Lead-based paint testing
technologies: summary of an
EPA/HUD field study.
Author: Schmehl, R. L.; Cox, D. C. Dewalt, F. G. Source: American Industrial Hygiene Association
Journal v. 60 no4 (July/Aug. 1999) p. 444-51 ISSN: 0002-8894 Number: BAST99049841 Copyright:
The magazine publisher is the copyright holder of this article and it is reproduced with permission. Further
reproduction of this article in violation of the copyright is prohibited.
Keywords: lead-based paint, chemical test kits, X-ray fluorescence.
The U.S. Centers for Disease Control and Prevention (CDC) has recognized lead poisoning as one of the
most common and devastating environmental diseases of young children.(FN1) Lead-based paint (LBP)
in older housing, especially LBP in poor condition, is often implicated either directly or indirectly in
elevated blood lead levels of children younger than 6 years of age. Exposure to lead in paint can come
from paint chips, from dust caused by abrasion of paint on friction or impact surfaces, and from the
deterioration of interior or exterior painted surfaces. Reflecting an increasing awareness of the public
health threat posed by LBP, the federal government first enacted the Lead-Based Paint Poisoning
Prevention Act of 1971,(FN2) which was later amended by enactment of the Housing and Community
Development Act of 1987. In October 1992 the Residential Lead-Based Paint Hazard Reduction Act(FN3)
became law and became the most comprehensive federal legislation regarding lead-based paint and
lead-based paint hazards.
To meet the requirements of Section 1017 of the Residential Lead-Based Paint Hazard Reduction Act,
the U.S. Department of Housing and Urban Development (HUD), with substantial input from U.S.
Environmental Protection Agency (EPA), prepared and issued its guidelines(FN4) for the conduct of
federally supported work involving LBP in housing. To support the development of the LBP inspection
chapter of the guidelines and update the lead testing fact sheets available from the National Lead
Information Center Clearinghouse, EPA and HUD sponsored a field evaluation study of the available
lead-testing technologies.(FN5,6) Chemical test kits and X-ray fluorescence instruments, which were the
portable lead-testing technologies commonly in use at the time of the study, were of particular interest
because of the advantages of speed, cost, and minimal destructiveness that they offered relative to
laboratory analysis. This article describes the design of the study and summarizes its major findings.
PAINT TESTING TECHNOLOGIES
It was acknowledged that the most accurate method for measuring the amount of lead in paint was to
remove a sample of paint from the surface and subject it to laboratory analysis. In the laboratory the
sample is pulverized and dissolved in an acid solution before its lead content is assayed using any of a
number of complex instruments. This process requires considerable time for sample collection, transport,
and laboratory turnaround before a lead measurement is obtained. Laboratory measurement is also
expensive: Paint sample collection requires skill, which increases associated labor costs, and the persample cost of laboratory analysis alone is substantial ($5 to $25 in 1997 U.S. dollars). The laboratory
cost varies with the laboratory, the analysis turnaround time, and the number of samples submitted, with
fewer samples commanding a higher unit price. Damage from sampling for laboratory analysis is an
unavoidable consequence, making the repair of the damaged surfaces an additional cost.
To overcome the disadvantages of laboratory measurement, and especially to reduce the cost of
performing LBP testing, the lead detection industry developed several portable (nonlaboratory)
technologies to test for lead in paint. At the start of the EPA/HUD field study in 1993 the two most
commonly used portable technologies for LBP testing were chemical test kits and portable X-ray
fluorescence (XRF) instruments.
Chemical test kits indicate the presence of lead in paint with a color change that occurs when chemicals
in the kit react with lead, which is referred to as a positive classification to lead. A measurement obtained
with a test kit is, therefore, not quantitative, but classified either positive or negative, depending on
whether the prescribed color change was observed. At the time of the study several brands of chemical
test kits were marketed to homeowners and other nonprofessional lead testers, and at least one chemical
test kit was developed for, and only made available to, certified professionals. The cost per test of the
commercial test kits ranged from approximately $1 to $5 (1997 U.S. dollars). In addition, no formal
technical training was required of users of the commercial test kits, there was less destruction of painted
surfaces than from paint sampling for laboratory measurements, and test results were quickly obtained.
