United States
Environmental Protection
Agency •
Risk Reduction
Engineering Laboratory
Cicninnati, OH 45268
Research and Development
EPA/600/SR-92/027 April 1992
EPA Project Summary
Asbestos Concentrations
Two Years after Abatement in
Seventeen Schools
John R. Kominsky, Ronald W. Freyberg, James A. Brownlee, and
Donald R.Gerber
Airborne asbestos concentrations
were measured at 17 schools that un-
derwent an asbestos abatement in 1988.
These 17 schools, which involved 20
abatement sites, were part of a study
conducted by the U.S. Environmental
Protection Agency (EPA) and the New
Jersey Department of Health (NJDOH)
in 1988. The 1988 study showed that
asbestos concentrations measured in-
dependently by the NJDOH and EPA
during the clearance phase of the abate-
ment were elevated in the abatement
and perimeter areas compared with out-
door concentrations. The present study
was conducted to determine the cur-
rent levels of airborne asbestos under
simulated occupancy conditions and to
determine whether the elevated levels
found during the clearance phase were
still present 2 yr after abatement. In
1990, three sites showed significantly
higher mean asbestos concentrations
inside the building (i.e., the previously
abated area and/or perimeter area) com-
pared with those outdoors (p<0.05). In
1990, the mean asbestos concentration
measured in the perimeter area at one
site and in the previously abated area
at two sites were significantly higher
than those in 1988 (p<0.05). Variations
in asbestos levels between 1988 and
1990 may be due to sampling tech-
niques (i.e., passive and aggressive
versus modified aggressive), residual
air-entrainable asbestos from the 1988
abatement, or air-entrainable asbestos
from operations and maintenance ac-
tivities since 1988.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
In 1988, the Asbestos Control Service
of the New Jersey Department of Health
(ACS-NJDOH) and the Risk Reduction
Engineering Laboratory (RREL) of the U.S.
Environmental Protection Agency con-
ducted a cooperative study to document
Asbestos Hazard Emergency Response
Act (AHERA) clearance air-sampling prac-
tices and final clearance concentrations of
asbestos at 20 abatement projects in New
Jersey. The 20 abatement projects in-
volved 17 different schools. The results of
this study revealed discrepancies between
AHERA clearance results reported by the
Asbestos Safety Control Monitoring firms
employed by the building owner and those
reported independently by the ACS-
NJDOH and EPA-RREL Ten of the 20
sites would not have passed the AHERA
clearance test had the ACS-NJDOH and
EPA-RREL clearance data been used. The
1988 study further identified cases in which
elevated levels of asbestos in the perim-
eter areas outside the work site but inside
the building would have allowed the site
to pass the AHERA clearance test had
the perimeter concentrations been substi-
tuted for outdoor values as allowed by
AHERA.
These findings prompted a concern by
ACS-NJDOH and EPA-RREL regarding
the contamination levels of asbestos that
may be.present in the 17 schools 2 yr
after abatement. Therefore, a followup
Printed on Recycled Paper
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study was- conducted during the summer
of 1990 to determine the airborne asbes-
tos concentrations in these 17 schools
under simulated occupancy conditions.
Study Design and Methods
This study was conducted at the same
17 schools that were involved with the
1988 ACS-NJDOH and EPA-RREL study
that documented AHERA air monitoring
practices and final clearance concentra-
tions of airborne asbestos. The 17 schools
involved 20 abatement sites. Access to
each school was coordinated directly by
ACS-NJDOH. Area airborne asbestos con-
centrations were measured at each site in
the same three areas as in the previous
study: 1) previously abated area, 2) pe-
rimater (outside the abated area but in-
slda the building), and 3) outdoors. It was
recognized that true abatement and pe-
rimeter areas could not be separated
because the containment barriers present
during the 1988 abatement have been
removed. It was also recognized that in
the Interim since 1988, other sources (e.g.,
routine maintenance of asbestos-contain-
ing resilient floor tile) may have contrib-
uted to the current concentrations of air-
borne asbestos.
Site Documentation
For each of the 17 sites, the ACS-
NJDOH documented the history of the
abatement activities between 1988 and
1990 and operations and maintenance
(O&M) activities on any remaining asbes-
tos-containing material (ACM) in the pre-
viously abated area and perimeter area.
This Information was obtained from abate-
ment notices (N.JAC. 8:60-7), AHERA
management plans, and information pro-
vided by the designated person and/or
school officials.
Air Sampling Strategy
At each site, five area air samples were
collected in each of three areas: 1) the
previously abated work area, 2) the pe-
rimeter area (outside the previously abated
work area but inside the building), and 3)
outdoors. In addition to the area air
samples, three quality assurance samples
(ona closed and two open field blanks)
were collected at each school.
