1977). Irritant gases such as hydrogen chloride (HC)
and acrolein, which can produce prolonged deleteri-
ous effects on the respiratory tract (Amdur, 1986; Gad,
1990b; Stavert et al, 1991), may inflict damage leading to
delayed death even when incapacitation does not occur
during exposure (Crane et al, 1985; Gad, 1990a; Kaplan
etal, 1985). The combined effects of mixtures of irritant
gases and systemic toxicants from burning polymers
further complicare an appropriate end point selection
(Craneetal, 1977, 1990; Gad, 1990a; Kaplanetal, 1985),
making the interpretation of material “rankings” difficult.

Our continuing interest in combustion toxicol-
gy prompted us to compare the relative toxicity
rankings forsix polymers selected from different chemi-
cal classes. This selection was to represent a spectrum
of common aircraft polymers with the potential to
generate different combustion gas(es) capable of caus-
ing acute to delayed toxic effects. Names, chemical
units and possible primary toxic gases of these poly-
mers are given in Table 1. The selected polymers were
individually decomposed under identical experimen-
tal conditions and ranked using the LCs and t,values
(at a fixed sample weight) as criteria. Additional rats
were exposed to combustion products from each poly-
mer at its LC,, fuel load to determine t, at this defined

condition of equal lethality.

MATERIALS AND METHODS

Polymer Selection

Nylon 6/6, polyamide resin, polyethylene (high
density), polystyrene, chlorinated polyethylene (40%
chlorine content), and polysulfone resin were ob-
tained from Aldrich Chemical Company, Inc. (Mil-
waukee, WI); their respective catalog/lot_ numbers
were correspondingly 18,112-9/04, 19,105-1/
04642BV, 18,190-0/05, 18,242-7/10, 18,194-3/
03691CW, and 18,244-3/06, Polymers did not con-
tain pigments or fire retardants. Pure polymers were
used to ensure uniformity of sample composition and
were purchased in sufficient quantities to allow the
entire study to be conducted using the same batch lots
for individual polymers,

Specific polymers were selected to provide as
broad a range of gas compositions as possible while still
relating to polymers used in aircraft. Polyethylene is a
ptimary carbon monoxide (CO) producer (Spurgeon
etal, 1977), while Nylon 6/6 (Terrill et al, 1978) and
polyamide (Spurgeon et al, 1977) are known togener-
ate CO and hydrogen cyanide (HCN). Polystyrene is
a polymer with a benzene rin g in its structure (Harper,
1975) and has the potential to produce CO, benzene,

and heavy black smoke containing finely divided car-
bon particles. In addition to CO, chlorinated polyeth-
ylene and polysulfone can produce HC] and sulfur
dioxide (SO,), respectively (Terrill et al, 1978).

Animals

Male Sprague-Dawley rats (100-120 g) Were sup-
plied by Charles River Breeding Laboratories
(Wilmington, MA). On receipt, all rats were inspected
by aveterinarian and were housed, four to six per cage,
in stainless steel cages with mesh-wire floors (27 cmH
x45 cm Wx61 cm) inthecentralized animal facility
of the Institute. The facil ity was maintained at 22-
24°C with a relative humidity of 40-60% and a 12-hr
light (7 a.m.-7 p-m.)-dark (7 p.m.-7 a.m.) cycle using
fluorescent lights. Animals were allowed food and
water ad libitum. Rats were held in isolation for ten
days before use and were fasted overnight prior to the
exposure to the polymeric combustion products. Indi-
vidual animal weights were determined immediately
before the experiments; the weight range at use was
150-250 g.

Combustion/Exposure System

‘Thecombustion/exposuresystem used in thestudy
isshown schematically in Figure 1. Itconsisted of three
primary components: a combustion unit, an animal
chamber, and a mixing/cooling plenum.

‘The combustion unit was constructed from stain-
less steel with a triangular cross section; full length
quartz windows in the side of the unit allowed radiant
heat from four 2,000-watt quartz lamps (two on each
side) to impinge on the sample surface at approxi-
mately 45° angles. The unit, designed by H. W. Stacy
in the laboratories of Weyerhaeuser Company
(Longview, WA), was modified in our laboratory to
allow air circulation around the sample. This modifi-
cation minimized anaerobic pyrolysis and decreased
smoke buildup within the unit that would cause a
reduction in heat flux at the sample position. A hot-
wire igniter was suspended 1 cm above the sample
position to ignite the evolved gases. The polymer-test
sample was contained in a 7.6 cm X 22.9 cm stainless
steel combustion boat.