The other portable technology is a form of X-ray spectrometry--a method for identifying elements by
detecting characteristic energy emission. The first reported use of X-ray spectrometry was in 1912, when
an electron beam system was used to excite atoms that caused the characteristic energy to be
emitted.(FN7) In 1925 the methodology was refined by bombarding specimens with X-ray photons
instead of electrons, which began the emergence of XRF spectrometry.(FN8) Laboratory XRF
instruments became commercially available in the early 1950s(FN9) and the portable XRF instruments,
designed for measuring lead in paint, came into use much more recently. In addition to measuring lead in
paint, field portable XRF instruments have been used for identifying elements in a variety of substances
such as soil, water, and steel.
In general, XRF instruments direct high-energy gamma and X-rays into a surface. These high-energy rays
strike atoms in the surface, causing electrons to be ejected from their orbits, or shells. Characteristic Xray energy is emitted when another electron fills the void in the shell. The emitted energy is detected by
the XRF instrument and converted to a quantitative measure. For the lead atom, characteristic
frequencies are emitted from the K- and L-shells, its two innermost electron orbits. Energy emitted from
these shells (energy bands) will be referred to as K X-rays and L X-rays, respectively.
The portable XRF instruments that were evaluated in the EPA/HUD field study were generically referred
to as either direct readers or spectrum analyzers. These designations are related to what can be
displayed by the instrument. Direct readers display only the lead content values, whereas the spectrum
analyzers are capable of displaying an energy spectrum and lead content values. Another distinguishing
characteristic of these instruments is the energy band from which a quantitative measure is made: the K
X-rays or L X-rays. K X-rays, being of higher energy than L X-rays, are attenuated less by paint than L Xray energy. For this reason, K X-ray measurements are generally more useful for detecting lead in deeper
layers of paint. The XRF instruments in the field study made K X-ray measurements, L X-ray
measurements, or both.
The detection of lead in paint is complicated by the material underlying the paint, the substrate, and how it
affects the high-energy rays directed into the paint by the XRF instrument. Some of the gamma and highenergy X-rays from the radiation source that are directed into the paint will hit the underlying substrate
and "bounce" back to the instrument's detector. This phenomenon, referred to as backscatter (or
Compton effect) interferes with the detection of the energy emitted from the lead atom. Thus, the XRF
instrument must account for this backscatter to determine accurately the amount of lead in the paint. The
substrate effect on the backscatter--some substrates are more dense while others are more absorbing-will be referred to as substrate bias. The portable XRF instruments in the field study used different
methods to account for substrate bias with differing degrees of success, since substrate materials such
as brick, concrete, drywall, metal, plaster, and wood can have widely varying properties. A testing method
to further account for substrate bias is called substrate correction and is discussed below.
Unlike chemical test kits, XRF measurements are quantitative and are expressed in milligrams of lead per
square centimeter (mg/cm2). Due to the potential radiation hazard and instrument cost, varying from
$7000 to $45,000 (1997 U.S. dollars), XRF instruments are intended for use by professional testers only.
However, the XRF instruments evaluated in the study usually returned a measurement within a minute
and without damage to the painted surface. This speed of measurement allows extensive testing to be
performed on a given day and makes XRF testing an affordable alternative to laboratory analysis for
residential lead testing.
DESIGN OF THE FIELD STUDY
The purpose of the EPA/HUD field study was to evaluate portable lead-testing technologies under realworld conditions. Six chemical test kit brands and six XRF instrument models were chosen for evaluation.
To perform a controlled evaluation, all 12 products were tested on a common set of test locations chosen
from painted building components. Test locations were selected to reflect the range of conditions under
which LBP was found in residential structures, and in sufficient quantity for accurate estimates to be
derived. A pilot study, conducted in March and April 1993, was based on 100 test locations chosen from
multifamily public housing units in Louisville, Ken. The "full" study, conducted from July to October 1993,
was based on 750 test locations chosen from single-family public housing units in Denver, Colo., and 440
test locations chosen from multifamily public housing units in Philadelphia, Pa.
Five of the six chemical test kits evaluated in the EPA/HUD field study were commercially available,
representing each different type of test kit known to be marketed in the spring of 1993. The other, referred
to as the State sodium sulfide kit, was available only to professional testers certified by the State of
Massachusetts. Table I identifies the chemical test kits that were evaluated in the field study.
The evaluated XRF instrument models are identified in Table II. Two of these, the Pb Analyzer (TN
Technologies, Inc., Round Rock, Tex.) and the XL (Niton Corp., Bedford, Mass.), were prototypes that
were not available to professional testers at the time the study began. Three of the four commercially
available instruments were widely used in testing for LBP at the time of the study, the exception being the
X-MET 880 (Outokumpu Electronics, Bend, Ore.), which was more typically used for lead testing in soil.