Air sampling in the previously abated
work area and the perimeter area was
conducted in accordance with a modified
aggressive sampling protocol designed to
simulate normal building activity. The pro-
tocol involved sweeping only the floors
whh the exhaust of a 1-hp leaf blower at a
rate of 5 min/1000 ft2 of floor space. One
stationary fan (18-in diameter, axial flow)
per 10,000 ft1 was positioned with the air
directed toward the ceiling to maintain air
movement during sampling.
Sampling Methodology
Air samples were collected on open-
face, 25-mm-diameter, 0.45-nm-pore-size,
mixed cellulose ester (MCE) membrane
filters with a 5-nm-pore-size, MCE, backup
diffusing filter and cellulose support pad
contained in a three-piece cassette. The
filter cassettes were positioned approxi-
mately 5 ft above the floor on tripods, with
the filter face at approximately a 45° angle
toward the floor. The filter assembly was
attached to a 1/6-hp electric-powered
vacuum pump operating at a flow rate of
approximately 9 L/min. Air volumes ranged
from 975 to 1545 L. At the end of the
sampling period, the filters were turned
upright before being disconnected from
the vacuum pump and then stored in this
position. The sampling pumps were cali-
brated with a calibrated precision rotame-
ter both before and after sampling.
Analytical Methodology
The MCE filters were prepared and ana-
lyzed in accordance with the nonmandatory
transmission electron microscopy (TEM)
method, as described in the AHERA final
rule (40 CFR 763). A sufficient number of
grid openings were analyzed for each
sample to ensure a sensitivity (the con-
centration represented by a single struc-
ture) of no greater than 0.005 asbestos
structure per cubic centimeter (s/cm3) of
air sampled. In addition to the require-
ments of the nonmandatory TEM method,
the specific length and width of each struc-
ture were measured and recorded. The
Public Health and Environmental Labora-
tories of the New Jersey Department of
Health performed the TEM analyses on
the field samples under a separate coop-
erative agreement with EPA-RREL.
Statistical Analysis
All estimated concentrations were based
on the number of asbestos structures
counted. If no asbestos structures were
counted in a sample, that sample was
assigned an estimated concentration of 0
s/cm3.
Airborne asbestos concentrations mea-
sured in each of the three sampling loca-
tions were characterized by use of de-
scriptive statistics. Because the 20 sites
were likely to differ in their abatement
history and status with respect to the pres-
ence of asbestos-containing material, each
site was considered separately. The de-
scriptive statistics included the arithmetic
mean and standard deviation, minimum
and maximum concentration, and sample
size.
Analysis of variance (ANOVA) was used
to examine differences between concen-
trations measured in the previously abated
work area, perimeter area, and outdoors
at each site. When overall differences were
detected among the three sampling loca-
tions, the Tukey multiple comparison pro-
cedure was used to evaluate the pairwise
differences. A student's t-test was used to
compare airborne asbestos concentrations
measured in 1988 with those measured in
1990. The transformation ln(x + 0.002),
where x is the measured airborne asbes-
tos concentration, was applied to each
measurement before the ANOVA or t-test
was performed. The transformation was
used to make variances more equal and
to provide data that are better approxi-
mated by a normal distribution. The con-
stant 0.002, a value chosen to be smaller
than the majority of analytical sensitivities,
was used because some zero values were
present. The transformation was used only
for the ANOVA and t-test; it was not used
for any other part of the data analysis
(e.g., plots or descriptive statistics).
Results and Discussion
Site Descriptions
Table 1 presents the postabatement his-
tory and the remaining ACM at the 20
sites. Post-1988 abatement occurred at 1
(Site O) of the 20 sites in the previously
abated area and at 5 (Sites A, D, K, L,
and N) of the 20 sites in the perimeter
area. Table 1 lists the types of ACM that
were abated after 1988. At 14 sites, ACM
is still present in the previously abated
areas; at 18 sites, ACM is still present in
the perimeter areas. Resilient floor tile
acounts for a major portion of the ACM.
Airborne Asbestos Levels
Measured in 1990
Statistically significant differences be-
tween the three sampling locations (i.e.,
previously abated area, perimeter, and
outdoors) were detected at 4 of the 20
sites. The average concentration in the
previously abated area at Site B (0.015 s/
cm3) was significantly higher (p<0.05) than
the average outdoor concentration (0.001
s/cm3). Sites J and K showed average
perimeter concentrations (0.003 and 0.007
s/cm3, respectively) significantly higher
(p<0.05) than both the average concen-
tration in the previously abated area (0 s/
cm3 at both sites) and the average out-
door concentration (0 and 0.001 s/cm3,
respectively). The average concentration
in the previously abated area at Site R (0
s/cm3) was significantly less (p<0.05)
than both the average perimeter concen-
tration (0.011 s/cm3) and the average out-
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Table 1. Post-1988 Abatement History and Remaining Asbestos- Containing Material (ACM) at the
20 Sites
Abatement after 1988
Remaining ACM
Abatement Perimeter Material Abatement
Site area area abated? , area
A
B
C
D
£
F
G
H
1
J
K
L
M
N
O
P
Q
R
S
T
a AP
PB-TSI
FT
CEM-TSI
TR
CT
No Yes AP, PB-TSI ..