The animal chamber was constructed from
polymethylmethacrylate (PMMA) with an internal
volume of 203 L. Mixing/cooling of the combustion
gases took place in a 42-L plenum, constructed from
polycarbonate, positioned at the end of the animal
chamber and over the combustion unit, This plenum
was connected to the animal chamber by two 7-cm
PMMA intake and exit tubes. The cooled gases were


Farrar DG. The effect of the sensory irritant component
ofa combustion atmosphere derived from Douglas
Fir on the leg-flexion avoidance response of the rat.
J. Combustion Toxicol. 1980; 7:3-22.

Fenner, OH. Chemical and environmental properties of
plastics and elastomers. In: Harper CA, ed. Hand-
book of plastics and elastomers. New York, NY:
McGraw-Hill Book Company, 1975:4-1-81.

Finney DJ. Probit Analysis, 3rd ed. Cambridge: Cam-
bridge University Press, 1971.

Gad SC. Combustion toxicity testing, In: Gad SC, Ander-
son, RC, eds. Combustion toxicology. Boca Raton,
FL: CRC Press, 1990a:81-128.

Gad SC. Basics of inhalation toxicology and heat stress
physiology. In: Gad SC, Anderson RC, eds. Com-
bustion toxicology. Boca Raton, FL: CRC Press,
1990b:23-62.

Gossel TA, Bricker JD. Carbon monoxide, cyanides and
sulfides. In: Principles of clinical toxicology. New
York, NY: Raven Press, 1984:84-104.

Harper CA. Fundamentals of plastics and elastomers. In:
Harper CA, ed. Handbook of plastics and elas-
tomers. New York, NY: McGraw-Hill Book Com-
pany, 1975:1-1-121.

Hartung R, Ball GL, Boettner EA, Rosenbaum R,
Hollingsworth ZR. The performance of rats on a
Rotarod during exposure to combustion products
of rigid polyurethane foams and wood. J. Combus-
tion Toxicol. 1977; 4:506-22.

Kaplan HL, Grand AF, Switzer, WG, Mitchell, DS,
Rogers, WR, Hartzell, GE. Effects of combustion
gases on escape performance of the baboon and the
rat. J. Fire Sci, 1985; 3:228-44.

Levin BC, Paabo M, Birky MM. An interlaboratory
evaluation of the 1980 version of the National
Bureau of Standards test method for assessing the
acute inhalation toxicity of combustion products.
Washington, DC: Department of Commerce/Na-
tional Bureau of Standards: 1983; Publication no.
NBSIR 83-2678. Available from: National Tech-
nical Information Service, Springfield, VA 22161.
Order #PB83-198093.

Lieberman HR. Computation of psychophysical thresh-
olds using the probit technique. Behavior Research
Methods & Instrumentation 1983; 15:446-48.

N.Y. Article 15, Part 1120, Combustion Toxicity Test-
ing. Uniform Fire Prevention and Building Code
Council. Albany, New York: State of New York,
Department of State, 1986.

Sanders DC, Crane CR, Endecott BR. Inhalation toxi-
cology: V. Evaluation ofrelative toxicity to rats of
thermal decomposition products from two aircraft
seat fire-blocking materials. Washington, DC: De
partment of Transportation/Federal Aviation Ad-
ministration: 1985; Publication no. DOT/FAA-
AM-86-1. Available from: National Technical In-
formation Service, Springfield, VA 22161. Order
#ADA165034.

SAS/STATTM User’s Guide, Cary, NC: SAS Institute,
Inc., 1988.

Smith RP. Toxic responses of the blood. In: Klaassen CD,
Amdur, MO, Doull J, eds. Casarett and Doull’s
toxicology - the basic science of poisons, 3rd ed.
New York, NY: Macmillan Publishing Company,
1986:223-44.

Spurgeon JC, Speitel LC, Feher RE. Thermal decompo-
sition products of aircraft interior materials. Wash-
ington, DC: Department of Transportation/Fed-
eral Aviation Administration: 1977; Report no.
FAA-RD-77-20. Available from: National ‘Tech-
nical Information Service, Springfield, VA 22161.
Order #ADA039511/1GI.

