EPA 230-R-94-013b
April 1996
FINAL REPORT
for the
COMPREHENSIVE ABATEMENT PERFORMANCE STUDY
VOLUME II: DETAILED STATISTICAL RESULTS
Technical Programs Branch
Chemical Management Division
-------
Office of Pollution Prevention and Toxics
Office of Prevention, Pesticides, and Toxic Substances
U.S. Environmental Protection Agency
Washington, B.C. 20460
-------
The material in this document has been subject to
Agency technical and policy review and approved for
publication as an EPA report. Mention of trade names,
products, or services does not convey, and should not
be interpreted as conveying, official EPA approval,
endorsement, or recommendations.
This report is copied on recycled paper.
11
-------
CONTRIBUTING ORGANIZATIONS
This study was funded and managed by the U.S. Environmental
Protection Agency. The study was conducted collaboratively by
two organizations under contract to the Environmental Protection
Agency, Battelle Memorial Institute and Midwest Research
Institute. Each organization's responsibilities are listed
below.
Battelle Memorial Institute (Battelle)
Battelle was responsible for the design of the study, for
producing the design documentation and the Quality Assurance
Project Plan, for developing training for the field teams, for
recruiting cooperators for the study, for providing team leaders
for the field teams, for auditing the field teams, for data
management of combined study data, for auditing the study data,
for conducting the statistical analysis of the data, and for
writing the final report.
Midwest Research Institute (MRI)
Midwest Research Institute was responsible for participating
in the planning for the study, for writing certain chapters and
appendices in the Quality Assurance Project Plan, for designing
and producing a vacuum device for collecting field samples, for
developing training for the field teams, for providing the
technicians who collected the field samples, for auditing the
field teams, for conducting the laboratory analysis of the field
samples, for managing the data associated with the field samples,
for auditing the laboratory results, and for contributing
sections of the final report.
U.S. Environmental Protection Agency (EPA)
The Environmental Protection Agency was responsible for
managing the study, for reviewing the design and the Quality
Assurance Project Plan, for assessing the performance of the
recruiters and the field teams, for reviewing audit reports, for
reviewing the final report, and for arranging the peer review of
the design and the final report. The EPA Work Assignment
Managers were Ben Lim and John Schwemberger. The EPA Project
Officers were Janet Remmers, Jill Hacker, and Phil Robinson.
-------
TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY xv
1.0 INTRODUCTION AND SUMMARY 1
1.1 INTRODUCTION AND BACKGROUND 1
1.2 STUDY APPROACH 3
1.2.1 Study Objectives 3
1.2.2 Study Design 6
1.2.3 Sampling Design 13
1.2.4 Sample Selection, Collection and
Analysis Procedures 18
1.3 STUDY RESULTS 19
1.3.1 Assessment of Long-term Abatement
History 19
1.3.2 Characterization of Lead Levels 29
1.3.3 Correlation of Lead Levels in Different
Media and Locations 35
1.3.4 Comparison of Cyclone and Wipe
Dust Sampling 37
1.3.5 Results of the Quality control and
Data Verification Procedures 37
1.4 DISCUSSION 38
2.0 DESCRIPTIVE STATISTICS 46
2.1 DUST COLLECTED 46
2.2 AREA SAMPLED 49
2.3 LEAD LOADING, LEAD CONCENTRATION, AND
DUST LOADING 49
2.4 CLASSIFICATION OF HOUSES 56
2.5 DESCRIPTIVE PLOTS 60
2.6 ESTIMATED LEVEL OF DETECTION AND LEVEL
OF QUANTIFICATION 64
3.0 STATISTICAL MODELS 67
3.1 MIXED RANDOM AND FIXED EFFECTS MODEL 67
3.2 CENTERING AND SCALING OF COVARIATES 72
3.3 MODEL SELECTION 78
IV
-------
TABLE OF CONTENTS
(Continued)
Page
3.3.1 Phase 1: Abatement Effects
(Stepwise Regression) 79
3.3.2 Phase 2: Non-Abatement Factors
(Stepwise Regression) 79
3.3.3 Phase 3: Mixed Model Screening
(Backward Elimination) 80
3.4 HYPOTHESIS TESTS 80
4.0 MODELING RESULTS 82
4.1 SUMMARY OF MODELING RESULTS 83
4.2 DETAILED MODELING RESULTS 87
4.2.1 Analysis of Abatement
and Random Effects 87
4.2.2 Analyses of Abatement and
Random Effects by Sample Type 105
4.2.3 Analysis of Non-Abatement Factors Ill
4.2.4 Non-Abatement Effects by Sample Type .... 120
5.0 CORRELATIONS 125
5.1 BETWEEN-HOUSE CORRELATIONS 125
5.2 WITHIN-HOUSE CORRELATIONS 134
6.0 WIPE VERSUS VACUUM COMPARISON 143
6.1 ALL SUBSTRATES COMBINED 146
6.2 ADJUSTING FOR SUBSTRATE EFFECTS 147
7.0 COMPARISONS WITH OTHER STUDIES 149
7.1 COMPARISON OF CAP STUDY DATA AND CAP
PILOT STUDY DATA 149
7.2 COMPARISON OF CAP STUDY DATA AND HUD
ABATEMENT DEMONSTRATION DATA 153
7.3 COMPARISON OF DUST LEAD LOADINGS BETWEEN
THE CAP STUDY AND OTHER STUDIES 162
8.0 OUTLIER ANALYSES 169
v
-------
TABLE OF CONTENTS
(Continued)
Page
8.1 APPROACH 169
8.2 DATA GROUPS 169
8.3 THE OUTLIER TEST 170
8.4 RESOLUTION OF OUTLIER QUESTIONS 175
8.5 DATA CERTIFICATION 175
9.0 STATISTICAL ANALYSIS OF QUALITY CONTROL DATA 178
9.1 BLANK SAMPLES 179
9.1.1 Field Quality Control 180
9.1.2 Sample Prep Quality Control 185
9.1.3 Instrumental Analysis Quality Control . . . 187
9.2 RECOVERY SAMPLES 188
9.2.1 Sample Preparation Quality Control 189
9.2.2 Instrumental Analysis Quality Control . . . 194
9.3 DUPLICATE SAMPLES 195
9.3.1 Field Quality Control 195
9.3.2 Sample Preparation Quality Control 196
9.4 TIME TREND ANALYSES 198
10.0 REFERENCES 201
LIST OF APPENDICES
APPENDIX A. CONDENSED DATA LISTING A-l
APPENDIX B. ADDITIONAL EXPLANATORY VARIABLES CONSIDERED
FOR INCLUSION IN THE STATISTICAL MODELS .... B-l
APPENDIX C. MIXED MODEL RESULTS BY SAMPLE TYPE C-l
APPENDIX D. LABORATORY CONTROL CHARTS FOR
QUALITY CONTROL SAMPLES D-l
VI
-------
TABLE OF CONTENTS
(Continued)
Page
APPENDIX E. SUMMARY OF INTERVIEW RESULTS E-l
APPENDIX F. SAMPLE SIZE CONSIDERATIONS F-l
APPENDIX G. PROTOCOL FOR VACUUM SAMPLING OF SETTLED DUST . . G-l
APPENDIX H. PROTOCOL FOR WIPE SAMPLING OF SETTLED DUST . . . H-l
APPENDIX I. PROTOCOL FOR COMPOSITE SOIL SAMPLING 1-1
LIST OF TABLES
Table 1-1. Number of Houses Abated in the HUD
Demonstration 7
Table 1-2. Number of Unabated Houses Tested by XRF in the
HUD Demonstration 11
Table 1-3. Summary of Environmental Sampling Planned for
the CAP Study 15
Table 1-4. Symbols Used to Denote Sample Types in Tables
and Figures 21
Table 1-5. Estimates of Effects of Primary Abatement
Factors on Lead Loading and Lead Concentration;
Controlling for Significant Covariates 22
Table 1-6. Condition of Abated Substrates, by Method of
Abatement 28
Table 1-7. Descriptive Statistics for Lead Loading (ug/ft2),
Lead Concentration (ug/g), and Dust Loading
(mg/ft2) by Sample Type 30
Table 1-8. Modeled Geometric Mean Lead Loadings by House Type
for Floor, Window Stool, and Window Channels
(ug/ft2) 31
Table 1-9. Descriptive Statistics for Lead Levels Observed
VII
-------
TABLE OF CONTENTS
(Continued)
Page
in Various Field Studies 33
Table 1-10. Significant Between-House and Within-House
Correlations 36
Table 1-11. Vacuum/Wipe Multiplicative Bias Estimates .... 37
Table 2-1. Descriptive Statistics for Amount of Dust
Collected (ing) and Area Sampled (ft2) by
Sample Type 47
Table 2-2. Correlations of Log Lead Loading Versus Log
Lead Concentration for Dust Samples 56
Table 2-3. Interior Abatement Method for Each House (ft2) . 57
Table 2-4. Exterior Abatement Method for Each House (ft2) . 58
Table 2-5. Square Footages of Components with XRF Results
at or Above 1.0 mg/cm2 in Unabated Houses ... 59
Table 2-6. Distribution of Unabated, E/E, and Removal
Units; Interior and Exterior Abatement
History 60
Table 2-7. Estimated Level of Detection by Instrument
Batch 66
Table 2-8. Potential Instrumental Measurement Error:
Calculated Results 66
Table 3-1. Explanatory Variables that are Significant
for at Least One Sample Type 70
Table 3-2. Average Percent Abated by E/E Methods,
by Abatement Method Classification for
Interior, Exterior and Room Level
Abatement 74
Table 3-3. Centering and Scaling Parameters for
Model Covariates 74
VI11
-------
TABLE OF CONTENTS
(Continued)
Page
Table 3-4. Parameter Interpretation After Centering
and Scaling 76
Table 4-1. Summary of Effects of Significant Primary
Abatement Factors 84
Table 4-2. Ratio of Levels of Unabated Rooms to those
in Abated Rooms, Both Within Abated Units .... 85
Table 4-3. Summary of Samples Excluded from Model
Fit Due to Missing Data on Covariates 88
Table 4-4. Estimates of Effects of Primary Abatement
Factors on Lead Loading; Controlling for
Significant Covariates 89
Table 4-5. Estimates of Effects of Primary Abatement
Factors on Lead Concentration; Controlling
for Significant Covariates 90
Table 4-6. Estimates of Effects of Primary Abatement
Factors on Dust Loading; Controlling for
Significant Covariates 91
Table 4-7. Exponents for Deriving Geometric Means
in E/E and Removal Houses 97
Table 4-8. Multiplicative Effects of Secondary
Abatement Factors 102
Table 4-9. Multiplicative Effects of Non-Abatement
Factors 115
Table 5-1. Correlations Among Sample Types for Between-
House Random Effects: Lead Loading 126
Table 5-2. Correlations Among Sample Types for Between-
House Random Effects: Lead Concentration .... 130
Table 5-3. Correlations Among Sample Types for Between-
House Random Effects: Dust Loading 131
IX
-------
TABLE OF CONTENTS
(Continued)
Page
Table 5-4. Correlations Among Sample Types for Within-
House Random Effects: Lead Loading 137
Table 5-5. Correlations Among Sample Types for Within-
House Random Effects: Lead Concentration .... 138
Table 5-6. Correlations Among Sample Types for Within-
House Random Effects: Dust Loading 139
Table 6-1. Vacuum versus Wipe Comparison Data: Room
Geometric Mean Floor Lead Loadings (ug/ft2) . . . 144
Table 6-2. Vacuum/Wipe Multiplicative Bias Estimates .... 148
Table 7-1. Comparison of CAP Lead Levels with HUD
Demonstration Pre- and Post-Abatement
Lead Levels 155
Table 7-2. Descriptive Statistics for Floor Dust Lead
Loadings (ug/ft2) by Abatement Efficacy
Field Study 163
Table 7-3. Descriptive Statistics for Window Stool
Dust Lead Loadings (ug/ft2) by Abatement
Efficacy Field Study 165
Table 7-4. Descriptive Statistics for Window Channel
Dust Lead Loadings (ug/ft2) by Abatement
Efficacy Field Study 166
Table 8-1. CAP Study Outliers - Field Samples 171
Table 8-2. CAP Study Outliers - Laboratory QC Samples . . . 173
Table 9-1. QC Sample Categorization Matrix 179
Table 9-2. Net Weight Results for Trip and Field Blanks . . 181
Table 9-3. Results of Quality Control Analyses 184
x
-------
TABLE OF CONTENTS
(Continued)
LIST OF FIGURES
Page
Figure 1-1. Estimated multiplicative effects of
abatement from mixed model ANOVA:
lead loading 25
Figure 1-2. Estimated multiplicative effects of
abatement from mixed model ANOVA:
lead concentration 25
Figure 2-1. Amount of dust collected (mg) by sample type . . 48
Figure 2-2. Area sampled (ft2) by sample type 50
Figure 2-3. Lead loading (ug/ft2) by sample type 52
Figure 2-4. Lead concentration (ug/g) by sample type .... 53
Figure 2-5. Dust loading (mg/ft2) by sample type 54
Figure 2-6. Geometric mean lead loading (ug/ft2), lead
concentration (ug/g), and dust loading
(mg/ft2) by sample type (unabated units) .... 61
Figure 2-7. Geometric mean lead loading (ug/ft2), lead
concentration (mg/ft2) , and dust loading
(mg/ft2) by sample type (abated units) 61
Figure 2-8. Lead loading (ug/ft2) by sample type and
method of abatement 62
Figure 2-9. Lead concentration (ug/g) by sample type
and method of abatement 62
Figure 2-10. Dust loading (ug/ft2) by sample type and
method of abatement 63
Figure 3-1. Total square feet abated indoors vs.
