f/EPA
United States
Environmental Protection
Agency
National Exposure Research
Laboratory
Research Triangle Park, NC 27711
September 1997
Research and Development
EPA/600/R-95/112
An Intercomparison of
Grinding Techniques Used for the
Preparation of Lead-in-Paint Samples
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An Intercomparison of Grinding Techniques
Used for the Preparation of Lead-in-Paint Samples
Prepared For:
Work Assignment Manager
S. L. Harper
National Exposure Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
EPA Contract Nos. 68-D1-0009 and 68-D5-0040
RTI Project Nos. 91U-6660-014/91U-6970-255
Prepared By:
L. L. Hodson, E. D. Hardison, A. A. Leinbach,
M.. J. Messner, D. A. Binstock, and W. F. Gutknecht
Center for Environmental Measurements and Quality Assurance
Research Triangle Institute
Research Triangle Park, NC 27709-2194
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DISCLAIMER
The information in this document has been funded wholly or in part by the
United States Environmental Protection Agency (U.S. EPA) under EPA Contract Nos.
68-D1-0009 and 68-D5-0040 to Research Triangle Institute (RTI). It has been
subjected to the Agency's peer and administrative review, and it has been approved
for publication as an EPA document. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
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ACKNOWLEDGMENT
This document was prepared under the direction of Ms. Sharon L. Harper,
National Exposure Research Laboratory (NERL), U.S. Environmental Protection
Agency, Research Triangle Park, NC.
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EXECUTIVE SUMMARY
The method used to grind a dried paint sample prior to acid digestion and
measurement (by inductively coupled plasma (ICP) emission spectrometry or some
other means), may affect the recovery of lead from the paint. In this study, five
grinding techniques were compared. These were: (1) grinding with a glass rod at
room temperature in a 50-mL centrifuge tube, (2) grinding with a glass rod at dry ice
temperature in a 50-mL centrifuge tube, (3) grinding with a mortar and pestle, (4)
grinding with a motorized blender, and (5) grinding with a cryogenic mill that operated
at liquid nitrogen temperature. Preliminary testing of these five different procedures
using 2" x 2" paint samples removed from real-world fiberboard walls and wooden
cabinet boards showed no statistical differences in precision or bias of the measured
lead content when a minimum of 5 minutes of grinding was performed with the
manual methods. The mortar and pestle and the glass rod/room temperature
centrifuge tube techniques were selected for more rigorous examination because of
their relative ease of use. This second phase of the study involved optimizing the
grinding time using 1" x 1" paint samples. Ten out of twelve tests demonstrated no
statistical differences in the lead analysis results between the two methods or
between grinding for 30 seconds versus 5 minutes. In the two statistically different
tests, more lead was recovered from a sample ground with the mortar and pestle than
from a sample ground with the glass rod in a centrifuge tube. When particle size
analyses were conducted on the ground paint samples, it was observed that manual
grinding times beyond 1 Vz minutes did not affect the particle size distribution. Since
ten out of twelve tests had already shown that the lead recovered after 30 seconds
of grinding was equivalent to 5 minutes grinding, no lead measurements were
conducted on the paints ground for 11/z minutes. Based on the particle size results,
it is recommended that a minimum of 1 to 1 % minutes of grinding be performed. .
The ground paint should have the consistency of coarsely ground coffee or cornmeal.
in
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TABLE OF CONTENTS
Section Page
Disclaimer i
Acknowledgment . ii
Executive Summary iii
List of Tables vi
1.0 Introduction 1
1.1 Purpose of the Study 1
1.2 Limitations to the Study 1
1.3 Study Approach 1
2.0 Experimental 3
2.1 Phase I: Description of Grinding Techniques and Analysis 3
2.2 Phase II: Optimization of Mortar and Pestle
and Glass Rod/Room Temperature Procedures 6
3.0 Results 7
3.1 Paint Description 7
3.2 Sample Weight 7
3.3 Quality Assurance 8
3.4 Lead Recoveries 10
3.5 Particle Size 10
4.0 Discussion 18
4.1 Method Overview 18
4.2 Glass Rod/Room Temperature Grinding 18
4.3 Glass Rod/Cryogenic Grinding 20
4.4 Mortar and Pestle 20
4.5 Motorized Mechanical Grinder 20
4.6 Cryogenic Motorized Mechanical Grinder 21
4.7 Lead Recoveries 21
4.8 Particle Size Histograms 22
5.0 Conclusions 23
6.0 References 25
IV
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APPENDICES
Appendix A Diagrams of Cabinet Boards and Wall Sections
Appendix B Phase I Data
Appendix C Phase II Data
Appendix D Statistical Data Interpretations
Appendix E Histograms of Particle Size Distribution
v
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LIST OF TABLES
Table Page
1 Summary of 4-in2 Paint Sample Weights - Phase I 8
2 Summary of 1-in2 Paint Sample Weights - Phase II 8
3 Duplicate Analyses 9
4 Summary of Lead Concentrations Determined Using Various
Paint Grinding Techniques - Phase I 12
5 Results of Analysis of Residue Remaining Following
Microwave Digestion 13
6 Summary of Lead Concentrations Determined Using
Various Paint Grinding Techniques - Phase II 14
7 Particle Size of Ground Paint 15
8 Overview of Five Paint Grinding Techniques 19
VI
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SECTION 1.0
INTRODUCTION
1.1 PURPOSE OF THE STUDY
An early study to evaluate laboratory methods for digestion of paint, soil, and
dust samples showed that the recovery of lead from paint chips was dependent, in
part, upon the extent of the grinding of the paint.1 Finely ground paint chips tended
to yield higher lead levels than crushed paint chips. To test the hypothesis that the
method of grinding may affect the ability to extract the lead from ground paint, five
different procedures for grinding of paint samples were applied to a series of samples;
processing was completed using acid/microwave digestion and analysis by inductively
coupled plasma (ICP) emission spectrometry.1 The grinding procedures tested
included: (1) using a solid glass rod to crush and grind the paint in a centrifuge tube,
(2) using a solid glass rod to crush and grind the paint in a plastic centrifuge tube
while the centrifuge tube was immersed in dry ice, (3) grinding the paint with a glass
mortar and pestle, (4) grinding the paint in a Bel Art Products Micro Mill,2 and (5)
grinding the paint in a Spex freezer mill.3
1.2 LIMITATIONS TO THE STUDY
Paint samples vary greatly in both physical and chemical composition. Paint
sample thickness may vary from a fraction of a millimeter to several millimeters. Paint
samples may be brittle or rubbery; outer layers of multilayered paint are often found
to be latex, which is rubbery and difficult to grind. Due to resource limitations, only
a few different samples of paint were included in this evaluation of grinding
techniques. The conclusions reached with these samples may not apply to all paint
samples.
1.3 STUDY APPROACH
Using a hot-air gun, twenty-five 4-in2 samples of paint were removed from
sections of both wooden cabinet doors and fiberboard walls. A group of five paint
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samples of each type (doors and walls) was randomly assigned to each of the five
grinding procedures (Section 1.1). After each sample was ground, determination of
the concentration of lead was performed. The concentrations of lead for samples
prepared using each of the grinding techniques were statistically evaluated to
determine any differences in bias and precision that could be attributed to the grinding
techniques. Particle analysis was performed on a limited number of the ground
samples.
Preliminary testing on all five methods with 4-in2 paint samples showed no
statistical differences in precision or bias of the measured lead content when a
minimum of 5 minutes of grinding was performed with the manual methods. Two
techniques (the glass mortar and pestle method and the glass rod/plastic centrifuge
tube at room temperature method) were selected for a second phase of testing to
optimize grinding times because of their relative ease of use. This time 1-in2 samples
were collected to match the HUD guidelines.4 The lead concentrations were
statistically evaluated for differences in bias and precision for 30-second versus
5-minute grinding times. Particle size analyses were also conducted on the 30-second
verus 5-minute ground samples. Since the histograms of the particle size distributions
were different for the 30-seconds versus 5-minute samples, several more 4-in2 and
1-in2 samples were selected for grinding 1 - 1 Vz minutes for particle size analyses.
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SECTION 2.0
EXPERIMENTAL
2.1 PHASE I: DESCRIPTION OF GRINDING TECHNIQUES AND ANALYSIS
2.1.1 Removal of Paint Samples
Two wooden cabinet doors and two sections of fiberboard wall taken from
inside two different single family houses were selected as sources of paint samples
for this test. The dwellings, which were built in the 1940's, were also used for an
earlier pilot study for in-situ testing of lead in paint.5 Originally ten inch (10" by 10")
squares were to be drawn on each door and wall section, and each square divided
into twenty-five 2" x 2" squares. However, it was necessary to modify the 10" x
10" square approach to accommodate the dimensions of the wall and board sections
(See Appendix A) to obtain the 4-in2 samples. The 4-in2 sections were numbered and
circumscribed with a scalpel. The paint was then removed using a spatula and a hot-
air gun. The hot air gun [Ungar 6970HD Heavy Duty Gun] was set to the lower
temperature (700°F) and an edge of the section heated just enough to soften the
paint. The softened edge was lifted with a spatula and then more of the paint was
heated. This process was continued until the entire section of paint was removed.