No No -
No No
No Yes PB-TSI
No No
No No
No No
No No
No No
No No
No No
No Yes FT, TR
No No
No Yes AP
Yes No CEM-TSI
No No
No No
No No
No No
No No
FT
FT
None
CEM-TSI
FT
None
None
FT
None
CEM-TSI
None
FT, TR
None
None
TR
FT
FT
FT
FT
None
Perimeter ,.
area
FT
FT
None
CEM.TSI.FT
FT
FT
FT
FT.AP
FT
FT
FT
FT
None
FT
FT
FT
FT
FT
FT
FT.CT
= Acoustical Plaster
= Preformed Block Thermal System Insulation
= Floor Tile
= Cementitious Thermal System Insulation
= Transite
= Ceiling Tile
door concentration (0.013 s/cm3). In all
other cases the numerical differences were
not statistically significant.
Structure and Morphology and
Length Distributions of 1990
Samples
The TEM analysis of 100 samples col-
lected in the previously abated area, 95
samples collected in the perimeter area,
and 85 samples collected outdoors yielded
a total of 196 asbestos structures. Of
these, 95% were chrysotile and 5% were
amphibole. Approximately 85% of the
structures observed on the samples col-
lected in the previously abated area and
95% of the structures observed on the
perimeter area samples were less than 5
(xm in length. Ninety-two % of the asbes-
tos structures observed on the outdoor
samples were less than 5 u.m in length.
Comparison of 1988 and 1990
Airborne Asbestos Levels
Table 2 presents the mean arithmetic
concentrations of airborne asbestos mea-
sured in the previously abated area, pe-
rimeter area, and outdoors in 1988 and
1990. Figure 1 presents a comparison of
mean work area concentrations measured
in 1988 and 1990; .Figure 2 presents a
like comparison of mean perimeter con-
centrations. The diagonal line in each fig-
ure represents concentrations that were
the same for both sampling locations. Sites
that fall above the line indicate that con-
centrations, on the average, were higher
in the sampling location represented on
the vertical axis. Similarly, sites falling be-
low the line indicate that concentrations,
on the average, were higher in the sam-
pling location represented on the horizon-
tal axis.
Abatement Area
Three sites (Sites A, E, and I) showed
higher mean asbestos concentrations in
1990; the increase was statistically signifi-
cant (p<0.05) at Site E. Sixteen sites (Sites
B - D, F - H, J - O, and Q - T) showed
lower mean asbestos concentrations in
1990; the decrease was statistically sig-
nificant (p<0.05) at 11 sites (Sites C, D, F,
H, K - O, Q, and T). The asbestos con-
centration at one site (Site P) did not
change.
Perimeter Area
Nine sites (Sites A, B, E, F, I, J, N, O,
and R) showed higher mean asbestos con-
centrations in 1990; the increase was sta-
tistically significant (p<0.05) at Sites E and
R. As noted in the preceding subsection,
She E also showed a statistically signifi-
cant increase in the asbestos concentra-
tion in the abatement area. Eleven sites
(Sites C, D, G, H, K, L, M, P, Q, S, and T)
showed a lower mean asbestos concen-
tration in 1990; the decrease was statisti-
cally significant (p<0.05) at six sites (Sites
D, H, L, P, R, and T).
The reasons for the variation in asbes-
tos concentrations between 1988 and 1990
are not discernible. The decrease in as-
bestos concentrations in the previously
abated area may be due to the reduction
of air-entrainable asbestos or to the sam-
pling technique. Regarding the latter, the
1988 measurements were made under
aggressive sampling conditions during the
AHERA clearance phase of the abate-
ment, whereas the 1990 measurements
were made under less aggressive sam-
pling conditions. The increase in asbestos
concentrations measured at Site E in 1990
may be due to maintenance activities (such
as buffing and stripping of the resilient
floor tile) rather than the sampling tech-
nique. Subsequent to the 1988 abatement,
which involved the removal of asbestos-
containing suspended ceiling panels, Site
E did not undergo any abatement. The
building contains no ACM other than the
resilient floor tile (Table 1).
The increase in asbestos concentrations
in the perimeter areas in 1990 may be
due to the presence of residual asbestos-
containing dust resulting from the 1988
abatement action or subsequent opera-
tions and maintenance activities (e.g.,
maintenance activities on resilient floor tile)
or to some nontypical simulated activity. If
the asbestos-containing dust was present
in 1988, the passive sampling protocol
used may not have been adequate to
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T»blo2. Maan Concentrations of Airborne Asbestos Measured in 1988 and 1990 at 20 Sites
Mean asbestos concentration,
Abatement area
SHo
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
1988
0.002
0.016
0.060
0.079
0
0.024
0.007
0.016
0
0.004
0.063
0.118
0.322
0.100
0.004
0.005
0.099
0.002
0.012
0.049
1990
0.007
0.015
0.001
0.001
0.004
0.001
0.001
0
0.001
0
0
0.002
0
0.007
0.001
0.005
0.019
0
0.003
0.001
Perimeter
1988
0.001
0.008
0.002
0.062
0
0.002
0.010
0.062
0
0.001
0.008
0.060
0.002
0.003
0.003
0.007
0.055
0
0.003
0.030
1990
0.011
0.010
0.001
0.001
0.006
0.005
0.001
0
0.011
0.003
0.007
0.001
0
0.004
0.018
0
0.010
0.011
0.001
0.001
Outdoors
1988
0
0.001
0.004
0.052
0
0.001
0
0.003
0.006
0.001
0
0.004
0.002
0.004
0.001
0.003
0.007
0
0
0.015
1990
0
0.001
0
0
0
0
0.001
0
0.001
0
0.001
0
0
0.001
0.001
0
0.001
0.013
0
0.005
reentrafn the asbestos into the air. Con-
versely, a decrease In concentration at
some sites suggests that air-entrainable
asbestos was not as prevalent.
Conclusions
The following are the principal conclu-
sions reached during this study:
Four of the 20 sites sampled in 1990
under simulated occupancy conditions
showed significantly higher airborne
asbestos concentrations in the previ-
ously abated area and/or perimeter
area than outdoors. None of the four
sites underwent an asbestos abate-
ment action after 1988, and the as-
bestos-containing material remaining
in the sites was primarily resilient floor
tile.
• Three of the 20 sites showed signifi-
cantly higher airborne asbestos con-
centrations in the previously abated
area and/or perimeter area in 1990
than in 1988. Variations in asbestos
levels between 1988 and 1990 may
be due to sampling techniques, re-
sidual air-entrainable asbestos from
the 1988 abatement action, or air-
entrainable asbestos from operations
and maintenance activities since 1988.
Recommendations
• Although these data provide valuable
information regarding the residual lev-
els of asbestos under simulated con-
ditions of occupancy 2 yr after abate-
ment, they may not be representative
of concentrations measured during
actual conditions of occupancy.
Followup air monitoring should be con-
ducted to determine their representa-
tiveness. The results of this sampling
may help to direct future research
efforts aimed at characterizing the ef-
fectiveness of asbestos abatement
programs and at evaluating the need
for EPA guidance on postabatement
management practices.
• The four sites showing elevated as-
bestos concentrations should be
evaluated to determine the sources
of asbestos and to identify appropri-
ate corrective measures.
The full report was submitted in fulfill-
ment of Contract No. 68-CO-0016 by IT
Environmental Programs, Inc., under the
sponsorship of the U.S. Environmental Pro-
tection Agency.
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I
I
0.35
0.30
0.25 .
0.20-
0.15
0.10 •
0.05
0.00
M
D
« C
T
H
Each letter in the graph
indicates the site label.
N
The diagonal line represents
concentrations that were the
same in 1988 and 1990.
0.000 0.005 0.010 0.015 0.020 , 0.025
1990 Average Concentration in the Previously Abated Work Area, s/cm3
0.35
0.30
%
£
2
"8
0.25
If
0.20 3
0.15
0.10 1
• 0.05 >
I
. 0.00
0.030
Figure 1. Comparison of postabatement (1988) work area concentrations with work area concentrations two years after abatement (1990).
0.07-
0.06-
0.05-
.| 0.04
5
0.03
S. 0.02
•*: 0.01 -
1
0.00
H D
Q
Each letter in the graph
indicates the site label.
The diagonal line represents
concentrations that were the
same in 1988 and 1990.
0.010 0.015 0.020
1990 Average Perimeter Concentration, s/cm &
0.07
0.06
<
2
1
- 0.05
0.04
0.03
0.02
§••
- 0.01 -J
-0.00
0.025
Figure 2. Comparison of postabatement (1988) perimeter concentrations with perimeter concentration two years after abatement (1990).
•&U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40237
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J.R. Kominsky and R.W. Freyberg are with IT Environmental Programs, Inc.,
Cincinnati, OH 45246. J.A. Brownlee andD.R. Gerberare with the New Jersey
Department of Health, Trenton, NJ 08625.
T.J. Powers Is the EPA Project Officer (see below).
The complete report, entitled "Asbestos Concentrations Two Years after Abatement
In Seventeen Schools," (Order No. PB92-158 476/AS; Cost: $17.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
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