REFERENCE

NBS

PUBLICATIONS

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NAFL INST OF STANDARDS & jECH R. .0.

A1 11 02484836 _

?ar«.'s'm»c*.'SSirpu»- 5-3277

Polystyrenes: A Review of the Literature

on the Products of Thermal Decomposition

and Toxicity

Joshua L. Gurman

Laura Baler

Barbara C. Levin

March 1986

Sponsored in part by:

U.S. Consumer Product Safety Commission

Bethesda, MD 20207

~QC

100

.056

85-5277

1986

tras RES2AECH IITFOUMATION CENTER

NBSIR 85-3277

POLYSTYRENES: A REVIEW OF THE LITERATURE

ON THE PRODUCTS OF THERMAL DECOMPOSITION

AND TOXICITY

^

Joshua L. Gurman

Laura Baler

Barbara C. Levin

March 1 986

Sponsored in part by:

U.S. Consumer Product Safety Commission

Bethesda, MD 20207

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

Table of Contents

Page

List of Tables iv

List of Figures vi

Abstract 1

1. Introduction 2

2. Chemistry 3

2.1 Polymerization 3

2.2 Thermal Decomposition Processes 4

2.3 Thermal Degradation Products 4

2.3.1 Vacuum Degradation 6

2.3.2 Degradation in Inert Atmospheres 6

2.3.4 Summary on Thermal Degradation Products 17

3. Toxicity of Thermal Decomposition Products 17

3.1 The Cup Furnace 19

3.1.1 Dow Chemical Company Test Method 19

3.1.2 The National Bureau of Standards Toxicity Test Method . 21

3.1.3 The University of Utah Test Method 23

3.2 Tube Furnace Combustion Systems 24

3.2.1 DIN 53436 Toxicity Test Protocol 24

3.2.2 FAA/CAMI Toxicity Protocol 29

3.2.3 NASA/USF Toxicity Protocol 30

3.2.4 Japanese Toxicity Test Protocols 34

3.3 Combustion Ovens 39

3.3.1 University of Pittsburgh Toxicity Protocol 39

3.3.2 Harvard Medical School Toxicity Test Method 43

3.3.3 General Electric/Southern Research Institute Test

Method 45

3.3.4 University of Michigan Toxicity Protocol 47

4.0 Conclusions 49

5.0 Acknowledgements 50

References 52

iii
List of Tables

Page

Table 1. Volatile Combustion Products of Polystyrenes Under Varying

Experimental Conditions 58

Table 2. Flash Pyrolysis of Polystyrene at Different Temperatures in

Nitrogen Atmospheres 61

Table 3. The Low-Boiling Point Volatile Products from Radiant Pyrolysis

of a Polystyrene in Nitrogen or Air Atmosphere 62

Table A. Styrene Evolution During Thermal Decomposition of

Polystyrenes 63

Table 5. Summary of Toxicity Protocols 64

Table 6. Results from the Dow Chemical Co. Test 65

Table 7 . Results from the NBS Test 66

Table 8. Results from the University of Utah Test 67

Table 9. Results from the DIN 53436 Test 68

Table 10. Concentration-Response Data from a Polystyrene Decomposed

via the NASA/USF Toxicity Test Method 69

Table 11. Toxicity of Pyrolysis Gases from a Polystyrene Rigid Foam

Insulation Decomposed Under the NASA/USF Toxicity Test

Method 70

Table 12. Toxicity of Pyrolysis Gases from a Polystyrene Foam Decomposed

Under the NASA/USF Toxicity Test Method 71

Table 13. Relative Toxicological Comparisons of a Polystyrene Foam

and Other Materials in the Test of Kishitani and Yusa .... 72

Table 14. Results from the Nishimaru Test 73

Table 15. Comparison of Various Materials Under the Nishimaru Test ... 74

Table 16. Toxicological Evaluation of GM 47 and GM 49 Polystyrene Foams

Under the University of Pittsburgh Toxicity Test method ... 75

Table 17. Results from Polystyrene Television Cabinets Tested Under the

Harvard Medical School Tests 76

Table 18. Analysis of Gases in the Animal Chamber from Thermal

Decomposition of Polystyrene in the Harvard Medical

School Test 77

iv
List of Tables (continued)

Page

Table 19. Amount of Material Necessary to Produce Mortality in 50% of the

Rats Under the GE/SRI Test 78

Table 20. Results from the University of Michigan Test 79

V
List of Figures

Figure 1. Structure of Styrene and Polystyrene

Page

80

Vi
POLYSTYRENES: A REVIEW OF THE LITERATURE ON THE

PRODUCTS OF THERMAL DECOMPOSITION AND TOXICITY

By

Joshua L. Gurman , Laura Baier and Barbara C. Levin

Abstract

The current English literature through 1984 on the products

of pyrolysis and combustion from polystyrenes and the toxicity of

those products is reviewed. Among 57 compounds detected by

chemical analyses of the thermal decomposition products produced

under various atmospheric conditions (vacuum, inert, and

oxidative), the main volatile component is the styrene monomer.

Evidence is provided that the mass fraction of styrene increases

with furnace temperatures at least through 500°C. At 800“C and

above, the concentration of styrene decreases. In oxidative

atmospheres, carbon monoxide (CO), carbon dioxide (COj) and

oxidative hydrocarbons are formed. The concentrations of CO and

COo are a function of temperature and combustion conditions, i.e.,

greater amounts are produced in the flaming than in the non- flaming

mode. Eleven different test procedures were used to evaluate the

toxicity of the pyrolysis and combustion atmospheres of

polystyrenes. The more toxic environments produced under flaming

conditions appear to be mainly attributable to CO and COj.

Incapacitating effects observed during exposures to non-flaming

effluents are not due to CO and COj but rather to some other

toxicant, probably the styrene monomer. When compared to other

common materials used in buildings and residences, polystyrenes, in

general, are among the least toxic.

Keywords: Combustion products; fire data; literature reviews; polystyrene;

pyrolysis products; test methods; toxicity.

NBS Research Associate, American Iron and Steel Institute

NBS Guest Worker, University of Pittsburgh Graduate School of Public

Health

1
1. Introduction

Polystyrenes, which constitute one of the major classes of synthetic

polymers in use today, have a variety of applications, ranging from food and

medical packaging to home insulation. They have also been commonly used to

simulate wood for decorative purposes. Polystyrene is a generic term, which

denotes a nximber of forms, e.g., crystal, impact or expandable. Improvements

designed to enhance the physical properties of this class of polymers have been

in the areas of impact resistance, gloss levels, resistance to stress-cracking

by fats and oils, flame resistance and purity. These improvements in material

characteristics and the ease with which polystyrenes are processed have made

commercial use of this synthetic material economically favorable [1,2]^.

Enhancing the physical properties of polystyrenes has not been the only

concern facing manufacturers and consumers. For many years researchers have

investigated the effects of heating polystyrenes under various conditions [3].

The nature of the gaseous products produced when polystyrenes degrade during

industrial processing and in fire situations and the toxicity of these gases

have been a primary focus of many research studies. In this report, the

English literature published through 1984 on the volatile pyrolysis and

combustion products of polystyrene and the toxicity of these products is

reviewed.

^ Numbers in brackets refer to the literature references listed at the

end of this report.

2
2. Chemistry

2.1 Polymerization

Polystyrenes are amorphous, high molecular weight linear polymers.

Unless modified with special additives, they are constituted of covalently

bound units of the styrene monomer, which is composed solely of carbon and

hydrogen and contains a benzene ring in its structure (Fig. 1) [2,4].

Not all forms of polystyrenes, however, are simply homogeneous polymers

of the styrene monomer. In order to enhance its physical properties, specific

additives are incorporated into the polymer. For example, commercial impact

polystyrenes have an elastomer, generally polybutadiene, incorporated as a

block copolymer into the matrices in order to strengthen their mechanical

properties [1,5]. Expandable polystyrene beads or foams may contain 3-7% of a

volatile blowing agent (e.g., pentane) which is used in processing this

product. Fire resistant polystyrenes usually contain halogenated additives

and antimony oxide which are incorporated during polymerization [1,5].

The polymerization of the styrene monomer is a thermodynamically favored

reaction [2]. Most styrene-containing plastics are polymerized by a free

radical mechanism, where polymerization of the styrene monomer is initiated

either thermally or through the use of catalysts.

3
2.2 Thermal Decomposition Processes

The thermal degradation of various polystyrenes has been studied under a

wide range of temperatures. The temperatures quoted are those of the furnace

or heating device and not necessarily the temperature of the polystyrenes being

heated. In most cases, the temperature of the furnace increases faster than

that of the material studied. The evolved products may or may not be directly

related to the furnace temperature depending on the apparatus design.

Michal [6] studied the thermooxidative degradation of a polystyrene

(standard polystyrene, Krasten 127) between 400 and 800°C. Parikh [7]

calculated from his studies that no degradation of a pure polystyrene would

occur below 227°C, while 100 percent would decompose at 332“C when the material

was exposed for 2 hours. The mean temperature at which a sample of polystyrene

(GM51 [8]) spontaneously ignites was found by three laboratories who participated in an inter laboratory evaluation of the National Bureau of Standards

(NBS) Toxicity Test Method to be 520 + 62°C [9].

While still not completely understood, the mechanism of the thermal

degradation of polystyrenes is considered to be a radical chain reaction [10].

This process is essentially a reverse of the polymerization process.