Spurgeon JC, Filipczak RA, Feher RE, Sternik SJ. A
procedure for electronically monitoring animal re-
sponse parameters using the rotating wheel. J. Com-
bustion Toxicol. 1979; 6:198-207.

Stavert DM, Archuleta DC, Behr MJ, Lehnert, BE.
Relative acute toxicities of hydrogen fluoride, hy-
drogen chloride, and hydrogen bromide in nose-
and pseudo-mouth-breathing rats. Fundam. Appl.
Toxicol. 1991; 16:636-55.

Terrill JB, Montgomery RR, Reinhardt CF. Toxic gases
from fires. Science 1978; 200:1343-47.

*U.S.GP0:1991-661-063/40010

ht


driven into the animal chamber by a box fan attached
to the intake tube. A flexible tube between the floor of
the chamber and the bottom of the combustion unit
provided controlled recirculation of the chamber air
around the test sample, into the plenum, and back into
the animal chamber. Internal volume of the entire
combustion/exposure system was 265 L.

There were four self-closing ports in the animal
chamber wall. These ports were used for the rapid
insertion (or removal) ofindividual cylindrical PMMA
insert cages at the beginning (or end) of the defined
exposure period. Each insert cage of 8.3 cm in internal
diameter and of 27.9 cm in length had a removable
screen at the chamber end and 48 1.3-cm holes in the
cage surface to allow the diffusion of combustion
products. Inside the chamber, there were also four 30-
cm-diameter rotating cages covered with polypro-
pylene screens. All rotating cages were mounted on a
motor-driven shaft, and their perimeter speed (and
required walking speed for the rats) was 6.4 cm/sec. In
use, the animal chamber body was fitted over the cages,
and the system was sealed against a gasket embedded
in the chamber base. Animals were contained in the
insert cages for the LC,, studies and in the rotating
cages for the t, determinations.

Determination of LC,,s

One rat was placed in each of the four insert cages,
which were then inserted into the chamber through
the self-closing ports. A weighed sample of the selected
polymer was placed in the sample boat, and the entire
system was sealed. Oxygen resupply, gas sampling, and
temperature monitoring devices were connected, and
the power setting control for the radiant heat assembly
was set at mark 55 to supply the desired incident heat
flux level. This setting was a compromise between an
output that would adequately decompose the sample
during a 10-min heating period and a physiological
requirement for maintaining the chamber tempera-
ture below 35°C (Crane and Sanders, 1986). The heat
flux at the sample position increased from 4.0 watts/
cm? at 10 sec after initiation to 5.2 watts/em? at 10
min; external room temperature was maintained at
16°C to further control the animal chamber tempera-
ture,

Atzero time, the heater power supply, recirculating
fans, timer, and hot wire igniter were activated simul-
taneously. The polymer sample was observed for the
first indication of decomposition (melting, smoke)
and for the time of ignition. Oxygen was resupplied
manually when gas chromatographic analysis (at 1.5-
min intervals) indicated a decrease below the ambient
concentration (21% v/v). The power to the radiant

heat assembly was turned offat 10 min. From the zero
time, animals were exposed to the combustion prod-
ucts for 30 min. Initial exposures for the LC,, determi-
nations began at the 16-g level (60 mg/L) of the
polymers, and this level was adjusted upward or down-
ward as needed to obtain lethality between zero and
100%. A minimum of two fractionally lethal levels
(16-83%), based on 12 rats each, was obtained for each
polymer for the estimation of LC,, values. ‘The rats
were removed immediately at 30 min; survivors were
housed in individual cages and observed for 14 days, at
which time total mortality in each group was recorded.
The LC, values are expressed in mg/L and were
calculated by dividing the initial sample weight of the
polymer by the internal volume (265 L) of the system.
Accordingly, the 16-g sample is equivalent to 60 mg/
L.