Each sample was placed in a labeled plastic cup. The paint samples were then
weighed. Five groups of five samples from each door and each wall section were
then randomly assigned to the five preparation methods described in the following
sections. Thus each grinding method was used for five paint samples from each of
two cabinet doors and five paint samples from each of two wall sections.
2.1.2 Glass Rod/Room Temperature Grinding
The paint sample was placed in a labeled 50-mL plastic centrifuge tube. Using
a tapered glass rod, the paint was broken into small pieces and then ground for
approximately 5 minutes, using the glass rod like a pestle, until a fine powder (similar
to coarsely ground coffee or corn meal) was obtained. After grinding, the tube
containing the ground sample was capped for storage.
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2.1.3 Glass Rod/Cryogenic Grinding
The paint sample was placed in a labeled 50-mL centrifuge tube and capped.
The tube was immersed 1/3 to 1/z way in a styrofoam cooler containing crushed dry
ice (solid C02). The paint was chilled for 5-10 minutes, and then a tapered glass rod
was used to grind the paint in the tube while it remained immersed in the dry ice.
The paint was ground for 5 minutes until a fine powder (similar to coarsely ground
coffee or corn meal) was obtained. After grinding, the tube was capped and removed
from the dry ice. The paint remained in the tube for storage.
2.1.4 Mortar and Pestle
The paint sample was placed in a clean, glass, 2-ounce mortar and ground with
a glass pestle for 5 minutes until only fine powder (similar to coarsely ground coffee
or corn meal) was obtained. The ground paint was transferred back into a labeled
sample cup.
2.1.5 Motorized Mechanical Grinder
The paint sample was placed in a Bel Art Products Micro-Mill and ground for
30 seconds; this small electric grinder uses a rotating blade to perform the grinding.2
The ground paint was transferred back into a labeled sample cup. The mill was
thoroughly cleaned between samples using a brush and laboratory wipes.
2.1.6 Cryogenic Motorized Mechanical Grinder
The paint sample was placed in a sample tube with a steel impactor rod, the
tube was capped, and the sample was placed in a cryogenic mechanical mill, the
Spex Industries Model 6700 freezer mill.3 The sample was chilled in liquid nitrogen
for 5 minutes and ground for 15 seconds. The cold, brittle paint chips were ground
as the steel impactor rod rapidly moved electromagnetically back and forth along the
length of the plastic sample tube. After allowing a 20-minute warm-up time, the
sample was transferred back into a labeled sample cup.
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2.1.7 Digestion and Analysis
A 0.1 g aliquot of each ground paint sample was weighed into a 50-mL, plastic
centrifuge tube and digested by the Environmental Protection Agency (EPA) National
Exposure Research Laboratory's (NERL's) microwave method prior to analysis by ICP
emission spectrometry.6
2.1.8 Particle Size Analysis
One sample representing each material and each method of grinding described
in Sections 2.1.2 through 2.1.6 was subjected to analysis by polarized light
microscopy (PLM) to determine the average, mode, range and frequency of particle
sizes. In preparation for this analysis, a random pinch of each paint was deposited
in deionized water on a slide, and a cover slip was placed on top. The Olympus BHA
microscope used for the particle analysis was calibrated using a Walton-Beckett
graticule with a stage micrometer. The particle size statistics were performed using
a Microsoft Excel spreadsheet.
2.1.9 Residue Analysis
Wall and board paint samples were selected for an analysis of the residue
remaining following the microwave digestion. Three aliquots were selected from
samples which had been ground using the glass rod/room temperature technique.
The samples were digested, decanted and the remaining residue redigested prior to
analysis. The samples which had been ground using the glass rod/room temperature
technique were then reground using a mortar and pestle, and three aliquots were
removed for normal analysis followed by residue analysis.
A particle size analysis was conducted on the original samples ground with the
glass rod/room temperature technique and those that were reground using a mortar
and pestle.
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2.2 PHASE II: OPTIMIZATION OF MORTAR AND PESTLE AND GLASS
ROD/ROOM TEMPERATURE PROCEDURES
2.2.1 Sample Selection
The Phase II test samples consisted of 1" x 1" pieces of paint removed from
one cabinet door and one wall board previously used in Phase I. Additionally, to
provide information on behavior of an exterior paint with grinding, an exterior board
from a different site dating from the 1950's was used as a third substrate. The
1" x 1" sections were selected for Phase II to more closely match the HUD guidelines
for removal of lead paint verification samples.4 Ten 1" x 1" contiguous areas were
marked on each of the three substrates, numbered, and circumscribed with a scalpel,
and the paint was removed using a spatula and the heat-gun. The paint samples
were weighed and placed in labeled 50-mL plastic centrifuge tubes.
2.2.2 Preparation and Analysis
Five samples from each substrate were assigned to either the mortar and pestle
method or the glass rod/room temperature method. Each 1" x 1" sample was ground
for 30 seconds/a 0.1 g aliquot was removed, and the remaining sample was ground
for 4 1/2 more minutes. A second 0.1 g aliquot was removed from the sample that
had been ground for a total of 5 minutes. The 0.1 g aliquots were digested by the
microwave method and analyzed by ICP emission spectrometry.6
2.2.3 Particle Size Analysis
In Phase II, particle size analyses were conducted on the 30-second and 5-
minute ground samples. Since the average particle size was less for a sample which
was ground for 5-minutes versus 30-seconds, it was decided to determine the
optimum time for obtaining a fine powder of paint similar to the 5-minute samples.
Therefore additional 4-in2 and 1-in2 samples were collected from the three substrates
and ground for 11/2 minutes. These samples were analyzed only for particle size
distributions, since earlier results demonstrated for 10 out of 12 samples that there
was no statistical differences in the amount of lead observed in samples ground for
30-seconds versus 5-minutes.
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SECTION 3.0
RESULTS
3.1 PAINT DESCRIPTION
The paint from the cabinet doors consisted of three layers: white over bright
green over beige. The top layer of white paint was somewhat rubbery compared to
the brittleness of the green and beige paints, and it is presumed that the white paint
was a latex paint while the other two layers were oil-based paints.
the paint from the fiberboard consisted of three layers: white over green over
beige. Again, the white paint was somewhat rubbery compared to the brittleness of
the green and beige paints. It was difficult to remove the paint from the fiberboard
and a thin layer of fibrous fiberboard material remained on the back of the paint
sections. A spatula was used to scrape and remove this material prior to grinding.
The paint on the exterior board consisted of two layers: beige over green. The
beige top layer was somewhat rubbery compared to the brittleness of the green.
3.2 SAMPLE WEIGHT
The paint samples were weighed prior to grinding and removing the 0.1 g
aliquots for digestion. The 4-in2 samples of Phase I weighed an average of 2.3 g for
the wall sections and 1.2 g for the cabinet door sections (see Table 1). The relative
standard deviations (RSD) for n = 25 per substrate were 7.6% and 13.6% for the two
wall sections and 9.7% and 14.3% for the two door sections.
The 1-in2 samples of Phase II (see Table 2) weighed an average of 0.6 g for the
wall sections, 0.3 g for the cabinet door sections, and 0.5 g for the exterior board
sections. The RSD for n = 10 per set ranged from 3.9% to 8.0%.
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TABLE 1.
SUMMARY OF 4-in2 PAINT SAMPLE WEIGHTS - PHASE I
Avg. wt (g)
RSD (%)
n =
Wall Section
6
2.46
7.57
25
Wall Section
7
2.23
13.6
25
Cabinet Door
5
1.31
9.67
25
Cabinet Door
8
0.99
14.3
25
TABLE 2.
SUMMARY OF 1-in2 PAINT SAMPLE WEIGHTS - PHASE II
Avg. wt (g)
RSD (%)
n =
Wall Section 7
0.59
3.89
10
Cabinet Door 5
0.31
7.99
10
Board X
0.52
4.33
10
3.3 QUALITY ASSURANCE
The data quality was assessed three ways, including the analysis of National
Institute of Standards and Technology (IMIST) Standard Reference Materials (SRMs),
the analysis of duplicate samples, and the analysis of blanks. The average recovery
for the NIST 1579 SRM (certified value 11.87% Pb) was 98% and ranged from
92.7% to 101.9% for the six analyses.
One sample for each method on each substrate was selected for duplicate
extraction and analysis. For twenty duplicate pairs, the mean difference in lead
concentration was 0.175% with a range of 0.0% to 0.56% (Table 3). The mean
concentration measured in these duplicates was 2.56% lead.
Six blank extractions were conducted. No lead concentration above the limit
of detection (LOD) of 0.005% lead was observed in the blanks.
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TABLE 3.
DUPLICATE ANALYSES
Grinding
Procedure
Glass Rod,
Room
Temperature
x ± Std. Dev.
Glass Rod,
Dry Ice
x ± Std. Dev.
Mortar & Pestle
x ± Std. Dev.
Bell Art Mill
x ± Std. Dev.
Spex Freezer Mill
x ± Std. Dev.
