vvEPA
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1-81-041 July 1981
Project Summary
Microwaves,
Hyperthermia, and
Human Leukocyte Function
Norbert J. Roberts, Jr., Shin-Tsu Lu, and Sol M. Michaelson
The objective of this study is to
determine whether exposure to micro-
waves (2450 MHz) affects the func-
tion of human leukocytes in the resting
state and during antigenic or mitogenic
challenge. This publication is a sum-
mary report of the construction and
calibration of a waveguide exposure
system for the exposure of human
mononuclear leukocytes to 2450 MHz
(CW) microwave energy. A description
of the dual vial waveguide exposure
facility for in vitro irradiation of human
leukocytes is presented. Calorimetric
determinations of specific absorption
rates (SAR) were made using heating
curves measured with a microwave
transparent Vitek 101 Electrothermia
Monitor. The correlation between
SAR and forward power was highly
significant (r = 0.95). At a forward
power of 0.55 W, the averaged SAR
was approximately 33 mW/ml. How-
ever, inhomogeneity and significant
resonance absorption were noted in
the dual vial waveguide exposure
facility. A 30-point measurement of
SAR distribution revealed that the
SAR at any of the measured points
could range between 0.12- and 3.94-
fold of the average SAR within the
given vial. Measurements indicated
that this variability in SAR values did
not create significant thermal gradients
within the vials when external agita-
tion was applied.
This Project Summary was devel-
oped by EPA's Health Effects Research
Laboratory, Research Triangle Park,
NC, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Microwave radiation has many cur-
rent uses that result in public exposure,
with very little information available on
the effects of microwaves on man.
Investigators have reported increased
spontaneous transformation of lympho-
cytes from animals that have been ex-
posed to microwaves. These effects are
still of unknownfunctional significance.
Quantisation of thermal variables is
difficult but it is critical to understanding
these effects. This study will determine
whether microwave exposure of human
mononuclear leukocytes in vitro will
similarly affect these cells, and will
determine whether such effects are
beneficial or detrimental and finally, will
determine the influence of thermal flux
in these reactions. In addition, the
studies will explore the effects of micro-
wave-induced hyperthermia on the
function of human leukocytes in host
defenses that are pertinent when chal-
lenged by bacteria, viruses, toxic foreign
material and neoplastic tissue.
Human mononuclear leukocytes will
be exposed in vitro to microwaves in a
37°C environment to effect no change
in temperature and to attain tempera-
tures in the range of 37 to 42°C, to
provide a definition of temperature-
response relationship. Low equivalent
-------
power densities (<0.5-10 mW/ml) will
be specifically examined. Exposure
without temperature increase will be
studied initially. The function of these
cells, measured by transformation re-
sponse to mitogen or antigen, will be
assayed and compared to that of cells
treated concurrently in a like fashion
with the exception of microwave expo-
sure. The latter cells, in studies of
temperatures >37°C, would have their
temperature set by exposure to appro-
priate ambient temperature conditions.
This report details the construction
and calibration of the dual vial waveguide
system to be used for the in vitro expo-
sure of human leukocytes at 2450 MHz.
Technical Discussion
The study reached these objectives:
(1) design, acquisition and construction
of the microwave dual vial exposure
system; and (2) dosimetry analysis of
the system. Analysis of dosimetric and
thermal characteristics constituted the
major scientific effort after system
procurement and construction.
Figure 1 shows the block diagram of
the waveguide exposure facility for cell
exposure to microwaves. The waveguide
exposure chamber dimensions are
shown in Figure 2.
Calorimetric determination of specific
absorption rate (SAR) was made using a
microwave transparent Vitek 101 Elec-
trothermia Monitor. SAR values were
determined using heating curves at
Coaxial
Termination
f
^-XXV>
~r
!