Determination of ts at a Fixed Weight of Polymers

Sample combustion procedures were identical for
the t, studies, except that one rat was placed in each of
the four rotating cages. A weighed sample (16 g) of the
selected polymer was placed in the sample boat, and
the entire system was sealed. At zero time, the cage
rotation motor, heater power supply, recirculating
fans, timer, and hot wire igniter were activated simul-
taneously. As described in the LC,, determination, the
polymer sample was observed for the first indication of
decomposition and for the time of ignition; oxygen
was resupplied manually when a decrease below the
ambient concentration was indicated by the gas analy-
sis. The power to the radiant heat assembly was turned
offat 10 min. Time-to-incapacitation (t,) was recorded
(from zero time) when each rat could no longer walk
in the rotating cage, that is, when the rat would begin
to slide or tumble. When all rats were incapacitated,
cage rotation was stopped, the assembly atmosphere
was exhausted into a fume hood, and the animals were
removed. At least 12 rats were exposed, four at a time,
to obtain the mean t; for each polymer.

Determination of ts at LC,,s of Polymers

Incapacitation times (ts) were also determined for
each polymer at the sample weights corresponding to
their calculated LC,, values, that is, at a condition
where the combustion products from each of the six
polymers exhibited equal lethality. Twelve rats were
exposed to the LC,, concentration for each polymer
using the same procedure described for the 16-g (60
mg/L) t, exposure.


SIDE VIEW

Fig. 1. Schematic Drawing of Combustion/Exposure System.

1. Animal Exposure Chamber; 2. Gas Sampling Inlet; 3. Oxygen Inlet; 4. Thermocouple
(air temperature); 5. Muffin Fan (recirculation assembly); 6. Chamber: Connecting Tubes;
7. Mixing/Cooling Plenum; 8. Gas Deflector; 9. Hot Wire Igniter; 10. Heat Lamp
Reflectors (with two 2,000-watt quart lamps cach); 11. Sample Combustion Unit;
12. Sample Combustion Boat; 13. Combustion Chamber Air Plenum; 14. Flexible Air
Recirculation Tube; 15. Muffin Fan (chamber air mixing); 16. Cage Motor Drive Shaft;
17. Individual Rotating Cage; 18. Insert Cage Sleeve (self- closing); 19. Individual Rat Insert
Cage



from 10.5 to 19.5 min (Table 4). When the 16-g ts
were compared with those obtained at the LC,, sample
weight, they all changed in the expected direction, that

is, the larger sample weights produced shorter ts.

Our findings demonstrated that the polymer
rankings by LC, and byt, are different. This could be
because of the involvement of different mechanisms of
action of pyrolysis products at these end points. There-
fore, the toxicity rankings of polymers should be
carefully evaluated in terms of the specific end point
utilized and its relation to the intended use of such
rankings.

SUMMARY AND CONCLUSIONS

In the study the relative rankings of six polymers
by two toxicological indices were compared. Labora-
tory rats were exposed to the combustion products
from the polymers (i) at varying polymer weights to
determine LC,,s, (ii) ata fixed 16-g weight (60 mg/L.)
of each polymer to determine ts, and (iii) at the LC,
polymer weights determined in (i) to establish the
variation in t, values under the defined condition of
equal lethality. All exposures were performed under
identical pyrolysis conditions. LC,, and t, end points
did not produce thesamerelative toxichazard rankings
for the polymers, At LC,,s, t, values ranged from 10.5
to 19.5 min, indicating a wide variation in the inca-
pacitating toxicity of these polymers.

Although 1-provides-a-usefil measure-of relative
ime-to-escape when appli ival in a fire
environment, inter is i It
hat delayed deaths i i i-
tation does not occur during the acute exposure. LC,
< —
nieastirements may be preferable when describing the
absolute lethality caused by combustion products, but
they give little indication of time available for escape,
thats, the length of time before incapacitation occurs,
Thus, the LC,, would appear to be an inappropriate
end point for use in addressing the toxic hazard of
smoke in terms of the relative time available forescape.
The relative toxic hazard rankings for materials by the
two end points are not likely to be comparable, and this
incomparability is probably due to the involvement of
different mechanisms of action for polymeric combus-
tion products at these end points. Therefore, the
Principal use for the relative toxic rankings should
determine which toxicological index is more appropri-
ate.

REFERENCES

Amdur MO. Air pollutants, In: Klaassen CD, Amdur,
MO, Doull J, eds. Casarett and Doull’s toxicology
~ the basic science of poisons, 3rd ed. New York,
NY: Macmillan Publishing Company, 1986:801-
24,

Alarie Y, Anderson RC, Stock MF, Dombroske RL,
Keller LW, Hayduk LW, Park RE. Toxicity of
thermal decomposition products: An attempt to
correlate results obtained in small scale with large
scale tests. J. Combustion Toxicol. 1981; 8:58-68.