Sample ID
Wall 6-4
Wall 7-5
Board 5-5
Board 8-1
Wall 6-24
Wall 7-25
Rnarri R-95
Rnarrl o.*)A
Wall 6-7
Wall 7-8
Rnarri R-7
Board 8-8
Wall 6-1 1
Wall 7-12
Board 5-14
Board 8-12
Wall 6-18
Wall 7-1 fi
Board 5-13
Rnarri R-9O
% Pb
Initial
1.59
1.39
3.31
4.41
1.48
1.49
3D9
A. *3*3
1.87
0.708
9 QR
4.49
1.66
1.06
3.39
3.46
1.64
1 94
3.63
A CQ
% Pb
Duplicate
1.62
1.02
3.45
4.97
1.25
1.49
) 00
A 91
1.81
0.653
) C7
4.36
1.76
1.34
3.63
3.52
1.74
1 *3n
3.81
44.1
Difference
in % Pb
0.03
0.37
0.14
0.56
0.28 ± 0.24
0.23
0.00
01 Q
01 9
. 1 f.
0.14 ± 0.10
0.06
0.055
OA1
0.13
0.16 ± 0.17
0.10
0.28
0.24
0.06
0.17 ± 0.11
0.10
Onfi
0.18
01 ft
0.13 ± 0.06
Relative %
Difference
1.89
36.3
4.23
12.7
13.8 ± 15.7
18.4
0.0
671
. / I
2QC
.OO
6.99 ± 8.09
3.31
8.42
ICQ
2.98
7.67 ± 6.06
6.02
26.4
7.08
1.73
10.3 ± 10.9
6.10
4QA
.O'r
4.96
A r\o
4.99 ± 0.83
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3.4 LEAD RECOVERIES
The lead concentrations determined from paint samples ground using the five
techniques in Phase I are summarized in Table 4. Statistical interpretations included: (1)
an examination of the structure of error, which concluded that using the BSD rather than
the standard deviation (SD) was valid: (2) an F-test on In-transformed computed
variances: and (3) a Youden test for ranking.7 These statistical interpretations (Appendix
D) showed no differences for the Phase I study in terms of bias and precision between
the five grinding techniques.
An analysis of the residue remaining following the microwave digestion was
conducted for 12 samples. In all cases, the lead content of the residue was less than 2%
of the lead content of the initial extract (Table 5).
Table 6 is a summary of Phase II results, comparing the two grinding techniques
and optimizing grinding times. Student's t-test was utilized to determine if there was a
difference in lead concentration dependent upon (1) grinding time (30 seconds versus 5
minutes) or (2) grinding technique (mortar and pestle versus glass rod/room temperature).
Statistically significant differences at the 95% confidence limit were observed for two out
of 12 tests. A statistically significant difference was observed for the 30-second grinding
of Board X, with 4.9% lead in the paint ground using the glass rod/room temperature
technique and 7.1% lead in the paint ground using the mortar and pestle technique. A
statistically significant difference was also observed for the 5-minute grinding of Cabinet
Door 5, with 3.5% lead in the paint ground using the glass rod/room temperature
technique and 4.6% lead in the paint ground using the mortar and pestle technique. No
other significant differences were noted; i.e., a grinding time of 5 minutes versus 30
seconds did not statistically alter the concentration of lead in the paint for any of the
three substrates tested.
3.5 PARTICLE SIZE
Paint samples representing each substrate type and grinding method and grinding
method combination were analyzed by PLM at 400x. The particle sizes, shown in Table
7 and presented as histograms in Appendix E, ranged from 0.9 to 634 microns (//m). The
10
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mode (most frequent value) ranged from < 1.2 //m to 24//m. In general, the glass
rod/centrifuge tube at room temperature and the 30-second mortar and pestle techniques
yielded larger average particle sizes than the methods using either longer grinding times
or mechanical grinders (see histograms in Appendix E). Comparison of the particle size
distributions resulting from both the 2" x 2" and 1" x 1" starting materials from Wall
Section No. 7 and Cabinet Door No. 5 showed similar mean sized particles.
11
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TABLE 4.
SUMMARY OF LEAD CONCENTRATIONS DETERMINED USING VARIOUS PAINT GRINDING TECHNIQUES
PHASE I
Grinding
Technique
A) Glass Rod
X
RSD (%)
B) Dry Ice/Glass Rod
X
RSD(%)
C) Mortar & Pestle
X
RSD(%)
D) Bel Art Mill
X
RSD{%)
E) Spex Freezer
X
RSD(%)
Wall Section 6
(n = 5)
% Pb mg Pb/cm2
1.87 1.82
16.1 21.9
1.72 1.65
14.9 23.5
1.58 1.46
17.5 20.3
1.56 1.54
13.2 19.8
1.50 1.42
5.8 10.7
Wall Section 7
(n = 5|
% Pb mg Pb/cm2
1.30 1.12
17.8 21.9
1.28 1.13
16.9 31.6
1.14 0.985
30.4 42.5
1.14 1.00
29.3 42.0
1.18 1.07
18.3 18.8
Cabinet Door 5
(n = 5)
% Pb mg Pb/cm2
3.83 2.03
18.9 20.5
3.58 1.81
11.6 14.9
3.51 1.77
23.7 34.0
3.52 1.76
10.0 11.5
3.74 1.92
15.8 19.4
Cabinet Door 8
(n = 5)
% Pb mg Pb/cm2
4.1 1.66
11.4. 15.2
4.02 1.54
24.5 21.8
4.40 1.67
11.1 31.2
3.30 1.19
11.4 16.0
4.94 1.87
6.9 12.3
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TABLE 5.
RESULTS OF ANALYSIS OF RESIDUE REMAINING
FOLLOWING MICROWAVE DIGESTION
Substrate
Wall Section 7
Wall Section 7
Wall Section 7
Wall Section 7
Wall Section 7
Wall Section 7
Cabinet Doors
Cabinet Doors
Cabinet Doors
Cabinet Doors
Cabinet Doors
Cabinet Doors
Sample
Aliquot No.
5a
5b
5c
5d
5e
5f
8a
8b
8c
8d
8e
8f
Grinding Technique
Glass Rod/Centrifuge Tube8
Glass Rod/Centrifuge Tube8
Glass Rod/Centrifuge Tube8
Mortar & Pestle"
Mortar & Pestle"
Mortar & Pestle"
Glass Rod/Centrifuge Tube"
Glass Rod/Centrifuge Tube8
Glass Rod/Centrifuge Tube8
Mortar & Pestle"
Mortar & Pestle"
Mortar & Pestle"
/ug Pb
Sample
829
860
854
917
1,020
935
6,040
4,390
3,890
3,630
4,110
3,920
MO Pb
Residue
14.3
14.5
10.8
11.1
18.6
10.8
10.8
82.3
70.0
41.8
46.0
59.2
Residue as % of
Total Pb
1.8
1.7
1.3
1.2
1.8
1.2
1.8
1.9
1.8
1.2
1.1
1.5
a.
Samples were initially ground for 5 minutes using a glass rod/centrifuge tube method and three aliquots
removed for analysis.
b. The samples that were initially ground for 5 minutes using a glass rod/centrifuge tube method were
reground using a mortar and pestle for 3 minutes and three aliquots removed for analysis.
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TABLE 6.
SUMMARY OF LEAD CONCENTRATIONS DETERMINED USING VARIOUS
PAINT GRINDING TECHNIQUES - PHASE II
(n = 5)
A) Glass Rod/Centrifuge Tube
t = 30 seconds
X
RSD(%)
B) Glass Rod/Centrifuge Tube
t = 5 minutes
X
RSD(%)
C) Mortar & Pestle
t = 30 seconds
X
RSD(%)
D) Mortar & Pestle
t = 5 minutes
X
RSD(%)
Wall Section 7
1.12
8.8
1.01
9.0
1.03
12.2
1.06
10.8
Cabinet Door 5
3.68
18.4
3.53
26.9
4.44
16.5
4.61
14.7
Board X
4.86
13.9
5.18
6.4
7.07
21.1
6.13
15.6
14
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TABLE 7.
PARTICLE SIZE OF GROUND PAINT
Procedure
Glass Rod,
Room Temperature, 5 min
Glass Rod reground by
Mortar & Pestle,
5 min + 3 min
Glass Rod/Dry Ice, 5 min
Mortar & Pestle, 30 s
Mortar & Pestle, 1 .5 min
Mortar & Pestle, 1 .5 min
Mortar & Pestle, 5 min
Bel Art Mill, 30 sec
Spex Freezer Mill, 1 5 sec
Wall Section 7
Particle
Diameter
X, urn
40.9
17.5
23.9
50.7
15.8
11.4
9.7
13.5
10.2
s
32.4
25.1
22.6
54.5
36.0
35.0
8.4
8.8
14.7
Mode
24
6
12
9.2
<1.2
2.4
6
6
2.4
Range
Um)
2.4 - 204.0
1.2- 150.0
1.2 - 120.0
6.1 -314.2
<1.2- 186.0
<1.2 -324.0
1.2 -44.4
1.2-42.0
1.2- 126.0
Sample
Size (in2)
4
4
4
1
1
4
4
4
4
Note: Mode is the most frequent value in a data set.
