EPA#540-F-00-010
OSWER #9285.7-38
April 2000
SHORT SHEET:
TRW RECOMMENDATIONS FOR
SAMPLING AND ANALYSIS OF SOIL AT
LEAD (Pb) SITES
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, DC 20460
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NOTICE
This document provides guidance to EPA staff. It also provides guidance to the public and to the
regulated community on how EPA intends to exercise its discretion in implementing the National
Contingency Plan. The guidance is designed to implement national policy on these issues. The document
does not, however, substitute for EPA's statutes or regulations, nor is it a regulation itself. Thus, it
cannot impose legally-binding requirements on EPA, States, or the regulated community, and may not
apply to a particular situation based upon the circumstances. EPA may change this guidance in the
future, as appropriate.
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U.S. ENVIRONMENTAL PROTECTION AGENCY
TECHNICAL REVIEW WORKGROUP FOR LEAD
The Technical Review Workgroup for Lead (TRW) is an interoffice workgroup convened by the U.S.
EPA Office of Solid Waste and Emergency Response/Office of Emergency and Remedial Response
(OSWER/OERR).
CO-CHAIRPERSONS
Region 8 NCEA/Washington
Jim Luey Paul White
Denver, CO
MEMBERS
Region 1 NCEA/Washington
Mary Ballew Karen Hogan
Boston, MA
NCEA/Cincinnati
Region 2 Harlal Choudhury
Mark Maddaloni
New York, NY NCEA/Research Triangle Park
Robert Elias
Region 4
Kevin Koporec OERR Mentor
Atlanta, GA Larry Zaragoza
Office of Emergency and Remedial Response
Region 5 Washington, DC
Patricia VanLeeuwen
Chicago, IL Executive Secretary
Richard Troast
Region 6 Office of Emergency and Remedial Response
Ghassan Khoury Washington, DC
Dallas, TX
Associate
Region 7 Scott Everett
Michael Beringer Department of Environmental Quality
Kansas City, KS Salt Lake City, UT
Region 10
Marc Stifelman
Seattle, WA
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TRW Recommendations for Sampling and Analysis
of Soil at Lead (Pb) Sites
Background
Incidental ingestion is the major pathway of exposure to lead
in soil and dust.1 The assumption implicit in this exposure
pathway is that ingested soil and dust lead is best represented
by the lead concentration in the particle size fraction that
sticks to hands (and perhaps clothing and other objects that
may be mouthed). EPA lead models consider this fraction to
be the primary source of the ingested soil and dust. Several
studies indicate that the particle size fraction of soil and dust
that sticks to hands is the fine fraction and that a reasonable
upper-bound for this size fraction is 250 microns (um) (Kissel
eta/., 1996;SheppardandEvenden, 1994; Driver eta/., 1989;
Duggan and Inskip, 1985; Que Hee, et a/., 1985; Duggan,
1983). This is also the particle size fraction that is most likely
to accumulate in the indoor environment, as a result of depo-
sition of wind-blown soil and transport of soil on clothes,
shoes, pets, toys, and other objects.
A TRW review of data from CERCL A sites has demonstrated
that the lead concentration in the fine fraction often differs
from the lead concentration in the total soil sample. The
fraction less than 250 um is most often measured, but data are
available on smaller size fractions as well. This difference in
lead concentration between the fine fraction and the total soil
sample has also been reported by a number of investigators
(Fergusson and Ryan, 1984; Fergusson and Schroeder, 1985;
Kitsa et a/., 1992), and enrichment of lead and other metal
contaminants in the fine fraction is suggested. In the develop-
ment of his de minimis model for lead exposure to children,
Stern(1994) recommended a generic correction for enrichment
of lead in the exposure fraction.
Lead concentration data for the fine (<250 um) fraction
(Midvale data) were used in the calibration of the EPA Inte-
grated Exposure Uptake Biokinetic (IEUBK) Model for Lead
in Children, and in the characterization of lead bioavailability
in soil, using either in vivo or in vitro studies (Casteel eta/.,
1997; Maddaloni eta/., 1998; Ruby eta/., 1996).