Crane CR, Sanders DC, Endecott BR, Abbott JK, Smith
PW. Inhalation toxicology: I. Design of a small-
animal test system. II. Determination of the relative
toxic hazards of 75 aircraft cabin materials. Wash-
ington, DC: Department of ‘Transportation/Fed-
eral Aviation Administration: 1977; Publication
no. FAA-AM-77-9. Available from: National Tech-
nical Information Service, Springfield, VA 22161.
Order #ADA043646/9GI.

Crane CR, Sanders DC, Endecott BR, Abbott, JK.
Inhalation toxicology: IV. Times to incapacitation
and death for rats exposed continuously to atmo-
spheric hydrogen chloride gas. ‘Washington, DC:
Department of Transportation/Federal Aviation
Administration: 1985; Publication no. FAA-AM-
85-4. Available from: National Technical Informa-
tion Service, Springfield, VA 22161. Order
#ADA157400.

Crane CR, Sanders DC. Inhalation toxicology: VIII.
Establishing heat tolerance limits for rats and mice
subjected to acute exposures at elevated air tem-
peratures, Washington, DC: Departmentof Trans-
portation/Federal Aviation Administration: 1986;
Publication no. DOT/FAA/AM-86/8. Available
from: National Technical Information Service,
Springfield, VA 22161. Order #ADA173031.

Crane CR, Sanders DC, Endecott BR. Inhalation toxi-
cology: X. Times to incapacitation for rats exposed
continuously to carbon monoxide, acrolein, and to
carbon monoxide-acrolein mixtures. Washington,
DC: Department of Transportation/Federal Avia-
tion Administration: 1990; Publication no. DOT/
FAA/AM-90/15. Available from: National Tech-
nical Information Service, Springfield, VA 22161.
Order #ADA230639/LP.


- ; This document is available to the public'through
the National Technical Information Serviee,

. ; 2 J
U.S. Department .
of Transportation

Inhalatjon. Toxicology: XII.
Comparison of Toxicity
Rankings of Six Polymers by
Lethality and by
Incapacitation in Rats

DonaliC. Sanders -
Boyd R. Endecott: :
Arvind K. Chaturvedi...

Civil Aeromedical Institute
Federal Aviation Administration

Oklahoma City, Oldahoma ."” me

Final Report.

Springfield, Virginia 22161, Be:


Farrar DG. The effect of the sensory irritant component
ofa combustion atmosphere derived from Douglas
Firon the leg-flexion avoidance response of the rat.
J. Combustion Toxicol. 1980; 7:3-22.

Fenner, OH. Chemical and environmental properties of
plastics and elastomers. In: Harper CA, ed. Hand-
book of plastics and elastomers. New York, NY:
McGraw-Hill Book Company, 1975:4-1-81.

Finney DJ. Probit Analysis, 3rd ed. Cambridge: Cam-
bridge University Press, 1971.

Gad SC. Combustion toxicity testing, In: Gad SC, Ander-
son, RC, eds. Combustion toxicology. Boca Raton,
FL: CRC Press, 1990a:81-128.

Gad SC. Basics of inhalation toxicology and heat stress
physiology. In: Gad SC, Anderson RC, eds. Com-
bustion toxicology. Boca Raton, FI: CRC Press,
1990b:23-62.

Gossel TA, Bricker JD. Carbon monoxide, cyanides and
sulfides. In: Principles of clinical toxicology. New
York, NY: Raven Press, 1984:84-104.

Harper CA. Fundamentals of plastics and elastomers. In:
Harper CA, ed. Handbook of plastics and elas-
tomers. New York, NY: McGraw-Hill Book Com-
pany, 1975:1-1-121.

Hartung R, Ball GL, Boettner EA, Rosenbaum R,
Hollingswoith ZR. The performance of rats on a
Rotarod during exposure to combustion products
of rigid polyurethane foams and wood. J. Combus-
tion Toxicol. 19775 4:506-22.

Kaplan HL, Grand AF, Switzer, WG, Mitchell, DS,
Rogers, WR, Hartzell, GE. Effects of combustion
es on escape performance of the baboon and the

rat. J. Fire Sci. 19855 3:228-44.