15
-------
TABLET. CONTINUED
PARTICLE SIZE OF GROUND PAINT
Procedure
Glass Rod,
Room Temperature, 5 min
Glass Rod reg round by
Mortar & Pestle,
5 min + 3 min
Glass Rod/Dry Ice
Mortar & Pestle,
30s
Mortar & Pestle, 1.5 min
Mortar & Pestle, 1 .5 min
Mortar & Pestle,
5 min
Bel Art Mill, 30 sec
Spex Freezer Mill, 1 5 sec
Wooden Cabinet Door 5
Particle
Diameter
X Cum)
34.5
21.5
17.4
61.0
11.7
10.0
15.4
14.8
13.7
s
107.0
34.1
29.0
56.0
32.3
19.0
23.7
26.8
23.7
Mode
3.1
1.5
3.1
12.1
1.2
<1.2
3.1
3.1
6.1
Range
(/urn)
0.9 - 634.4
1.5-201.3
1.5- 152.5
3.1 -292
1.2-198.0
<1.2 -120.0
1.5- 167.8
1.5- 183.0
0.9- 152.5
Sample
Size (in2)
4
4
4
1
1
4
4
4
4
Note: Mode is the most frequent value in a data set.
16
-------
TABLE 7. CONTINUED
PARTICLE SIZE OF GROUND PAINT
Procedure
Mortar & Pestle,
30 sec
Mortar & Pestle, 1.5 min
Mortar & Pestle,
5 min (Trial 1)
Mortar & Pestle,
5 min (Trial 2, new sample)
Board X
Particle Diameter
X Um)
51.9
6.3
51.9
8.4
s
50.4
16.2
44.5
11.6
Mode
24.4
1.2
24.4
<1.2
Range
(//m)
6.1 -375.2
1.2- 156.0
3.0 - 244
< 1.2 -90.0
Sample
Si7ft (in2!
1
1
1
1
Note: Mode is the most frequent value in a set of data.
17
-------
SECTION 4.0
DISCUSSION
4.1 METHOD OVERVIEW
The five paint grinding techniques vary in performance parameters. An
overview of the grinding techniques is presented in Table 8.
4.2 GLASS ROD/ROOM TEMPERATURE GRINDING
This method is relatively easy to perform. No electrical power is required.
There is minimal opportunity for contamination because the sample remains in the
collection/storage tube and a clean glass rod is used for each sample. To obtain a
fine, uniform powder from the paint, approximately 5 minutes of grinding time was
necessary. The consistency of the final product depends on the characteristics of the
dried paint, the grinding time, and the individual pressure applied. The latex paint in
these samples could not be ground into a fine powder but ended up as small chips
1-2 mm in diameter with a rubber-like consistency. The fact that the latex paint
material was not ground as finely as the oil-based paint material did not present a lead
measurement problem because the latex usually contains little lead; that is, reduced
extraction efficiency with the larger latex particles was not expected to significantly
affect the overall lead analysis result. However, the larger latex particles did affect
attempts at subsampling. It was difficult to remove a subsample that had a mixture
of small oil-based particles and larger latex-based particles that was representative of
the original paint sample. That is, representative subsampling was difficult to
achieve. The wall board paint chips (which had a backing similar to cardboard) also
were difficult to grind. Also, the paint particles became electrostatically charged and
accumulated at the top of the plastic centrifuge tube.
18
-------
TABLE 8.
OVERVIEW OF FIVE PAINT GRINDING TECHNIQUES
Equipment/Material
Approximate Costs in 1997
Time to process one sample
(condition, grind, cleanup)
Electricity requirements
Safety considerations
Skill level
* least *** most
Opportunity for
contamination
Minimum sample size
Maximum sample size
Sample transfer from
collection container?
Glass Rod/
Centrifuge
Tube at Room
Temp.
~$1.00
<5 min.
No
No
*
No
~0.2 g
~8g
No
Glass Rod/
Centrifuge
Tube in Dry
Ice
~$1.00
(plus cost of
dry ice)
14 min.
No
Dry Ice
**
No
~0.2 g
~8g
No .
Mortar
and
Pestle
$14.00
(glass)
<5 min.
No
No
*
Minimal
~0.2 g
~8g
Yes
Bel Art
Products
Mill
$800-
$1000
15 min.
Yes
No
*
Yes
~0.5 g
-8g
Yes
Spex
Freezer
Mill
~ $3,000
(plus cost
of liquid
nitrogen)
20 min.
Yes
Liquid
Nitrogen
***
Yes
-0.2 g
~4g
Yes
19
-------
4.3 GLASS ROD/CRYOGENIC GRINDING
This method was very similar to the room temperature grinding. One
disadvantage to this method is the requirement of an ice bucket and dry ice. The
centrifuge tube was immersed in the dry ice for up to 10 minutes prior to grinding.
This increases the preparation time, unless an assembly line approach is taken; i.e.
Samples No. 2 and No. 3 can be chilled while Sample No. 1 is being ground.
Handling dry ice also requires the use of gloves and safety glasses. These samples
were not as electrostatically charged as those ground at room temperature, but daily
relative humidities were not recorded, and humidity could contribute to the
electrostatic charges observed. Also, there was potential problem of condensation
of water vapor into the cold samples.
4.4 MORTAR AND PESTLE
This classic method of grinding a sample is very effective. A freshly cleaned,
acid-rinsed glass mortar and pestle were used for each sample. Because cleaning
facilities may be limited in the field, several pre-cleaned mortars and pestles are
recommended, increasing the equipment burden. The samples can be ground to a
fine consistency in 1 - 11/2 minutes.
The problems encountered in grinding dried latex paint and paint chips with
wallboard backing were the same as those encountered with the glass rod methods.
The biggest disadvantage of this method is that it can be very tiring when multiple
samples are ground.
4.5 MOTORIZED MECHANICAL GRINDER
The Bel Art Products Mill is similar in design to a "coffee grinder." This mill
was fast, requiring only 30 seconds of grinding time. An external power source
(electricity) is required. The time required to properly clean the mill between samples
can be as much as 5-10 minutes. The possibility for cross-contamination exists
because all paint chips come into contact with the mill. The ground paint chips were
similar in appearance to those from the previously discussed methods in that the latex
20
-------
paint yielded visible small chips in conjunction with the fine powder of the other paint
components.
4.6 CRYOGENIC MOTORIZED MECHANICAL GRINDER
The Spex freezer mill requires electricity and liquid nitrogen. The liquid nitrogen
could be a problem for field use because the reservoir is fairly large (2L) and requires
frequent replenishing. It would be necessary to train the operator in the proper
handling of liquid nitrogen and the use of personal protective equipment.
The paint was placed in a plastic cylinder with a steel impactor rod and then
chilled for 5 minutes. The actual milling time was only 15 seconds, but the sample
cylinder had to be removed and allowed to warm to a reasonable temperature before
handling. This warm up can take up to 20 minutes. If several cylinders and steel
impactor rods were available, this technique could be adapted to an assembly line
approach. The opportunity for cross-contamination occurs if the sample cylinders and
steel rods are not properly cleaned. The paint was ground to a fine powder but,
consistent with the other methods, the latex chips appeared larger in size than the
other paint constituents.
4.7 LEAD RECOVERIES
As stated, statistical analyses in Phase I of the study showed no differences
in the methods in terms of bias and precision. In Phase II, statistically significant
differences were observed for only two out of twelve tests. It is noted in these
evaluations that the RSDs are large, which would impact the statistical analyses.
These large RSDs reflect, at least in part, the variability in lead in paint from location
to location as has been observed in another study.5 Differences in the samples are
reflected in the variations in the weights of the samples of the same area as
presented in Tables 1 and 2. The conclusion about the equivalency of the five
methods is further supported, however, by two other pieces of evidence. First, the
average difference between the pairs of duplicate samples for the five methods (Table
3), with the exception of the glass rod/room temperature technique, are very similar,
21
-------
indicating equivalency of sample homogeneity; they are statistically equivalent at the
95% confidence level. Second, the residue values for the two methods expected to
yield the lowest recoveries (glass rod/room temperature and mortar and pestle) are
less than 2%, indicating greater than 95% recovery.
4.8 PARTICLE SIZE HISTOGRAMS
The physical characteristics of the scraped paint sample appear to affect the
particle size distribution of the ground.sample. The paint removed from the fiberboard
had an outer latex layer that made the sample more "rubbery" and difficult to grind;
the paint from the boards was more brittle and easier to grind.
Histograms showing the particle size distributions for the different grinding
techniques are presented in Appendix E. Immersing the centrifuge tube in dry ice
before grinding with a glass rod reduced the mean particle diameter to approximately
half that obtained by grinding with a glass rod at room temperature for both the wall
and board paint samples. However, there was a more notable effect on the shape of
the histogram for the wall sample than the board sample, with a shift toward smaller
particle sizes. Regrinding the samples by mortar and pestle had a more dramatic
effect on the histogram of the wall sample, resulting in a histogram similar to that for
the board sample that was reground by mortar and pestle.
The histograms from the experiments to determine the effect of grinding time
showed significant differences between 30 seconds and 1.5 minutes of grinding with
the mortar and pestle for both wall and board paint samples. The longer grinding time
reduced the mean particle diameter from 61.6 //m (for 30 seconds) to 11.7 //m for
Cabinet Door 5 and from 51.9 //m (for 30 seconds) to 6.3 //m for Board X. However,
increasing the grinding time from 1.5 minutes to 5 minutes did not. significantly affect
the histograms for either sample.
The Bel Art Mill and the Spex freezer mill ground both samples (Cabinet Door
5 and Wall Section 7) to approximately the same mean particle diameter (10 - 15 //m).