-•
^
> 6.*30
J5.40
( Pov
\Sou
Plexiglass holder
/ 'Low density styrofoam spacer
1 /_/ CC II ,
O /i
A - 'i - rv-
0 0.95 ^ 0-
-*lt " ll
\ ta- "*J3/
2.90 J'c
« f /? ifn hi IA.O /r/ih
•JO.UU "• •
f/ns/dej
11.80
f /1.00 •*
(Inside)
Figure 2. Dual vial waveguide exposure chamber.
steady state [Ln( ATss-AT) = Ln ATss-k-t].
Heating analysis was employed for the
following reasons: (1) deviation from
linearity occurs consistently earlier in
the cooling curve than in the heating
curve; and-(2) a slower and larger devia-
tion is noted in the cooling constant
determined by cooling analysis than by
heating analysis. Table 1 shows the
calorimetric determination of SAR using
u
1
WR430 WR430 \
Sham Exposure
Agitator \
Jacketed Incubator
Figure 1. Microwave exposure system
heating analysis. Specific absorption
rates were also determined from the
power reading sampled by,4he bidirec-
tional coupler. SAR determinations of
the dual tube waveguide exposure
facility are shown in Table 2.
Determination of SAR under different
dosimetric procedures is shown in Table
3. SAR determinations using muscle
phantom material in the vials and
medium in the vials with agitation but
no insulation and under non-steady-
state conditions gave the highest SAR
values. A 30-point measurement of
SAR distribution in the vials using
muscle phantom material showed 0.12
to 3.94-fold variation from the averaged
SAR for the vial.
Conclusions
Inhomogeneity and significant reso-
nance absorption were noted in the dual
vial waveguide exposure facility. A 30-
point measurement of SAR distribution
revealed that the SAR at any of the
measured points could range between
0.12- and 3.94-fold of the average SAR
within the given vial. However, such
variable SARs did not create significant
thermal gradients within vials when
external agitation was applied. The
differences in averaged SAR between
vials of the present dual-vial waveguide
system were not significant, irrespective
of the method of quantitation used. This,
as well as the fact that much lower
averaged SAR values are planned for
-------
able 1 . Calorimetric Determination of SAR Using Heating Analysis
Forward
Power" (W) &.Tss(°Cf kfrnin'^f SAR (mW/mlf
0.22
0.33
0.45
0.55
0.55
0.67
0.67
0.77
0.78
0.78
0.79
0.89
0.89
J.OO
1.01
1.01
1.10
1.13
1.18
1.28
2.28
3.04
3.47
4.91
4.53
4.79
4.57
6.98
6.44
5.63
5.10
7.24
6.40
6.60
7.03
7.43
6.40
8.10
9.24
9.39
-0.0617
-0.0928
-0.0710
-0.0794
-0.0961
-0.0751
-0.0921
-0.0763
-0.0856
-0.0824
-0.0864
-0.0798
-0.0841
-0.0783
-0.0882
-0.0942
-0.09O2
-0.0896
-0.0809
-0.0909
-0.0838
±0.0087 (mean ±S.D.)
9.54
15.96
16.70
26.49
29.57
24.45
28.59
35.68
37.89
31.48
29.92
39.22
36.54
35.12
42.10
47.54
39.20
49.26
50.78
57.95
*A7"ss = steady state temperature increment.
bk = cooling constant.
CSAR: specific absorption rate.
'able 2. Comparison of SAR's for Right and Left Vials
the biological work, indicates that this
exposure system can provide an assess-
ment of the importance of inhomoge-
neous SAR in the absence of substantial
compromise by thermal mechanisms.
Recommendations
The construction and dosimetry mea-
surement phase of this project has gone
well. The dosimetry should go a long
way in evaluating the data of human
leukocytes exposed to microwaves. It is
recommended that this project proceed
to the evaluation of the effects of micro-
waves on human leukocytes exposed at
2450 MHz in this exposure system.
Forward Power
(mW -20.4 dB)
0.1
0.5
0.8
1.0
1.5
1.8
2.0
2.5
2.8
2.85
3.0
3.5
3.8
4.0
5.0
5.1
6.0
6.1
7.0
7.2
8.3
8.4
9.2
10.0
SAR, Left Vial
0.93
4.70
7.51
9.40
14.09
16.92
18.80
23.51
—
26. 80
28.21
32.91
35.74
37.61
—
47.97
—
57. 38
65.84
—
—
78.98
86.48
93.98
SAR, Right Vial
0.93
4.69
7.50
9.38
14.08
16.88
18.78
23.46
26.30
—
28.17
32.89
35.71
37.60
47.03
—
65.43
—
—
67.73
78.07
—
86.54
94.06
* US. GOVERNMENT PHNTING OFFICE 1M1 -757-012/7213
-------
Table 3. Determinations of SAR with Different Dosimetric Procedures
Procedure Right Vial Left Vial
Muscle phantom,"
Urn d/dt
f-0
Culture medium, agitated,
non-insulated, non-steady-state
Culture medium, agitated,
insulated, linear heating rate
Culture medium, agitated,
non-insulated, steady-state
58.7 ±46.2 (30f 76.1 ±63.9 (30f
63.4 ± 45.4 (29)
80.0 ± 23.1 (4) 72.9 ± 9.2 (4)
34.1 ±2.9 (4) 31.3 ±3.2 (4)
26.4 ±4.4 (4) 28.8 ±0.7 (4)
^Multiple points measured within the vial.
"Mean ± S.D. (no. of determinations).
NorbertJ. Roberts, Jr., Shin-Tsu Lu, and SolM. Michaelson are with the Univer-
sity of Rochester School of Medicine, Rochester, NY 14642.
Ralph J. Smialowicz is the EPA Project Officer (see below).
The complete report, entitled "Microwaves, Hyperthermia, and Human Leuko-
cyte Function." (Order No. PB 81 -208 951; Cost: $6.50, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, MA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
-------
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1-81-042 July 1981
Project Summary
Determinants of Cancer and
Cardiovascular Disease
Mortality in Mining
Counties of California
R. A. Ziskind, D. F. Smith, J. L Hahn, and G. Spivey
The purpose of this research effort
was to design an epidemiological
study protocol to evaluate the influence
of environmental asbestos exposure
on mortality from lung cancer, meso-
thelioma. and cardiovascular disease
in the asbestos mining areas of Cali-
fornia. Mortality data (1968-1978)
and emissions data (both anthropo-
genic) were reviewed in an effort to
determine the most preferable study
area. The area selected for future
study was Western Calaveras and
Tuolumne Counties which contain the
Calaveras serpentine deposit. Selec-
tion criteria included suitable popula-
tion base, sufficient number of deaths,
evidence of elevated airborne and
waterborne asbestos concentrations,
and the existence of archives contain-
ing ambient air sampler filters for
preceding years. A questionnaire was
developed for obtaining information
from next-of-kin of decedents in the
study area though interviewing was
not attempted. Next-of-kin interviews
are expected to be a component of
future studies. Necessary elements of
quality assurance were identified and
documented as part of protocol design.
This Project Summary was devel-
oped by EPA's Health Effects Research
Laboratory, Research Triangle Park.
NC, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This epidemiological study evaluates
the hypothesis that asbestos-related
health effects have been observed
among populations not occupationally
exposed. The study was divided into four
conceptual tasks:
Epidemiological protocol design. I n
this segment, alternative study ap-
proaches were evaluated. The mortality
data base, the sources, and the exposure
to asbestos were considered.
Questionnaire development. In con-
cert with protocol design and exposure
findings, the primary data-gathering
mechanism for obtaining subject infor-
mation from survivors was drafted, pre-
tested, revised, and submitted.
Source inventory and exposure char-
acterization. All anthropogenic and
natural emission sources of asbestos
were delineated and quantified in each
California study area. Existing occupa-
tional and ambient data were reviewed
to establish inhalation and ingestion
population exposure.
Quality assurance. Elements of qual-
ity assurance were to be identified and
documented as part of the protocol
design.
The initial components of this study
were the source inventory and exposure
characterization. A summary of the
-------
principal findings are given here.