The MAP-3 (Scitec Corp., Kennewick, Wash.) and Pb Analyzer provided both K X-ray and L X-ray
measurements. The Microlead I (Warrington, Inc., Austin, Tex,) and XK-3 (Princeton Gamma-Tech, Inc.,
Princeton, N.J.) provided only K X-ray measurements, and the XL and the X-MET 880 provided only L Xray measurements. The MAP-3, Pb Analyzer, XL, and X-MET 880 are spectrum analyzers. The Microlead
I and XK-3 are direct readers.
Development of a design for the EPA/HUD field study was complicated by two major factors:.
(1) the large number of measurements to be made at each test location, representing all chemical test
kits and XRF instruments, plus the collection of at least one paint sample for laboratory analysis; and.
(2) the destructiveness of paint sample collections and chemical test kit applications to the painted
surfaces.
Because multiple destructive testing could not be conducted at exactly the same place, subareas of each
test location were allocated to test kits, XRF instruments, and paint sampling in a consistent manner to
ensure comparability of results. This was done by using a standardized format or template that was
demarked on each test location. The "standard" templates used in the pilot and full studies are shown at
the top of Figure 1, with several variations shown below them. A template was applied horizontally if
possible, or else rotated, as necessary, to fit on a painted building component. In a few cases, the
template needed to be altered, as shown, to fit. A paint sample was collected from one of the areas
marked with a "P" that was randomly selected. Randomization was also used to allocate testing areas
marked with a "T" to the six chemical test kits evaluated in the study. The area marked with an "X" was
allocated to XRF testing.
TESTING PROCEDURES
TEST LOCATION IDENTIFICATION
Prior to the start of field testing, test locations were selected from each of the housing units used in the
study. For each test location a template was drawn on the painted surface and assigned a unique
number.
CHEMICAL TEST KIT MEASUREMENT
After all test locations were identified and marked with templates in a housing unit, the chemical test kit
operators began to collect measurements. With one exception, the test kit operators did not have specific
scientific background or prior training, but were chosen to represent typical homeowners who might
purchase a test kit for personal use. The exception was the operator of the State sodium sulfide kit, who
was a Massachusetts state-certified inspector. The nonprofessional testers were screened to ensure that
they were able to detect the color changes that signified a positive indication of lead. The nonprofessional
chemical test kits were rotated among the nonprofessional testers during the course of the study to make
it difficult for a tester to become more proficient with any one test kit. After each tester had completed
testing at a test location, the used area of the template was covered to prevent subsequent testers from
observing the result.
PAINT SAMPLE COLLECTION AND LABORATORY ANALYSIS
For each test location, paint samples were collected for laboratory analysis. The paint samples were
analyzed by inductively coupled plasma atomic emission spectroscopy. After the paint samples were
collected, the unused P areas of the templates were also scraped to expose the substrate. This created a
bare area in each template that had the same dimensions as the X area. This bare area became one of
the XRF instrument testing areas.
XRF INSTRUMENT TESTING
XRF instrument testing began after paint sampling was completed in a housing unit. The XRF instrument
operators were trained and licensed employees of lead testing companies. XRF instrument testing was
conducted at the designated X area and at the bare area of each template. Measurements on the bare
areas were made both directly on the bare substrate and on National Institute of Standards and
Technology (NIST) standard reference material (SRM) films placed over the bare areas. The NIST SRMs
used for this purpose had a lead level of 1.02 mg/cm2. The measurements taken on a NIST SRM film
(with a 1.02 mg/cm2 lead level) placed over bared areas were obtained to examine the performance of
substrate correction, a procedure used with some XRF instruments to reduce the bias associated with the
substrate underlying the paint.
XRF testing was based on a nominal 15-second reading time for a full-strength radioactive source. Actual
reading times were adjusted either automatically by the instrument or manually by the operator to account
for the decay of the radioactive source in the instrument due to its age. Accordingly, the actual reading
time would necessarily increase as the source decays.
EVALUATION OF TESTING RESULTS
For chemical test kits evaluated in the EPA/HUD field study, classification accuracy was the primary
criterion used to measure performance. XRF instruments were evaluated by both classification accuracy
and bias and precision estimates. Classification accuracy was measured relative to the federal standards
of 1.0 mg/cm and 0.5% lead by weight for defining LBP, as designated by Title X. Many state and local
governments also have adopted these standards.