percent encapsulated/enclosed indoors:
Abated units 75
XI
-------
TABLE OF CONTENTS
(Continued)
Page
Figure 4-1. Geometric mean lead loading (ug/ft2),
lead concentration (ug/g) , and dust loading
(mg/ft2) in unabated units after controlling
for effects of significant factors 92
Figure 4-2. Estimated multiplicative effects of
abatement from mixed model ANOVA: lead
loading 95
Figure 4-3. Estimated multiplicative effects of
abatement from mixed model ANOVA: lead
concentration 95
Figure 4-4. Estimated multiplicative effects of
abatement from mixed model ANOVA: dust
loading 96
Figure 4-5. Variance component estimates from mixed
model ANOVA: lead loading 99
Figure 4-6. Variance component estimates from mixed
model ANOVA: lead concentration 99
Figure 4-7. Variance component estimates from mixed
model ANOVA: dust loading 100
Figure 4-8. Foundation soil lead concentration vs.
HUD Demonstration XRF/AAS levels 112
Figure 4-9. Floor dust lead concentration vs.
substrate 114
Figure 4-10. Boundary soil lead concentration vs.
age of house 119
Figure 4-11. Exterior entryway dust lead concentration . . . 119
Figure 5-1. Scatterplot matrix of unit-level
random effects for different sample
types: lead loading (ug/ft2) 128
XII
-------
TABLE OF CONTENTS
(Continued)
Page
Figure 5-2. Scatterplot matrix of unit-level random
effects for different sample types:
lead concentration (ug/g) 132
Figure 5-3. Scatterplot matrix of unit-level random
effects for different sample types:
dust loadings (mg/ft2) 133
Figure 5-4. Scatterplot matrix of room-level random
effects for different sample types:
lead loading (ug/ft2) 140
Figure 5-5. Scatterplot matrix of room-level random
effects for different sample types:
lead concentration (ug/g) 141
Figure 5-6. Scatterplot matrix of room-level random
effects for different sample types:
dust loadings (mg/ft2) 142
Figure 6-1. Vacuum versus wipe comparison: geometric
means of side-by-side floor lead loading
(ug/ft2) measures 145
Figure 7-1. Comparison of CAP Pilot and CAP Study
results: unit geometric mean lead
loading (ug/ft2) by sample type 150
Figure 7-2. Comparison of CAP Pilot and CAP Study
results: unit geometric mean lead
concentration (ug/g) by sample type 151
Figure 7-3. Comparison of CAP Pilot Study and CAP Study
results: unit geometric mean dust
loading (mg/ft2) by sample type 151
Figure 7-4. Comparison of CAP Pilot Study and CAP Study
results: component geometric mean dust
loadings (mg/ft2) by sample type 152
Figure 7-5. CAP versus HUD Demonstration pre-abatement
Xlll
-------
TABLE OF CONTENTS
(Continued)
Page
lead loadings: floor, window channel,
and window stool dust 154
Figure 7-6. CAP versus HUD Demonstration pre-abatement
lead concentration: foundation soil 154
Figure 7-7. CAP vacuum and CAP wipe Demonstration
wipe results: geometric mean floor
lead loading by room 157
Figure 7-8. CAP vacuum versus HUD Demonstration wipe
results: geometric mean window stool
lead loading by room 157
Figure 7-9. CAP vacuum versus HUD Demonstration wipe
results: geometric mean window channel
lead loading by room 158
Figure 7-10. CAP wipe, vacuum and HUD Demonstration wipe
versus HUD Demonstration XRF/AAS results:
geometric mean floor lead loading
(ug/ft2) by room 159
Figure 7-11. CAP vacuum and HUD Demonstration wipe
versus HUD Demonstration XRF/AAS results:
geometric mean window stool lead loading
(ug/ft2) by room 159
Figure 7-12. CAP vacuum and HUD Demonstration wipe
versus HUD Demonstration XRF/AAS results:
geometric mean window channel loading
(ug/ft2) by room 160
Figure 7-13. CAP versus HUD Demonstration results:
geometric mean foundation soil lead
concentration (ug/g) by side of unit 161
Figure 7-14. CAP soil concentration (ug/g) and HUD
Demonstration soil concentration (ug/g)
versus HUD Demonstration XRF/AAS results:
geometric mean by side of unit 161
xiv
-------
Figure 9-1.
Figure 9-2 .
Figure 9-3.
Figure 9-4.
TABLE OF CONTENTS
(Continued)
Page
Individual measurements and tolerance bounds
for ug lead/sample in blank samples 186
Individual measurements and tolerance bounds
for percent recovery in recovery samples .... 191
Individual measurements and tolerance bounds
for the ratio of duplicate samples 197
Time trend analyses in instrumental detection
level by instrument batch 200
xv
-------
EXECUTIVE SUMMARY
In response to requirements mandated by the Lead-Based Paint
Poisoning Prevention Act, in 1989 the U.S. Department of Housing
and Urban Development (HUD) initiated the Lead-Based Paint
Abatement Demonstration Study in seven urban areas across the
U.S. The objectives of this study were to assess the cost,
worker hazards, and short-term efficacy of various lead-based
paint abatement methods. Among other conclusions, the FHA
portion of this study estimated that abatement costs for a
single-family dwelling could range from $2000 to $12,000. One
question which was not answered by the HUD Abatement
Demonstration was that of the long-term efficacy of the abatement
methods. Therefore, in 1990 the U.S. Environmental Protection
Agency (EPA), in cooperation with HUD, initiated the
Comprehensive Abatement Performance (CAP) Study to address this
question.
The CAP Study was a follow-up to HUD Abatement Demonstration
activities performed in Denver, Colorado. There were four
primary objectives of the CAP Study: (1) assess the long-term
efficacy of two primary abatement methods, (2) characterize lead
levels in household dust and exterior soil in unabated homes and
homes abated by different abatement methods, (3) investigate the
relationship between lead in household dust and lead from other
sources, in particular, exterior soil and air ducts, and (4)
compare dust lead loading results from cyclone vacuum sampling
and wipe sampling protocols. To address these objectives, the
CAP Study collected approximately 30 dust and soil samples at
each of 52 HUD Demonstration houses in Denver, approximately two
years after the abatements had been completed. The houses were
all occupied at the time of the CAP Study field sampling, though
they had not been continuously occupied between the completion of
xvi
-------
the abatements and the field sampling. The samples were analyzed
for their lead content, and these lead measurements were then
used in detailed statistical analyses addressing the four study
questions.
The CAP Study included two approaches for assessing
abatement efficacy, one direct approach and one indirect
approach. In the direct approach CAP Study lead measurements,
made at HUD Demonstration houses two years after abatement, were
compared with pre-abatement lead measurements made at those same
houses. Since pre-abatement dust lead measurements were limited,
the CAP Study also included an indirect approach to assessing
abatement efficacy. In this approach, lead levels were measured
in dust and soil samples collected both at abated HUD
Demonstration houses, and at the same time at unabated HUD
Demonstration houses found to be relatively free of lead-based
paint. The performance of the abatement methods was then
assessed by comparing the lead levels at abated houses with those
at unabated houses. Sampling at unabated houses provided a
measure of the amount of lead introduced to the housing
environment from low levels of lead in paint and sources other
than lead-based paint. If the environmental lead levels at
abated houses were found to be similar to those at unabated
houses, this was taken as an indication that abatement either
lowered pre-abatement lead levels, or at least did not
significantly raise lead levels at abated houses. However, if
lead levels at abated houses were higher than at unabated houses,
this was taken as an indication that abatement failed to
completely eliminate the lead hazard because lead was introduced
to these environments either immediately through inadequate dust
control during abatement, or more gradually over time. Clearly,
an important limitation of the direct assessment of abatement
efficacy is that the pre-abatement lead levels at abated houses
were not available (except for foundation soil and limited
xvii
-------
numbers for floors and window stool1 dust), and therefore, one
can only conjecture about whether the observed post-abatement
lead levels represent an improvement or worsening of the housing
environment.
The results of the CAP Study from the direct approach of
comparing post-abatement and pre-abatement lead levels were that
for the two sample types for which a comparison was possible
(foundation soil and window stools), there was no evidence that
post-abatement lead levels are significantly higher than pre-
abatement levels. Both pre-abatement and CAP results for window
stool dust samples averaged between 175 and 200 ug/ft2. In soil
at the foundation of the house, levels were near 240 ug/g. These
results are based on dust lead measurements made on window stools
at 10 CAP Study abated houses, as well as soil lead measurements
made at 24 CAP Study abated houses. A few floor dust samples
obtained from three houses were also available for comparison,
but were deemed insufficient for making substantive conclusions.
These results are tempered by the fact that because of the small
number of houses for which data were available, as well as the
large variability in observed lead levels, relatively large
differences between post-abatement and pre-abatement lead levels
could not be judged to be statistically significant. For
example, the confidence interval for the average ratio of post-
abatement to pre-abatement levels on window stools was 0.37 to
3.46. In addition, further complicating the comparison of post-
abatement and pre-abatement dust and soil lead measurements was
the fact that different sampling and analysis protocols were used
in the CAP Study and HUD Demonstration. Perhaps most
The window stool was defined as the horizontal board inside
the window which extends into the house interior — often called
the window sill. In contrast, the window channel was defined as
the surface below the window sash and inside the screen and/or
storm window.
xviii
-------
significantly, the CAP Study utilized vacuum dust sampling while
the HUD Demonstration utilized wipe dust sampling.
The indirect assessment of abatement efficacy found that
abatement appears to have been effective, in this case in the
sense that there is no evidence that post-abatement lead levels
at abated houses were significantly different than lead levels at
neighboring unabated houses found to be relatively free of lead-
based paint. There were two exceptions to this statement;
however, both of these exceptions were anticipated and are
logically explained. First, lead concentrations in air ducts
were significantly higher in abated houses than in unabated
houses; air ducts were not abated in the HUD Demonstration. In
addition, lead concentrations in the soil outside abated houses
were significantly higher at the foundation and at the boundary
than corresponding lead concentrations outside unabated houses.