Levin BC, Paabo M, Birky MM. An interlaboratory
evaluation of the 1980 version of the National
Bureau of Standards test method for assessing the
acute inhalation toxicity of combustion products.
Washington, DC: Department of Commerce/Na-
tional Bureau of Standards: 1983; Publication no.
NBSIR 83-2678. Available from: National Tech-
nical Information Service, Springfield, VA 22161.
Order #PB83-198093.

Lieberman HR. Computation of psychophysical thresh-
olds using the probit technique. Behavior Research
Methods & Instrumentation 1983; 15:446-48.

NY. Artide 15, Part 1120, Combustion Toxicity Test-
ing, Uniform Fire Prevention and Building Code
Coundil. Albany, New York: State of New York,
Department of State, 1986.

Sanders DC, Crane CR, Endecott BR. Inhalation toxi-
cology: V. Evaluation ofelative toxicity to rats of
thermal decomposition products from two aircraft
seat fire-blocking materials. Washington, DC: De-
partment of “Transportation/ Federal Aviation Ad-
ministration: 1985; Publication no. DOT/FAA-
'AM.86-1. Available from: National Technical In-
formation Service, Springfield, VA 22161. Order
#ADA165034.

SAS/STATTM User’s Guide. Cary, NC: SAS Institute,
Inc., 1988.

Smith RP. Toxic responses ofthe blood. In: Klaassen CD,
Amdur, MO, Doull J, eds. Casarett and Doull’s
toxicology - the basic science of poisons, 3rd ed.
New York, NY: Macmillan Publishing Company,
1986:223-44.

Spurgeon JC, Speitel LC, Feher RE. Thermal decompo-
sition products of aircraft interior materials. Wash-
ington, DC: Department of ‘Transportation/Fed-
eral Aviation Administration: 1977; Report no.
FAA-RD-77-20. Available from: National Tech-
nical Information Service, Springfield, VA 22161.
Order #ADA039511/1GI.

Spurgeon JC, Filipezak RA, Feher RE, Sternik SJ. A
procedure for electronically monitoring animal re-
sponse parameters using the rotating wheel. J. Com-
bustion Toxicol. 1979; 6:198-207.

Stavert DM, Archuleta DC, Behr MJ, Lehnert, BE.
Relative acute toxicities of hydrogen fluoride, hy-
drogen chloride, and hydrogen bromide in nose-
and pseudo-mouth-breathing rats, Fundam. Appl.
Toxicol. 1991; 16:636-55.

‘Terrill JB, Montgomery RR, Reinhardt CF. Toxic gases
from fires. Science 1978; 200:1343-47.

+U.S.GPO:1991-661-063/40010


Table 2. Toxicity Ranking for Polymers by their LC,, Values

Polymer LC,, (mg/L)
Polyamide .....sssssecconssessesnesssssnsecesansseennnnaseegsnaee 45.7
Polystyrene 56.6

Chlorinated Polyethylene

Table 3. Times-to-Incapacitation (ts) for Rats Exposed to
Combustion Products from Polymers at a Fixed Weight of 16 g
(60 mg/L)

Polymer t; (min)*
Mean + S.D.

Nylon 6/6...
Polyamide.
Polyethylen
Polystyrene

Chlorinated Polyethylene ........-+:20000 18.4+ 1.69"

Statistical Analysis

_ Estimation of the LC,,s was accomplished
using a program translated from Applesoft Basic
(Lieberman, 1983) to IBM Basic containing a
probit transformation (Finney, 1971). All ¢,
related data were analyzed at @ = 0.05 using
analysis of variance and Duncan’s multiple-range
test forstatistical pairwise differences between the
groups (SAS/STAT, 1988); values are presented
as the mean + S.D. (1 2 12) and a difference

between two means was considered significant at
pS0.05.