Classification accuracy was reported in terms of misclassified results called false negative and false
positive results. Relative to a given standard, a lead test result was classified as a false negative if the
laboratory measurement was equal to or greater than the standard (positive) and, for chemical test kits, a
color change was not observed (negative). Similarly, for XRF instruments a lead measurement was
classified as a false negative if the laboratory measurement was equal to or greater than the standard
(positive) and the XRF measurement was less than the standard (negative). In other words, a false
negative result is one in which the laboratory measurement was classified positive but tested negative
according to a chemical test kit or XRF instrument result for the same test sample. A lead test result was
classified as false positive if the laboratory measurement was less than the standard (negative) and, for
chemical test kits, a color change was observed (positive). For XRF instruments a lead test result was
classified as a false positive if the laboratory measurement was less than the standard (negative) and the
XRF measurement was equal to or greater than the standard (positive). In other words, a false positive
result is one in which the laboratory measurement was classified negative but tested positive according to
a chemical test kit or XRF instrument result for the same sample. None of the products evaluated in the
study achieved a perfect performance, i.e., no false negatives or false positives with respect to either
federal standard.
The fact that the XRF measurements were quantitative allowed a wider range of criteria to be applied to
the evaluation of XRF instruments in the study. In addition to simple positive-negative classification
regimes, the introduction of an inconclusive range was possible, whereby the status of a measurement
that falls in an interval about the standard is deferred to laboratory testing. With an inconclusive range of
0.4 mg/cm2 to 1.6 mg/cm2, e.g., an XRF measurement is classified as negative if it is less than or equal
to 0.4 mg/cm2, as positive if it is greater than or equal to 1.6 mg/cm2, and as inconclusive otherwise. The
quantitative relationship of XRF measurements to the laboratory-measured lead levels was expressed in
the form of a statistical model, which was used to obtain estimates of the bias and precision (standard
deviation) at lead levels of interest.
Furthermore, the statistical model was used to determine the need for and effectiveness of substrate
correction. Substrate correction was carried out by first calculating the averages, by substrate and by
housing unit, of XRF measurements obtained on a NIST SRM film (with a 1.02 mg/cm2 lead level) placed
over bared areas on the template, and subtracting 1.02 mg/cm2. The resulting "correction value" was
then subtracted from all XRF measurements obtained on painted surfaces within the same housing unit
that shared the same substrate type. The need for substrate correction was indicated by the presence of
bias, and its effectiveness was assessed according to the reduction in bias when substrate correction was
performed. Classification performance with and without substrate correction was also used to illustrate
the effectiveness of substrate correction. A marked improvement in the classification performance with
substrate corrected measurements would demonstrate the effectiveness of substrate correction.
MAJOR FINDINGS AND CONCLUSIONS
LABORATORY ANALYSIS OF PAINT SAMPLES
Laboratory analysis of paint samples taken at the 1290 test locations in the EPA/HUD field study revealed
a distribution of lead levels similar to a large-scale national survey of lead in U.S. housing.(FN10) The
distribution had lognormal characteristics, skewed toward lower values, with increasing sparseness at
higher lead levels.
Two sources of variation in laboratory-measured lead levels were assessed in the study, using different
kinds of duplicate measurements. A "laboratory duplicate" refers to an additional laboratory subsample
and measurement obtained on the same primary (P template area) paint sample. A "field duplicate" refers
to a laboratory measurement obtained on a paint sample taken a short distance from where the primary
paint sample was taken, but at the same test location. Findings on the two sources of variation are
summarized below.
VARIATION BETWEEN LABORATORY DUPLICATES WAS RELATIVELY SMALL
The median ratio of the largest to smallest measurement in a laboratory duplicate pair was 1.13, and the
95th percentile was 1.4, for smooth surfaces with no unusual difficulty in paint removal. These results
apply to measurements reported in both area (mg/cm2) and percentage by weight units. For rough
surfaces such as brick or concrete, the estimated median ratio was 1.2 and the estimated 95th percentile
ratio was 1.8. This magnitude of variation had a minor effect on the identification of LBP: only two of the
171 pairs (1%) straddled the 1.0 mg/cm2 federal standard, and only three pairs (2%) straddled the 0.5%
lead by weight federal standard.
SPATIAL VARIATION IN LEAD LEVELS OVER A PAINTED BUILDING COMPONENT WAS
RELATIVELY IMPORTANT
A field duplicate paint sample was taken approximately 9 inches away from the primary paint sample at
10% of the test locations in the full study. Median and 95th percentiles of ratios of largest to smallest
measurements were 1.6 and 3.7 in Denver; 1.3 and 2.1 in Philadelphia. These statistics are for area
(mg/cm2) units; for percentage by weight units the corresponding statistics were slightly lower. Of the 128
field duplicate pairs in the study, 10 (8%) straddled the 1.0 mg/cm2 federal standard, and 8 (6%)
straddled the 0.5% lead by weight federal standard. The greater variation between field duplicates than
laboratory duplicates points to noticeable spatial variation in lead levels at relatively short distances.
VARIATION IN LABORATORY-MEASURED LEAD LEVELS AFFECTED THE EVALUATION OF THE
PORTABLE LEAD-MEASUREMENT TECHNOLOGIES
Chemical test kits and XRF instruments were evaluated according to their ability to recognize the true
amount of lead in paint. But the true lead levels of the test locations in the EPA/HUD field study were not
perfectly known. Spatial variation and laboratory analysis variation both had consequences for the
analyses of the chemical test kit and XRF instrument testing data. Modeling and simulation studies were
used to account for these types of variation in the analyses.
XRF TECHNOLOGIES
The primary conclusion of the EPA/HUD field study with respect to XRF technologies is that, with certain
qualifications, portable XRF instruments can be effective tools for identifying LBP in residential structures,
relative to the 1.0 mg/cm2 federal standard. These qualifications are listed below.
USE OF K X-RAY MEASUREMENTS
The use of K X-ray XRF measurements was found to be a viable way to test for LBP when appropriate
inconclusive ranges and substrate correction procedures, where it reduces bias, were applied. This is
illustrated in Figure 2, where false positive and false negative rates for each of the four XRF instruments
that provided K X-ray measurements in the field study are presented in the form of bar charts. For each
instrument it was possible to have false positive and false negative rates both less than 5%, provided that
an inconclusive range was used, and substrate correction was performed if needed.
Results based on L X-ray measurements were not shown in Figure 2. The X-MET 880 XRF instruments
provided L X-ray measurements only, which exhibited high false negative rates, and therefore were not
included in Figure 2. The results for the XL instruments were excluded since that model of instrument
used in the field study was a prototype instrument that has been subsequently replaced with a marketable
version.
USE OF SUBSTRATE CORRECTION AS NEEDED
Substrate correction reduced the bias exhibited by some K X-ray XRF instruments. The Microlead I and
XK-3 benefitted the most from substrate correction, and their improvement in classification performance is
apparent in Figure 2. Note that there are specific substrates where substrate correction did not show the
apparent improvement shown in Figure 2. The XK-3 and Microlead I instruments are direct readers.
Substrate corrected results were not shown for the Pb Analyzer and the MAP-3. Substrate correction did
not substantially improve the results for these instruments; however, substrate correction may still
improve their classification performance on specific substrates. The MAP-3 and Pb Analyzer instruments
are spectrum analyzers.
USE OF AN INCONCLUSIVE RANGE, WITH LABORATORY CONFIRMATION OF INCONCLUSIVE
XRF RESULTS
A reasonable classification goal is to obtain false positive and false negative rates less than 5% each.
With XRF measurements it was possible to achieve this goal with the use of an inconclusive range. As
Figure 2 indicates, an inconclusive range of 0.4 mg/cm2 to 1.6 mg/cm2 achieved this goal simultaneously
for all K X-ray instruments evaluated in the EPA/HUD field study, provided that substrate correction was
performed if needed. Figure 3 shows the inconclusive rates for the K X-ray instruments under this
inconclusive range. Between 18 and 27% of the samples tested would have required confirmation with a
laboratory measurement, depending on the instrument, and using substrate correction if needed. Figure 4
demonstrates that, without an inconclusive range, the K X-ray XRF instruments tested in the study did not
always achieve the 5% goal for both false positive and false negative rates.
USE OF A SINGLE (NOMINAL 15-SECOND) READING
Prior to the EPA/HUD field study, a common practice was to average multiple XRF measurements at the
same test location, or use a greater than 15-second reading time. The belief was that, by simple rules of
statistical sampling, a prescribed reduction in the variation of the resulting measurement could be
achieved in this manner. But the study found that acceptable error rates could be achieved with single
readings of nominally 15 seconds' duration. Moreover, multiple or longer XRF measurements reduce only
variation that was attributable to the instrument. The other primary source of variation, due to spatial
variation in lead levels across a painted building component, could not be reduced in this manner. If
multiple XRF readings on a component are done in an LBP inspection, an effort should be made to take
the readings at well-separated locations on the building component to make effective use of the additional
time expended.