However, the particle size range was larger for the board samples than for the wall
samples ground by each mill.
22
-------
SECTION 5.0
CONCLUSIONS
For Phase I of this study, statistical interpretations, including an F-test on In-
transformed computed variances and a Youden test for ranking, showed no
differences in bias and precision for lead measurements made on samples prepared
by five different grinding techniques when a minimum of five minutes of manual
grinding was used.
For Phase II, two techniques (the mortar and pestle method and the glass
rod/centrifuge tube method at room temperature), were selected to determine
optimum grinding times for three different substrates. Tests demonstrated at the
95% confidence level using Student's t-test, that a minimum of 30 seconds of
grinding yielded lead concentrations equivalent to that obtained after 5 minutes of
grinding for 10 out of 12 comparisons. There was a difference in grinding techniques
as observed in the amount of lead determined after a 30-second grinding, with 7.1 %
lead measured in the sample ground using a mortar and pestle and 4.9% lead
measured in the sample ground by glass rod/centrifuge tube. A similar disparity was
noted after a 5-minute grinding, with 4.6% lead measured in the sample ground by
mortar and pestle and 3.5% lead measured in the sample ground by glass
rod/centrifuge tube. This second finding is in conflict with the statistical
interpretations of the Phase I study.
The mortar and pestle and the glass rod/centrifuge tube (at room temperature)
techniques can be easily adapted to field use. Both techniques require no electricity
and minimal support materials. It is essential that the mortar and pestle and the glass
rod be thoroughly cleaned between paint samples to prevent cross-contamination.
The "optimum" grinding time will depend upon the paint and the individual performing
the grinding (i.e., how much force is exerted on the paint). Histograms showed that
the particle size distributions did not change significantly after 1 % minutes of
23
-------
grinding. Therefore, it is recommended that the paint be manually ground for a
minimum of 1 to 11/z minutes. The ground paint should have the consistency of
coarsely ground coffee or cornmeal.
24
-------
SECTION 6.0
REFERENCES
1. Williams, E. E., D. A. Binstock, J. A. O'Rourke, P. M. Grohse, and W. F. Gutknecht.
Evaluation of Hotplate- and Microwave-Based Methods for Extracting Lead in Paint,
Dust, and Soil with Measurement by Atomic Absorption Spectrometry and
Inductively Coupled Plasma Emission Spectrometry. EPA 600/R-94/147, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1995, 98 pp.
2. Bel Art Micro-Mill. Bel-Art Products, 6 Industrial Rd., Pequannock, NJ, 07440, (201)
694-5000.
3. Spex Freezer Mill. Spex Industries, Inc., 3880 Park Avenue, Edison, NJ, 08820,
(908)549-7144.
4. HUD Guidelines for Testing, Abatement, Clean-Up and Disposal of Lead Based
Paint in Housing. The National Institute of Building Sciences, The Department of
Housing and Urban Development, 1989.
5. Gutknecht, W.F., L.L. Hodson, K.K. Luk, D.A. Binstock, C.C. Van Hise, and
A. R. Turner. Pilot Field Study for the Assessment of Techniques Used for Field
Measurement of Lead in Paint. EPA 600/R-97/057, U.S. Environmental Protection
Agency, Research Triangle Park, NC., September, 1997.
6. Binstock, D. A., D. L. Hardison, P. M. Grohse, and W. F. Gutknecht. Standard
Operating Procedures for Lead in Paint by Hotplate- or Microwave-based Acid
Digestions and Atomic Absorption or Inductively Coupled Plasma Emission
Spectrometry. EPA 600/R-91/213. U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1991, 19 pp. *Available from NTIS, Springfield, VA;
NTISPB92-114172.
7. Youden Test for Ranking. Taylor, J.K., Statistical Techniques for Data Analysis, pp.
92-94, Lewis Publishers, 1990.
25
-------
APPENDIX A
Diagrams of Cabinet Boards and Waif Sections
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X
3
-------
APPENDIX B
Phase I Data
-------
Resolution of Paint Grinding Techniques: Procedure A (glass rod)
Sample
ID
Wall 6-4
Wall 6-6
Wall 6-13
Wall 6-20
Wall 6-22
Avg
sd
RSD %
Wall 7-5
Wall 7-9
Wall 7-11
Wall 7-18
Wall 7-22
Avg
sd
RSD %
Board 5-5
Board 5-8
Board 5-15
Board 5-19
Board 5-21
Avg
sd
RSD %
Board 8-1
Board 8-6
Board 8-15
Board 8-16
Board 8-25
Avg
sd
RSD %
Paint
Sample
Weight
(g)
2.3138
2.6393
2.4009
2.4144
2.6692
2.4875
0 . 1574
6.33
1.7879
1.9999
2.5956
2.3422
2.4787
2.2409
0.3376
15.07
1.2568
1.4622
1.254
1.4841
1.3778
1.3670
0.1093
8.00
1.1495
1.018
1
1.257
0.8419
1.0533
0 . 1577
14 . 98
Analysis
Aliquot
Weight
(g)
0.1032
0.1068
0.1013
0.1076
0.103
0.1027
0.1024
0.1023
0.1068
0.1006
0.1009
0.1038
0.105
0.1023
0.1064
0.1037
0.1047
0.1006
0.1019
0.1078
Pb Cone.
Measured
by ICP
(%)
1.59
2.33
1.8
1.64
2
1.8720
0.3019
16.13
1.39
1.16
0.968
1.54
1.44
1.2996
0.2319
17.84
3.31
4.55
4.65
3.62
3.05
3.8360
0.7269
18.95
4.41
4.36
4.44
3.36
3.88
4.0900
0.4677
11.43
Pb Cone.
Measured
by ICP
(ug/g)
15900
23300
18000
16400
20000
18720
3019
16.13
13900
11600
9680
15400
14400
12996
2319
17.84
33100
45500
46500
36200
30500
38360
7269
18.95
44100
43600
44400
33600
38800
40900
4677
11.43
Total Pb
in Paint
Sample
(ug)
36789
61496
43216
39596
53384
46896
10298
21.96
24852
23199
25125
36070
35693
28988
6338
21.86
41600
66530
58311
53724
42023
52438
, 10732
20.47
50693
44385
44400
42235
32666
42876
6526
15.22
Paint
Sample
Weight
(g/cm2) I
0.0897
0.1023
0.0930
0.0936
0.1034
0.0964
0.0061
6.33
0.0693
0 . 0775
0.1006
0.0908
0.0960
0.0868
0.0131
15 . 07
0.0487
0.0567
0.0486
0.0575
0.0534
0.0530
0.0042
8.00
0.0445
0.0394
0.0388
0.0487
0.0326
0.0408
0.0061
14.98
Pb Cone.
Measured
by ICP
(ug/cm^)
1426
2383
1675
1534
2069
1817
399
21.96
963
899
974
1398
1383
1123
246
21.86
1612
2578
2260
2082
1628
2032
416
20.47
1964
1720
1721
1637
1266
1661
253
15.22
-------
Resolution of Paint Grinding Techniques: Procedure B (dry ice and glass rod)
Sanple
ID
Wall 6-5
Wall 6-10
Wall 6-14
Wall 6-16
Wall 6-24
Avg
sd
RSD %
Wall 7-3
Wall 7-6
Wall 7-15
Wall 7-20
Wall 7-25
Avg
sd
RSD %
Board 5-2
Board 5-9
Board 5-12
Board 5-16
Board 5-25
Avg
sd
RSD %
Board 8-2
Board 8-7
Board 8-14
Board 8-17
Board 8-24
Avg
sd
RSD %
Paint
Sanple
Weight
(g)
2.7417
2.6778
2.231
2.4076
2.1735
2.4463
0.2565
10,48
1.7809
1.9188
2.3969
2 . 5352
2.5463
2.2356
0.3604
16.12
1.2193
1.2007
1.3845
1.3845
1.3388
1.3056
0 . 0894
6.85
1.2671
1.0275
0.9091
0 . 9309
0.8741
1.0017
0.1589
15.86
Analysis
Aliquot
Weight
(g)
0.1062
0.1058
0.1078
0.1056
0.1044
0.1006
0.1063
0.1009
0 . 1072
0.108
0.1042
0.1061
0.1022
0.1003
0.1023
0 . 1018
0.1021
0.1015
0.1029
0 . 1056
Pb Gone.
Measured
by ICP
(%)
1.67
2.16
1.62
1.68
1.48
1.722.0
0.2575
14.96
1.04
1.08
1.28
1.49
1.49
1.2760
0.2155
16.89
3.74
3.43
4.15
3.57
3.02
3 . 5820
0.4143
11 . 57
3.53
3.17
3.48
5.61
4.33
4.0240
0.9847
24.47
Pb Gone.
Measured
by ICP
(ug/g)
16700
21600
16200
16800
14800
17220
2575
14 . 96
10400
10800
12800
14900
14900
12760
2155
16.89
37400
34300
41500
35700
30200
35820 .