However, soil was also not abated during the HUD Demonstration;
and these higher lead levels might in part be due to differences
in the age of these houses, since on average the abated houses in
this study were 17 years older than unabated houses. As with the
caveat stated above, these results must also be tempered by the
fact that not finding a significant difference in lead levels at
abated and unabated houses for all other building components and
sampling locations does not prove that no such differences exist.
The CAP Study was designed to detect approximately two-fold
differences between lead levels at abated and unabated houses
under specified variance assumptions. For example, although the
estimate of 1.76 for the ratio of lead loadings on floors in
abated to unabated houses was not significantly different from
one, the 95 percent confidence interval for this ratio was from
about 0.87 to 3.5.
The CAP Study also assessed abatement by comparing
encapsulation and enclosure methods versus removal methods. No
significant differences among lead levels could be attributed to
xix
-------
these two types of abatement methods, except for air ducts which,
as stated above, were not abated. Air duct dust lead levels were
higher in houses abated primarily by encapsulation and enclosure
methods than in houses abated primarily by removal methods. It
is important to note, however, that houses abated primarily by
encapsulation and enclosure methods on average had greater
amounts of abatement performed than houses abated primarily by
removal methods. The CAP Study also performed a visual
inspection of abated surfaces and recorded their condition as
being intact, partially intact, or minimally intact. Less than
60% of the surfaces abated by encapsulation and chemical
stripping methods were found to be intact, while more than 70% of
the surfaces abated by all other methods were found intact.
With regard to the second study objective, lead levels were
found to vary greatly for different media and sampling locations.
Minimum individual lead concentrations for most sample types were
typically on the order of 10 ug/g except in air ducts and window
channels where levels were at least 50 ug/g. Maximum individual
lead concentrations were lowest for boundary and entryway soil
samples (1073 and 1068 ug/g, respectively) and highest for window
stool and window channel dust samples (48,272 and 45,229 ug/g,
respectively). Minimum individual lead loadings for all sample
types were typically only 1 to 4 ug/ft2. Maximum individual lead
loadings were lowest for floor dust samples (334 ug/ft2 by wipe
and 11,641 ug/ft2 by vacuum) and highest for window channel dust
samples (244,581 ug/ft2) . Dust lead loadings were also evaluated
in comparison with the HUD interim dust standards (HUD, 1990b).
Geometric mean lead loadings for both floors and window stools at
both abated and unabated houses were found to be well below their
respective HUD standards of 200 and 500 ug/ft2. On floors,
geometric mean lead loadings were also well below the EPA
guidance standard of 100 ug/ft2 (EPA, 1994). In addition, for
both of these sample types, more than 75 percent of the samples
xx
-------
collected in the CAP Study had lead loadings below their
respective HUD standards, in both abated and unabated houses.
However, geometric mean window channel lead loadings at both
abated and unabated houses were found to be well above the HUD
interim standard of 800 ug/ft2, and well over half of individual
observations were above this standard, at both abated and
unabated houses.
Three primary results were found for the third CAP Study
objective. First, significant correlations in lead
concentrations at the house level were found for four pairs of
sample types: window channels and window stools (correlation
coefficient of 0.40), entryway soil and boundary soil (0.56),
boundary soil and window stools (0.38), and entryway soil and
interior entryway dust (0.29) . Second, at the house level,
significant correlations in dust lead loadings were found for two
pairs of sample types: window channels and window stools (0.56),
and air ducts and exterior entryways (0.41). Third, significant
correlation was observed between dust lead concentrations at
interior and exterior entryways (0.37). However, at the room
level, no significant correlations in dust lead loadings were
found. House level correlations were based on house averages;
room level correlations were based in most cases on single
measurements. The fact that more house level correlations were
significant suggests that differences in lead levels are more
related to broad differences among houses than to location-
specific characteristics within houses.
Results for the fourth study objective found that when
combined across substrates, the average difference between lead
loadings measured by the cyclone vacuum method and by the wipe
method was insignificant. Differences were overshadowed both by
large side-by-side variability in the two methods, and a strong
substrate effect. This latter effect was apparently related to
the smoothness of the substrate. On linoleum, the two methods
xxi
-------
were approximately equivalent, whereas on tile, lead loadings
measured by the cyclone were lower than those measured by wipe,
and on wood, lead loadings measured by the cyclone were higher.
These results should be considered when setting environmental
standards and choosing sampling methods for testing regulatory
compliance.
The CAP Study results provide potentially important
information about the role of relatively high-cost abatement
procedures for eliminating, or controlling, residential lead-
based paint. The CAP Study found no significant differences
between post-abatement and pre-abatement lead levels for exterior
soil and the limited number of window stool dust lead
measurements available. It also found no significant differences
between post-abatement lead levels at abated houses and lead
levels at unabated houses, with the exception of air duct dust
and exterior soil which were not abated in the HUD Demonstration.
In addition, for both floors and window stools the geometric mean
lead loadings at abated houses were well below the "Lead-Based
Paint: Interim Guidelines for Hazard Identification and Abatement
in Public and Indian Housing" (HUD, 1990b) standards of 200 and
500 ug/ft2. The lead loading geometric mean for floors at abated
houses was also well below the EPA standard of 100 ug/ft2 for
floors (EPA, 1994). These results all suggest that the abatement
activities were effective, in the sense that they do not appear
to have increased lead levels at abated houses above interim
standards. However, the CAP Study also found that the geometric
mean dust lead loading for window channels at abated houses was
well above the HUD interim standard of 800 ug/ft2, although the
same result was found for unabated houses relatively free of
lead-based paint.
Comparisons between the wipe method and the vacuum method
used to collect dust in the CAP Study indicate that results from
wipe samples would likely be below the clearance standards for
xxii
-------
floors and window stools. For window channels, differences
between wipe and vacuum methods, especially on wood, preclude
concluding definitively that results from wipe samples would
exceed the clearance standard for window channels.
XX 111
-------
Study Conclusion
The conclusion of this study is that lead-based paint
abatements are effective. This conclusion is based on the study
finding that there is no evidence that post-abatement lead levels
at abated houses were significantly different from lead levels at
unabated houses relatively free of lead-based paint, save for two
exceptions. The two exceptions, differences in lead levels
between the abated and unabated houses in air ducts and exterior
soil, are explained by the fact that air ducts and soil were not
abated. There are caveats to the study that should be kept in
mind when interpreting and assessing the results and conclusion.
The principal caveats are these: no biological monitoring was
done in the study, and the study was designed to detect
differences approximately a factor of two or larger between the
abated houses and the unabated houses.
xxiv
-------
1.0 INTRODUCTION AND SUMMARY
1.1 INTRODUCTION AND BACKGROUND
In response to requirements mandated by the Lead-Based Paint
Poisoning Prevention Act (as amended by Section 566 of the
Housing and Community Development Act of 1987), the Residential
Lead-Based Paint Hazard Reduction Act of 1992, and other
legislation, the U.S. Environmental Protection Agency (EPA), U.S.
Department of Housing and Urban Development (HUD), U.S.
Department of Health and Human Services, and other federal
agencies are conducting a broad-based program of research,
demonstration, and policy actions aimed at reducing the incidence
of childhood lead poisoning in the U.S. An important part of the
federal program is to identify and abate lead-based paint hazards
in privately-owned and public housing. Toward this end, HUD
initiated two important studies in 1989, the HUD National Survey
of the incidence of lead-based paint in housing, and the HUD
Lead-Based Paint Abatement Demonstration.
The HUD National Survey sampled both public and private
housing in order to estimate the number of housing units with
lead-based paint, the total housing surface area covered with
lead-based paint, the condition of the paint, and the incidence
of lead in household dust and surrounding soil (HUD, 1990a). The
National Survey found that approximately 57 million homes, or 74
percent of all occupied housing units built before 1980, have
some lead-based paint. Older homes are more likely to contain
lead-based paint; 90 percent of housing units built before 1940
have lead-based paint. Within the 57 million homes there are on
average 580 square feet of interior surfaces and 900 square feet
of exterior surfaces covered with lead-based paint.
The HUD Abatement Demonstration was a research program in
ten cities which assessed the costs and short-term efficacy of
alternative methods of lead-based paint abatement. A variety of
1
-------
abatement methods were tested in approximately 120 multi-family
public housing units in three cities -- Omaha, Cambridge, and
Albany -- and similar methods were tested in 172 single-family
housing units in the FHA inventory in seven metropolitan areas --
Baltimore, Birmingham, Denver, Indianapolis, Seattle, Tacoma, and
Washington (HUD, 1991). The FHA demonstration evaluated two
classes of abatement methods, encapsulation and enclosure
methods, versus removal methods. The study found that the cost
of encapsulation and enclosure abatements ranged from about $2000
to $8000 per housing unit, while the cost of removal abatements
ranged from about $2000 to $12,000 per housing unit (HUD, 1990a).
Although the HUD Abatement Demonstration did assess the
short-term efficacy of certain lead-based paint abatement
strategies, it was not intended to evaluate the longer-term
performance of these approaches. Therefore, in 1990 the EPA
Office of Pollution Prevention and Toxics (formerly the Office of
Toxic Substances) initiated the Comprehensive Abatement
Performance (CAP) Study to further evaluate the abatement
strategies used in the HUD Abatement Demonstration.
This report presents the detailed statistical results of the
CAP Study. There are two reports: Volume I presents the overall
study results and conclusions, while Volume II (this report)
presents more detailed results from the statistical analyses
performed. Within Volume I the study approach, results, and
discussion of results are presented in Sections 2, 3, and 4,
respectively. Among the results presented in Volume II are
descriptive statistics, explanation of the statistical models,
evaluation of the abatement methods, correlations among lead
levels in sampled media and locations, comparison of vacuum and
wipe sampling methods, comparison of CAP Study and HUD Abatement
Demonstration results, results from statistical outlier analyses,
and analysis of field and laboratory quality control data.
-------
1.2 STUDY APPROACH
Whereas the HUD Demonstration was intended to focus on the
short-term cost-effectiveness of abatement methods, the CAP Study
provided important information about the longer-term effec-
tiveness of these same methods. Although clearance testing of
lead levels in dust was done immediately after abatement in the
HUD Demonstration, the longer-term performance of the abatement
methods after these houses were reoccupied was not assessed. The
CAP Study was therefore necessary to preclude spending large sums
of money abating lead-based paint using methods that may prove in
the long term to be ineffective at maintaining low lead levels in
household dust.
High levels of lead in household dust pose serious health
risks to occupants regardless of the source. Therefore the CAP
Study also collected important information as to how lead from
other media and locations may be deposited into household dust.
It is possible that lead can be redeposited in homes after the
house is reoccupied where the lead-based paint hazard has been
removed or contained. Either prior to abatement or during the
abatement process itself, leaded dust may have been deposited in
the ventilation system or other parts of the house which, when
reoccupied by new residents, could spread throughout the house.
Also, activity patterns of the occupants may re-introduce lead
from exterior soils.
1.2.1 Study Objectives
To help address the above concerns, the specific objectives
of the CAP Study were as follows:
|1) Assess the long-term efficacy of two primary abatement
methods;
-------
Characterize lead levels in household dust and exterior
soil in unabated homes and homes abated by different
abatement methods;
Investigate the relationship between lead in household
dust and lead from other sources, in particular,
exterior soil and air ducts, and
Compare dust lead loading results from cyclone vacuum
sampling and wipe sampling protocols.
These objectives were intended to address at least three
important concerns presented in the HUD Comprehensive and
Workable Plan (HUD, 1990a): the durability of various abatement
methods over time, the importance of adequate dust control during
the abatement process, and the possible redeposition of lead from
a variety of locations, such as exterior soil and air ducts. The
fourth objective addresses a critical issue related to the
measurement and characterization of dust lead levels within a
house.
The HUD Demonstration intended to eliminate the lead-based
paint hazard from housing environments either by containing the
lead-based paint with encapsulation or enclosure methods, or by
eliminating the lead-based paint with removal methods.
Encapsulation and enclosure methods attempt to chemically bond or
mechanically affix durable materials over painted surfaces, while
removal methods attempt to either scrape or chemically strip
lead-based paint from painted surfaces, or to completely remove
and replace painted components (e.g., windows, doors,
baseboards).
There are at least two performance concerns with these
abatement methods. First, conducting the abatement methods
themselves might generate large amounts of leaded dust that could
be deposited throughout the housing environment. And second, the
performance of the abatement measures might degrade over several
months or years following abatement, allowing the lead hazard to
-------
be reintroduced to the housing environment. Encapsulation and
enclosure methods do not attempt to remove lead-based paint from
housing surfaces and therefore may have a greater potential to
degrade. Both encapsulation and enclosure methods, as well as
removal methods have the potential to spread leaded dust
throughout the housing environment during abatement.
For the CAP Study, the ideal direct approach to assessing
the long-term efficacy of the abatements performed in the HUD
Demonstration would have been to collect pre-abatement dust and
soil lead measures, and compare them with measures collected
after abatement at the same locations. If the post-abatement
measurements were not higher than pre-abatement lead levels, this
could be taken as an indication that abatement had a positive
effect on the housing environment. While the CAP Study did
perform this direct assessment of abatement efficacy, only
foundation soil samples and a limited number of dust samples were
taken during the HUD Demonstration prior to abatement. Thus,
only limited direct information could be obtained about the
effects of abatement.
Realizing these limitations, the approach for addressing the
first objective of the CAP Study also included an indirect
assessment of abatement efficacy. In this second approach post-
abatement dust and soil samples were collected and chemically
analyzed for lead approximately two years after abatement both at
abated houses, and at the same time at unabated houses known to
be relatively free of lead-based paint. The performance of the
abatement methods was then assessed by comparing the lead levels
at abated houses with those at unabated houses. Sampling at
unabated houses provided a measure of the amount of lead
introduced to the housing environment from low levels of lead in
paint and sources other than lead-based paint abatement. If the
environmental lead levels at abated houses were found to be
-------
similar to those at unabated houses, this was taken as an
indication that abatement either lowered pre-abatement lead
levels, or at least did not significantly raise lead levels.
However, if lead levels at abated houses were significantly
higher than those at unabated houses, this was taken as an
indication that abatement failed to completely eliminate the lead
hazard because lead was introduced to these environments either
immediately through inadequate dust control during abatement, or
more gradually through redeposition over time.
Comparing post-abatement levels of lead in abated houses to
levels in unabated houses does not necessarily reflect the degree
to which abatement lowered levels of dust and soil lead compared
to pre-abatement levels. However, it does provide a basis for
discerning whether abatement reduces dust and soil lead levels to
levels present in houses with no apparent need for abatement
(based on portable X-ray fluorescence readings of lead levels in
paint). The levels of lead in dust and soil were primarily
assessed by the concentration of lead present in samples,
measured as the weight of lead (in micrograms, ug) in a sample
divided by the total weight of the sample (in grams, g). Higher
lead concentrations at abated houses were generally taken as an
indication that paint had contributed additional lead to the
environment over that which had been deposited from other non-
paint sources, such as prior fallout from automotive emissions.
For dust, the lead levels were also assessed by the lead loading
present, which is measured as the weight of lead (ug) collected
in a sample divided by the total surface area sampled (in square
feet, ft2). The lead loading, which takes into account both the
lead concentration present as well as the dustiness of the
environment, provides a measure that can be combined with room
dimensions to assess the total amount of lead to which residents
are exposed.
-------
1.2.2 Study Design
Of the 172 single-family dwellings abated during the HUD
Abatement Demonstration, three of these houses had pilot
abatements performed, while the other 169 were completely abated.
Soil was not abated at any of these houses. The distribution by
city of these 169 houses is presented in Table 1-1. The specific
houses for abatement were selected by first identifying older
Table 1-1. Number of Houses Abated in the HUD Demonstration
City
Baltimore
Birmingham
Denver
Indianapolis
Seattle/Tacoma
Washington
Total
Interior Abatement
Category*
Encap/
Enclos
11
8
33
17
12
6
87
Removal
9
12
18
10
10
3
62
Exterior Abatement
Only**
Encap/
Enclos
2
5
3
1
—
11
Removal
1
1
4
3
—
9
Total
20
23
57
34
26
9
169
* Each house was classified according to the abatement category accounting
for the largest square footage of interior abatement.
** For houses having only exterior abatement performed, each house was
classified according to the abatement category accounting for the largest
square footage of exterior abatement.
housing likely to contain lead-based paint and then testing
painted surfaces for lead using portable X-ray fluorescence
(XRF). Houses abated in the HUD Abatement Demonstration were
those found to have a significant number of structural components
covered by paint with a high concentration of lead. When
surveying houses for lead-based paint, HUD considered all painted
surfaces both on the interior and exterior of the house.
The HUD Demonstration originally included six different
abatement methods: encapsulation, enclosure, and four removal
methods (i.e., chemical stripping, abrasive stripping, heat-gun
stripping, and complete removal or replacement of painted
7
-------
components). Because of the diversity of housing components
containing lead-based paint, it was generally true that no single
abatement method could be used uniformly throughout a given
house. One important consideration in the CAP Study was the
appropriate way in which to summarize and classify the abatement
activities conducted at each house. Detailed information was
collected by HUD which listed each type of interior and exterior
structural component abated in the Demonstration, along with the
-------
linear or square footage abated and the abatement method used.
For the CAP Study, each house was primarily classified according
to the abatement category (i.e., encapsulation/enclosure versus
removal methods) accounting for the largest square footage of
interior abatement. However, at many HUD Demonstration houses, a
great deal of exterior abatement was also performed. Therefore,
the data interpretation also considered which specific methods
were used on both the interior and exterior of the house. Two
other important considerations for the data interpretation are
the sometimes widely different square footages abated at
different houses and the different mix of methods used.
Selection of Abated Housing Units
Initial plans for the CAP Study included selection of
housing units from all seven urban areas in the FHA portion of
the HUD Demonstration. However, after conducting a pilot sam-
pling and analysis program (EPA, 1995a), and subsequently
developing a cost estimate for the CAP Study, it was decided that
the CAP Study would only be conducted in Denver, where 57 of the
169 abated houses were located (Table 1-1). Because the number
of abated houses in Denver was limited, all reoccupied houses
were initially included for recruitment in the CAP Study. A
preliminary statistical power analysis was conducted to examine
the magnitude of the differences between dust lead levels in
abated and unabated houses that could be detected with 80 percent
power. The analysis utilized the available information about
both the abated and unabated houses in Denver, as well as the
results from the CAP Pilot Study. For the purposes of the
analysis, it was assumed that two abated houses would be sampled
for every one unabated house sampled. Power analysis results
indicated that approximately 40 abated houses (and therefore 20
unabated houses) would be sufficient to detect two-fold
-------
differences between the dust lead levels in abated and unabated
houses. (This analysis is described in detail in Appendix F.)
Given the initial set of 57 abated houses in Denver, 70% of these
houses had to be successfully recruited into the study.
Selection of Unabated Housing Units
Only foundation soil samples and a limited number of dust
samples were collected at the abated houses prior to abatement.
This hindered the use of each abated house as its own control to
provide a direct assessment of abatement performance. Therefore,
in order to use the levels of lead measured in dust and soil
samples at abated houses as a measure of the performance of
abatement at those houses, lead levels associated with other
environmental sources had to be characterized. Therefore, in
addition to abated houses, dust and soil samples were collected
from unabated houses that were previously tested by XRF in the
HUD Demonstration and found to be relatively free of lead-based
paint. The objective in measuring lead levels at unabated houses
was to determine whether lead levels observed at abated houses
were in fact greater than those found at houses having very few
components covered with lead-based paint and therefore presumably
affected primarily by non-paint sources of lead.
Some consideration was given to the idea of including a
second type of unabated house, where significant amounts of lead-
based paint were known to be present, and no abatement activities
had yet been performed. Presumably, environmental lead levels
measured in interior dust and exterior soil at these houses would
have been significantly higher than those measured at abated
houses and at houses that were known to be relatively free of
lead-based paint. Houses with unabated lead-based paint could
have supplied at least two additional interesting comparisons to
the CAP Study:
10
-------
If it were demonstrated that no significant difference
exists between environmental lead levels at houses with
unabated lead-based paint and houses that contain
relatively little lead-based paint, then this result
might suggest that non-paint sources of lead dominate
the housing environment.
If environmental lead levels at abated houses were
found to be significantly lower than those with
unabated lead-based paint hazards, then this would
indirectly suggest that abatement is successful in
lowering lead levels at houses with lead-based paint.
Although these and other comparisons would have been quite
informative, houses with unabated lead-based paint were not
included in the CAP Study. The primary reason for excluding
these houses was that they should be subsequently abated to
protect residents' safety; however, EPA could not identify a
suitable mechanism to conduct these abatements.
In the FHA portion of the HUD Demonstration, a total of 132
houses were tested by XRF for lead-based paint, but were not
abated (Table 1-2). When performing the XRF tests, three
replicate XRF readings were made at each sampling location and
decisions at each location were based on the average of those
three readings. When interpreting the results, an average
reading greater than or equal to 1.0 mg/cm2 was considered to be
a positive indication that lead-based paint was covering the
tested component. While only a single round of XRF testing was
performed at unabated houses, in some cases a second round of XRF
and/or AAS testing was performed at abated houses to confirm
inconclusive XRF results.
Unabated houses for the CAP Study were recruited from the
set of unabated houses in Denver that were tested by XRF in the
HUD Demonstration. For the purpose of identifying unabated
houses, the detailed XRF results were used under the assumption
that they provided an accurate and current assessment of these
11
-------
houses. Using a criterion that equally weighted (1) the
percentage of housing components testing positive by XRF for
lead-based paint, and (2) the average XRF testing result, the 40
unabated houses in Denver were prioritized. Seventeen unabated
houses were sampled for the CAP Study, including 16 houses from
Table 1-2. Number of Unabated Houses Tested by XRF in
the HUD Demonstration
City
Baltimore
Birmingham
Denver
Indianapolis
Seattle/Tacoma
Washington
Total
Number of LBP Building Components*
0
1
4
13
5
10
4
37
1-2
6
5
10
9
3
2
35
3-9
3
—
14
5
2
4
28
10 or More
10
5
3
—
5
9
32
Total
20
14
40
19
20
19
132
Number of structural components for which XRF testing identified the
presence of lead-based paint.
among the 31 with the lowest XRF results, and a 17th house which
was 36th on the prioritized list. The 36th house on the
prioritized list was recruited because it was the duplex to the
27th house which had already been recruited.
oŁ Housin Units
The FHA regional property disposition office in Denver was
contacted with a request to complete a record of property
disposition form for each abated and unabated home in the region.
From this form the following data were obtained: name, address
and telephone number of the purchaser; date of settlement;
investor versus owner/occupant status of purchaser; date property
was listed for sale; an indication of whether the house was
cleared after abatement; and ages of children of owner/occupants.
Appointments were scheduled with residents using a
12
-------
combination of mailed information packets, telephone calls, and
on-site visits by a recruitment team. A total of 83 houses (32
unabated, 51 abated) were approached during the recruitment phase
of the CAP Study. Appointments were confirmed and two field
teams collected samples during March and April of 1992 from 52 of
these houses (17 unabated, 35 abated). Eight houses (5 unabated,
3 abated) refused to participate in the study. Remaining houses
were either vacant or unreachable. An audit of the field
sampling activities was performed during the second week of
sampling. No significant problems were identified during this
audit.
Selection oŁ Rooms in Housing Units
Generally, two rooms were randomly selected from each
housing unit for sampling. In unabated houses, the two rooms
were selected from those rooms where XRF measurements had been
taken in the room, and the average XRF reading was less than or
equal to 0.2 mg/cm2. In abated houses, where possible two rooms
were selected with at least 50 square feet of abatement.