RESULTS AND DISCUSSION

On the basis of calculated LC,, values, the six
polymers were ranked in the decreasing order of
their toxicity as: polyamide > polystyrene ~ Ny-
lon 6/6 > polysulfone > polyethylene > chlori-
nated polyethylene (Table 2). The most toxic
polymer in the series was polyamide (smallest
LC,,), while chlorinated polyethylene was the
least toxic (largest LC,,). In general, polymers
containing C, H, N, and/or O with the potential
to primarily generate CO and/or HCN exhibited
acute effects, while polymers that also contained
ClorS produced delayed effects, possibly by the
generation of HCI or SO,, All deaths with Nylon

ide, polyethylene, and_ polystyrene
occurred either during the 30-min exposure pe-

*Mean t, values denoted with the same symbol are not signifi-
cantly different from each other. However, tsaredifferent from
other ¢, values marked with the different symbol, at pS 0.05 by
Duncan’s multiple-range test.

Table 4. Times-to-Incapacitation (ts) for Rats Exposed to
Combustion Products from Polymers at their Respective
LC,, Fuel Loads

Polymer +, (min)*
Mean +S.D.

Nylon 6/6
Polyethylene

Polystyrene ... 14.11.59
Chlorinated Polyethylene 14.6 + 1.03*
Polyamide ... 15.042.99%

Polysulfone.. 19.5 £1.05"

*Mean t, values denoted with the same symbol are not signifi-
cantly different from each other, but t, values are statistically
different from other t, values marked with the different symbol
(PS 0.05).

fiod or within 5 min post exposure.Jn contrast,
forinat caused
Four of the 13 deaths for chlori-
nated polyethylene were noted from 1 hour to 2
days after the exposure, while 11 of the 13
polysulfone deaths occurred from several hours
to 14 days post exposure. This trend is consistent
with the acute and/or delayed toxicity associated
with these gases (Amdur, 1986; Gad, 1990b;
Gossel and Bricker, 1984; Smith, 1986).

The ranking of these polymers by t, at a fixed
weight of 16 g (60 mg/L), from most toxic
(shortest t,) to least toxic (longest t), is given in
Table 3. Their t, values ranged from 6.6 to 21.1
min. Polyamide and Nylon 6/6 remained near.
the most toxic level when evaluated by both end

ints (Tables 2 & 3). Polyethylene shifted from
Ee next-to-last place (when ranked by LC,,) to
the middle for t, ranking. Although chlorinated
polyethylene and polysulfone switched their po-
sitions in the rankings, both remained at the
lower toxicity levels when evaluated by both
toxicological indices. The t, values for the six
polymers at their LC,, sample weights ranged

‘Wh


INHALATION TOXICOLOGY: XII. COMPARISON OF TOXICITY
RANKINGS OF SIX POLYMERS BY LETHALITY AND BY

INCAPACITATION IN RATS

INTRODUCTION

Polymeric materials are used in the construction
of aircraft interiors. These materials have the potential
to produce toxic gases in a fire involvement; this
potential warrants the study of their relative toxicity to
allow selection on the basis of safety. One of the
commonly used toxicological indices for ranking tox-
icity of polymeric materials is lethality (Gad, 1990a;
N.Y., 1986), generally represented as LC,, (amount of
a material to produce thermolysis products lethal to
50% of the exposed animals within thedefined param-
eters of exposure and observation periods). The LC,,
determination includes the immediate, as well as de-
layed, deaths that occur during the exposure and
observation periods of the experiment. Time to physi-
cal incapacitation (Crane et al, 1977; Spurgeon et al,
1979), shock avoidance (Hartung et al, 1977), respira-
tion rate depression (Alarie et al, 1981), and hind leg-
flexion (Farrar, 1980) are other indices used by

investigators. These indices primarily reflect acute
effects of the combustion products and are more
applicable to predicting relative escape time from a fire
environment. Although several studies have been con-
ducted for relative rankings of polymers by LC,, or by
time-to-incapacitation « (Crane et al, 1977; Gad,
1990a; N.Y., 1986; Sanders et al, 1985), little effort
has been expended to compare rankings of polymers
on the basis of their combustion product toxicity by
each of these two end points under identical experi-
mental conditions (Levin et al, 1983). Depending
upon the chemistry of a polymer and the mechanism
of toxicity of its combustion gases, a polymer may
produce acute and/or delayed toxic effects. Therefore,
the selection ofan end point should be associated with
the intended use of the resultant rankings.