4143
11,57
35300
31700
34800
56100
43300
40240
9847
24.47
Total Pb Paint Pb Gone.
in Paint Sanple Measured
Sanple Weight by ICP
(ug) (g/cm2 (ug/cm2)
45786
57840
36142
40448
32168
42477
9969
23.47
18521
20723
30680
37774
37940
29128
9192
31.56
45602
41184
57457
49427
40432
46820
6964
14.87
44729
32572 -
31637
52223
37849
39802
8679
21.81
0.1062
0.1038
0.0865
0.0933
0.0842
0.0948
0.0099
10.48
0.0690
0.0744
0.0929
0.0982
0.0987
0.0866
0 . 0140
16.12
0.0472
0.0465
0.0536
0.0536
0.0519
0.0506
0.0035
6.85
0.0491
0.0398
0.0352
0.0361
0.0339
0.0388
0.0062
15.86
1774
2241
1401
1567
1247
1646
386
23.47
718
803
1189
1464
1470
1129
356
31.56
1767
1596
2226
1915
1567
1814
270
14 . 87
1733
1262
1226
2024
1467
1542
336
21.81
-------
Resolution of Paint Grinding Techniques: Procedure C (mortar and pestle)
Sample,
ID
Wall 6-2
Wall 6-7
Wall 6-12
Wall 6-19
Wall 6-23
Avg
sd
RSD %
Wall 7-1
Wall 7-8
Wall 7-13
Wall 7-17
Wall 7-23
Avg
sd
RSD %
Board 5-3
Board 5-7
Board 5-11
Board 5-20
Board 5-24
Avg
sd
RSD %
Board 8-3
Board 8-8
Board 8-13
Board 8-18
Board 8-23
Avg
sd
RSD %
Paint
Sample
Weight
(g)
2.423
2.631
2.2869
2.2178
2.3491
2.3816
0.1587
6.66
2.0692
1.6668
2.3255
2.1541
2.5248
2.1481
0.3207
14.93
1.0072
1.296
1.3482
1.4967
1.2327
1.2762
0.1792
14.04
1.2593
0.9333
1.0239
0.8517
0.7486
0 . 9634
0.1941
20.15
Analysis
Aliquot
Weight
(g)
0.1043
0.1077
0.101
0 . 1022
0.105
0.1055
0.1094
0.1021
0.1029
0.1029
0.1032
0.1
0.1022
0.1084
0 . 1078
0.1003
0.103
0.1027
0.1036
0 . 1082
Pb Cone.
Measured
by ICP
(%)
1.25
1.87
1.61
1.81
1.34
1.5760
0.2758
17.50
0.891
0.708
1.44
1.16
1.52
1.1438
0 . 3476
30.39
2.87
2.98
4.73
4.02
2.94
3.5080
0.8312
23.70
5.06
4.49
4.55
4.18
3.74 .
4.4040
0.4874
11.07
Pb Gone.
Measured
by ICP
(ug/g)
12500
18700
16100
18100
13400
15760
2758
17.50
8910
7080
14400
11600
15200
11438
3476
30.39
28700
29800
47300
40200
29400
35080
8312
23.70
50600
44900
45500
41800
37400
44040
4874
11.07
Total Pb
in Paint
Sample
(ug)
30288
49200
36819
40142
31478
37585
7625
20.29
18437
11801
33487
24988
38377
25418
10810
42.53
28907
38621
63770
60167
36241
45541
15470
33.97
63721
41905
46587
35601
27998
43162
13445
31.15
Paint
Sample
Weight
(g/cm2)
0.0939
0.1020
0.0886
0.0859
0.0910
0.0923
0.0062
6.66
0.0802
0.0646
0.0901
0.0835
0 . 0978
0.0832
0.0124
14.93
0.0390
0.0502
0.0522
0.0580
0.0478
0.0495
0.0069
14.04
0.0488
0.0362
0,0397
0.0330
0.0290
0 . 0373
0.0075
20.15
Pb Cone.
Measured
by ICP
(ug/cm2)
1174
1906
1427
1556
1220
1456
295
20.29
714
457
1298
968
1487
985
419
42.53
1120
1497
2471
2331
1404
1765
599
33.97
2469
1624
1805
1380
1085
1673
521
31.15
-------
Resolution of Paint Grinding Techniques: Procedure D (Bel Arts Products Micro Mill)
Sample
ID .
Wall 6-3
Wall 6-9
Wall 6-11
Wall 6-17
Wall 6-25
Avg
sd
RSD %
Wall 7-4
Wall 7-7
Wall 7-12
Wall 7-19
Wall 7-21
Avg
sd
RSD %
Board 5-1
Board 5-10
Board 5-14
Board 5-17
Board 5-22
Avg
sd
RSD %
Board 8-4
Board 8-9
Board 8-12
Board 8-19
Board 8-22
Avg
sd
RSD %
Paint
Sample
Weight
(g)
2.3094
2.7504
2.4115
2.4201
2.7049
2 . 5193
0.1958
7.77
1.7809
1.9703
2.4146
2.2965
2.5511
2 . 2027
0.3190
14.48
1.2312
1.2478
1.2681
1.4023
1.3137
1.2926
0.0687
5.31
n/a
0.9141
0.9747
0.8654
0.9331
0.9218
0.0453
4.92
Analysis
Aliquot
Weight
(g)
0.1039
0.1082
0.1044
0.1065
0.1019
1 0.1006
0.1023
0.1038
0.1051
0.1034
0.1001
0.1043
0.1017
0.105
0.1005
0 . 1044
0.1007
0.1029
0.1065
0 . 1036
Pb Cone.
Measured
by ICP
(%)
1.35
1.84
1.66
1.37
1.6
1.5640
0.2062
13.19
0.816
0.912
1.06
1.25
1.66
1.1396
0.3339
29.30
3.51
3.93
3.39
3.75
3.01
3.5180
0.3529
10.03
3.18
2.99
3.46
3
3.88
3.3020
0.3750
11.36
Pb Gone.
Measured
by ICP
(ug/g)
13500
18400
16600
13700
16000
15640
2062
13.19
8160
9120
10600
12500
16600
11396
3339
29.30
35100
39300
33900
37500
30100
35180
3529
10.03
31800
29900
34600
30000
38800
33020
3750
11.36
Total Pb
in Paint
Sample
(ug)
31177
50607
40031
33155
43278
39650
7864
19.83
14532
17969
25595
28706
42348
25830
10847
41.99
43215
49039
42989
52586
39542
45474
5238
11.52
27332
33725
25962
36204
30806
4939
16.03
Paint
Sample
Weight
(g/cm2) |
0 . 0895
0.1066
0.0934
0.0938
0.1048
0 . 0976
0.0076
7.77
0.0690
0.0763
0.0936
0.0890
0.0989
0.0854
0 . 0124
14.48
0.0477
0.0484
0.0491
0.0543
0.0509
0.0501
0.0027
5.31
0.0354
0.0378
0.0335
0.0362
0.0357
0.0018
4.92
Pb Gone .
Measured
by ICP
[ug/cm2)
1208
1961
1551
1285
1677
1536
305
19.83
563
696
992
1112
1641
1001
420
41.99
1675
1900
1666
2038
1532
1762
203
11.52
1059
1307
1006
1403
1194
191
16.03
-------
Resolution of Paint Grinding Techniques: Procedure E (Spex Freezer Mill)
Sample
ID
Wall 6-1
Wall 6-8
Wall 6-15
Wall 6-18
Wall 6-21
Avg
sd
RSD %
Wall 7-2
Wall 7-10
Wall 7-14
Wall 7-16
Wall 7-24
Avg
sd
RSD %
Board 5-4
Board 5-6
Board 5-13
Board 5-18
Board 5-23
Avg
sd
RSD %
Board 8-5
Board 8-10
Board 8-11
Board 8-20
Board 8-21
Avg
sd
RSD %
Paint
Sample
Weight
(g)
2.6394
2.3447
2.2122
2.607
2.4714
2.4549
0 . 1792
7.30
2.2094
2.2653
2.6764
2.2096
2.3912
2.3504
0.1968
8.37
1.2682
1.1333
1.2387
1.4199
1.5795
1.3279
0 . 1740
13.11
0.98
1.0966
1.0085
0 . 8232
0.9769
0.9770
0.0987
10.10
Analysis
Aliquot
Weight
(g)
0.1069
0.1072
6.1089
0 . 1047
0.1047
0.1008
0.1059
0.1011
0 . 1016
0.1006
0.1019
0.1002
0.1031
0.1051
0.1029
0.1007
0 . 1013
0.1037
0.1013
0 . 1057
Pb Gone.
Measured
by ICP
(%)
1.45
1.42
1.51
1.64
1.46
1.4960
0.0868
5.80
1.05
1.1
0.986
1.24
1.53
1.1812
0.2162
18.31
3.03
4.56
3.63
3.42
4.08
3.7440
0.5930
15.84
5.14
4.56
5.13
4.59
5.3
4.9440
0.3437
6.95
Pb Cone.
Measured
by ICP
(ug/g)
14500
14200
15100
16400
14600
14960
868
5.80
10500
11000
9860
12400
15300
11812
2162
18.31
30300
45600
36300
34200
40800
37440
5930
15.84 .