However, this was not possible in 18 of the abated houses. In
these houses, one unabated room was then selected where the
average XRF reading was less than 0.2 mg/cm2. Unabated rooms
were sampled to determine whether abatement in other rooms of
these houses may have caused increased lead levels in the
unabated rooms. Additionally, in 13 houses with higher abatement
square footages and two abated rooms already being sampled, an
unabated room was also sampled. This was done to avoid a
potential bias in the study results toward contrasts in houses
requiring small amounts of abatement.
13
-------
Design Limitations
There were certain specific limitations in the design of the
CAP Study which are important to mention. The primary design
limitation forms the basis for sampling unabated houses. As
discussed above, to assess abatement efficacy one would ideally
like to compare pre-abatement levels in each house with levels
observed after abatement. This direct type of comparison was
performed to the extent possible, however only foundation soil
and a limited number of dust measures taken prior to abatement
were directly comparable to the measures taken in the CAP Study.
Therefore, an indirect measure of the effect of abatement was
obtained by comparing post-abatement levels with levels in houses
previously identified as relatively free of lead-based paint.
Another important design limitation was that the CAP Study
houses abated primarily by encapsulation/enclosure methods had,
on average, more abatement performed than those abated primarily
by removal methods. Therefore, it is possible that any higher
lead levels found in encapsulation/enclosure homes may be
attributable to greater initial lead levels and greater amounts
of lead-based paint present.
In addition, other minor distinctions exist among the groups
of houses which should be understood in interpreting the results.
The discussion of significant factors provided in Sections 3 and
4 of this report details dependencies of the factors related to
abatement group. For example, on average, abated houses were 17
years older than unabated houses. This fact was controlled for
in estimating the effect of house age.
1.2.3 Sampling Design
During the CAP Study a variety of environmental samples were
collected along with questionnaire and field inspection
information to help assess the performance of abatement methods
14
-------
used in the HUD Demonstration. The environmental samples that
were collected are summarized in Table 1-3. All samples were
chemically analyzed to measure the amount of lead present. The
results for vacuum dust samples were presented on both a
concentration basis (i.e., micrograms of lead per gram of dust,
ug/g) and a loading basis (i.e., micrograms of lead per unit area
sampled, ug/ft2) . Only lead loading results were presented for
wipe dust samples and only lead concentration results for soil
core samples. All houses were sampled during a five-week period
in late winter/early spring of 1992. Although seasonal
variations have been documented in previous studies (EPA, 1995c) ,
this short sampling interval reduced the need to control for such
variations in comparisons associated with the study objectives.
The environmental sampling planned for the study included
both regular samples (vacuum dust and soil cores) and field
quality control samples (wipe versus vacuum dust, blanks,
and side-by-side samples) intended to assess sampling variability
and potential sample contamination. Field quality control
samples were collected using the same procedures as regular
samples. The role of each type of sample listed in Table 1-3 for
meeting these objectives was as follows:
Vacuum dust from floor perimeter and window stools --
Provided primary measure of performance for interior
abatement (the window stool was defined as the
horizontal board inside the window--often called the
window sill) ;
Vacuum dust from window channels -- Provided measure of
performance for interior abatement, possible measure of
performance for exterior abatement, and possible
transport of exterior soil from outside to inside the
house (the window channel was defined as the surface
below the window sash and inside the screen and/or
storm window);
Vacuum dust from air ducts -- Primarily to provide
measure of lead level in dust that has not been
15
-------
disturbed by cleaning and may be more indicative of
previous levels of lead in the household dust at a
particular home; provided measure of source contribu-
tion to interior dust lead levels;
Vacuum dust from interior and exterior entryway floor -
- Provided measure of possible transport of exterior
soil from outside to inside the house;
Soil cores -- Combined with pre-abatement measures,
provided primary measure of performance of exterior
abatement. Also provided measure of possible transport
of exterior soil lead into the house.
Table 1-3. Summary of Environmental Sampling Planned
for the CAP Study
Sample Type
Regular Samples
1 . Vacuum dust
a. Perimeter floor
b . Window channel
c. Window stool
d. Air ducts
e. Int. entryway floor
f. Ext. entryway concrete
2 . Soil cores
a. Near foundation
b. Property boundary
c. Entryway
Quality Control Samples
3 . Wipe vs . vacuum
a. Floor wipe dust
b. Floor vacuum dust
4. Blanks
a. Vacuum dust field blank
b. Vacuum dust trip blank
c. Soil core field blank
d. Wipe dust field blank
5. Side-by-side samples
a. Vacuum dust floor
b. Soil cores
Number of Samples Planned
For 17
Unabated
houses
2
2
2
2
2
2
2
2
2
0
0
1
1
1
0
1
1
For 22
Abated
Houses (a)
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
For 13
Abated
Houses*'
3
3
3
3
2
2
2
2
2
2
2
1
1
1
1
1
1
16
-------
Total Samples
23
28
32
(a) 22 houses where sampling was conducted in two rooms.
(b) 13 houses where sampling was conducted in three rooms.
• Wipe versus vacuum dust from floors -- Provided
consistency check against earlier results from HUD
Demonstration and other studies by examining dust
levels sampled using vacuum and wipe procedures from
adjacent surfaces (recall that the HUD Demonstration
Study collected wipe dust samples);
• Vacuum, wipe, and core blank samples -- Provided
assessment of potential sample contamination and
uncertainty in sample weighing; and
• Vacuum dust and soil core side-by-side samples --
Provided assessment of short-scale sampling
variability.
Interior and Exterior Dust
Rooms were selected for sampling primarily to collect floor,
window stool, and window channel dust samples. Some of the most
important points related to dust sampling are as follows:
Sampling was in general performed in two different
rooms of each unabated house -- this provided a measure
of the variability in background lead levels within a
house.
With one exception, sampling was performed in either 1
or 2 abated rooms for each abated house -- sampling 2
abated rooms provided a measure of the variability in
abatement performance within a house*.
Sampling was performed in 1 unabated room in most
abated houses** -- the CAP Study pilot sampling and
No abated rooms were sampled in one abated house — this house had only
exterior abatement performed. One abated room was sampled in 18 abated
houses. Two abated rooms were sampled in 16 abated houses.
No unabated rooms were sampled in three abated houses. One unabated
room was sampled in 29 houses. Two unabated rooms were sampled in three
houses .
17
-------
analysis program demonstrated that unabated rooms in
abated houses may contain significant amounts of leaded
dust (EPA, 1995a). This leaded dust may be due to
undetected and unabated lead-based paint in unabated
rooms, or to deposition from abatements performed in
other rooms of the house.
If the rooms selected for sampling did not contain an
entry, or if there were no air ducts present, or if
side-by-side vacuum/wipe comparison samples could not
be collected there (e.g., rooms were carpeted),
additional rooms were selected from which these samples
could be collected.
Abated rooms in abated houses were randomly selected
from rooms with at least 50 ft2 of abatement performed.
In houses where the required number of rooms satisfying
this condition was not available, rooms with the
largest square footage abated were selected.
In each of the rooms targeted for sampling, sampling
was performed on floors, window channels, and window
stools. For abated houses this provided a means to
assess differences in the way an abatement method
performed with respect to different structural
components, and for unabated houses this provided a
further measure of the within-house variability of
background lead levels.
In each abated house, an uncarpeted room was selected
in which to compare the vacuum and wipe dust sampling
protocols. To perform this comparison, two vacuum
samples and two wipe samples (each sample from a 1 ft2
area) were collected side by side in a random
configuration from the floor perimeter. Where
possible, these samples were collected from one of the
originally selected rooms, but in some cases, it was
necessary to select an additional room. (See previous
footnotes * and **.)
Sampling was performed in one supply air duct in each
selected room; in cases where more than one supply air
duct was available in a room, the air duct for sampling
was randomly selected from those available. If no
airducts were available in a room, then (where
possible) an air duct was selected from a nearby room.
Sampling was performed immediately inside and outside
the front and rear entryways of each house -- for both
18
-------
abated and unabated houses, these samples provided a
means of assessing possible transport of lead from
exterior to interior locations.
Exterior Soil
As noted earlier, the HUD Demonstration evaluated the
abatement of both interior and exterior painted surfaces, and in
fact, for many houses exterior abatement was the most significant
activity performed. Furthermore, the same abatement method might
be expected to perform quite differently on interior and exterior
surfaces. Therefore, the CAP Study evaluated both interior and
exterior abatement.
Exterior foundation soil sampling provided the primary means
for assessing the effects of exterior lead-based paint and
abatement. In this assessment, lead concentrations measured in
soil samples taken close to the foundation were compared with
those measured in samples taken at the property boundary which
were as far as possible from the foundation, and therefore,
primarily affected by only background sources of lead, rather
than lead-based paint. During the HUD Demonstration, no soil
abatement was performed. Therefore, if elevated lead levels were
found in the foundation soil, they could be due either to the
earlier presence of lead-based paint, or to the exterior
abatement activities. It is also possible that airborne lead
deposition may be greater in the vicinity of walls than in open
areas.
Some of the most important points to note for the soil
sampling are as follows:
Soil samples were collected both at the foundation of
each house and at the property boundary -- for abated
houses this provided a measure of both soil potentially
affected by lead-based paint and/or abatement (i.e., at
the foundation) versus soil affected mostly by
background sources (i.e., at the property boundary);
19
-------
for unabated houses this provided a measure of the spa-
tial variations in background soil lead levels.
Samples were collected from two randomly selected sides
of the house -- for abated houses this provided a
measure of the variability in lead-based paint and/or
abatement performance effects, while for unabated
houses this provided another measure of the spatial
variations in background soil lead levels.
Samples were collected immediately outside the front
and rear entryways -- for both abated and unabated
houses this provided a means for assessing possible
transport of exterior lead into the house.
1.2.4 Sample Selection. Collection And Analysis Procedures
For dust collection, a cyclone vacuum was the primary
sampling device used. The area vacuumed was nominally 1-ft2 for
floor samples, and nominally the entire accessible surface for
window stools, channels, and air ducts. Two one-square foot wipe
samples of surface dust were also collected from uncarpeted
floors in abated houses.
Soil samples were collected with a soil recovery probe
consisting of a 1-inch internal diameter plastic butyrate liner
and a 12-inch stainless steel core sampler with cross-bar handle
and hammer attachments. Each sample was a composite consisting
of three soil cores, each 0.5 inches in depth as measured from
the top of the soil surface. A new plastic liner was used for
each sample, and the probe was cleaned with wet disposable wipes
between each sample. To reduce cross-contamination, only the
plastic liner was used where soil conditions allowed.
Sample preparation procedures for dust and soil samples were
carried out using versions of EPA SW846 Method 3050, which
included use of nitric acid and hydrogen peroxide for sample
digestion. Sample digestates for all sample types were analyzed
for lead levels using Inductively Coupled Plasma Atomic Emission
Spectrometry (ICP-AES) at the 220 nanometer emission line.
20
-------
1.3 STUDY RESULTS
This section provides a summary and analysis of the CAP
Study results. The statistical methods, models, and results are
more completely described later in this report. The discussion
of results is organized according to the study objective to which
they pertain.
1.3.1 Assessment of Long-Term Abatement Efficacy
The CAP Study included two approaches for assessing
abatement efficacy, one direct approach and one indirect
approach. In the direct approach CAP Study lead measurements,
made at HUD Demonstration houses two years after abatement, were
compared with pre-abatement lead measurements made by HUD at
those same houses. The indirect approach involved comparing lead
levels measured in dust and soil samples collected both at abated
HUD Demonstration houses, and at the same time at unabated HUD
Demonstration houses found to be relatively free of lead-based
paint.
Coitipaxison of Pre-.Abatement and Post-.Abatement Lead Levels
The results of the CAP Study from the direct approach of
comparing post-abatement and pre-abatement lead levels follow.
