United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/8R-92/127 December 1992
EPA Project Summary
Mutagenicity of Emissions from
the Simulated Open E3urning of
Scrap Rubber Tires
P. M. Lemieuxand D. M. DeMarini
Discarded automobile tires have be-
come a serious health concern, largely
because the growing number of stock-
pile fires has focused attention on the
potentially harmful products of incom-
plete combustion (PICs) emitted into
the atmosphere from uncontrolled burn-
ing of scrap tires. This report describes
a follow-up to a small-scale combus-
tion study that was designed to collect,
identify, and quantify the products emit-
ted during the simulated open com-
bustion of scrap tires. During the pre-
vious study, it was found that total es-
timated emissions of semi-volatile or-
ganics ranged from 10 to 50g/kg of tire
material burned. Mono- and polyaro-
matic hydrocarbons were the predomi-
nant emission products identified. For
the follow-up study described in this
report, the extracts from this study were
subjected to bioassay directed fraction-
ation to determine mutagenic poten-
cies of the extracts. The results from
these bioassay studies were then com-
pared to data from other conventional
combustion sources indicate relative
potencies of the emissions from un-
controlled burning of tires. The frac-
tionated extracts were then subjected
to further gas chromatography/mass
spectroscopy (GC/MS) analysis to de-
termine the classes of compounds giv-
ing the highest mutagenic potencies.
In addition, a sample from an actual
tire burn was subjected to the same
bioassay analyses to determine the rel-
evance of the initial small-scale simu-
lations to actual field samples from a
full-scale tire fire.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This study is a follow-up to a study
performed for the EPA's Control Technol-
ogy Center (CTC) to characterize emis-
sions from the simulated open burning of
scrap tiresi. The full report of the results
from the initial study is available. For
clarity, a summary of the initial study is
included in this report.
Summary and Conclusions
Characterization of Emissions
The primary goal of this project was to
characterize potentially harmful emissions
from the simulated open burning of scrap
tires. The simulation was necessarily
crude, because it would be extremely dif-
ficult to match the burning of the equiva-
lent of two tires with a 6 million tire, full-
scale, stockpile fire. Nevertheless, the
study allowed the investigators to identify
and measure gaseous emissions and di-
rectly relate this information to a mass
burn rate. This task was accomplished by
accurately measuring dilution volumes,
sample volumes, and weights of tire ma-
terial combusted.
The dilution air added to the burn hut
was used not only to control known vol-
umes introduced, but also to simulate am-
Printed on Recycled Paper
-------
biant conditions. It is probable that the
same types of compounds identified dur-
ing this study are emitted during an actual
fire, but whether the average gaseous con-
centrations and estimated emissions are
comparable is uncertain. A comparison
with limited data collected at a Winches-
ter, Virginia, fire by the National Institute
for Occupational Safety and Health
(NIOSH), indicates that reasonable agree-
ment exists within several measurement
areas. Many of the same compounds
were Identified in actual plume samples.
Particularly good agreement exists in poly-
cyclic aromatic hydrocarbon (PAH) plume
measurements. NIOSH reported that am-
bient concentrations of total PAHs are gen-
erally within the same order of magnitude
as average gaseous concentrations ob-
tained during testing. Measurements of
carbon monoxide (CO) and metals also
indicate simitar agreement. Both lead and
zinc measurements show similar values in
both gaseous and relative concentrations
between the two metals. It may be rea-
sonable to assume that the estimates ob-
tained during this study may be within an
order of magnitude of emissions realized
from actual stockpile fires.
The results from the airborne metals
portion of the study were inconclusive.
Maximum values were presented, often
based on detection levels. Emissions of
lead and zinc may reach significant quan-
tities. Chemical analysis of the flyash
reveals that zinc comprises nearly 50% of
the total residue. Evidently, the other
metals known to be contained in tires re-
main in the ash residue. Although no
attempt was made to analyze ash resi-
due, significant quantities of metals present
in the ash could potentially be leached out
into groundwater systems, posing another
major problem.