Earlier studies in our laboratory illustrated that
ranking the relative toxic hazard of materials using t
as the end point produces a rank-order different from
that based on time-to-death asa criterion (Crane et al,

Table 1. Chemical Units and Possible Combustion Gases of Polymers

Polymer Primary Toxic
Name Chemical Unit Gas(es) Produced
Nylon 6/6 (-NH(CH,),NHCO(CH,),CO-], .
Polyamide -NH(CH,), NHCO(CH),CO-]

Polyethylene «0... .ssescsseesoee (-CH,CH,,)...

Polystyrene .....esseecssssseeseees (-CH,CH(C,H))-], ...

Chlorinated Polyethylene... (CH,CH,),; (Cl = 40%)...

Polysulfone ...

U-C,H;-4-C(CH)),C,H,4-0C,H,4-50,CH,4-0-]

*From Fenner (1975), Harper (1975), and Aldrich Chemical Company, Inc. (Milwaukee, WI) 1990-1991 Catalog/

Handbook of Fine Chemicals.

*Gases indicated are based on the chemical units of polymers. The references for the production of some of the gases are

given in the introduction section of the text.


ACKNOWLEDGEMENT

The authors gratefully acknowledge the invaluable assistance of
Mr. James L. Sershon for his expert care and preparation of the animals
used in this investigation.

iti

ot ene


Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA/AM-91/17

a

4. Title and Subtitle 5.” Report Date
INHALATION TOXICOLOGY: XII. COMPARISON OF TOXICITY. December 1991

RANKINGS OF SIX POLYMERS BY LETHALITY AND BY
INCAPACITATION IN RATS

6. Performing Organization Code

8. Performing Organization Report No

7. Author's)Donald C. Sanders, M.S., Boyd R. Endecott, B.S.
and Arvind K. Chaturvedi, Ph.D.

9. Performing Organization Nome and Address 10. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute

P. 0. Box 25082 7
Oklahoma City, OK 73125-5066

+ Contract or Grant No.

|. Type of Report and Period Covered

12. Sponsoring Agency Name ond Address
Office of Aviation Medicine

Federal Aviation Administration

800 Independence Avenue, SW 14.
Washington, DC 20591

Sponsoring Agency Code

15. Supplementary Notes

This work was performed under task AM-B-90-TOX-58,

16, Abstract
Polymeric aircraft cabin materials have the potential to produce toxic gases

in fires. Lethality (LCs9) in animal models is a standard index to rank polymers on
the basis of their combustion product toxicity. However, the use of times-to-
incapacitation (t,s) may be more realistic for predicting relative escape times from
a fire environment. Therefore, LCsgs and tis for six pure polymers of different
chemical classes were determined and compared. The polymers were polyamide (I),
polystyrene (II), Nylon 6/6 (III), polysulfone (IV), polyethylene (V) and chlorinated
polyethylene (VI). In the study, male Sprague-Dawley rats (150-250 g), 12 animals per
fuel loading, were exposed to the pyrolysis products from selected weights of each
polymer for 30 min in a 265-L combustion/exposure system, and LC.sys were determined
following a 14-day observation period. For each polymer, tis were also measured at
16 g, that is, 60 mg/L, and at their respective LCs9s using the inability of rats (n
2 12) to walk in rotating cages as a criterion for incapacitation. The LCs s (mg/L)
of the polymers had the order of I (45.7) < II (56.6) = III (58.1) < IV (63.2) <v
(75.5) < VI (87.5), while their tis (min) at 16 g (60 mg/L) had the order of III
(6.6) = IT (7.3) < V (11.7) © IE (12.0) < VI (18.4) < IV (21.1). Based on the ts
(min) at LCsgs, the polymers were grouped into III & V (10.5, 11.0); I, Il & VI
(14.1-15.0); and IV (19.5). The two toxicological end points, LC.y and t;, did not
exhibit the same relative toxic hazard rankings for these polymers. Also, t,s were
not equal at the LCs) concentrations, a condition of equal lethality. These findings
demonstrate the possible involvement of different mechanisms of action for the
combustion products of these polymers at the selected end points,

17. Key Words 18, Distribution Stotement

Inhalation-toxicology; aircraft interior] Document is available to the public
polymers; toxicity rankings; lethality; through the National Technical
time-to-incapacitation; animal exposure/] Information Service, Springfield,

combustion system; ranking comparison VA 22161
19. Security Classif. (of this report) 20. Security Classil. (of this page) Zi. No. of Poges | 22, Price
Unclassified Unclassified ll

Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized