, immunoassay, lead detection, lead contamination, lead screening, heavy metals, analyzer,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Environmental Chemistry, Health Risk Assessment, Chemicals, Monitoring/Modeling, Analytical Chemistry, Environmental Monitoring, assays, environmental measurement, analyzer, lead-based paint, immunochromatographic test stripThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.