The values obtained by on-line analyz-
ers for normal combustion gases showed
that, as burn rate increased, the amount
of CO, sulfur dioxide (SO2), and unburned
hydrocarbons also increased. High burn
rate conditions were not fully evaluated,
so greater quantities of these gases, par-
ticularly SOj, may be emitted during a
stockpile fire. Tires contain a significant
amount of sulfur, so high emissions of
SO,, while likely only a minor contributor
to tne acid rain problem, could have sig-
nificant local consequences.
This study was designed to identify the
potential chemical hazards from tire fires
on a small-scale, simulation basis. The
study reveals the potential for the emis-
sion of great amounts of organic com-
pounds, primarily aromatics, some of which
may be extremely harmful. Although the
estimates of average gaseous concentra-
tions and estimated emissions are crude,
the trends presented in regard to burn
rate may be helpful in directing further
research and control efforts. The fact that
the shredded (5 X 5 cm cubes) condition
resulted in a lower burn rate than the
chunked (one-quarter to one-sixth of whole
tires) condition indicates that the gaps be-
tween the tire material provide the major
avenue of oxygen transport. Oxygen trans-
port appears to be a major if not the
controlling mechanism for sustaining the
combustion process. This fact could have
advantageous implications for those at-
tempting to combat tire fires. It may be
possible to fill the gaps between tires with
a foam inhibitor, potentially suffocating the
fire from within.
The extreme complexity of the organic
emissions confounded attempts to quan-
tify all compounds present. In fact, only
around 10 % of the chromatographic peaks
were identified, although most of the or-
ganic mass was identified. This suggested
that a different approach to emissions
measurements, one that applies to com-
plex mixtures, might be useful. The CTC
provided additional funding to examine the
complex mixtures resulting from simulated
open combustion of scrap tires with the
bioassay-directed fractionation technique.
The relative potency of the emissions could
then be compared to other well-character-
ized combustion sources.
Mutagenicity of Emissions
In general, the mutagenic potency of
the semi-volatile organics (those collected
on XAD resin) was similar for chunked or
shredded tires. However, the mutagenic
potency of the particulate organics (those
collected on filters) was 2-10 times greater
than that of the semi-volatile organics.
Chunked tires produced more potent or-
ganics as assayed in the presence of 59,
but shredded tires produced more potent
organics as assayed in the absence of
S9. This difference is a reflection of the
different classes of chemical mutagens
that likely were produced under the two
combustion conditions. Based on addi-
tional data, these results suggest that the
particulate organics from chunked tires
contain more PAHs than are present in
the effluent produced by shredded tires.
This is likely due to the greater burn rate
that was achieved with chunked tires, lead-
ing to the production of PAHs.
In general, the mutagenic emissions
factors (revertants/kilogram of tires or
reverants/megajoule of heat) were similar
for the semi-volatile organics produced by
chunked or shredded tires as assayed in
the presence or absence of S9. The
mutagenic emission factors for the par-
ticulate organics were much greater than
those for the semi-volatile (XAD bound)
organics.
The average of the chunked and shred-
ded particulate mutagenic emission factor
for the open burning of tires as assayed in
Salmonella strain TA98 in the presence of
S9 was compared to that of other com-
bustion emissions. The results showed
that the mutagenic emission factor for open
tire burning is the greatest of any other
combustion emission studied previously.
For example, it is 3-4 orders of magnitude
greater than the mutagenic emission fac-
tors for the combustion of oil, coal, or
wood in utility boilers. Table 1 illustrates
the mutagenic emission factors derived
from this study.
interestingly, the mutagenic emission
factor for the open burning of tires was
most similar to the values for the open
burning of wood (in residential fire places)
and plastic (in agricultural fields). These
open burning conditions are characterized
by poor combustion parameters, resulting
in elevated levels of PICs and, thus,
elevated mutagenic emission factors. Open
burning, regardless of the feed stock or
fuel, appears to result in greater mutagenic
emission factors than does controlled com-
bustion as provided by various types of
incinerators or boilers.