Two distinct California asbestos min-
ing and milling areas were researched.
One is associated with a serpentine
deposit running through the junction of
Fresno and San Benito Counties (herein
referred to as the New Idria Deposit).
The second is located throughout the
western sections of Calaveras and
Tuolumne Counties (the Calaveras De-
posit). The preferable study area was
determined to be that associated with
the Calaveras Deposit. Selection criteria
included greatest population base, evi-
dence of elevated airborne and water-
borne concentrations of asbestos, and
the existence of archives of useful
ambient air sampler filters dating back
over seven years.
For the case of the New Idria Deposit,
the mining areas are sufficiently remote
to make it unlikely that any population
center will be affected. One mill is
located near a community and limited
airborne asbestos measurements point
to significant concentrations there at
the time taken.
By contrast, the Calaveras Deposit
area has a greater at-risk population as
a result of mining and milling of asbestos
and other minerals. In addition, airborne
background ambient levels taken up-
wind or remote from known sources are
elevated. No waterborne asbestos mea-
surements were made specifically for
the water distribution systems serving
the Calaveras Deposit area; however,
measurements on San Francisco Bay
water district reservoirs located in
western CalaverasandTuolumneCoun-
ties show higher than average concen-
trations for those with supplies passing
through serpentine formations. The
oldest ambient data uncovered for the
Calaveras Deposit area was reported in
the California Department of Health
Study of 1965-1967. Asbestos concen-
tration was measured by dust sample
collection through impingers. Quantifi-
cation was by optical microscopy. Mea-
sured ambient levels (upwind at a large
mine site, etc.) on two separate occa-
sions ranged between 0.1 and 2 million
particles per cubic fcfot of air. A federal
study at about the same time of the area
"Environmental Survey of Asbestos
Mining and Milling in California" De-
cember, 1966, Public Health Service
Division of Occupational Health, suggests
the equivalence 10 total fibers/cc = 1
mppcf by impinger. In the cited ambient
concentrations (from the NIOSH Rec-
ommended Asbestos Standards), the
levels across the country are summar-
ized as generally < 10 ng/m3 with
occasional peaks as high as 100 ng/m3
(by electron microscopy). Using optical
microscopy, ambient levels are generally
less than 0.01 fibers > 5 /um/cc with
peak values as high as 0.03 fibers > 5
//m/cc. Use of the Public Health Service
equivalence 6 fibers > 5 //m/cc = 1
mmpcf by impinger yields the mine area
ambient (upwind) concentration range
0.6-12 fibers/cc.* Further, use of the
NIOSH suggested equivalent 20 fibers
> 5 ism in length (as determined by
optical microscopy) per nanogram of
asbestos yields the mine ambient range
12-240 ng/m3. Thus, the ambient levels
detected at upwind locations in the
vicinity of a Calaveras mine/mill are at
the extreme high end of the surveyed
range.
High volume air sampler filters from
the Calaveras Deposit area population
centers have been located in the Cali-
fornia Air Resources Board archives
dating back to the early 1970s. They can
be utilized to quantify airborne asbestos
concentration and they therefore ap-
proximate exposure data. Coupled with
the water assay, they will establish the
quantitative relationship among popu-
lation centers in the serpentine area
and the other areas of Calaveras and
Tuolumne Counties. Also, they will
provide the basis for stratifying the
populations according to inhalation and
ingestion exposure.
Based upon the source and exposure
information available to this study, the
potential study group was defined as
those people who died in Calaveras and
Tuolumne Counties during the last ten
years. Approximately 4,300 people will
be included. Exposure of the prelim-
inarily identified group is expected to be
significant; principally due to general
ambient sources rather than a dominant
single point source. Exposure may be
differentiated among the group members
between air and water, with either
predominating in particular residential
segments. This approach will permit
investigation of the relative importance
of different exposure routes and will
facilitate interpretation of possible
dose-effect relationships. Water distri-
bution systems for the area through the
last ten years were described.
•Note: The current NIOSH recommended standard
is 0.1 fiber/cc for an 8-hour time-weighted
average.
Conclusions
There are two principal areas of
California in which asbestos mining and
milling activities are conducted. This
study investigated both areas and sur-
veyed the anthropogenic and natural
sources of asbestos emissions into the
environment. The county areas which
constitute both regions are principally
rural; the cities generally contain less
than 6,000 people. The only large cities
in Calaveras, Fresno, Monterey, San
Benito, and Tuolumne Counties are
located apart from the serpentine areas.
The coincidence of asbestos mining and
milling with such less-urbanized county
areas is a favorable factor; people in
more populous urban centers are ex-
posed to a number of toxic substances in
their ambient environment.
Based upon the synthesis of published
literature, a field survey, and the review
of the limited asbestos monitoring infor-
mation available, the study concluded
that airborne and waterborne asbestos
levels in particular areas of Calaveras
and Tuolumne Counties may be elevated
with respect to background. In the other
principal serpentine area (San Benito,
Fresno, Monterey), insufficient infor-
mation is available to estimate exposure.
In these latter areas, mining activities
are relatively isolated from population
areas. However, ore transport and
milling are in the King City-San Lucas
areas. Isolated airborne data taken in
King City showed elevated concentra-
tions; more extensive mill site data
(provided by the mill management)
appears somewhat lower. The single
piece of waterborne assay information
from the Coalinga vicinity is insufficiently
documented to be definitive.
Upwind data taken at Calaveras as-
bestos during 1965-1967 range from
12-240 ng/m3 extrapolated to electron
microscope concentrations from optical
microscopy counts of fibers greater than
5 yum. Ambient concentrations across
the country are generally below 10
ng/m3.
High volume air quality sampler filters
were located in the archives of the
California Air Resources Board for a
number of sites in Calaveras and
Tuolumne Counties. Samples of 24- and
48-hour duration date back to the early
1970s. These asbestos analyses are
practical and may be utilized to provide
an exposure mapping of the areas of inter
est.
Water distribution systems in Cala-
veras and Tuolumne Counties have
been identified. Sources, routes, and
-------
reatment differ throughout the area. No
specific asbestos analyses of the water
jsed for local supply was found. Based
jpon several available measurements
if elevated asbestos content in serpen-
ine deposit area reservoirs (which
;erve San Francisco Bay communities),
water sampling and analysis should be
jerformed for chrysotile asbestos.
Based upon available air and water
Jata, elevated asbestos exposure to the
jeneral population may have occurred
n areas of Calaveras and Tuolumne
bounties.
Recommendations
Water sampling and air/water anal-
ysis should be conducted to define ex-
sosure to the population by place of
•esidence. Parallel with that effort,
nformation from the California death
ape rolls can be initially extracted on an
mnual basis for both counties. These
apes can be processed according to
:ause of death (ICO system) with case
md control groups extracted, and dis-
tase mortality rates compiled. The
statistical adequacy of all cause-of-
leath categories of interest would then
3e determined. All diseases associated
with occupational exposure to asbestos
would be considered. In addition, all
itatistically adequate death category
loputations can be contrasted as a
unction of exposure. The product of this
iffort is the delineation of the range of
correlation of mortality categories with
ixposure. This may suggest additional
:ause-of-death categories. These steps
will be followed by the final study
components which will include the
detailed data gathering by survivor
questionnaire and medical records and
he comprehensive data analyses.
/?. A. Ziskind, D. F. Smith, J. L Hahn, and G. Spivey are with Science Applica-
tions, Inc., Los Angeles, CA 90067.
John Acquavella is the EPA Project Officer (see below).
The complete report, entitled "Determinants of Cancer and Cardiovascular
Disease Mortality in Asbestos Mining Counties of California," (Order No.
PB 81 -208 985; Cost: $11.00, 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:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
> U£ GOVERNMENT PfdNTINO OfFRE. 1981 -757-012/7211
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
HS
U b
------- |