51400
45600
51300
45900
53000
49440
3437
6.95
Total Pb
in Paint
Sample
(ug)
38271
33295
33404
42755
36082
36762
3935
10.71
23199
24918
26389
27399
36585
27698
5214
1.8 . 83
38426
51678
44965
48561
64444
49615
9644
19.44
50372
50005
51736
37785
51776
48335
5951
12.31
Paint
Sample
Weight
(g/cm2) (
0.1023
0.0909
0.0857
0.1010
0.0958
0.0951
0.0069
7.30
0.0856
0 . 0878
0.1037
0.0856
0.0927
0.0911
0 . 0076
8.37
0.0491
0.0439
0.0480
0.0550
0.0612
0.0515
0.0067
13.11
0.0380
0.0425
0.0391
0.0319
0.0379
0.0379
0 . 0038
10.10
Pb Gone.
Measured
by ICP
[ug/cm2)
1483
1290
1294
1657
1398
1425
152
10.71
899
966
1023
1062
1418
1073
202
18.83
1489
2003
1742
1882
2497
1923
374
19.44
1952
1938
2005
1464
2006
1873
231
12.31
-------
Height of a 1 square inch sample (g>
Door 4*5
* 26
» 27
* 28
* 23
* 30
» 31
« 32
tt 33
» 34
» 35
flvg
s. d.
HSD
Wall #7
0. £8
0. 31
0. 31
0. £8
0. 32
0. 3O
0. 28
0. 32
0. 36
y. 31
0. Jl
y. 0£
7.93
# £6
* £7
*. £8
»» £3
« 3O
*» 31
* 3£
« 33
« 34
* 35
0. 58
y.60
0. 54
0. 58
0. 57
0.57
0. 53
C». 6£
0. 61
y. 53
O. 53
0. 0£
3. 89
Board X
* 1
* £
* 3
# 4
* 7
* 8
10
0. 51
0. 51
0. 5
0. 53
0, 55
0. 56
0. 43
0. 54.
0. 51
0. S3
0. 52
0. 0£
4. 33
-------
APPENDIX C
Phase II Data
-------
Lead Concentration in Paint (%)
Grinding time
30 sec
5 rnin diff
Door ft 5
glass rod
cent r i f uge
Avg
s. d.
RSD
rnortar
pestle
ftvg
s. d.
RSD
ft 7
glass rod
centri fuge
ftvg
s. d.
RSD
rnortar &
pestle
s. d.
RSD
ft
ft
ft
ft
ft
ft
ft
ft
ft
3
ft
ft
ft
ft
26
27
28
32
'34
29
30
31
33
J5
26
27
28
32
34
2. 74
4. 17
3. 81
3.28
4. 41
3. 68
0. 68
18. 4
3. 29
4. 99
5. 06
4. 15
-------
APPENDIX D
Statistical Data Interpretations
-------
Following a log-transformation of measurement data, variances were estimated
for each grinding technique. These were then compared using an F test. No
significant differences were found at the 1% level (critical value = 3.4). The table
below shows the estimated standard deviation (In-scale) and F ratios, where F = max
(s*x/s2y, s2v/s2x)- The greatest ratio found, 3.17, is less than the critical value.
Procedure A
(glass rod) 0.165961
Procedure B
(dry ice glass rod) 0. 1 6941 6
Procedure C
(Mortar) 0.223662
Procedure D
(grinder) 0.17162
Procedure E
(Spex) 0.125582
A
0.165961
1
1 .04207
1.816241
1.069365
1 .746449
E
0.169416
1 .04207
1
1.742916
1.026193
1.819923
£
0.223662
1.816241
1.742916
1
1 .69843
3.171973
£
0.17162
1 .069365
1.026193
1.69843
1
1.867591
£
0.125582
1 .746449
1.819923
3.171973
1.867591
1
F crit = 3.4
MAX = 3.171973
-------
Lead Concentration 1n Paint (X)
Grinding time
Board
glass rod
centrifuge
Avg
s.d.
RSD
mortar &
pestle
Avg
s.d.
RSD
Stats F =
grind s pooled
methods t test
30 sec
3.7
44
08
92
14
86
0.67
13.9
2 5.36
4 8.48
6 5.8
8 8.62
10 7.08
7.07
1.49
21.1
4.76
1.1552
2.21 < 1.6866
DIFFERENCE
5 mln dlff
Statistics on 30 s
vs. 5 mln grinding
5.
5.
5.
5.
4.
5.
0.
6
5.
6
4.
7.
6.
6.
0.
15
53
25
34
14
65
18
33
.4
43
.5
99
43
29
13
95
.6
-1.83
0.19
-0.26
-0.22
0.49
-0.33
0.90
-275
-0.07
1.98
0.81
1.19
0.79
0.94
0.74
79.0
F
s
t
no
F
s
t
no
= 4.12
pooled 0.5281
test 0.32 < 0.
difference
* 2.46
pooled 1.2495
test 0.94 < 1.
difference
77
82
8.33 (Failed)
Alt method
0.95 < 1.1564
no difference
-------
Lead Concentration 1n Paint (%)
Grinding time
Door 15
30 sec
glass rod
centrifuge
Avg
s.d.
RSD
mortar 4
pestle
Avg
s.d.
RSD
Stats F =
grind. s pooled
methods t test
26
27
28
32
34
1 29
# 30
t 31
# 33
# 35
18.4
3.29
4.99
5.06
4.15
4.69
4.44
0.73
16.5
1.15
0.7054
0.76 < 1.0299
no difference
5 rain dlff
Statistics on 30 s
vs. 5 m1n grinding
2.20 0.54
3.44 0.73
4.03 -0.22
3.22 0.06
4.74 -0.33
3.53 0.16 F =1.96
0.95 0.46 s pooled = 0
26.9 297.9 t test 0.15 <
no difference
4.23 -0.94
5.46 -0.47
4.83 0.23
3.68 0.47
4.84 -0.15
4.61 -0.17 F = 1.15
0.68 0.56 s pooled = .
14.7 -325 t test 0.17 <
no difference
1.95
0.4808
1.08 < 0.7020
DIFFERENCE
.8261
1.20
7054
1.02
-------
COMPARING AVERAGE PERFORMANCE
O«W JO-110
(1) Choose a, the ityniftcance level of the test.
(Actually, th« procedure outlined will give
s significance level of only approximately
CxampU
(1) Let a - .06
(2) Compute: Xt and *1, £« and **», for the
and n» measurements from A and B.
(2)
(3) Compute:
and
the estimated variances of J?A and Jt«,
respectively.
(4) Compute the "effective number of degrees
of freedom"
u, decide that A and B
differ with regard to their average perform-
ance; otherwise, decide that there is no
reason to believe A and B differ in average
perf.orma
(3)
(4)
(6)
*, - 3166.0
*i - 6328.67
»4 -*
*, - 2240.4
*». - 221,661.3
*, .- 9
6328.67
4~~
- 1582.17
V, -
221.66U
- 24629.03
(26211.20)*
500652.4 -r 60668911.9
687027005
/- 61159564
- 11^33 - 2
- 9.233
jr-V
- 1262
-2
u - 2.262 V2621L20
-.-2.262(161.9)
" - 366 2
(7) (*.« .-! J?i| - 925.6, which, is larger than
K. Conclude that A and B differ with
regard to average performance.
Experimental Statistics, National Bureau of Statistics Handbook 91, U.S. Department of
Commerce, M.G. Natrella, ed., Aug. 1963
-------
1.
2.
COMPARING AVERAGE PERFORMANCE (WHEN F TEST FAILED)
= 0.05
xA = 5.18 S2A = 0.1089 n = 5
xB = 6.13 S2B = 0.9025.n =
= 0.1089 = 0.0218
Vn = 0.9025 = 0.1805
f_ (.0218+.1805)2
02182 ^ .18052
5+1 + 5+1
f = 5.43
f1 = 5
5. ti-«/2for5df=2.571
6. M = 2.571 (0.0218+ 0.1805f
At =-1.1564
7. - Is (XA-XB)> 1.1.564 ?-
5.18 - 6.13 > 1.1564?
.9500 > 1.1564 No
Therefore, no reason to believe that they are different
-------
APPENDIX E
Histograms of Particle Size Distribution
-------
60
TE-Sample No. 8, Board 5 (4in2)
Glass Rod/ Room Temperature
Ground 5 Minutes
50 -
40 '
&
3 30
Cn
£
20 -
10
52
21
2 -
-(
Median 4.6
Meanis 34.5 ± 107
Mode 3.1
Flange 0.9 - 634.4
1 fc?iia -1
10
20 25 30 35 40
45 50 55 60
Particle Size in Microns
65 70 75 80 85 90 95 >95
-------
50
TE-Sample No. 9, Board 5 (4in2)
Glass Rod/ Dry Ice
Ground 5 Minutes
43
40
Median 6.1
Mean±s 17 A ±29
Mode 3.1
Range 1.5-152.5
30 -
1
20 -
10
27
1 1
H h
1 1
1 1
10 15 20 25 30 35 40
45 50 55 60
Particle Size in Microns
65 70 75 80 85 90 95 >95
-------
TE-Sample No. 7, Board 5 (4in2)
Mortar & Pestle
Ground 5 Minutes
JU -
40
Frequency
w
o
20
10 -
n _,
iwxvMviwXv:-:*:-:^ * - -* .-«. ^ ...-......*...-.. » I;-:-:-:-:-:-:-:-:-:-:-:
Mprlian fi 1 sissSSSs:;;;
5!:;j5;-:$:-SSS?S5:?S^^ IVlCUlon 0 . 1 ;::j;:;s;;₯::i
::;;':::'"'"''y::i::::':::;::;::::-iv:::;;:: ::*:::: w-i'KvKwWvW-w:*^?^ ;;;;.;;:;::
^dVS&S^SSS^^ft'W-^'^^^ 14 iC^illT :x>-:-tt>>>-
15'4 ± 23/7 llfl
It
i
&
>£
:::'
>x"
S:
II
:i:|:
^
::>::
|
:'>'.'
;:-.:
^
1
§
:'?
x-:':
w.
i^
1
1
1
1
I
0 1
3-l Will
!?§ii!;:
sJSJsisix;
;₯.:₯^₯;KSS
liiiii
iSSSftj;
ssiiiii
:₯;':₯M-r₯:-:-:-:-:
.-.-:;A--,₯: "
5:s;S»
SiSSS
sisiiS
:::-::::-
l;I?i
;l';l'!ls
111
ill
::₯:₯S^
SS:jS|:
S38;
SiSJs
111;
isli
;-;:;:₯:₯
SsSi
₯:₯:₯:₯:
«?fi₯:
JsSSg
HI
1
Siii;
^S
11
1
1
i
241
i
i
i
i
..YS;s*/.-.-.-.'".i'S.v.<-^ -:-:-:::-:-:;::
1.5-167.8 111
3i;:5S;:W:;:i;;:;:i;ffi^ \ iiB^jjiB
i'S:₯:::::i;5:::::Wft!!:::i::!W:::ffi::i^^^
K:₯:>:S::;::::₯:₯ff:₯:W;S₯ft₯^ft^^
^;t;5;W:s?W?5B;Si^^^
*,vy.tfv.-..-.VM^
^^^^^&^^S^^^^^^^^^^^^ff^^^^MK^^^0^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^'^^^jl^^^^^^^^^^^^!&
SWf ::!:₯:::::::SW « : fcSSSJSSSfffi^^^
::::::::::₯:::₯:₯:₯:::₯:: :siW:i:K^^^^
imSK;^-?;;??^^
;:₯:JJj;₯:₯:J;%5>5^:;:;::g₯.:;:;
:):>^:;:^:;:^:v:v;v:₯;-;j;:%::;:x^^;^^
:₯H:::S:i::W:₯i;!S₯S^S₯'^₯l^
S?;Wf:>W:₯S₯:Wft₯fffi:«iWftw;i:K;::;^
m;»5;:sM^^
ssssssss^
:₯:::₯:₯:₯:₯:₯:₯:₯:₯:₯:₯:₯:::W»;:»fS₯:::₯ft:>^^
5 10 15 20 25 30
35 40 45 50 55 60 65 70 75
Particle Size in Microns
80
85 90 95
-------
50
TE-Sample No. 10, Board 5 (4in2)
Bell Art Mill
Ground 30 Seconds
Median 6.1
Meanis 14.8 ±26.8
Mode 3.1
Range 1.5-183.0
30
&
a
s
o"
123
20
10
'3;
I
40 45 50 55 60 65
Particle Size in Microns
5 10 15 20 25 30 35
70 75 80 85 90 95 >95
-------
50
TE-Sample No. 6, Board 5 (4in2)
Spex Freezer Mill
Ground 15 Seconds
40
40 -
Median 6.1
Meanis 13.7 ±23.7
Mode 6.1
Range 0.9-152.5
30 -
29
I
O"
20 -
10 -
1,
, _ , _ ,
i i
5 10 15 20 25 30 35 40
45 50 55 60
Particle Size in Microns
65 70 75 80 85 90 95 >95
-------
50
LG-Sample No. 5, Wall 7 (4in2)
Glass Rod/Room Temperature
Ground 5 Minutes
40 -'
Median 32.4
Mean ± s 40.9 ± 32.4
Mode 24.0
Range 2.4 - 204.0
30
S
20
10 -
11
16
4 4
1
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 >95
Particle Size in Microns
-------
50
LG-Sample No. 3, Wall 7 (4in2)
Glass Rod/Dry Ice
Ground 5 Minutes
40
Median
Mean ± s
Mode
Range
15.0
23.9 ±22.6
12.0
1.2- 120
30 - '
a
.
3 3
222
1
»«gpt t K«a < ^a8* I , , _ .. fSffi,* i Ksfissf' > fw&f . Fwj
45 50 55 60 65 70 75 80
5 10 15 20 25 30 35 40
85 90 95 >95
Particle Size in Microns
-------
50
LG-Sample No. 1, Wall 7 (4in2)
Mortar & Pestle
Ground 5 Minutes
40 -
35
30
30
Median
Mean ± s
Mode
Range
6.0
9.7 ±8.4
6.0
1.2-44.4
I
20
15
16
10
10 15 20 25 30 35 40 45 50 55 60
Particle Size in Microns
65
70
75
80
85
90
95 >95
-------
50
LG-Sample No. 4, Wall 7 (4in2)
Bell Art Mill
Ground 30 Seconds
40
30
I
£
fe
20
11
10 --
35
0 f Ka»J ]
19
16
10
2 -2
.[. .
,
Median 12.0
Meanis 13.5 ±8.8
Mode 6.0
Range 1.2-42.0
,
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 >95
Particle Size in Microns
-------
50
LG-Sample No. 2, Wall 7 (4in2)
Spex Freezer Mill
Ground 15 Seconds
40 -r
Median 6.0
Meanis 10.2 ± 14.7
Mode 2.4
Range 1.2-126.0
30 - :
6-
1
20
30
10 --
12-
t
1 1 1
5 10 15 20 25 30 35 40 45 50 55 60 65
Particle Size in Microns
70 75 80 85 90 95 >95
-------
50
TE-SampIe No. 36, Board 5 (lin2)
Mortar & Pestle
Ground 30 Seconds
40 --
30 -
g
I
20
10
10
4 *
4 -4-
Median 42.7
Mean±s 61.0 ±56
Mode 12.1
Range 3.1-292.8
4 4
23
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 >95
Particle Size in Microns
-------
LG-Sample No. 37, Board 5 (I'm2)
Mortar & Pestle
Ground 1 1/2 Minutes
71
70
Median 2.4
Mean±s 11.7 ±32.3
Mode 1.2
Range 1.2-198
45 50
Particle Size in Microns
0 0 0 0%
i .............. i .............. \ ..... t ma
55 60 65 70 75
0000
1 1 1
80
85 90 95 >95
-------
LG-Sample No. 38, Board 5 (4in2)
Mortar & Pestle
Ground 1 1/2 Minutes
65
00000
t Mflft t 1 1 1 ( (
Median 3.6
Meanis 10 ±19
Mode <1.2
Range <1.2-120
30 35
40 45 50 55 60 65
Particle Size in Microns
70 75
80
85 90 95 >95
-------
50
TE-Sample No. 36, Wall 7 (lin2)
Mortar & Pestle
Ground 30 Seconds
40
Median 32.0
Mean ± s 50.6 ± 54.5
Mode 9.2
Range 6.1-314.2
30
§
er
20 --
10 -
13
13
5
11
44 4
12
1
1.
80 85 90 95 >95
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
Particle Size in Microns
-------
LG-Sample No. 37, Wall 7 (lin2)
Mortar & Pestle
»
Ground 1 1/2 Minutes
ou -
70
60
50 -
Frequency
jk
0
30
20
10
n .
73
PI
i
9
\
S
i
i
i
i
^t~
,
Median 3.6
JMeani s 15. 8 ±36
Mode <1.2
Range <1.2-186
-
' .
;
^
13
I\
6' ' 5
1 0 0 0 1-1 0 0.0 0 0 0 0 r--i 0 0
10 15 20 25 30 35 40 45 50 55 60
Particle Size in Microns
65 70
75
80
85 90 95 >95
-------
50
95
-------
50
TE-SampIe No. 11, Board X (lin2)
Mortar & Pestle
Ground 30 Seconds
40
Median 36.6
Mean±s 51.9 ±50.4
Mode 24.4
Range 6.1-375.2
30 --
S
tn
20 --
10 -
14
| tSffSI [ fWif [ gagl f
12
4 4
i i
15
10 15 20 25 30 35 40 45 50 55 60 65 70 75
Particle Size in Microns
80 85 90 95 >95
-------
50
TE-Sample No. 8, Board 5 (4m2)
Glass Rod/ Room Temperature
Ground 5 Minutes, Followed by
3 Minutes with a Mortar & Pestle
40
30
8
20
10
40
222
1 1
Q j KSSSt i BSffig ^ BBSS* ^ KXKj ^ JSHH | «gfS» ^ jgjKa
5 10 15 20 25 30 35
Median 9.2
Mean±s 21.5 ±34
Mode 1.5
Range 1.5-201.3
* H f-
40 45 50 55 60 65
Particle Size in Microns
70 75 80 85 90 95 >95
-------
50
LG-Sample No. 5, Wall 7 (4in2)
Glass Rod/ Room Temperature
Ground 5 Minutes, Followed by
3 Minutes with a Mortar & Pestle
40
35
30 -.
fr
s
g.
£
20 --
10
22
11
. 1 .1
Median 6.0
Meanis 17.5 ±25
Mode 6.0
Range 1.2-150.0
2 2
1
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 >95
Particle Size in Microns
------- |