The high-pressure liquid chromatogra-
phy (HPLC)-generated mutagrams were
similar for the particulate organics result-
ing from the open burning of either
chunked or shredded tires. This suggests
that there were only minor differences in
the chemical composition of the two efflu-
ents. Chemical analysis of selected mu-
tagenic HPLC fractions identified PAHs
has a major contributor to the mutagenic
activity of the organics. In addition, oxy-
genated PAHs, such as anthraquinone,
and various aromatic compounds that con-
tained ring nitrogens, such as acridine,
were also present in mutagenic fractions.
The mutagenic potency of the unfrac-
tionated particulate organics in various
strains of TA98 in the absence of S9
showed that little of the mutagenic activity
was due to mononitroaromatics, but as
much as two-thirds of the mutagenic ac-
tivity (in the absence of S9) was due to
either dinitroaromatics or other types of
nitroarenes or aromatic amines that re-
quire metabolic conversion to arylhydro-
xylamines and then esterification in order
to be mutagenic.
Through the auspices of colleagues at
McMaster University in Hamilton, Ontario,
Canada, we were able to obtain samples
-------
of particulate organics from the effluent of
a large open tire burn that occurred dur-
ing 2 weeks in Hagersville, Ontario, in
February 1990. This real-world sample
had a similar mutagenic potency as did
the EPA sample. In addition, the
mutagram contained several of the same
mutagenic fractions (particularly the PAH-
containing fraction) as did the EPA
mutagram, and the Canadian sample also
showed evidence that various types of
nitroarenes or aromatic amines were
present as in the EPA sample. Chemical
analysis also showed great similarity be-
tween the Canadian and EPA samples.
Based on these chemical and biological
measurements, the EPA tire burn simu-
lated reasonably well a major real-world
tire burn of the type experienced in
Hagersville, Ontario. This conclusion
should provide some confidence in ex-
trapolating from the EPA simulated tire
burn to real-world tire burns.
Considering (a) the relatively high mu-
tagenic potency of the particulate organ-
ics, (b) the high mutagenic emission fac-
tors, and (c) the presence of many mu-
tagens/carcinogens, especially PAHs, in
the effluent from the open burning of tires,
such burns pose a genuine environmental
and health hazard. Because of the fre-
quent occurrence of unwanted combus-
tion at tire piles, and the potential environ-
mental and health risks posed by such
combustion, prudence would suggest that
such piles be reduced or eliminated in
size and number. Used tires may be
recycled, used in asphalt for roads, or
incinerated under controlled condition in
combustion devices for cogeneration of
power. Any of these uses would appear
to be preferable to the environmental and
health risks posed by the open burning of
tires.
Table 1. Mutagenic Potencies and Mutagenic Emission Factors of DCM-Extractable Organics in TA98'
' ' "*"""" " "'"" • XAD (revertants per)
Filter (revertants per)
Day Condition
1 Chunk
Shred
2 Chunk
Shred
Bum
rate
(kg/h)
9.4
1.1
3.5
1.3
Filt.
EOMb
4.5
22.6
6.8
16.7
S9 ng
+ 2.2
1.9
+ 0.7
1.0
+ 2.1
1.4
+ 4.3
8.9
m3
1536
1326
623
890
1573
1049
4726
9781
Kg of
fuel
X105
14.88
12.85
0.17
0.25
18.76
12.51
59.26
122.65
MJof
heat
42690
36866
487
717
53822
35891
170016
351822
MO
12.0
2.3
4.3
8.9
10.4
2.3
7.0
7.0
m3
403608
77358
29335
60716
192379
42545
61397
61397
Kg of
fuel
X 10s
873.61
167.44
484.23
100.25
1036.52
229.23
769.25
769.25
MJof
heat
2506387
480385
1389255
2875455
2973775
657660
2206978
2206978
a DCM = dichloromethane
b EOM = extractable organic matter
•U.S. Government Printing Office: 1993 — 750-071/60175
-------
D.M. DeMarini Is with the U.S. EPA, Health Effects Research Laboratory, Research
Triangle Park, NC27711.
PaulM. Lemieux is the EPA Project Officer (see below).
The complete report, entitled "Mutagenicity of Emissions from the Simulated Open
Burning of Scrap Rubber Tires," (Order No. PB92- 217009/AS; Cost: $19.00;
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:
Air and Energy Engineering 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
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-92/127
------- |