CHEMICAL TEST KITS
The EPA/HUD field study concluded that chemical test kits were not a reliable means to discriminate
accurately between lead-based paint and nonlead-based paint, as defined by the federal standards of 1.0
mg/cm2 and 0.5% lead by weight. Specific findings are presented below.
NONE OF THE CHEMICAL TEST KITS WERE ABLE TO ACHIEVE LOW (5% OR LOWER) RATES OF
BOTH FALSE POSITIVE AND FALSE NEGATIVE RESULTS
False positive and false negative rates obtained for the chemical test kits evaluated in the EPA/HUD field
study are presented in Figures 5 and 6. These rates indicate a wide range in performance: false negative
results dominated with one kit, false positive results dominated with two kits, and with the remaining three
kits false positive and false negative results were more evenly balanced. For each kit, at least one, and
sometimes both, of the two rates was well above 5%.
SIMILAR MISCLASSIFICATION RATES WERE OBTAINED USING EITHER THE 1.0 MG/CM2 OR THE
0.5% LEAD BY WEIGHT FEDERAL STANDARD
This is made clear graphically in Figures 5 and 6. The chemical test kits evaluated in the study did not
appear to be better suited to one standard than to the other.
AN OPERATING CHARACTERISTIC CURVE WAS ESTIMATED FOR EACH CHEMICAL TEST KIT
AND SUBSTRATE COMBINATION
Enhancements were made to the operating characteristic model to allow model fitting of cases in which
either the limiting probability, as the lead level increased, was less than 1.0 or the limiting probability, as
the lead level approached zero, was positive. Both cases were observed with the test kit data.
COMPARISON OF AREA UNITS AND PERCENTAGE BY WEIGHT UNITS
The two federal standards for defining LBP, as designated by the Residential Lead-Based Paint Hazard
Reduction Act of 1992, are 1.0 mg/cm2 and 0.5% lead by weight. Lead level measurements in area units
and in percentage by weight units are both ratios that use the mass of lead as a numerator. Area of the
scraped paint sample is the denominator used for area units, and mass of the scraped paint sample is
used for percentage by weight units. Because paint samples of a fixed area have varying mass due to the
composition and thickness of paint, and possibly because of the inclusion of substrate material, there is
no precise relationship between the two units of measure.
The scatter plot in Figure 7 shows lead level measurements in area units (horizontal axis) and in
percentage by weight units (vertical axis) for 388 test locations with wood substrates in the EPA/HUD field
study. Both axes are plotted on a log-scale to enhance viewing. Although the relationship between the
twounits is not perfect, it is strong, with a correlation of about 0.97. The correlation across all substrates
was 0.95, and a lead level of 1.0 mg/cm2 corresponded to approximately 0.96% lead by weight, or nearly
twice the alternative federal standard. Nonetheless, similar classification results were usually obtained
with either standard, as Figures 5 and 6 illustrate, due to sparseness in the distribution of lead levels near
both standards.
THE FUTURE OF LEAD-TESTING TECHNOLOGIES
As lead-testing technologies that are portable, fast, and non- or minimally destructive have increased in
usage, their ability to detect LBP in a reliable manner has become increasingly important. The EPA/HUD
field study found that, of the technologies tested, only K X-ray XRF instruments used under the conditions
outlined above met this criterion. But much room for improvement remained, and the development of
portable technologies has continued since the completion of the study. Chemical test kits continue to be
evaluated through HUD-sponsored research. Likewise, XRF instrument evaluations have continued
through their testing at a laboratory facility.
During the EPA/HUD field study, portions of painted building components from selected test locations
were removed and mounted at a laboratory facility. These materials, referred to as the LBP sample
archive, have been used for evaluating XRF instruments. An EPA publication that describes this testing is
titled Archive Operations and Protocols.(FN11) Data from archive testing have been used to develop XRF
Performance Characteristic Sheets, which provide up-to-date information on how to do testing in
residential housing with XRF instruments, and are available from the National Lead Information Center (1800-424-LEAD). A description of the associated methodology is found in the EPA report titled
Methodology for XRF Performance Characteristic Sheets.(FN12) The LBP sample archive has partially
filled a void left by the completion of the EPA/HUD field study, until another mechanism can be designed
to evaluate both nondestructive and destructive technologies for testing for lead-based paint.
Growing demand for residential LBP testing is expected to continue. The EPA/HUD rule implementing
Section 1018 of the Residential Lead-Based Paint Hazard Reduction Act of 1992, which applies to most
private housing in the United States built before 1978, gives prospective home buyers the option to
conduct an LBP inspection, or a risk assessment, at the buyer's expense, before being obligated by the
sales contract or lease. Sellers, landlords, and real estate agents share legal responsibility for disclosing
LBP and LBP hazards, for distributing information on how to deal with LBP, and for developing sales
contracts and leases that comply with the rule.(FN(3,13)) The volume of LBP testing that the Section
1018 rule could generate is substantial: about 50 million owner-occupied housing units in the United
States were built before 1978.(FN(10)) With nearly half of all owner-occupied housing units in 1993
having been acquired during the previous 10 years,(FN(14)) it is expected that housing built before 1978
will change ownership in substantial numbers well into the future.
ADDITIONAL INFORMATION
The EPA/HUD field study is documented in a summary report(FN(5)) and at length in a technical
report.(FN6) Both reports are available from the National Lead Information Center Clearinghouse
(telephone 1-800-424-LEAD). The technical report can also be ordered from the National Technical
Information Service (telephone 1-800-553-NTIS) by referring to its NTIS number, PB96-125026.
Information on other EPA scientific and technical lead studies can be found on the EPA Lead Home Page
at the following address: http://www.epa.gov/opptintr/lead/index.html.
Added material.
R.L. Schmehl.
D.C. Cox.
F.G. Dewalt.
M.M. Haugen.
R.A. Koyak.
Quan Tech, 1911 N. Fort Myer Drive, Suite 1000, Arlington, VA 22209-1607;.
J.G. Schwemberger Jr.
J.V. Scalera.
Technical Branch, National Program Chemicals Division, Office of Pollution Prevention and Toxics, Office
of Prevention, Pesticides and Toxic Substances, U.S. Environmental Protection Agency, 401 M Street,
S.W., Mail Code 7404, Washington, D.C. 20460.
ACKNOWLEDGMENTS
Bill Wisner of HUD was the liaison between EPA and HUD. He played a critical role by identifying suitable
sites for the EPA/HUD field study. Cindy Stroup of EPA was the branch chief of the Technical Programs
Branch and initiated this study. In addition to the authors, other key contributors to the study were Paul
Constant, Donna Nichols, Jack Balsinger, and Nancy Friederich of Midwest Research Institute; and John
Jones and Connie Reese of QuanTech, Inc. Dr. Mary McKnight reviewed the portions of the manuscript
that dealt with technical background on XRF instruments.
TABLE 1. Summary of Test Kits Included in the EPA/HUD Field Study.
(TABLE) Color for
Chemistry Positive Lead Summary of Chemical
Test Kit Type Classification Application to the Paint
Lead Zone(trademark) (Enzone, Inc., Davie, FL) proprietary red/pink Beveled cut through paint layers,
chemicals applied to exposed paint
edges
LeadCheck(trademark) Swabs (HybriVet Systems, Inc., rhodizonate red/pink Beveled cut through paint
layers,
Natick, MA) chemicals applied to exposed paint
edges
Frandon(trademark) Lead Alert rhodizonate red/pink Core sample cut through paint
All-in-One: coring (Pace Environs, Inc., layers, chemicals applied to
Cary, NC) crushed core sample
Frandon(trademark) Lead Alert: sanding rhodizonate red/pink Paint dust captured from sanding
through paint layers, chemicals
applied to paint dust
The Lead Detective(trademark) (Innovative Synthesis sodium sulfide black Beveled cut through paint,
chemicals
Corp., Newton, MA) applied to exposed paint edges
Massachusetts State Certified Professional sodium sulfide black Beveled cut through paint, chemicals
applied to exposed paint edges.
TABLE II. Summary Listing of XRF Instruments Included in the EPA/HUD Field Study.
(TABLE) X-Rays Source
Make and Model Detected Type(FNA) Detector Type
Pb Analyzer (prototype) (TN Technologies, Inc., K and L Cd109 (30) cooled mercuric iodide
Round Rock, TX)
MAP-3 (Scitec Corp., Kennewick, WA) K and L Co57 (40) ambient silicon
Microlead I revision 4 (Warrington, Inc., Austin, TX) K Co57 (10) cesium iodide
XK-3 (Princeton Gamma-Tech, Inc., Princeton, NJ) K Co57 (10) proportional counter (xenon gas)
XL (prototype) (Niton Corp., Bedford, MA) L Cd109 (10) silicon
X-MET 880 (Outokumpu Electronics, Bend, OR) L Cd109 (5)(FNB) proportional counter (argon gas)
Cm244 (100)(FNB).
FOOTNOTES
A Parenthetical numbers are approximate source strengths for new sources in millicurie.
B A number of radiation sources are sold for this instrument; only the sources shown were used for lead
measurements in the study.
FIGURE 1. Standard and nonstandard templates used at test locations in the EPA/HUD field study.
FIGURE 2. XRF instrument misclassification rates, with inconclusive range, across all test locations in the
EPA/HUD field study.
FIGURE 3. XRF instrument inconclusive rates across all test locations in the EPA/HUD field study.
FIGURE 4. XRF instrument misclassification rates, without inconclusive range, across all test locations in
the EPA/HUD field study.
FIGURE 5. Chemical test kit misclassification rates across all test locations in the EPA/HUD field study.
FIGURE 6. Chemical test kit misclassification rates across all test locations in the EPA/HUD field study.
FIGURE 7. Laboratory lead-level measurements of 388 primary paint samples obtained from test
locations with wood substrates: area versus percentage by weight units.
FOOTNOTES
1. U.S. General Accounting Office: Toxic Substances: Status of EPA's Efforts to Develop Lead Hazard
Standards (GAO/RCED-94-114). Washington, DC: U.S. General Accounting Office/Resources,
Community, and Economic Development Division, 1994. p. 1.
2. "Lead-Based Paint Poisoning Prevention," U.S. Code, Title 42, Pt. 4831 et seq. 1971 ed.
3. "Residential Lead-Based Paint Hazard Reduction," U.S. Code, Title 42, Pt. 4851 et seq. 1992 ed.
4. U.S. Department of Housing and Urban Development: Guidelines for the Evaluation and Control of
Lead-Based Paint Hazards in Housing (HUD-1539-LBP). Washington, DC: U.S. Department of Housing
and Urban Development/Office of Lead-Based Paint Abatement and Poisoning Prevention, 1995.
5. U.S. Environmental Protection Agency: A Field Test of Lead-Based Paint Testing Technologies:
Summary Report (EPA 747-R-950-002a). Washington, DC: U.S. Environmental Protection Agency/Office
of Prevention, Pesticides, and Toxic Substances, 1995.
6. U.S. Environmental Protection Agency: A Field Test of Lead-Based Paint Testing Technologies:
Technical Report (EPA 747-R-95-002b). Washington, DC: U.S. Environmental Protection Agency/Office
of Prevention, Pesticides, and Toxic Substances, 1995.
7. Moseley, H.G.J.: The high frequency spectra of the elements. London, Edinburgh, Dublin Philosoph.
Mag. J. Sci. 26:1024-1034 (1913).
8. Coster, D., and J. Nishina: On the Quantitative chemical analysis by means of X-Ray spectrum. Chem.
News J. Ind. Sci. 130:149-152 (1925).
9. Jenkins, R.: X-Ray Fluorescence Spectrometry. New York: John Wiley & Sons, 1988. pp. 51-53.
10. U.S. Environmental Protection Agency: Report on the National Survey of Lead-Based Paint in
Housing, Appendix II: Analysis (EPA 747-R-95-005). Washington, DC: U.S. Environmental Protection
Agency/Office of Prevention, Pesticides, and Toxic Substances, 1995.
11. U.S. Environmental Protection Agency: Archive Operations and Protocols (EPA 747-R-97-004).
Washington, DC: U.S. Environmental Protection Agency/Office of Prevention, Pesticides, and Toxic
Substances, 1997. pp. 2-19, 2-40.
12. U.S. Environmental Protection Agency: Methodology for XRF Performance Characteristic Sheets
(EPA 747-R-95-008). Washington, DC: U.S. Environmental Protection Agency/Office of Prevention,
Pesticides, and Toxic Substances, 1997.
13. U.S. Environmental Protection Agency: EPA and HUD Real Estate Notification and Disclosure Rule
(EPA 747-F-96-001). Washington, DC: U.S. Environmental Protection Agency/Office of Prevention,
Pesticides, and Toxic Substances, 1996.
14. U.S. Department of Commerce and U.S. Department of Housing and Urban Development: American
Housing Survey for the United States in 1993 (H150/93). Washington, DC: U.S. Government Printing
Office, 1995.