Post- vs. Pre-Abatement. For the two sample types for which
a comparison was possible, that is window stools and
exterior soil, there was no evidence that post-abatement
lead levels were significantly higher than pre-abatement
levels. Pre-abatement lead loadings and lead loadings
measured during the CAP Study averaged between 175 and 200
ug/ft2. Pre-abatement foundation soil lead concentrations
and lead concentrations measured during the CAP Study
averaged near 240 ug/g.
21
-------
This result is based on 21 dust lead measurements made on
window stools at 10 CAP Study abated houses, as well as 45 soil
lead measurements made at 24 CAP Study abated houses.
These results are tempered by the fact that because of the
number of houses for which data were available, as well as the
large variability in observed lead levels, relatively large
differences between post-abatement and pre-abatement lead levels
could not be judged to be statistically significant. For
example, the confidence interval about an average ratio of post-
abatement to pre-abatement levels for window stools was 0.37 to
3.46. This means that even if post-abatement levels were 3 times
higher than pre-abatement levels, they would not be judged to be
significantly higher. In addition, further complicating the
comparison of post-abatement and pre-abatement dust and soil lead
measurements was the fact that different sampling and analysis
protocols were used in the CAP Study and HUD Demonstration.
Perhaps most significantly, the CAP Study primarily utilized
vacuum dust sampling while the HUD Demonstration exclusively
utilized wipe dust sampling.
Modeling Results
Table 1-4 provides a summary of the sample types and
abbreviations used to represent each sample type in subsequent
22
-------
Table 1-4. Symbols Used to Denote Sample Types in
Tables and Figures
Sample
Type
Dust
Soil
Symbol
ARD
WCH
WST
FLW
FLR
EWI
EWO
EWY
FDN
BDY
Description
Vacuum dust samples collected from an air duct within
the unit
Vacuum dust samples collected from a window channel
within the unit
Vacuum dust samples collected from a window stool
within the unit
Wipe dust samples collected from a floor within the
unit
Vacuum dust samples collected from a floor within the
unit
Vacuum dust samples collected from inside an entryway
to the unit
Vacuum dust samples collected from outside an
entrvwav to the unit
Soil core samples collected adjacent to an entryway
to the unit
Soil core samples collected at the foundation of the
unit
Soil core samples collected at the boundary of the
property
tables and figures. The results of the CAP Study from the
indirect approach of comparing post-abatement lead levels at
abated houses with lead levels at unabated houses relatively free
of lead-based paint were determined by fitting a series of
statistical models to data collected for all sample types, that
is, dust and soil sampled at several different locations. Table
1-5 displays estimates of the effects of the primary abatement
factors on lead loadings and lead concentrations. The third
column of Table 1-5 provides the number of samples included in
the model for each sample type. The fourth column contains the
estimated geometric mean in houses which were not abated. The
log standard error of these estimates appears in parentheses
below each estimate. The estimated geometric mean is to be
23
-------
interpreted as the average lead level in typical unabated houses.
Table 1-5.
Estimates3 of Effects of Primary Abatement Factors on
Lead Loading and Lead Concentration; Controlling for
Significant Covariates
[ARD]
[FLR]
1.15
(0.44)
.754
[ARD]
[FLR]
[BDY]
24
-------
Geometric mean in unabated houses after controlling for effects of significant factors.
Ratio of levels in abated rooms of abated houses to those in unabated houses.
Ratio of levels in E/E houses to those in removal houses.
Ratio of levels in unabated rooms of abated houses to those in abated rooms of the same
houses.
Floor wipe samples were only collected in abated houses; the geometric mean in
abated houses was 11.3 ug/ft2 after controlling for significant factors.
25
-------
That is, it represents the estimated average when the significant
covariates included in the model are fixed at the nominal levels
(e.g., typical unabated house was owner occupied, built in 1943,
etc.). Nominal levels and effects of these factors are discussed
in Section 4 of this report.
The fifth column in Table 1-5 displays the estimated ratio
of levels in abated rooms of typical abated houses to levels in
typical unabated houses. The abated houses were divided into two
categories, according to their predominant method of abatement:
encapsulation/enclosure (E/E) or removal. The sixth column
contains the estimated impact of abatement method, which should
be interpreted as the ratio of levels in abated rooms of typical
E/E houses to levels in abated rooms of typical removal houses (a
precise definition of "typical" is provided in Volume II). The
seventh column in this table gives an estimate of the ratio of
levels in unabated rooms of abated houses to levels in abated
rooms of abated houses. The log standard error and significance
level appear beneath each of these estimates. The latter
represents the observed significance of a test that the ratio
equals 1.
The models used to estimate these primary effects included
various secondary abatement factors and additional non-abatement
factors. Secondary abatement factors included total square feet
abated by each method, the abatement contractor, phase of
abatement, and XRF measures taken during the HUD Demonstration.
The non-abatement factors included those related to sampling
substrate and protocol deviations, as well as resident-related
factors such as cleanliness, ownership, occupation, and
activities. The specific factors included in each model and
their effects are described in detail in Section 4 of this
report.
In the subsequent discussion of the results, an effect is
described as being "statistically significant" if the associated
p-value is less than 5 percent. The reader is referred to
26
-------
Appendix C of this report for specific p-values. These p-values
can be interpreted as the probability that the observed result
may have occurred simply by chance. Therefore, small p-values
represent situations where the results are unlikely to be simply
chance events.
The estimated ratios in Table 1-5 (i.e., columns 5-7) are
displayed graphically in Figures 1-1 and 1-2 for lead loading and
lead concentration, respectively. Reference lines are provided
on these plots at a level of one (1) which indicates that the
lead levels in both types of houses or rooms were equal. An
asterisk indicates that the effect was significant at the 5
percent level. A bar which rises above the reference line for
the 'Abatement' factor indicates that for this sample type levels
were higher in abated houses than in unabated houses. A bar
which rises above the reference line for the 'Method (E/R)'
factor indicates that the levels in E/E houses were higher than
those in removal houses. If the 'Unabated room' effect is
greater than one, then levels in unabated rooms of abated houses
were higher than in abated rooms. The results presented in this
table and these figures are discussed in the subsequent sections.
Comparison of Levels in Abated and Unabated Houses
The first objective of the CAP Study was to assess the long-
term efficacy of abatements performed in the HUD Demonstration
Study. The following conclusions can be made from the CAP Study
results.
Abated vs. Unabated Houses. Only in air ducts and soil were
geometric mean lead levels significantly higher in abated
houses than in unabated houses. In soil, lead concentra-
tions were significantly higher than corresponding levels
outside unabated homes at the foundation and at the property
boundary. Neither soil nor air ducts was abated in the HUD
Demonstration.
27
-------
As indicated in the fifth column of Table 1-5, lead
concentrations were about 1.6 times higher in the air ducts of
28
-------
10.0
1 1.0
0.1
Factor
Abatement
Method (E/R)
Unabated Room
Sample Type
Figure 1-1.
Estimated multiplicative effects of abatement from
mixed model ANOVA: Lead Loading.
10.0
1.0
Factor
i 1 Abatement
ESI Method (5/R)
i^ Unabated Room
*
* \
-1 \
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\
*
*
-------
bated houses than in unabated houses. Lead loadings were on
average 4.7 times greater in the abated homes, reflecting that
ducts in the abated houses were also dustier than in unabated
houses. On average, lead concentrations in soil were 82 percent
greater at the foundation and 63 percent greater at the boundary
of abated houses. The difference between the percentage
estimates was statistically significant, reflecting a greater
contrast between levels at abated and unabated houses in
foundation soil than in boundary soil. This suggests that the
contrasts between abated and unabated houses is, at least in
part, due to lead-based paint. However, it is important to note
that air ducts and soil were not abated in the HUD Demonstration.
Also, abated houses in this study were 17 years older than
unabated houses.
Coitipaxison oŁ Levels in Unabated and .Abated Rooms oŁ .Abated Homes
To determine whether levels in abated houses varied
systematically between abated and unabated rooms, dust samples
were collected from floors, window stools, and window channels in
both types of rooms, and the following results were found.
Abated vs. Unabated Rooms. Lead levels were not
significantly different between unabated rooms of abated
houses and abated rooms of those same houses.
The seventh column in Table 1-5 lists the estimated
multiplicative factor by which geometric mean lead levels in
unabated rooms were lower (or higher) than geometric mean lead
levels in abated rooms. No differences were statistically
significant, although on floors and window channels lead loadings
were somewhat lower in unabated rooms (with p values between 0.05
and 0.10) .
Convoarison of Abatement Methods
30
-------
In addition to general assessments of abatement efficacy,
measures were taken to assess different methods of abatement.
E/E vs. Removal. Only in air ducts were mean lead levels
significantly higher in houses abated by encapsulation/
enclosure methods than in houses abated by removal methods.
Lead loadings and lead concentrations were significantly higher
in the air ducts of E/E houses than in removal houses. Two facts
are important to note here. First, houses at which E/E methods
were used generally had more lead-based paint present than houses
at which removal methods were used. Second, air ducts, which
were the only sample type for which significant differences were
found with respect to E/E versus removal were not abated in the
HUD Demonstration.
Floor lead loadings were on average twice as large in E/E
houses as they were in removal houses. This was very nearly
statistically significant (p=0.053), suggesting a difference
worth recognizing. Noting that the difference in lead
concentrations between abated and unabated houses was not
signifcant, it is evident that the difference in lead loading is
due primarily to increased dust loading in the abated houses.
In addition to sampling and analysis, at the time of
sampling each abated substrate in a room or exterior area
selected for sampling was visually inspected. Its condition was
recorded as either completely (70 percent or more) intact,
partially (50 to 70 percent) intact, or minimally (less than 50
percent) intact. Table 1-6 displays a summary of this data by
method of abatement. Specific abatement methods are
distinguished within the general E/E and removal categories.
Visual Inspection Results. At least 70 percent of the
substrates abated by enclosure, heat gun, and removal and
replacement were completely intact at the time of sampling,
Less than 60% of those substrates abated by chemical
stripping and encapsulation methods were completely intact,
31
-------
The components which were removed and completely replaced
were in the best condition; 95 percent of these were completely
intact. When interpreting these results, it should be noted that
Table 1-6.
Condition of Abated Substrates, by Method
of Abatement
Category
E/E
Removal
Method
Enclosure
Encapsulation
Chemical Stripping
Heat Gun
Removal & Replacement
Completely
intact
40 (80%)
109 (58%)
30 (56%)
40 (70%)
38 (95%)
Partially
Intact
10 (20%)
68 (36%)
18 (33%)
17 (30%)
2 (5%)
Minimally
Intact
0
10 (6%)
6 (11%)
0
0
the abated houses were unoccupied at the time of abatement, and
were not continuously occupied between the completion of
abatement and the time of CAP Study sampling. Lack of
temperature control and lack of regular cleaning may have more
strongly affected the encapsulation or chemical stripping methods
than the other abatement methods. Unoccupied houses may not have
been heated in the winter, causing temperature swings which could
lead to cracking or peeling.
With regard to interpreting all of the modeling results in
this section, the reader should be aware of the large number of
statistical tests involved in an analysis of this sort. Two or
three primary abatement effects were estimated for each sample
type listed in Table 1-5. This represents a total of 41 tests at
the 5 percent significance level. If all these tests were
independent, even if there were no true effects, one would expect
about two effects to be identified as significant
(41(0.05)=2.05). In fact, the tests are not independent.
Concentration measurements are very much related to loading
measurements. The exact impact of this dependence is impossible
to quantify, however this relationship effectively reduces the
32
-------
actual number of tests being performed. In total, six of the 41
tests produced significant results.
1.3.2 Characterization of Lead Levels
The second objective of the CAP Study was to characterize
lead levels in household dust and exterior soil for abated and
unabated houses. The following three subsections present these
levels, and compare them with interim clearance standards, as
well as with results observed in other studies.
Descriptive Statistics
Table 1-7 presents a summary of descriptive statistics
associated with the CAP Study. In addition to the geometric mean
and the arithmetic mean, the minimum and maximum values are
listed with the log standard deviation. The sample sizes in this
table are sometimes greater than those presented in Table 1-5.
This is because the results presented in the earlier tables
controlled for various significant covariates. In cases where
the significant covariates were unknown, samples were
excluded from fitting the models. The results in Table 1-7
should be given less weight in interpreting the data, because
they do not control for factors found to be significant.
However, they are useful for comparing the CAP Study with other
studies where covariates were not controlled in the reporting of
results.
Lead levels were found to vary greatly for different media
and sampling locations. Minimum individual lead concentrations
for most sample types were usually on the order of 10 ug/g except
in air ducts and window channels where levels were at least
50 ug/g. Maximum individual lead concentrations were lowest for
boundary and entryway soil samples (1073 and 1068 ug/g,
respectively) and highest for window stool and window channel
33
-------
dust samples (48,272 and 45,229 ug/g, respectively). Minimum
individual lead loadings for sample types were in general only 1
to 4 ug/ft2 with window channels being the only exception.
Maximum individual lead loadings were lowest for floor dust
samples (334 ug/ft2 by wipe and 11,641 ug/ft2 by vacuum) and
highest for window channel dust samples (244,581 ug/ft2) .
34
-------
Table 1-7.
Descriptive Statistics for Lead Loading (ug/ft ) , Lead Concentration
(ug/g) , and Dust Loading (mg/f t2) by Sample Type
Measurement
Air
Duct
(Vacuum
Entrywa
y
Interio
r
(Vacuum
Entryway
Exterior
(Vacuum)
co
Cn
Dust
Lead
Loading
(lig/ft2)
Number of Samples
Geometric Mean
Arithmetic Mean
LN Standard
Deviation
Minimum
Maximum
11641.25
Number of Samples
Geometric Mean
Arithmetic Mean
LN Standard
Deviation
Minimum
Maximum
Dust
Loading
(mg/ft2)
Number of Samples
Geometric Mean
Arithmetic Mean
LN Standard
Deviation
Minimum
Maximum
Entrywa
Foundati
on
-------
Modeling Results
The lead loadings and lead concentrations from the CAP Study
models were summarized in Table 1-5, as well as in the following
points:
Lead Loadings. Geometric mean dust lead loadings in
unabated houses varied from a low of 16 ug/ft2 for floor
vacuum dust samples to a high of 1604 ug/ft2 for window
channel samples.
Lead Concentrations. Geometric mean lead concentrations
varied in unabated houses from lows of 86 ug/g for boundary
and foundation soil samples and 137 ug/g for floor vacuum
dust samples to a high of 851 ug/g for window channel dust
samples.
Results from modeling geometric mean lead loadings by housing
category are provided in Table 1-8 for floor, window stool, and
window channel samples based on an estimation procedure outlined
in Section 3 (EPA, 1995b). This procedure uses the ratio
estimates presented in columns 4, 5, and 6 of Table 1-5, along
with exponents reflecting typical proportions abated by each
method.
Table 1-8.
Modeled Geometric Mean Lead Loadings by House Type
for Floor, Window Stool, and Window Channels
(ug/ft2)
Sample Type
Floor
Window Stool
Window Channel
Unabated
16.2
38.1
1604
Abated
28.5
70.1
1379
Removal
17.3
36.5
2134
E/E
35.0
91.7
1152
Comparisons with HUD and EPA Standards
In addition to comparing relative lead levels among
unabated, E/E, and removal houses, these levels in each housing
36
-------
category can be compared against "Lead-Based Paint: Interim
Guidelines for Hazard Identification and Abatement in Public and
Indian Housing" (HUD, 1990b) abatement clearance standards.
These standards for floor, window stool, and window channel dust
samples are 200, 500, and 800 ug/ft2. The EPA has proposed a
reduced standard of 100 ug/ft2 for floors, maintaining the 500
ug/ft2 and 800 ug/ft2 standards for window stools and window
channels, respectively (EPA, 1994). Geometric mean floor vacuum
lead loadings for unabated houses, abated houses, E/E houses, and
removal houses were all well below the EPA standard of 100
ug/ft2. Similarly, geometric mean window stool lead loadings for
these four classes of houses were well below the HUD/EPA standard
of 500 ug/ft2. In addition, for both of these sample types, more
than 75 percent of the samples collected in the CAP Study had
lead loadings below their respective standards, in both abated
and unabated houses. However, geometric mean window channel lead
loadings at both abated and unabated houses were found to be well
above the HUD/EPA interim standard of 800 ug/ft2, and well over
half of individual observations were above this standard, at both
abated and unabated houses. It is interesting to note that
modeled window channel lead loadings in typical abated houses
were actually lower than those for the unabated houses; and that
lead loadings were lower in houses abated by encapsulation/
enclosure methods than in houses abated by removal methods.
However, the variability in both of these measures prevented
either of these differences from being declared statistically
significant.
Coitipaxisons with. Other Studies
Lead levels observed in the CAP Study were usually
equivalent to, or below, levels observed in several other
studies, with one notable exception being the HUD National
37
-------
Survey. Table 1-9 presents lead loadings in floor, window stool,
and window channel samples for the CAP Study and four other
studies. Along with the geometric mean lead loadings, these
38
-------
Table 1-9.
Descriptive Statistics for Lead Levels Observed
in Various Field Studies
Sample
Type
Study
House Type
Sample
Size
25%
Geom.
Mean
75%
High XRF(21
Low XRF(3)
Traditional
Abatement
Modified Abatement
Traditional
Abatement
Modified Abatement
Traditional
Abatement
Modified Abatement
na
na
na
na
na
na
na
na
na
5.13
1.41
na
na
na
na
na
na
HUD
Demonstration'
National Survey
High XRF(21
Low XRF(31
329
38
Traditional
Abatement
Modified Abatement
Traditional
Abatement
Modified Abatement
Traditional
Abatement
Modified Abatement
na
na
na
na
na
na
na
na
na
na
na
na
HUD
Demonstration1
National Survey
High XRF(:
Low XRF(3)
Traditional
Abatement
Modified Abatement
Traditional
Abatement
Modified Abatement
Traditional
Abatement
Modified Abatement
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
39
-------
tables also present the 25th and 75th percentile lead loadings
when they were available. The following main conclusion can be
made from this table:
Comparison with Other Studies. CAP Study lead loadings were
at or below those in the other studies, with three
exceptions. First, the CAP Study geometric mean window
channel lead loadings (approximately 2500 ug/ft2) were
significantly higher than those recorded for the HUD
Demonstration Study (approximately 500 ug/ft2) . Second, for
floor, window stool, and window channel samples, the CAP
Study geometric mean lead levels were typically at least an
order of magnitude higher than for National Survey samples.
Third, CAP Study geometric mean lead loadings for window
channels were approximately twice as high as post-abatement
levels in the second Kennedy-Krieger Study.
The greater observed window channel lead loadings might be due to
the fact that the CAP Study sampled only in Denver, while the HUD
Demonstration Study sampled in Denver and six other metropolitan
areas. The difference might also be due to increased sample
recovery achieved in the CAP Study using cyclone vacuum sampling
as opposed to the HUD Demonstration Study wipe sampling. Also,
it may be that lead re-accumulated from sources, such as soil and
air ducts, in the period between abatement and sampling, or that
CAP Study houses were dustier due to differences in cleaning
practices.
The second case in which CAP Study lead loadings were
relatively high was in comparison with HUD National Survey
results. For floor, window stool, and window channel samples,
the CAP Study lead levels were typically at least an order of
magnitude higher than for National Survey samples. Some of these
differences are accounted for by low sample recoveries obtained
in the HUD National Survey. Vacuum versus wipe field testing by
40
-------
EPA (EPA, 1995a) indicated that the vacuum sampling protocol used
in the HUD National Survey recovered only about 20% of the lead
dust that would be recovered by a wipe sample. Wipe sample
results tended to be less than or equivalent to those from the
CAPS vacuum sampler. Hence there is likely to be at least a five
fold difference between CAPS vacuum dust results and National
Survey vacuum dust results, which would account for some of the
differences in lead loadings between the CAP Study and the
National Survey.
1.3.3 Correlation of Lead Levels in Different
Media and Locations
The third objective of the CAP Study was to investigate the
relationship between lead levels in different media (i.e., dust
and soil) and different sampling locations (e.g., floors, window
channels, foundation soil). These relationships were quantified
by between-house and within-house correlation coefficients.
Between-house correlations reflect house-to-house relationships
among different sample types, such as between air ducts and
window channels. Within-house correlations are similar measures,
except they are based on room-to-room differences within a house,
after controlling for house average lead levels. For some pairs
of sample types (e.g., entryway interior and floor vacuum), there
were insufficient data available to estimate the within-house
correlations after fitting the statistical model. Correlation
coefficients were calculated for both lead loadings and lead
concentrations. However, only a relatively small number of
correlation coefficients were found to be significant. The
significant relationships found are presented in Table 1-10 and
summarized in the following points:
Between-House Correlations for Lead Loadings. At the house
level, significant correlations in dust lead loadings were
found for three pairs of sample types. These were between
window channels and window stools (correlation coefficient
41
-------
of 0.56), between air ducts and exterior entryways (0.41),
and between floor (wipe) samples and exterior entryways
(0.44) .
Between-House Correlations for Lead Concentrations.
Significant correlations in lead concentrations at the house
level were found for four pairs of sample types. These were
between lead concentrations in window channel and window
stool dust (0.40), between entryway soil and boundary soil
(0.56), between boundary soil and window stool dust (0.38)
and between entryway soil and interior entryway dust (0.29).
42
-------
Table 1-10. Significant Between-House and Within-House
Correlations
Response
Between-House
Lead Loading
Between-House
Lead
Concentration
Within-House
Lead Loading
Within-House
Lead
Concentration
Correlated Sample Types
Air duct and exterior
entryway dust
Window channel and window
stool
Floor (wipe) and exterior
entryway dust
Window channel and window
stool
Window stool and boundary
soil
Interior entryway and
entryway soil
Entryway soil and
boundary soil
No significant
correlations
Interior entryway and
exterior entryway dust
Correlation DF* Significance
0.41 36 .01
0.56 41 <.01
0.44 27 .02
0.40 41 .01
0.38 44 .01
0.29 44 .05
0.56 44 <.01
- - -
0.37 31 0.03
Within-House Correlations. At the room level, no
significant correlations in dust lead loadings were found.
However, significant correlation was observed between
interior and exterior entryway dust lead concentrations
(0.37) .
The reader should note that there were a total of 50
correlation tests performed. With a 5 percent significance
level, one could expect about two to three significant
relationships simply by chance. A total of eight significant
correlations were identified.
This column lists the degrees of freedom available to estimate
correlation after controlling for significant model factors.
43
-------
1.3.4 Comparison oŁ Cyclone and Wipe Dust Sampling
A final objective of the CAP Study, which was not originally
stated at the study design stage but which evolved during the
course of the study, was to compare the performance of two dust
sampling protocols: cyclone vacuum sampling and wipe sampling.
The results of this comparison are presented in Table 1-11, and
can be summarized as follows:
Vacuum vs. Wipe Ignoring Substrate. Lead loadings from
side-by-side wipe and (cyclone) vacuum dust samples were not
significantly different when pooled across the various
substrates sampled in the CAP Study.
Vacuum vs. Wipe by Substrate. The performance of these two
sampling protocols was found to be different for different
substrates. On tile and linoleum surfaces cyclone vacuum
lead loadings were not found to be significantly different
from wipe lead loadings. Cyclone lead loadings were higher
than wipe lead loadings on wood surfaces (3.9 times higher).
The 95% confidence interval for the ratio of vacuum to wipe
recovery on wood was 1.13 to 13.59.
Table 1-11. Vacuum/Wipe Multiplicative Bias Estimates
Substrate
Tile
Linoleum
Wood
Combined
Sets of
Observations
5
18
9
33
Estimated
Vacuum/wipe
Multiplicative
Bias
0.69
1.02
3.92
1.38
Lower
Confidence
Bound
0.12
0.42
1.13
0.75
Upper
Confidence
Bound
3.90
2.44
13.59
2.54
1.3.5 Results of the Quality Control and Data
Verification Procedures
Results of the quality control (QC) procedures confirmed
that the sampling and analytical protocols employed in the CAP
Study produced data of sufficient quality. Analysis of the blank
samples suggested little if any procedural contamination. The
majority of blanks were measured with a lead content below the
44
-------
instrumental level of detection. Despite some procedural
problems in their creation and analysis, the results for the
recovery samples indicated very good method performance. Spiked
duplicate samples created in the laboratory exhibited very good
agreement. Finally, there was no significant evidence of a time-
based trend in any of the QC samples.
Additional data verification procedures included a
laboratory review of potential outliers statistically identified
in the data, an audit of the data management system, and a
laboratory quality assurance audit. The results of these
procedures further verified the accuracy of the data upon which
the analyses were based. Moreover, a statistical analysis audit
confirmed that the reported statistical analyses were correctly
performed.
The inherent variability between field samples, however, was
evident in the results of the side-by-side field samples.
Despite being collected side-by-side, a number of the pairs were
measured to have very different lead contents. Greater inherent
variation was seen in dust samples than in soil samples. The
median ratio of the larger to the smaller of two side-by-side
vacuum dust lead loadings in the CAP Study was about 2.33. The
median ratio for lead concentrations was 2.07. These results
suggest that studies to assess abatement performance and
potential lead hazards must be carefully designed to control for
these complicating sampling variations. For example, random
selection of sampling locations was incorporated into the CAP
Study design to eliminate biases in sample selection.
1.4 DISCUSSION
The CAP Study demonstrated that an accurate assessment of
potential lead hazards can be seriously complicated by the high
degree of variability commonly found in environmental lead
45
-------
measures. Lead determinations can depend heavily on the sampling
and analysis procedures used, and they can vary greatly among
similar housing environments and among different sampling
locations within a single housing environment.
Pre- vg . PQSt-.Abatement Lead Levels
The CAP Study included two approaches for assessing
abatement efficacy, one direct approach and one indirect
approach. The results of the CAP Study from the direct approach
of comparing post-abatement and pre-abatement lead levels were
that for the two sample types for which a comparison was
possible, abatement appears to have been effective, in the sense
that there is no evidence that post-abatement lead levels were
significantly higher than pre-abatement levels. This result is
based on dust lead measurements made on window stools at 10 CAP
Study abated houses, as well as soil lead measurements made at 24
CAP Study abated houses. Several floor dust samples were also
available for comparison, but were deemed insufficient for making
substantive conclusions.
These results indicate that while the abatements may not
have reduced lead levels in dust and soil from their pre-
abatement condition, the abatements were successfully performed
without raising lead levels in these two media. This finding is
significant since the pre-abatement lead levels in dust and soil
were already relatively low in comparison with levels found by
other field studies. However, these results are tempered by the
fact that because of the small number of houses for which data
were available, as well as the large variability in observed lead
levels, relatively large differences between post-abatement and
pre-abatement lead levels could not be judged to be statistically
significant. For example, the confidence interval about an
average ratio of post-abatement to pre-abatement levels on window
46
-------
stools was 0.37 to 3.46, indicating that three-fold differences
would be judged insignificant. In addition, further complicating
the comparison of post-abatement and pre-abatement dust and soil
lead measurements was the fact that different sampling and
analysis protocols were used in the CAP Study and HUD
Demonstration. Perhaps most significantly, the CAP Study
utilized vacuum dust sampling while the HUD Demonstration
utilized wipe dust sampling.
Lead Levels in .Abated vs. Unabated Houses
The indirect assessment of abatement efficacy also found
that abatement appears to have been effective, in this case in
the sense that there is no evidence that post-abatement lead
levels at abated houses were significantly different from lead
levels at neighboring unabated houses found to be relatively free
of lead-based paint. There were two exceptions to this
statement; however, both of these exceptions were anticipated and
are logically explained. First, lead concentrations in air ducts
were significantly higher in abated houses than in unabated
houses; air ducts were not abated in the HUD Demonstration. In
addition, lead concentrations in the soil outside abated houses
were significantly higher at the foundation and at the boundary
than corresponding lead concentrations outside unabated houses.
This difference between soil lead concentrations at abated and
unabated houses was significantly more pronounced near the
foundation than it was at the boundary. This suggests that these
contrasts are due at least in part to lead-based paint at the
abated houses. However, soil also was not abated during the HUD
Demonstration; and these higher lead levels might in part be due
to differences in the age of these houses, since on average the
abated houses in this study were 17 years older than unabated
houses. As with the caveat stated above, these results must also
47
-------
be tempered by the fact that not finding a significant difference
in lead levels at abated and unabated houses for all other
building components and sampling locations does not prove that no
such differences exist. The CAP Study was designed to detect
approximately two-fold differences between lead levels at abated
and unabated houses under specified variance assumptions. For
example, although the estimate of 1.76 for the ratio of lead
loadings on floors in abated to unabated houses was not
significantly different from one, the 95 percent confidence
interval was from about 0.87 to 3.5.
Comparison of Abatement Methods
The CAP Study also assessed abatement by comparing
encapsulation and enclosure methods versus removal methods. No
significant differences among lead levels could be attributed to
these two types of abatement methods, except for air ducts which,
as stated above, were not abated. Air duct dust lead levels were
higher in houses abated primarily by encapsulation and enclosure
methods than in houses abated primarily by removal methods. The
CAP Study also performed a visual inspection of abated surfaces
and recorded their condition as being completely intact,
partially intact, or minimally intact. Less than 60% of the
surfaces abated by encapsulation and chemical stripping methods
were found to be completely intact, while more than 70% of the
surfaces abated by all other methods were found completely
intact.
These results suggest that both encapsulation/enclosure and
removal abatement methods can be performed in residential housing
environments without depositing significant amounts of residual
lead in dust and soil. Of course, proper dust control procedures
must be employed while conducting any lead-based paint hazard
abatement. However, while dust and soil lead levels were not
48
-------
found to be significantly different two years after abatement,
there is some indication from the visual inspection information
that residual problems may be seen in the future at locations
abated with encapsulation and chemical stripping methods.
Characterization of Lead Levels
With regard to the second study objective, lead levels were
found to vary greatly for different media and sampling locations.
Dust lead loadings were also evaluated in comparison with the HUD
and EPA interim dust clearance standards. Geometric mean floor
lead loadings at both abated and unabated houses were below the
EPA standard of 100 ug/ft2. Geometric mean window stool lead
loadings were found to be below the HUD/EPA interim standard of
500 ug/ft2. In addition, for window stools in both abated and
unabated houses, and for floors in unabated houses, more than 75
percent of the samples collected in the CAP Study had lead
loadings below their respective standards, in both abated and
unabated houses. The 75th percentile of floor lead loadings in
abated houses was about 104 ug/ft2. However, geometric mean
window channel lead loadings at both abated and unabated houses
were found to be well above the HUD interim standard of 800
ug/ft2, and well over half of individual observations were above
this standard, at both abated and unabated houses.
Most of the samples in the CAP Study were collected by a
vacuum method of dust collection. Clearance samples are usually
collected by a wipe method. In the CAP Study comparison of
vacuum and wipe methods, wipes tended to produce either
equivalent or lower lead levels than the vacuum used in the CAP
Study, with the most pronounced difference on wood substrates.
The CAP Study vacuum samples resulted in geometric mean lead
loadings that were less than the clearance standards for floors
and window stools. From the relationship between wipe and vacuum
49
-------
samples demonstrated in the CAP Study, it is plausible to infer
that wipe samples would also produce geometric mean lead loadings
less than the clearance standards for floors and window stools.
However, for window channels, the CAP vacuum samples were
generally above the clearance standard. Because of the
difference between vacuum and wipe samples, especially on wood,
it is not clear that wipe samples on window channels would exceed
the clearance standard.
Overall Assessment oŁ
The CAP Study found no significant differences between post-
abatement and pre-abatement lead levels for exterior soil and the
limited number of window stool dust lead measurements available.
It also found no significant differences between post-abatement
lead levels at abated houses and lead levels at unabated houses,
with the exception of air duct dust and soil which were not
abated in the HUD Demonstration. In addition, for both floors
and window stools the geometric mean lead loadings at abated
houses were well below the HUD standards of 200 and 500 ug/ft2.
These results all suggest that the HUD abatement activities were
effective, in the sense that they do not appear to have increased
lead levels at abated houses above interim standards. However,
the CAP Study also found that the geometric mean lead loading for
window channels at abated houses was well above the HUD interim
standard of 800 ug/ft2, although the same result was found for
unabated houses relatively free of lead-based paint.
Correlations Among Media and Sampling Locations
Three primary conclusions were found for the third CAP Study
objective. First, significant correlations in lead
concentrations at the house level were found for four pairs of
sample types: window channels and window stools (correlation
50
-------
coefficient of 0.40), entryway soil and boundary soil (0.56),
boundary soil and window stools (0.38), and entryway soil and
interior entryway dust (0.29) . Second, at the house level,
significant correlations in dust lead loadings were found for
three pairs of sample types: window channels and window stools
(0.56), air ducts and exterior entryway dust (0.41), and floor
(wipe) dust and exterior entryway dust (0.44) . And third, at the
room level, no significant correlations in dust lead loadings
were found. However, significant correlation was observed
between dust lead concentrations at interior and exterior
entryways (0.37) . House level correlations were based on house
averages; room level correlations were based in most cases on
single measurements.
The fact that significant correlations were found in the CAP
Study suggests that lead may be redistributed over time
throughout a residential housing environment. However, the fact
that more house-level correlations were significant suggests that
overall lead levels are more related to broad differences among
houses than to location-specific characteristics within houses.
Cyclone Vacui-Hn vs . Wipe Dust Sampling
Combined across substrates, the difference between dust lead
loadings measured by the cyclone vacuum method and by the wipe
method was not significant. Differences were overshadowed both
by large side-by-side variability in the two methods, and a
strong substrate effect. This latter effect was apparently
related to the smoothness of the substrate. On tile and
linoleum, the two methods were approximately equivalent, whereas
on wood lead loadings measured by the cyclone were higher than
those measured by wipe. Thus, the level of lead measured depends
on the way in which it is collected. This study has led to
several subsequent investigations of dust collection methods,
51
-------
including the Rochester Study of the relationship between
different dust collection methods and children's blood lead
levels, and an EPA laboratory study of different dust collection
methods.
Future Research
Several research issues have been raised but not addressed
by the CAP Study. The two main issues are discussed in this
section.
There has been no direct assessment of the relationship
between health risks and the environmental sampling being
performed in the CAP Study. In the CAP Study, an implicit
assumption was made that health risks are correlated with dust
and soil lead levels at residences. No blood or other health-
based observations were made at the houses sampled in the CAP
Study, precluding the assessment of abatement efficacy with
respect to the prevention of health risks.
The methods used for abatement in the CAP Study were
generally expensive. Removal and enclosure methods can be
particularly costly. Other less costly approaches to abatement
such as regular wet mopping, dust cleaning, paint stabilization,
and in-home education deserve consideration and study.
Other ongoing studies are investigating the efficacy of less
costly means of abatement. These include a dust cleaning
products study, the Repair and Maintenance Study in Baltimore,
the Milwaukee Low-Cost Efficacy Study, and additional low-cost
abatement studies in other cities co-funded by EPA and the
Centers for Disease Control and Prevention.
52
------- |