While estimates of the lead concentrations in the fine particle
fraction from sieved soil samples are considered to be most
relevant for assessment of current lead risks at sites, there is
'It is known that some children exhibit pica for soil (deliberate ingestion
of soil) and that these children may have soil ingestion rates well in
excess of the typical ingestion levels used in the IEUBK model or most
EPA risk assessments.
also value in obtaining data on the concentration of lead in
unsieved (total) soil samples (or alternately, joint data on
concentrations in both the total and fine soil fractions). Data
to compare concentrations of lead in fine and total fractions
are particularly important if either routine or confirmatory
site sampling during cleanup activities will use total soil
sample concentrations. In this case, data on the relative lead
concentrations in the two fractions may be used to develop
a site-specific "adjusted" cleanup level that would be appli-
cable to total soil sampling data.
Second, while it is generally expected that fine soil fractions
will be "enriched" in lead compared to total soil fractions, in
certain cases, the opposite situation may occur. In some soils,
the total soil fraction may contain high concentrations of lead
(e.g., if coarse materials from mining or industrial operations
contained high concentrations of lead). When coarser materi-
als contain high lead concentrations, concerns about the future
degradation of these coarser materials into finer particles
should be addressed by using the total soil concentration
for developing response actions at a site. In addition, total
soil concentrations would be more representative of deliber-
ate soil ingestion (pica) than fine fraction concentrations.
The following is a standard set of recommendations and pro-
tocols developed for the collection, preparation, and analysis
of lead in soil and dust for use in lead modeling exercises.
The goal is to assure that a given lead concentration in soil or
dust means the same thing in every case, because consistency
at sites is of major concern.
TRW Recommendations
Because the concentration from the fine fraction is relevant
for exposure from incidental soil ingestion, it is the pre-
ferred concentration input in modeling lead risks. Data on
the fine fraction (<250 um) is the recommended input for the
IEUBK and Adult Lead models.
• If there is a potential for the coarse fraction to contain a
higher concentration of lead than the fine fraction, then at
least 20% of the surface soil samples, or a minimum of 20
samples, should be analyzed for lead concentration in both
the coarse (>250 um) and the fine (<250 um) particle size
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fractions. This data should allow for statistical analysis to
compare concentrations in the total and fine fractions. In
addition, if prior soil sampling data are available, such analy-
sis may allow for comparison with earlier sampling data.
At sites where conditions are sufficiently uniform, the fine
fraction lead concentration may be estimated from the total
fraction lead concentration. This approach will be most
useful if the ratio between the concentrations in the two
fractions (the enrichment ratio) is constant across sampling
locations. For practical purposes, an enrichment ratio that
varies by 10%-20% may be sufficiently constant for most
applications. Statistical regression models can also be
useful in examining the relationship between concentra-
tions in the different soil fractions. For example, data may
support a regression model predicting the fine fraction
concentration from the total fraction concentration (po-
tentially with other covariates). It is recommended that
assistance from a statistician be obtained in developing and
evaluating such regression models. A few key points to
consider: An estimated slope relating the fine fraction con-
centration to the total concentration should not be used to
estimate fine fraction concentrations, instead predictions
should be based on the full regression analysis. The p-value
and r2 statistics output from most regression programs pro-
vide useful indicators for the presence of a relationship
between model variables, but are not sufficient to evaluate
the level of error in modeling. Regression models should
be presented so as to provide best estimates of the fine
fraction concentrations (the regression line) and to predict
errors about the regression line. Unless prediction errors
are relatively small (10-20% of the best estimates), it is
recommended that upper bound values for predicted fine
fraction concentrations be used for site applications.
Where substantial error exists in the prediction of fine
fraction concentrations, this should generally signal the
importance of measuring, rather than estimating, fine frac-
tion concentrations (especially in locations where the
exceedance of a cleanup goal may be in question).
A 250 urn (No. 60) sieve (ASTM, 1999) is the recommended
maximum sieve size that should be used for sieving soil
samples. Other sieve sizes may be used under certain cir-
cumstances, but both the cost of sample preparation and the
lead enrichment in the fine fraction are expected to increase
with decreasing sieve size.
If only one analysis is to be performed on soil at a lead
contaminated site, as is often done at a removal site, the
preference is for analysis of the fine fraction only, because
it provides the best characterization of the current risk
from exposure by incidental ingestion.
A reasonable preparation procedure consists of drying the
sample and then carefully sieving it though a No. 4 (4.75
mm) or a No. 10 (2.0 mm) sieve (ASTM, 1999) to remove
the "sticks and stones" (large debris). The resulting ma-
terial is the bulk or total soil sample. The suggested
methodology would be to sieve the entire weighed total
sample; then weigh and analyze both the coarse (> 250
urn) and fine (< 250 um) fractions and reconstruct the total
soil concentration using weighted averaging, or to simply
weigh and analyze only the fine fraction.
At this time, the TRW does not have any specific recommen-
dations for sample preparation and analysis of soil samples
for other metals or contaminants. Recommendations for con-
taminants other than lead may differ due to the differences in
the methodologies employed for the assessment of risk for
these contaminants, although samples analyzed for lead are
often analyzed for the full suite of metals through the EPA's
Contract Laboratory Program.
Definitions
Total soil sample: the soil that remains after passing a soil
sample through a No. 4 (4.72 mm) or a No. 10 (2.0 mm) sieve
to remove large debris, such as sticks and stones. The total
soil sample consists of the coarse and fine fractions.
Coarse fraction: the portion of the total sample that does not
pass through a 250 urn sieve.
Fine fraction: the portion of the total sample that passes
through a 250 um sieve. This is the fraction most likely to
stick to hands and be ingested.
Enrichment ratio: the concentration of lead in the fine frac-
tion relative to the concentration of lead in the total fraction.
This ratio will vary across and even within sites.
References
ASTM. 1999. American Society for Testing and Materials.
El 1-95 Standard Specification for Wire Cloth and Sieves for
Testing Purposes. West Conshohocken, PA: American Soci-
ety for Testing and Materials.
Casteel, S.W, R.P Cowart, C.P Weis, G.M. Henningsen, E.
Hoffman, WJ. Brattin, R.E. Guzman, M.F Starcost, J.T. Payne,
S.L. Stockham, S.V Becker, J.W Drexler, and J.R. Turk. 1997.
Bioavailability of lead to juvenile swine dosed with soil from
the Smuggler Mountain NPL site of Aspen, Colorado. Fund.
Applied Toxicol 36: 177-187.
Driver, J. H., J. J. Konz, and G. K. Whitmyre. 1989. Soil adher-
ence to human skin. Bull Environ Contam 7bx/co/43(6): 814-
820.
Duggan, M.J. 1983. Contribution of lead in dust to children's
blood lead. Environ Health Perspect 50: 371-381.
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Duggan, MJ. and MJ. Inskip. 1985. Childhood exposure to
lead in surface dust and soil: a community health problem.
Public Health Rev 13(1-2): 1-54.
Fergusson. J.E. andD.E. Ryan. 1984. The elemental compo-
sition of street dust from large and small urban areas related to
city type, source and particle size. Sci Total Environ 34: 101-
116.
Fergusson, J.E. and RJ. Schroeder. 1985. Lead in house dust
of Christchurch, New Zealand: sampling, levels and sources.
Sci Total Environ 46: 61-72.
Kissel, J.C., K.Y. Richter, andR.A. Fenske. 1996. Factors af-
fecting soil adherence to skin in hand-press trials. Bull Environ
Contam Toxico! 56(5): 722-728.
Kitsa, V, RJ. Lioy, J.C. Chow, J.G.Watson, S. Shupack, T.
Howell, and P. Sanders. 1992. Particle-size distribution of
chromium: total and hexavalent chromium in inspirable, tho-
racic, and respirable soil particles from contaminated sites in
New Jersey. Aerosol Sci TechnolYl'. 213-229.
Maddaloni, M, N. Lolacona, W. Manton, C. Blum, J. Drexler,
and J. Graziano. 1998. Bioavailability of soil-borne lead in
adults by stable isotope dilution. Environ Health Perspect
106: 1589-1594.
Que Hee, S.S., B. Peace, C.S. Clark, J.R. Boyle, R.L.
Bornschein, andPB. Hammond. 1985. Evolution of efficient
methods to sample lead sources, such as house dust and hand
dust, in the homes of children. Environ Res -38(1): 77-95.
Ruby, M.V, A. Davis, R. Schoof, S. Eberle and C.M. Sellstone.
1996. Estimation of lead and arsenic bioavailability using a
physiologically based extraction test. Environ. Sci. Technol
30: 422-430.
Sheppard, S.C. and W.G. Evenden. 1994. Contaminant en-
richment and properties of soil adhering to skin. J Environ
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Stern, A. H. 1994. Derivation of a target level of lead in soil at
residential sites corresponding to a de minimis contribution
to blood lead concentration. Risk Analysis 14: 1049-1056.
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