2.3 Thermal Degradation Products

Thermal decomposition of polystyrenes has been conducted under a variety

of different atmospheric conditions, e.g., vacuum, inert and oxidative. It is

4
generally agreed that the major volatile component produced from the thermal

degradation of polystyrenes under these atmospheres is the styrene monomer

[3,11-19,21-23]. Other commonly detected products are oligomers of styrene,

such as the dimer and trimer [13,15-17,19,20], toluene, benzene, ethylbenzene

and a-methylstyrene and, under oxidative conditions, species such as

benzaldehyde and benzoic acid [11-19]. Butadiene has also been identified as a

degradation product of polystyrenes containing polybutadiene [18,21]. A

summary list of the identified degradation products is provided in table 1.

Many problems were encountered in the evaluation of the literature on

polystyrenes. First, a large variety of experimental systems and conditions

has been used to degrade polystyrenes. Second, many types of polystyrenes,

with and without additives, have been studied without adequate specification of

the formulations. Third, tests have been run at temperatures ranging from

those used for industrial processing (150 to 320°C) [17,22] to those used to

simulate fire scenarios (as high as 1200°C) [3]. The following sections will

discuss the thermal degradation products that have been detected and identified

when polystyrenes have been decomposed under the three different atmospheric

environments: vacuum, inert, and oxidative.^

^ Examination of materials under oxygen-free conditions does not simulate

real fire situations. However, such studies provide information on the generation of thermal decomposition products under controlled experimental conditions

and possible effects of vitiated atmospheres which are common in fires. In

actuality, many of the products produced under inert atmospheres were also

detected in oxidative environments.

5
2.3.1 Vacuum Degradation

Straus and Madorsky [23] studied the decomposition of specially prepared

laboratory samples of polystyrene under vacuum. These samples were either

heated for 30 minutes at AOO and SOO^C, or for five minutes at 800 and 1200®C

in a platinum tube surrounded by a preheated moveable furnace. Ninety-eight

percent or greater volatilization of the samples occurred regardless of the

temperature. Using mass spectrometry, they identified styrene as the major

decomposition product, but noted that the fractional percent yield varied with

temperature. An average of 48.3 and 53.9 weight percent of the total volatiles

was styrene at 400 and 500°C, respectively, whereas, at 800 and 1200°C, an

average of 47.5 and 41.6 weight percent of the total volatiles was styrene.

Straus and Madorsky noted an increased fragmentation of the degradation

products at 800 and 1200°C over that found at 400 and 500°C; this was probably

due to secondary decomposition of the initial decomposition products. In other

words, greater amounts of low molecular weight hydrocarbons (C 3 and below) and

benzene were observed at the higher temperatures.

2.3.2 Degradation in Inert Atmospheres

The thermal degradation of polystyrenes under inert atmospheres has been

examined by a number of investigators [3,11-13,15-21,23-25,27]. VThile nitrogen

(Nj) was the gas most widely used to study polystyrene degradation under inert

conditions [11,15,17-21,24,25], helium (He) and argon (Ar) atmospheres were

also used [3,12,13,16,23,27]. Different degradation systems as well as a

variety of analytical techniques were employed; for example, pyrolysis-gas

6
chromatography (pyrolysis-GC) , thermogravimetric analysis-gas chromatography

(TGA-GC), gas chromatography-mass spectrometry (GC-MS), and thermogravimetric

analysis-gas chromatography-high resolution mass spectrometry ( TGA-GC -HEMS )

Many researchers have concentrated their efforts on measuring the styrene

monomer even though many other gaseous components have also been detected and

identified (Table 1).

Using pyrolysis-GC, Knight [11] investigated the influence of varying

both sample size and pyrolysis temperature on the decomposition of a laboratory

polymerized polystyrene. It is important to note that the flash pyrolysis of

the ultrathin, low mass samples needed for pyrolysis-GC may not be totally

indicative of the decomposition of larger mass samples. (This comparison is

discussed later and shown in table 4.) These studies by Knight, plus others

using this technique [12,18,20], were designed as an initial attempt to

determine the primary products and mechanism(s) of decomposition. Knight

determined from the flash pyrolysis of 1 to 5 yg samples at 550, 600, 650, and

700°C under a Nj flow rate of .030 2,/min, that styrene was the major

decomposition product and that the styrene yield increased with increasing

temperature (Table 2). Results from studies on 1 to 3 mg samples were

compared to those with the 1 to 5 yg samples and demonstrated that at 700 °C,

the smaller sample size produced a larger percent of styrene (Table 2).

Fuchs and Szepesy [12] also used pyrolysis-GC to examine the thermal

decomposition products from various polymers, including several different

polystyrenes. These polystyrene samples (0.1 mg) were initially dissolved in

benzene which was evaporated before the sample was subjected to flash pyrolysis

7
in an argon atmosphere (flow rate; 25 m2./min) for 0-15 seconds. The resulting

pyrograms contained four major peaks which were identified as styrene, toluene,

benzene and other light hydrocarbons. Styrene was the primary thermal decomposition product, constituting 97.3 percent of the total peak areas. Fuchs and

Szepesy concluded from their study that only the styrene concentration could be

accurately determined since the relative peak areas of the other pyrolysis

products were not consistent or totally reproducible.

Two different samples of polystyrenes (Krasten 127, a standard polystyrene, and Krasten 336, a polystyrene with an unspecified percent of

polybutadiene) were degraded in a nitrogen atmosphere (flow rate of 0.25

mH/min) at 510°C by Pacakova et al. [18]. Pyrolysis-GC was used for the

degradation and analysis of products in this study. Monomeric styrene

comprised 73.5 and 79.1 percent of the total volatiles produced from the

polystyrenes with and without polybutadiene, respectively. Butadiene monomers

and dimers, as well as vinyl-cyclohexene were also found in the degradation

gases of the polybutadiene-containing polystyrene samples. A number of other

saturated and unsaturated hydrocarbons were also detected.

Trojer [20] also used pyrolysis-GC to examine the decomposition products

and the evolution of hydrogen from a special laboratory formulated polystyrene.

The polystyrene samples were pyrolyzed under nitrogen atmospheres at

temperatures which ranged from 510 to 980°C. The hydrogen yield was observed

to increase with increasing temperature and pyrolysis time. The values ranged

from 0.8 to 26 percent.

8
A number of other investigations of the thermal decomposition of polystyrenes in inert atmospheres were performed under more realistic degradation

conditions, i.e., at slower pyrolysis rates and using larger masses. These

studies are described below.

The research efforts of Bouster et al. [16] concentrated on the kinetics

of decomposition of a commercial, expanded polystyrene sample. A qualitative

identification of the thermal degradation products was made when this polystyrene was degraded in helium at temperatures ranging from 300 to 370°C.

Styrene, toluene, ethylbenzene, and a-methylstyrene were identified. Similar

to the results of Knight, an increase in styrene evolution with an increase in

temperature was noted.

A combustion system composed of a Pyrex^ tube with a movable furnace was

used by Hoff et al. [17]. This apparatus permitted the degradation of small

samples and the maintenance of a continuous flow of gas through the furnace.

Two commercial polystyrenes and two impact polystyrenes in pellet form

(additives unknown) were thermally degraded at temperatures within the

industrial processing range (240-260°C) in nitrogen at flow rates of 20 to 30

m2-/min. At these temperatures, only about 0.2 to 1.2% of the total sample mass

was actually degraded. The gaseous products were analyzed by GC-MS. Styrene

was identified as the main volatile product. The yields of styrene were 9.1

-’Certain commercial equipment, instruments, or materials are identified in

this paper in order to adequately specify the experimental procedure. In no case does such identification imply recommendation or endorsement by the

National Bureau of Standards, nor does it imply that the equipment or material

identified is necessarily the best available for the purpose.

9
and 13 percent by weight of the conmercial polystyrene samples volatilized and

3.1 and 3.3 percent by weight of the impact polystyrene volatilized.

Brauman [15] heated 50 mg samples of a polystyrene at 350 and 450®C in a

tube furnace under a dried nitrogen flow of 75 cc/min. Using GC analysis, she

found that 18 to 19% of the total mass volatilized at 350°C was styrene,

whereas, at A50°C, styrene constituted 50 to 51% of the total mass volatilized.

A 700 mg sample degraded at 350°C produced approximately 37 percent monomeric

styrene; thus, at the same temperature, an increase in sample size resulted in

an increase in the percent monomer production. Although this result disagrees

with that obtained by Knight [11] who found that increasing the sample size

decreased the yield of styrene, this difference may be related to the different

decomposition conditions, namely, flash pyrolysis vs. a slower thermal degradation method.

To determine the extent to which the addition of a fire retardant would

affect volatiles generated, Brauman [15] analyzed the products from 700 mg

samples of a polystyrene with and without antimony trioxide and a chlorinated

wax. When the fire retarded polystyrene was heated at 350°C in nitrogen, the

organic volatiles contained 1.5 percent monomeric styrene, whereas the non-fire

retarded polystyrene sample produced 37 percent. In a similar fashion, an

overall reduction of other volatile organics (benzene, toluene, and

ethylbenzene) was observed for the fire retarded polystyrene sample. In

contrast, the total tar content from the fire retarded s£imple was approximately

5 times greater than that from the non-fire retarded polystyrene.

10
Using a radiant heating system in order to achieve a linear rate of

degradation of a long polystyrene rod, Brauman et al. [19] examined the

pyrolysis products of this rod decomposed under a controlled nitrogen flow of

15 8,/min and a flux level of 56 kW/m^. Low boiling point volatiles were

analyzed by GC. Once again, styrene was found to be the major product,

comprising 33.2 + 3.1% of the total volatiles recovered (Table 3).

A decrease in styrene yield with an increase in temperature was found by

Straus and Madorsky [23] when a thermally prepared polystyrene was decomposed

in a helium atmosphere. This result appears to disagree with those of Knight

[11] and Booster et al. [16], as discussed previously. However, the highest

temperatures examined in either of these investigations was 700°C, whereas

Straus and Madorsky used temperatures as high as 1200°C. In the work by Straus

and Madorsky, polystyrene samples, ranging in mass from 13.4 to 20.4 mg, were

heated either for 30 minutes at 500°C or for five minutes at 800°C or 1200°C.

Ninety-five percent or greater volatilization of the sample occurred at all

temperatures. With MS, an average of 50.9 weight percent of the total

volatiles was detected as the styrene monomer at 500°C, while only an average

of 10.7 and 0.6 weight percent styrene monomer was detected at 800 and 1200“C,

respectively. As previously mentioned, under vacuum pyrolysis, Straus and

Madorsky detected an average of 53.9, 47.5 and 41.6 weight percent styrene at

500, 800 and 1200°C, respectively. Straus and Madorsky attributed this

finding to a greater degree of fragmentation of the polystyrene decomposition

products which occur at high temperatures in a helium atmosphere.

11
Chang and Mead [13] did an extensive high-resolution mass spectrometry

study designed to analyze and identify the products of thermal decomposition

produced from a polystyrene foam degraded in an inert atmosphere. The authors

heated 3 mg samples of the polystyrene foam, in helium, starting at 200°C and

increasing the temperature at a rate of 15°C/min up to 500°C. In addition to

the decomposition products identified and listed in table 1, the authors

detected several aromatic and aliphatic components which they were unable to

identify. Although Chang and Mead conducted their experiments in an inert

environment, three gaseous compounds containing oxygen were detected: CO 2 ,

CgHgO, and CgHgO. The authors concluded that these compounds may have resulted

from oxygen leakage into the degradation or analysis systems or from oxygen

that was trapped or adsorbed in the polystyrene foam during processing.

Morikawa [25] investigated the effect of water vapor on the thermal

decomposition of a polystyrene in an inert atmosphere. In particular, he was

concerned whether CO could be produced from the reaction of the water vapor

with the polystyrene. Polystyrene samples of 0.5 g were heated in a tube

furnace at temperatures ranging from 600 to 1000°C. Morikawa, using GC

analysis, detected small amounts of CO when polystyrene was decomposed at

1000°C in the presence of water vapor. He hypothesized that CO evolution from

the polystyrene in an inert atmosphere containing water vapor probably occurred

as a result of one of the following two reactions:

(1) C + HjO > CO + H 2

12
(2) Cj^H2n+2 + m'HjO --> C„jH2ni+2 m'CO + 2m'H2

where m + m' = n.

2.3.3 Thermal Decomposition in an Oxidative Environment

Many investigators [6,17,19,22,25,28,29,30] studied the thermal

decomposition of polystyrene in air or other oxidative atmospheres. These

studies have been conducted in a variety of combustion systems, e.g., tube

furnaces, crucible furnaces and radiant furnaces. Although most of the studies

were very methodically performed, it is difficult to compare the results

because each investigator attempted to model what he believed to be the most

relevant combustion scenario and thermooxidative decomposition encompasses

everything from simple oxidative pyrolysis to fully involved flaming

combustion. Since polystyrene contains no oxygen in its molecular formulation,

it is only in oxidative degradation that one would expect to find appreciable

quantities of oxidized decomposition products, such as benzaldehyde, styrene

oxide, CO, and CO 2.

Hoff et al. [17], Morikawa [25], and Morimoto et al. [28] used tube

furnaces to study the thermooxidative decomposition of polystyrenes. Hoff et

al., using temperatures within the industrial processing range, heated

pellet-shaped samples of two commercial polystyrenes and two impact polystyrenes (additives unknown) for ten minutes in a dry air flow of 0.025 to

0.030 2,/min. Using GC and GC/MS techniques, 21 volatile products were

identified from the degradation of the polystyrenes at 240 and 250°C. Twentytwo compounds were detected and identified in the gaseous products of the

13
impact polystyrenes. Benzyl alcohol and cinnamaldehyde were identified as

decomposition products of the polystyrene but were not detected among the

decomposition products of impact polystyrenes. Methyl phenol, ethanol, and

acrolein were also detected among the volatiles produced by the impact polystyrenes, but were not found among the polystyrene degradation products.

The thermal degradation apparatus used by Pfaffli et al. [22] consisted

of a J-shaped glass tube inserted into a laboratory oven. Polystyrene samples

without additives were heated at 200, 350, and 500°C under a slight air flow

rate (0.7 2,/min). This experimental procedure was designed to simulate

industrial processing conditions. High pressure liquid chromatography (HPLC),

GC, GC-MS, and gas indicator tubes^ were used to identify the degradation

products. At 200 °C, trace amounts of styrene, ethylbenzene and cumene were

detected. Experiments conducted at 350 and 500°C produced about the same

amounts of styrene, but the concentrations of the aromatic and aliphatic

hydrocarbons and oxidized hydrocarbons were greater at 350“C than at 500°C.

Pfaffli et al. hypothesized that the reason for these results was that at the

higher temperature, a more rapid degradation and therefore, less effective

oxidation occurred. However, a greater amount of CO was evolved at 500 °C

(2.1%) than at 350 °C (0.4%). The authors concluded that the most important

thermal degradation products generated by this polystyrene from an industrial

hygiene point of view were the styrene monomer and oxidized aromatic compounds,

such as benzaldehyde, styrene oxide, acetophenone, and 1-phenylethanol.

^ The use of colorimetric tubes, such as Draeger tubes provides

unreliable and, at best, semiquantitative results [69].

14
Morikawa [25] examined the effect of water vapor and air supply rate on

the evolution of CO. A 500 mg sample of a commercial polystyrene was heated at

600°C with air flow rates from 0.5 to 1.5 2,/min. At each air flow rate, tests

were run with or without water vapor. In all cases, the evolution of CO

increased as the water vapor supply rate increased.

Morimoto et al. [28] used a quartz degradation tube placed vertically in

an electric furnace rather than horizontally (as in the conventional tube

furnace). The main gaseous hydrocarbons produced from 0.1 g samples of a

polystyrene under flaming combustion at 700°C with an air flow rate of 0.83 or

1.8 2,/min were methane, ethylene and acetylene. These compounds were

identified by infrared spectrophotometry. The quantity of acetylene increased

with the increase in air flow rate. In other experiments, Morimoto et

al. showed that acetylene could be produced from the combustion of methane and

ethylene. Therefore, they hypothesized that the acetylene in these polystyrene

decomposition experiments was probably due to the further combustion of methane

and ethylene. Among the oxidative products, CO and COj were identified as

major gaseous components.

Using a crucible furnace in the bottom of a 4.2 liter combustion chcimber,

Michal [29] degraded 20 to 25 mg samples of a polystyrene foam (Krasten 336)

under a limited supply of oxygen. These experiments were designed to closely

simulate actual fire conditions in which the oxygen supply may become

depleted. Carbon monoxide, the main concern of the author in these studies,

was analyzed by GC. The average weight percent of CO, which evolved during the

vitiated flaming combustion of the polystyrene samples, was 9.86 + 4.40%. From

15
these results, Michal concluded that laboratory tests demonstrate a high degree

of variance and may only be considered an approximation of the actual combustion of a material in real fire situations.

In later studies, Michal [6] degraded 0.1 to 0.5 gram samples of

polystyrene granules (Krasten 127) in a crucible furnace located in the bottom

of a 4.5 liter combustion chamber at temperatures of 500°C (non-flaming) and

600°C (flaming). Michal' s results indicated that as the sample size of the

polystyrene increased, the concentrations of CO and COj increased. He also

showed that flaming conditions produced greater concentrations of CO and COj

than non-flaming conditions.

Further work by Michal [30] on polystyrenes examined the effect of using

a larger combustion chamber, which consisted of an oval chamber with a total

capacity of 650 liters. In this larger chamber, where the ratio of sample

weight to chamber capacity is lower than in the 4.5 £. chamber, non-flaming

conditions exist at 600°C and flaming combustion occurs at 800 and at 1000°C.

Michal compared the gaseous concentrations of CO and COj from the degradation

of the polystyrene samples (Krasten 127) in both combustion chambers. Greater

quantities of COj and HjO but very low CO concentrations were observed in the

larger chamber when compared to the smaller chamber. Michal suggested that

these results were indicative of a more complete thermooxidation of the

polystyrene in the larger chamber.

Brauman et al. [19] used a radiant heat source to examine the degradation

of a polystyrene sample (Styron 666U) under simulated fire conditions i.e.

16
non-flaming radiant pyrolysis with a flux level of 5.6 W/cm^ in a controlled

air atmosphere with a flow rate of 15 2./min. The low boiling-point volatiles

were analyzed by GC. As in many of the previous studies cited, the principal

decomposition product was the styrene monomer, comprising 35.4 weight percent

of the total weight loss. A comparison of the low boiling point volatiles

produced during oxidative pyrolysis and those from inert pyrolysis (i.e.,

nitrogen, 15 2,/min) showed a qualitative as well as quantitative similarity in

the products (Table 3). Benzaldehyde and trace amounts of COj were the only

compounds not also found in a nitrogen atmosphere. Yields of CO were not

determined.

2.3.4 Summary on Thermal Degradation Products

Studies on the thermal decomposition products of polystyrenes have been

conducted under a variety of atmospheric and experimental conditions. The

major volatile product, regardless of conditions, is the styrene monomer. The

fractional percent yield of the evolved styrene depends on the combustion mode

(flaming or non-f Iciming) , furnace temperature, sample size, amount and types of

additives, concentration of water vapor, and air supply rates to the furnaces.

The many other chemical components that have been detected are listed in table

1 .

3. Toxicity of Thermal Decomposition Products

Toxicological evaluations of the thermal decomposition products from

various polystyrenes have been reported in a total of 11 different experimental

17
test systems. These protocols are briefly summarized in table 5, and have been

described in greater detail by Kaplan et al. [26].

Although each test system was designed to assess the toxicity of the

thermal decomposition products of various materials, the apparatus, experimental conditions, and measured endpoints vary substantially and generate

results that are not readily comparable. For example, some of the endpoints

measured were: ( 1 ) the mass of material that is loaded or consumed in the

furnace and which is necessary to produce a specific biological effect (i.e.,

incapacitation, death, or other physiological change); ( 2 ) the concentration

of material (mass loaded or consumed divided by the exposure chamber volume or

air dilution factor) which is needed to produce the above biological effects;

and (3) the time necessary to develop or exhibit a given biological effect. As

a result, for specified exposure times, data may be reported as the "lethal

loading" (LL 50 ) or "lethal concentration" (LCgg) necessary to kill 50% of the

exposed animals, or the "effective loading" (EL 50 ) or "effective concentration"

(EC 50 ) needed to produce some other biological effect in 50% of the test

animals. When the endpoint is based on the time needed to produce some

biological effect, such as death or incapacitation, the data have been reported

as Tjj or values, respectively.

The numerous test methods can also be classified in a variety of

different manners (e.g., static vs. dynamic atmospheres; isothermal vs. rsimped

temperatures, head-only vs. whole-body animal exposures, etc.). For the

purposes of this report, the results from the various test methods will be

discussed in sections distinguished by the type of combustion system used to

18
generate the exposure atmosphere. A total of three general combustion systems

have been used to evaluate polystyrene toxicity. They are: the cup furnace

(used in test methods 1-3 as noted in Table 5), the tube furnace (used in test

methods 4-8a), and various combustion ovens (used in test methods 8b-ll). Of

the test systems described in Table 5, only one (No. 3) has undergone a formal

inter laboratory evaluation. In addition, another test (No. 9) is presently

being considered by the state of New York for use in establishing a data base

on the combustion toxicity of materials.

3.1 The Cup Furnace

3.1.1 Dow Chemical Company Test Method

Potts and Lederer [31] designed a method for testing smoke toxicity for

the Dow Chemical Co. This test method consisted of a 160 liter, cubic exposure

chamber that contained a furnace in which a quartz beaker was placed. The test

materials were exposed to both flaming and non-flaming degradation conditions.

In each test, seven male Sprague-Dawley rats were placed in a cage set on the

floor of the exposure chamber. The whole-bodies of the rats were exposed to

the gaseous products for 30 minutes after which the chamber was vented with

fresh air for 15 minutes. Animal mortality was the principal toxicological

endpoint noted during the exposure and the lA day post-exposure observation

period, although a gross pathological examination was also used to assess the

toxic effects of smoke inhalation. During the exposure, the concentrations of

various gases (e.g., Oj, CO, COj, NO^^, formaldehyde (HjCO), acrolein, and

styrene) present in the chamber were monitored.

19
Potts and Lederer evaluated the toxicity of many synthetic and natural

materials, including polystyrenes and Douglas fir^. Three different samples of

polystyrenes were tested: (1) a polystyrene without additives (Styron 492U),

(2) a polystyrene with an additive designed to reduce flaming tendency and

decrease ease of ignition (Styron 6021.01), and (3) a polystyrene foam (Styrofoam) . Table 6 lists the animal fatalities and levels of gases present in the

chamber when approximately 40 mg/ 2, of the polystyrenes or Douglas fir samples

were degraded in the flaming and non-flaming modes in this test. The data

presented by Potts and Lederer demonstrate that these polystyrenes were less

toxic than wood (Douglas fir) in the non-flaming mode in this test. Under

flaming conditions, the toxicities of the polystyrene samples and the wood were

comparable. Of the gases monitored, CO, COj, HjCO, acrolein, and styrene were

noted to evolve during the non-flaming degradation of Styron 492 and Styron

6021.01, while only CO and COj were detected from the Styrofoam. Flaming

degradation of all the polystyrene samples resulted in significantly greater

quantities of CO and COj than in the non-flaming mode. Low quantities of NOj^

were also produced during the flaming exposures, whereas HjCO was produced from

the polystyrenes in both modes except for Styrofoam in the non- flaming mode.

Degradation of Styron 6021.01, which contained a flame retardant, produced

greater amounts of CO in both combustion modes than the other two polystyrene

samples

^ Douglas fir data are shown to allow a comparison of relative toxicity

within a test system. Wood is not a substitute for polystyrene in most

commercial products.

20
All deaths from polystyrene occurred during exposure and only from the

flaming combustion products. Due to the high concentrations of CO (>2700

ppm), Potts and Lederer concluded that the dominant cause of death in the

flaming mode was CO intoxication. They also suggested that the low O 2 (<15%)

levels produced during the flaming combustion of Styron 492U and Styrofoam SM

contributed to the cause of the lethalities. Recent results by Levin et

al. [32] indicate that 4600 ppm of CO in air are necessary to produce death in

rats in 30 minutes. Examination of Potts and Lederer 's data show that only the

flaming Styron 6021.01 produced enough CO to account for the deaths. However,

other data by Levin et al. have shown that COj will potentiate the toxicity of

the CO, such that in the presence of 5% CO^ (50,000 ppm), the animals will die

from 2500 ppm of CO [32]. Thus, the data in table 6 indicate that the combination of CO and COj is sufficient to account for the deaths that occurred. A

pathological examination of animals exposed to the non-flaming gaseous products

of polystyrene showed no specific adverse effects.

3.1.2 The National Bureau of Standards Toxicity Test Method

The development and interlaboratory comparison of the National Bureau of

Standards (NBS) Toxicity Test Method was described by Levin et al. [9,33].

Natural and synthetic materials, including a rigid polystyrene foam (GM51),

were examined by different laboratories using the NBS protocol. This toxicity

test method consists of a combustion system, an animal exposure chamber, and a

chemical analytical system. Materials are thermally decomposed, at both nonflaming and flaming temperatures, in a quartz beaker inserted into a cup

furnace located below a 2002. exposure chamber. All of the gaseous products are

21
circulated through analytical equipment, which continuously monitors CO, COj

and O 2 , and back to the exposure chamber. In each test, the heads of six rats

are exposed to the gaseous combustion products for 30 minutes, at which time

the surviving animals are withdrawn and held for lA days of observation. LC 50

values, based on deaths which occur during the 30 minute exposures plus the 14

day post-exposure period, are currently used as the biological endpoint for the

NBS protocol. However, incapacitation based on 30 minute EC 50 values and blood

carboxyhemoglobin (COHb) levels are also monitored and used to evaluate the

toxicity of a material.

The results for the toxicity of a polystyrene and Douglas fir obtained

from three of the laboratories who participated in the interlaboratory evaluation of the NBS test method, are listed in table 7. As reported by Levin

et al. , the polystyrene tested appeared to be more toxic in the fl2iming mode

than in the non-flaming mode [9]. EC 50 and LC 50 values for the flaming mode

were less than those values for the non-flaming mode. The CO concentration for

flaming polystyrene combustion at the 30 minute LC 50 was much greater than that

for non- flaming conditions and, consequently, the percent COHb at the 30 minute

LC 50 value was much greater for the flaming mode (67-78%) than the non-flaming

mode (at the highest concentration tested, 50 mg/ 2., the COHb was 6 %). Based

on pure CO- in-air studies at NBS, the concentration of CO in the flaming mode

was still too low to solely account for the deaths that occurred [9]. Since

CO 2 potentiates the toxic effect of CO, as mentioned earlier, the COj may have

played a role in these deaths. However, the COj concentrations were not

provided in reference 9.

22
3.1.3 The University of Utah Test Method

The NBS Test Method was based to a large extent upon the University of

Utah Test Method [26]. The main differences between the two test protocols are

as follows: (1) In the University of Utah test method, a polytetraf luoroethylene (PTFE) covered aluminum cone is placed over the mouth of the cup

furnace in the belief that it will shield the animals from the generated

radiant heat and aid in the distribution and mixing of the combustion products;

(2) the University of Utah uses a 60 8, exposure chamber, not the 200 8, chamber

described in the NBS test method; (3) four rats are exposed in the head-only

mode instead of the six rats exposed in the NBS procedure; and (4) in the

University of Utah test method, all animal deaths that occur during the 30

minute exposures and the first thirty minutes following exposure are recorded

as within-exposure deaths. In the NBS protocol, any deaths occurring after the

thirty minute exposure were considered post-exposure deaths.

Farrar et al. [34], using the University of Utah test method, assessed

the toxicities of the combustion products from fifteen plastics and compared

the results to that of Douglas fir (used as a reference material in this test

method). Among these materials were three samples of polystyrene foam. Farrar

et al. reported that the toxicity of the polystyrene foams was very low for the

non-flaming mode of combustion. EC 50 and LC 50 (30 minutes plus 14 days)

values, percent COHb, and CO concentrations in both the non-flaming and flaming

modes for the tested polystyrene focims are presented in table 8 . Low CO levels

(<360 ppm) and low COHb levels (<7%) were observed in the non-flaming mode.

Farrar et al. stated that incapacitation under the non-flaming conditions could

23
not be attributed to CO, but may be due to the presence of styrene in the

exposure atmospheres.

The flaming combustion of polystyrene was shown to be more toxic than the

non-flaming mode. The flaming EC 50 and LC 50 values for the polystyrene

materials were comparable to those of Douglas fir. Higher CO and COHb levels

were observed for the flaming mode than for the non- flaming mode for both the

polystyrenes and the wood. Farrar et al. state that CO is probably the lethal

agent in the flaming combustion of the polystyrene foams since high COHb levels

(66-75%) were observed at death. However, work at NBS on CO in air has shown

that COHb levels exceeded 80% before deaths occurred from 30 minute exposures

to CO alone [32].

One of the polystyrene foam samples, GM49, contained a fire retardant.

Farrar et al. did not find any significant difference in the measured toxicity

parameters which could be attributed to the fire retardant.

3.2 Tube Furnace Combustion Systems

3.2.1 DIN 53A36 Toxicity Test Protocol

The DIN 53436 test method was developed in the Federal Republic of

Germany. In this system, a moving horizontal tube furnace thermally decomposes

the sample in a flowing air stream to provide a "steady-state" concentration of

combustion products. The combustion air stream is diluted with room air prior

to introduction into the animal exposure chamber. The diluted effluent is

24
drawn past the animals and exhausted from the exposure chamber. Materials,

thermally decomposed in this system, are toxicologically evaluated based on

either an equal specimen volume or an equal mass per unit length.

Hofmann and Oettel [35] evaluated the toxicity of a variety of synthetic

as well as natural products, including seven different cellular polystyrenes

(i.e., Styropors P, F200, F210, KR2180, KR2180/1, KR2180/2 and F220). In each

test, the noses of six rats were exposed to the thermal decomposition products

of the polystyrenes for a total of 30 minutes. In order to compare material

results, tests were conducted using either samples of equal mass (5 grams) or

equal volume (300 mm x 15 mm x 10 mm). Thermal decomposition of the samples

was conducted at several isothermal furnace temperatures, ranging in 100 degree

increments from 300 to 600°C. In these experiments, the furnace traveled at a

rate of 10 mm/min over the tube containing the sample, while an airflow of 100

2,/hr was directed counter- current to the motion of the furnace through the

tube. The decomposition gases were subsequently diluted with an additional

airflow of 100 2,/hr before entering the animal exposure chamber. Experimental

results for the various polystyrenes and pine wood, including average levels of

COHb developed in the blood of test animals, along with corresponding death

ratios, are presented in table 9. Experiments conducted with 5 gram scimples (a

nominal exposure concentration of 50 mg/2,) showed low COHb levels (<15%) in

animals exposed to the polystyrenes decomposed at or below 400°C. These

results would suggest that little if any CO was produced at these temperatures.

For Styropor P, little CO was observed even at temperatures of 500°C. Styropor

P did not ignite and undergo open burning until the samples were heated at

600°C. At this temperature, CO concentrations were reported to reach levels

25
ranging from 5,000 to 10,000 ppm. These exposures produced an average 92%

mortality. In general, for these polystyrenes, when ignition and open burning

did not occur, comparatively little CO was produced (<100 ppm) and all animals

survived. In those tests where the material ignited, high COHb levels (>70%)

were observed and animals died. At temperatures below the autoignition point

of the samples (<500°C), little CO (<100 ppm) was measured, COHb levels were

observed to be low (<15%), and no lethality was observed. At and above the

autoignition temperature (generally about 500°C for most of these polystyrene

samples), the specimens burned, large quantities of CO were produced (>2000

ppm), the COHb levels were greater than 70%, and deaths occurred.

For those experiments performed using equal volumes of test material

(i.e., 300 mm X 15 mm X 10 mm), autoignition of the polystyrene samples was not

observed below 600°C. Although greater quantities of CO were produced in the

flaming mode than in the non-flaming mode, COHb levels did not exceed 41% and

no mortalities were observed. This low toxicity was attributed to the small

polystyrene sample mass actually charged in the tube furnace (i.e., approximately 1 gram, resulting in nominal exposure concentrations ranging from 16 to

27.7 mg/t). Conclusions reached from these tests, run with samples of equal

volume were:

1. This size polystyrene samples did not ignite below 600°C.

2. COHb levels were elevated only after exposure to the flaming

combustion products, and

26
3. No mortalities were observed because of the low sample mass

concentration tested.

Hofmann and Sand [36] examined the toxicity of the thermal decomposition

products of a number of synthetic materials, including a rigid expanded and a

non-cellular polystyrene. The test conditions were similar to those previously

described by Hofmann and Oettel. The results found with the rigid expanded

polystyrene closely paralleled that previously reported by Hofmann and Oettel

for Styropor P. In addition, the atmospheres produced by both polystyrenes,

when decomposed under similar non-flaming conditions, at temperatures not

exceeding 500°C, caused no animal deaths and low COHb (<15%) blood levels. At

600°C, where ignition and flaming was observed for both polystyrenes, the COHb

levels were substantially elevated (rigid expanded polystyrene: 80%; noncellular polystyrene: 75%) and 92 to 100% of the animals died.

Herpol and Minne [37] used the DIN apparatus to evaluate the toxicity of

15 different synthetic and natural materials. Two different expanded

polystyrene samples (normal and self-extinguishing) were evaluated. In each

experiment, the whole bodies of six Wistar rats (3 males and 3 females) were

exposed for 30 minutes to the thermal decomposition products from two gram

samples placed in the tube furnace and heated to 600°C. The furnace was

adjusted to move over the sample in 30 minutes. Airflow through the combustion

system and the dilution air were adjusted to 200 H/hr producing a nominal

exposure concentration of 10 mg/ 8,. No animal deaths were observed in any of

these experiments. These findings are, however, consistent with those observed

by Hofmann and Oettel for the polystyrene samples tested at equivalent volumes.

27
Herpol [38] evaluated the acute toxic effects of exposures to the thermal

decomposition products of 35 materials, of which one was a sheet-type,

chlorinated fire-retarded polystyrene. Ten gram samples were evaluated at

furnace temperatures of 400, 600 and 800°C. Animals were monitored for changes

in respiratory rate (monitored for 30 seconds at 6 minute intervals), COHb

levels, and lethality. Carbon monoxide concentrations in the exposure

atmosphere were also measured. Flaming combustion of the polystyrene samples

was observed at 600 and 800°C. At 400°C, no lethalities were observed, COHb

concentrations did not exceed background levels (i.e.,<15%), and the respiratory rate was only slightly perturbed, (i.e., it gradually decreased 20% during

the first 18 minutes but then increased such that there was only a 10% decrease

by the end of the exposure). At 600°C, all the exposed animals died, the

average COHb level was 68 + 1.8%, and the respiratory rate decreased almost

linearly to zero by the end of the 30 minute exposure period. At 800°C, only

72% of the exposed animals died and the average COHb levels obtained were 50 +

6.9% (surviving animals) and 53 + 5% (dead animals). In contrast with the

experiments run at the lower temperatures, the respiratory rates initially

increased slightly, i.e., about 10% above pre-exposure rates; however, by 14

minutes, the rates had started to decrease reaching 50% of the control rate by

the end of the exposure period. These toxicological findings are consistent

with the average CO concentrations observed at 600 (''^8000 ppm) and 800°C (''-2500

ppm)

Herpol and Vandevelde [39,40] also tested polystyrenes according to the

procedure outlined above for Herpol [38]. They did not report their raw data.

28
but only gave results corresponding to their own "Toxicity Index." The

"index" values calculated using this approach range from TX = 0, when all

animals survive the exposure, to TX = 100, when all animals die within the

first six minutes of exposure. To compare materials, the highest TX values

obtained for each material were used, irrespective of the temperature of

decomposition. The toxicity "index" value calculated for the sheet-type

chlorinated fire retarded polystyrene was 56.7 and when compared to the other

materials tested by Herpol, indicated that this polystyrene was one of the top

four toxic materials, only surpassed by a polyamide-polyester blend carpet with

foam backing, a plasticized PVC cable, and a 100% acryl-type jacquard

upholstery material. No direct correlation was made by the authors between the

level of CO produced and the extent of toxic effects.

3.2.2 FAA/CAMI Toxicity Protocol

Crane et al. [41] at the Federal Aviation Administration's Civil Aeromedical Institute (FAA/CAMI) developed a laboratory small-scale inhalation test

which used rats to assess the toxicity of commercial materials designed for

aircraft interiors. In this test system, 750 mg samples of materials are

thermally decomposed in a tube furnace at an isothermal temperature of 600°C.

The combustion atmosphere is recirculated at a rate of 4 2,/min through the

combustion and animal exposure chamber (total chamber volume equals 12.6 £.).

In each experiment, three Sprague-Dawley rats are placed in separate motorized

rotary cages and exposed in the whole-body mode to the decomposition products

for a maximum of 30 minutes. This mass loading is equivalent to a nominal

exposure concentration of approximately 60 mg/2,. Times-to-incapacitation (T^)

29
(the time which animals were unable to walk in the rotary cages) and times-todeath (T^) were monitored and recorded.

Using the FAA/CAMI test method, Hilado et al. [42,43] evaluated the

toxicity of four different synthetic materials, one of which was a polystyrene

(Styron 402 D). The thermal decomposition atmosphere generated from this

polystyrene did not incapacitate or kill any of the test animals. Compared to

the combustion atmospheres generated from the other three materials, the

decomposition products from this polystyrene were the least toxic.

3.2.3 NASA/USF Toxicity Protocol

The NASA/USF toxicity protocol was developed by Hilado at the University

of San Francisco (USF) [44] for the National Aeronautic and Space Administration (NASA). In this test, four Swiss-Webster male mice are allowed to move

freely in a 4.2 liter chamber while being exposed to thermal degradation

products from 1 gram samples of materials heated in a horizontal tube furnace.

The exposure chamber is connected to the furnace by a glass tube. Materials

are decomposed in the furnace set at either a fixed temperature or ramped at a

rate of 40°C/min. The system is designed such that either static or dynamic

combustion conditions may be generated. In the static mode, movement of the

combustion products into the exposure chamber is primarily due to thermal

expansion, while in the dynamic mode, a pump moves the decomposition products

through the system at flow rates of either 1 or 3 il/min. The nominal

calculated chamber concentration, based on a 1 gram mass loading and 30 minute

30
exposure, would be 2A0 mg/ 2, in the static mode and 33 or 11 mg/ 2, in the dynamic

mode depending of whether the air flow is 1 or 3 2,/min.

Hilado and his coworkers primarily centered their efforts on measuring

the exposure time necessary to produce a specific biological effect, such as

incapacitation (T^^) or death (T^j). These values were examined as a function

of the total amount of material consumed.

Hilado and coworkers in a series of studies [42,45-48] evaluated the

toxicity of several different commercially available polystyrene materials

(i.e., styrofoam pellets, rigid foam slabs, solid transparent sheet). Using

static flow conditions and ramped furnace temperatures (200 to 800°C at

40°C/min), they found that the decomposition products from these polystyrenes

caused mean times to incapacitation, (based on the observed times of staggering

by the animals) ranging from 13.6 to 20.7 minutes and mean times to death

ranging from 20.0 to 27.5 minutes.

Hilado and Huttlinger [49] also attempted to determine the quantity of a

polystyrene (Styron 402 D) which when thermally decomposed produced 50%

lethality in the exposed animals. Using the static flow conditions and the

ramped temperature mode, 0.1 to 5 gram samples were decomposed in the furnace.

In all experiments better than 99% of the mass charged in the furnace was

pyrolyzed. No correlation, however, was obtained between sample mass

decomposed and percent lethality or time-to-death (Table 10). Concentrations

of CO and CH4 also did not show any correlation with the mass of sample loaded

31
in the furnace or with death. These experiments highlight the variability in

results obtained with this test method.

Hilado and coworkers [42,45,46,47,50] also investigated the effect

temperature and heating rate had upon the toxicity of the thermal decomposition

products of various types of polystyrenes. Results from tests performed

isothermally at 800°C were compared with those from thermally ramped tests.

Mean for the polystyrene materials ranged from 6.0 to 12.5 minutes and the

mean death ranged from 15.4 to 22.1 minutes. The thermal degradation

products from the polystyrene decomposed at the higher isothermal conditions

resulted in shorter mean times to incapacitation and death. These results were

attributed to a more rapid and higher generation of CO at 800°C.

Hilado and coworkers [42,47,51] also examined the effects of air flow

rates through the furnace. Hilado and Huttlinger [51] tested a rigid polystyrene foam under both ramped and isothermal temperature conditions (800°C)

and under both static and dynamic chamber conditions (airflow rate of 1 2,/min).

Results under the various test conditions are presented in Table 11. Regardless of whether air flowed through the chamber or not, the mean times to effect

were shorter when the polystyrene was decomposed isothermally at 800°C than

under the ramped furnace conditions. The experiments conducted with an airflow

of 1 2,/min did, however, produce slightly shorter mean times to incapacitation

than those without any airflow. However, the main difference between the

static and dynamic exposure modes was that no animal deaths were observed under

the dynamic conditions. It is unclear why no deaths occurred when there

appears to be sufficient toxicant(s) generated under the dynamic exposure

32
conditions to produce incapacitation even earlier than under the static

conditions

The toxicity of the thermal decomposition products from a polystyrene

foam was examined along with that of three other materials (i.e., ABS, polycarbonate and polyethylene) under ramped temperature conditions (200-800°C at

A0°C/min) and under both static and dynamic exposure chamber conditions

(airflow rates of 1 and 3 2,/min) [42]. A summary of the mean times to

incapacitation and death, along with their standard deviations, and percent

mortality obtained under these various conditions are presented in table 12.

The results obtained with no air flow suggest that the effluent produced by

polystyrene at the isothermal temperatures of 600 and 800°C was more incapacitating than that produced by the ramped temperature condition. The effluents

at 800°C were more toxic than at 600°C. Only slight differences in the mean

time to death were seen for polystyrene under static conditions regardless of

the temperature of decomposition. Mortality, on the other hand, was lower at

600°C. With air flow through the system, at 600°C, times to incapacitation and

death were lower than with no air flow. At 800°C, times to incapacitation were

lower than in the static mode, but no deaths were observed. In the majority of

cases, polystyrene appeared to be slightly less toxic than ABS, polycarbonate

and polyethylene. Considering the large difference in exposure concentrations

tested (11, 33, and 240 mg/H), remarkably little differences in the mean times

to incapacitation or death were observed.

These observations were supported by results reported by Hilado and

coworkers [52,53] for tests where a polystyrene, as well as six other materials

33
(i.e., polyethylene, polycarbonate, polyoxymethylene, polyether sulfone and

Douglas fir), were decomposed isothermally from 200 to 800°C, at 100°C

intervals under static as well as dynamic air flow conditions (1 2,/min). For

all seven materials under the static chamber conditions, increasing furnace

temperature generally resulted in increased CO concentration, shorter mean

times to death and increased mortality. For polystyrene, no deaths were

observed below 400°C, whereas at 800°C, 95% of the animals died. With an air

flow of 1 2,/min, mortalities were only observed when the polystyrene was

decomposed at 600°C and 700°C. No deaths were seen below 600°C or at 800°C.

The authors concluded that, at lower temperatures, insufficient amounts of

toxicants were produced to cause death. While, at higher temperatures, the

toxicants were apparently produced so rapidly that they were not present in the

exposure atmosphere long enough to cause death.

3.2.4 Japanese Toxicity Test Protocols

Japanese researchers have developed several different methods to evaluate

and compare the toxicity of combustion products from building and furnishing

materials. Three different studies have been reported [54-56] in which the

toxicities of the thermal degradation products of rigid polystyrene foams were

compared to those of other commonly used materials. In all three studies,

neither the exact type nor the supplier of the materials was specified.

Although the experimental protocols were different, some similarities were

noted. The sample materials were heated in a quartz tube under dynamic airflow

conditions. In all cases, mice were exposed in a separate chamber through

which the gaseous effluents passed.

34
Kishitani [54] studied the toxicity of the thermal decomposition products

of ten building materials, including two different polystyrene foams. Three

grams of the foams were heated in a tube furnace in which the temperature was

raised from ambient to 740°C in 15 minutes. The heating rate was selected to

simulate the temperature increase expected in the initial stages of a fire.

Heat was provided to the test material by four propane burners placed under the

quartz tube through which air flowed at a rate 2 8,/min. For each material, a

total of 5 mice were exposed, one at a time, in a 56 8, glass chamber for 15

minutes. Measurements of T^j, COHb, three-day post-exposure observation of

surviving animals, electrocardiograms (EGG), and necropsy examinations of the

mice exposed to the polystyrene combustion products were recorded.

No mice died either during the exposures or the post-exposure observation

periods. However, the combustion products of these polystyrene foams were not

totally innocuous. Carboxyhemoglobin levels ranged from 17.5 to 34.5% and the

mucous membranes of the eyes and nasal passages of some of the mice were

injured. In addition, irregular pulses were observed in the ECGs. Kishitani

concluded that one or more irritant gases were present in the thermal

decomposition products of these polystyrenes and were responsible for the

effect on the ECGs and the mucous membranes of the animals. No attempt was

made to identify or speculate on the nature of the noxious gas(es).

Kishitani and Yusa [55] evaluated the toxicity of the thermal degradation

products of 15 different materials, one of which was a rigid polystyrene foam.

This study differed from the one of Kishitani, described above, in that the

35
mice were exposed to the combustion effluents produced when the materials were

isothermally heated at either 550 or 850°C. The test apparatus consisted of a

quartz combustion tube which was suspended in an electrically heated tubular

furnace and connected to a 55 8, glass exposure chamber. A 5 cm layer of

alumina marbles was placed in the combustion tube in order to dry the air and

increase gas dispersion. An airflow of A 2,/min supplied through the combustion

tube went into the exposure chamber. Temperatures in the exposure chamber did

not increase more than 2°C above ambient. The mass of material placed in the

tube furnace, was varied in order to obtain a concentration-response

relationship. The problem of loading a large enough sample of foam in the tube

furnace to produce incapacitation was overcome by thermally preconditioning the

samples in an oven at 150°C for 20 minutes to reduce their volumes and increase

their densities. The weight reduction, 7.4%, was attributed to the loss of

blowing agent and was not believed by the authors to effect the resultant

composition or toxicity of the combustion products. The toxicologic endpoint,

incapacitation, was based on the time necessary for collapse of the animals.

The exposure chamber contained five revolving cages which electrically

monitored the activity of each mouse. Routine visual observations were also

made. The time when a mouse could no longer make the cage revolve was

considered the time of incapacitation. The total test exposure was 15 minutes.

Kishitani and Yusa attempted to develop a relationship between the sample

mass loaded in the tube furnace and the average Tj^ obtained in each test. The

following empirical formula was derived:

W = k T^P

36
where W = sample mass in grams, = time to incapacitation in minutes, and k

and p are empirically derived regression coefficients. Various materials were

compared by ranking the total mass of material, W, which when heated in the

tube furnace produced an average collapse time of between 2.5 to 3.5 minutes

(Table 13). With the exception of polyvinyl chloride-A (PVC-A), polystyrene

produced combustion products which were less toxic than those of any other

material tested. (The unexpectedly low toxicity rating for PVC-A was suggested

by the authors to be due to the extremely large amount of inorganic filler used

in its formulation.)

Nishimaru et al. [56] evaluated the relative acute toxicities produced by

the inhalation of smoke and gases from pyrolyzing or burning plastics used for

insulation. Five different foams, two of which were polystyrenes, and a wood

(lauan) sample were tested at four different temperatures; 350, 450, 550, and

750°C. Temperatures were selected to simulate the early stages of fire

development. The test specimen was placed into a quartz tube and heated in an

electric furnace. Dry air flowed through the tube furnace and into the animal

exposure chamber at a rate of 5 2,/min. In most tests, eight male mice were

placed in individual revolving activity wheels, which were rotated solely by

the movement of the mice and were electronically monitored. The time to

incapacitation (T^^), i.e., the time at which the mouse stopped rotating the

cage, was then used as the measure of acute toxicity. Each test ended when all

the animals had collapsed. In a few experiments, materials were heated at

550°C for 10 minutes and a hybrid, male rabbit was exposed to the thermal

37
decomposition products along with the six mice. Measurements performed on the

rabbits included ECG's and respiratory tracings.

Gas concentrations (CO, CO 2 , and Oj) in the exposure chamber and the

incapacitation times calculated for both polystyrene foams at each temperature

are presented in Table 14. The greatest toxicity, as indicated by the shortest

average time to incapacitation, occurred at 550°C for both polystyrenes. This

temperature produced the highest concentration of both CO and CO 2 and the

lowest concentration of O 2

. The flaming which occurred at 550°C was also

longer than that at the other temperatures and it was noted that polystyrene

was more toxic in the flauning mode.

When compared to the other three foams (i.e., PVC, urea resin, and

polyurethane) and lauan wood decomposed at 550°C, the thermal decomposition

products from polystyrene foam appeared to be the least toxic (Table 15)

especially since a larger mass loading of polystyrene foam was degraded than

for any of the other foams. More animals were incapacitated and at shorter

times from the decomposition products of the lauan wood, which was the only

material with a mass loading equivalent to that of the polystyrene. However,

abnormalities were observed in the ECG wave patterns and the pneumatograms of

a rabbit exposed to the polystyrene combustion products. In particular, anoxia

with deep breathing was evident.

Since the polystyrene, when decomposed in the non- flaming modes, produced

relatively low levels of CO and CO 2 , the incapacitating effects are probably

caused by something other than CO and CO 2. Styrene, one of the major pyrolysis

38
products of polystyrene and a knovm irritant, was considered by the authors to

be a likely cause.

3.3 Combustion Ovens

3.3.1 University of Pittsburgh Toxicity Protocol

Prior to the establishment of the current version of the University of

Pittsburgh Test Method (to be described later), Alarie et al. [57] developed a

test procedure to evaluate the degree of sensory irritation evoked by exposure

to plastic decomposition products. In a 12 8, combustion chamber, a known

amount of material was ignited with a bunsen burner, which was removed after

ignition so that the continued combustion was self -propagating. Samples were

configured so as to burn like tapers from the top down. A constant airflow of

17 2,/min was maintained through the combustion chamber. The thermal decomposition products were further diluted by mixing them with varying amounts of fresh

air (i.e., 0, 17, 51, and 96 2,/min) to produce different exposure

concentrations of gaseous products in order to develop a concentration-response

relationship. In each test, four mice were placed in individual bodyplethysmographs such that only their heads were exposed to the various

dilutions of the gaseous effluents which were directed through the 2.3 2, glass

exposure chamber. Since sensory irritation was correlated with a reduction in

respiratory rate [58], Alarie et al. determined the concentration of the

gaseous products which reduced the respiratory rate by 50%; that concentration

was designated the RD 50 . The respiratory rates of the mice were monitored

before each test (control rates), during the three minute exposures to the

39
combustion products, and following the exposures to establish recovery times.

Concentration-response relationships were developed based on the amount of

material loaded in the combustion chamber and the total exposure airflow (i.e.,

combustion air and dilution air).

Two polystyrene materials (i.e., a sheet and a foam) were evaluated by

this procedure and compared to a polycarbonate sheet [ 57 ]. The calculated RD50

values for the polystyrene sheet was 6.0 mg/ 2, and that for the polystyrene foam

was 9.6 mg/ 2,. These RD50 values indicated that the irritant potencies of the

combustion products of these materials were as follows: polystyrene sheet >

polystyrene foam > polycarbonate sheet. The authors concluded that the sensory

irritancy was not due to the elevated CO or COj or decreased Oj, but was

probably due to small amounts of styrene monomer or some other styrene derivatives produced during combustion.

The current version of the University of Pittsburgh toxicity test method

is a dynamic flow-through system that uses a Lindberg furnace which is programmed to heat the sample at a ramped heating rate of 20 °C/min. Air and

combustion products are flushed through the oven and diluted with cooled air,

such that a total airflow of 20 2,/min passes through the animal exposure

chamber. In each experiment, four male mice are exposed in the head-only mode.

AO
Typical endpoints are the LLjo^, the amount of material loaded in the furnace

that kills 50% of the animals during a fixed exposure time (usually 30

minutes); the LT 50 , the time needed to kill 50% of the animals when exposed to

the LL 50 ; and the RD 50 , the loading of material in the furnace that reduces the

average respiratory rate of the animals to 50% of their pre-exposure control

values. Although continuous mass loss is measured throughout the experiments

in the University of Pittsburgh method, all biologic end-points are based on

the mass of material initially loaded in the furnace, not the total mass

consumed.

Alarie and Barrow [60] used respiratory rate depression (i.e., RD 50 ) as a

measurement endpoint to assess the relative toxicity of the thermal decomposition products of polymeric materials, including polystyrene. The RD 50 level

reported for the oxidative pyrolysis of a polystyrene was 0.18 mg/ 2, with 95%

confidence limits of 0.08-0.42 mg/Z,. This value may be compared to the RD 50

value (6.0 mg/ 2, with a 95% confidence limit of 4. 4-8. 4 mg/ 2,) for the same

material examined with the earlier method under flaming combustion. The

conclusion made by these investigators was that biologically significant

differences existed between the irritant effects produced by non-flaming

oxidative pyrolysis and open-flaming of polystyrene.

^The published literature uses the term LC 50 rather than LL 50 . The

authors of this review, however, have decided to use LL 50 to point out that in

this test method the endpoint is actually based on the amount of material

loaded into the furnace and is not the exposure concentration which has to

include some measure of atmospheric volume. In fact, it is somewhat difficult

to determine the actual exposure concentration over time, which depends on the mass loss rate and dispersion of thermal decomposition products in the airflow

through the oven.

41
Anderson and Alarie [61] evaluated the toxicity of the thermal decomposition products of three different polystyrenes, two of which were specially

formulated rigid polystyrene foams (GM47 and GM49 [ 8 ]) and one was a

commercially available polystyrene film. The formulations of GM47 and GM49

were alike except that GM49 contained an undefined fire retardant. The LLgo

values for these polystyrenes were 5.8, 9.8, and 10.0 grams, respectively.

Although Alarie provided values based only on the mass loading, a nominal LC 50

value in mg/ 2, may be estimated based on the exposure duration (30 minutes) and

the flow rate of the dilution air (20 2,/min) through the animal exposure

chamber. These nominal LC 50 values for GM47, GM49, and the polystyrene film

would be 9.7, 16.3, and 16.7 mg/ 2,, respectively. Although this is a possible

way to define a nominal LCgg, a more valid approach in a dynamic system, when

materials undergo rapid thermal decomposition, is to actually account for the

gas concentration which passes by the animals and the time period that the

animals are exposed. This latter time period is related to the time of total

mass loss. Based upon the information provided by Alarie and Anderson [62]

GM47 totally decomposed in approximately 6 minutes and GM49 took 8 minutes.

The LC 50 values based on the times of total mass loss for each sample would

then be 48.3 mg/ 2, for GM47 and 62.5 mg/ 2, for GM49. These LC 50 values are

approximately 4 to 5 times larger than those calculated based on the assumption

that decomposition occurred uniformly over the total exposure period and more

nearly resemble values reported with other test methods.

In addition to the LL 50 values, Alarie and Anderson [62,63] also measured

and calculated LT 50 (the time necessary to kill 50% of the animals exposed to

the 30 minute LL 50 ), LLT 50 (i.e., LL 50 times LT 50 ) and RD 50 values for GM47 and

42
GM49 (Table 16). Along with this toxicity data, the authors also provided

information on the mass loss and the CO production that occurred during the

decomposition of the polystyrenes. Both polystyrenes, i.e., GMA7 and GM49,

decomposed rapidly with the initial mass loss starting to occur at about 300°C

and the major portion of the mass being lost between 400°C and 500°C. Although

CO was released by both GM47 and GM49, the concentration produced by the fireretarded sample, GM49, was substantially greater (about 5000 ppm) than that

produced by GM47 (about 1500 ppm). The toxicity of the various materials

evaluated was compared with that of Douglas fir. Regardless of the endpoint

used for comparison, these polystyrenes, i.e., GM47 and GM49, were ranked by

the authors as more toxic than wood. (This test method is one of a few in

which polystyrene products are ranked as being more toxic than wood.)

3.3.2 Harvard Medical School Toxicity Test Method

This test method was developed and used by Dressier [64] in the evaluation of the toxicity of combustion effluents from consximer products. In this

method, the combustion system consists of a modified self -cleaning oven and is

connected to an animal exposure chamber which contains ten revolving, animal

exercise wheels. The time-of -useful-function (TUF) is the biological endpoint

and is defined as the time from the start of exposure to when the animal is

unable to voluntarily move in the exercise wheel. The combustion products are

recirculated through the furnace and exposure chamber.

With this test procedure, Robinson et al. [65] assessed the acute

toxicity of the combustion products from three polymeric materials commonly

43
used to manufacture television cabinets. These materials consisted of two

different polystyrenes, one of which was designated PS-SB-BR and contained a

brominated flame retardant and the other, designated PS, was not flame

retarded. The third material was a polyphenylene oxide (PPOP). Two sample

loadings were tested; the first (128 mg/e,) was considered equivalent to the

concentration produced by an 8 pound television cabinet being burned in a 100

cubic foot room. This mass loading was heated at 350, 400 and 450°C. The

second loading was equivalent to a nominal animal exposure concentration of 32

mg/e, and was only tested at 450°C. In each test, a total of 28 rats (i.e., 10

in exercise wheels, 18 in wire-mesh cages) were placed inside the exposure

chamber and exposed to the pyrolysis products from these materials for 20 min.

Both the TUF and the number of animal deaths were recorded during each experiment. Surviving animals were observed for 21 days to determine if the thermal

decomposition products resulted in post-exposure deaths.

The results of the mortality study are presented in table 17. When fuel

loads equivalent to 32 mg/ 8, were decomposed at 450°C, the flame retarded

materials produced no mortalities, while the non-flame retarded polystyrene

caused 10% of the animals to die. At the 128 mg/ 8, loadings, no deaths were

noted at 350°C, 0 and 82% deaths were observed when the flame retarded and nonflame retarded materials were heated at 400°C, respectively; whereas at 450°C,

51 and 93% of the animals died from exposure to the thermal decomposition

products from the flame retarded and non-flame retarded polystyrenes,

respectively. These results indicate that the non-flame retarded polystyrene

was more toxic than the flame retarded one. Additional results presented by

the authors showed that the flame retarded polystyrene was more toxic under

44
non- flaming decomposition at 450°C than when flaming occurred. These findings

are contradictory to the already discussed polystyrene results in which the

flaming mode of combustion was observed to be more toxic.

The results of the TUF measurements showed the same trend as the

mortality data (Table 17). Animals exposed to the higher concentration of nonflame retarded smoke produced at both 400 °C and 450 °C had the shortest TUF, 2

and 5 minutes, respectively. Compared to the other television cabinet

material, polyphenylene oxide, polystyrene appeared to be more toxic at the

higher loading.

The average concentrations of CO, COj and Oj generated in the exposure

chamber when the flame retarded and non-fl2ime retarded polystyrenes were

decomposed at 450°C are displayed in table 18 for the 3 and 12 minute

exposures. The lowest oxygen and highest CO and COj levels were obtained when

the non- fire retarded polystyrene sample was decomposed. These findings appear

to be consistent with the higher mortality and more rapid incapacitation caused

by exposure to this polystyrene.

3.3.3 General Electric/Southern Research Institute Test Method

Nelson, Hixson and Denine developed a test procedure to determine the

relative acute toxicities of the thermal degradation products from a variety of

materials [66]. In this method, different mass loadings of materials are

placed in a combustion furnace (i.e., a nominal 10 t Electric Multiple Unit

Furnace, type 66, or Lindberg Model 51442-S Box Furnace) and decomposed at

45
temperatures which varied between 805 and 880°C. The smoke generated in the

combustion furnace was drawn through a laminated rubber tube into a 740 2,

acrylic animal exposure chamber by an exhaust fan. As the smoke started to

fill the exposure chamber, the exhaust fan was turned off and the exhaust port

was sealed. Additional gaseous products and smoke were then transported and

mixed in the exposure chamber by natural convection. When the thermal degradation of the material was complete (as determined by visual observation of the

sample), the furnace was disconnected and the animal chamber was sealed. In

each test, ten Sprague-Dawley rats (5 males and 5 females) were placed into 5

cages located inside the animal exposure chamber and exposed to the gaseous

atmosphere produced. The timed animal exposure of 120 minutes officially began

when the combustion furnace was disconnected and the exposure chamber was

sealed. The apparent lethal concentrations (ALCgo) (i.e., the amount of test

material which, when decomposed under the specified test conditions, produced

mortality in 50% of the exposed animals) were determined for twelve synthetic,

including one high impact polystyrene sample, and two natural materials. The

concentrations of CO, COj, and Oj in the exposure chamber were analyzed and the

blood COHb levels of a minimum of four animals per test were measured following

removal of the animals from the exposure chamber. The ALC 50 data, which are

based either on the amount of material loaded or the amount of material

actually consumed, are presented in table 19. These values are presented

(based on the ALC 50 values for the amount of material loaded in the furnace)

from the most toxic to the least toxic. When the ALC 50 values of all 14

materials were compared, the high impact polystyrene was determined to be the

second most toxic material with an ALC 50 of 12.0 mg/2,. However, none of the

ALC 50 values differed by more than a factor of 6 (based on the amount of sample

46
loaded) and the high impact polystyrene was determined to be about twice as

toxic as red oak.

Table 19 lists the concentrations of CO and CO 2 in the exposure chamber

atmospheres at the ALC 50 values for each material. The COj levels were noted

to increase during the exposure period; this can be attributed to the respiration of the animals. The authors concluded that with the exception of wool, CO

in conjunction with the elevated CO 2 levels, was the primary cause of the

observed toxicities produced by these materials. All animals that died within

the two hour exposure period (except those exposed to wool products) were found

to have blood COHb levels in excess of 60%, mostly in the 70-80% range.

Surviving animals also exhibited elevated COHb levels, which, in some

instances, approached levels of 60%.

3.3.4 University of Michigan Toxicity Protocol

Two different test procedures, one static and the other dynamic, were

developed at the University of Michigan to study the toxicity of thermal

decomposition products of various combustible materials [67]. In the static

method, the test sample is rapidly decomposed by heating at 700°C in a Vycor

tube wrapped with resistance wiring for a period of 6 to 10 minutes. In each

test, a group of Sprague-Dawley rats (usually 15 per test) is exposed for a

period of 4 hours to the combustion products which are generated directly into

a 1500 liter stainless steel chamber.

47
The dynamic method involves slowly heating a sample material placed in a

furnace programmed to increase the temperature at a rate of either 3 or

5°C/min. An airstream of 1 S,/min flows through the furnace and is cooled and

further diluted with air flowing at a rate of 2 l/mln prior to passage through

the animal exposure system. After lAO minutes, the furnace temperatures

reaches about 700 to 800®C and the decomposition process is considered

essentially complete. At this time, all exposed animals are removed. In each

test, five rats are exposed to the thermal decomposition products from

different mass loadings. The chamber used for exposing the rats to the thermal

degradation products is a Pyrex glass column with side tubes attached so that

only the rats noses extend into the decomposition effluent airstream.

In both test methods, the primary biological endpoint is lethality. The

LL 50 values determined for the various materials tested are presented in Table

20. The LL 50 value for the polystyrene sample decomposed under static conditions was 29 grams; whereas, under the dynamic conditions, it was 4.3 grams.

In the static mode, polystyrene ranked as the sixth most toxic material among

eleven evaluated materials; while in the dynamic mode, it seemed to be the

least toxic material. The nominally calculated LCgg value for polystyrene in

the static exposure tests was 19.3 mg/ 8,, while in the dynamic exposure tests,

it was 10.2 mg/ 2,.

Cornish et al. [ 68 ] also investigated whether different animal species

would respond differently to thermal decomposition products from various

materials. Both rats and rabbits were exposed to the thermal decomposition

effluents generated when 20 grams of a material were decomposed under static

48
conditions. The results of this study were inconclusive with regard to

polystyrene since no mortalities were observed in either rats or rabbits at

this loading.

The two exposure systems described above are obviously quite different.

Under the static conditions, the animals are exposed to the total products

resulting from the thermal degradation for a period of 4 hours. In the dynamic

system, animals are exposed to the thermal decomposition products only during

the time in which they are being generated. Thus, in the dynamic system,

animals are exposed to specific decomposition products for only relatively

short times. Based on the actual LCgg values calculated, this polystyrene

appeared to be more toxic under dynamic than under the static exposure

conditions. This observation, that the LC 50 values are lower under dynamic

than under static conditions (i.e., more toxic) was also noted for the other

test materials. On the other hand, under the dynamic conditions, the

polystyrene was the least toxic of all the tested materials.

4.0 Conclusions

• In general, the main volatile product regardless of atmospheric

conditions is the styrene monomer. The concentrations ranged from 0.6 to

100% of the mass evolved.

• The composition and quantity of other evolved products depend greatly

upon the chemical formulations (mostly unspecified) and experimental

conditions

49
• The evolution of styrene is temperature dependent - increasing with

furnace temperatures up to 500“C and decreasing above 800“C.

• In oxidative atmospheres, CO and COj were formed and appeared to be

responsible for the animal deaths that occurred during the flaming

decomposition of polystyrenes.

• Effluents produced during flaming degradation of polystyrenes were

generally found to be more toxic than those produced under non-flaming

conditions.

• Animal incapacitation occurred during non-flaming decomposition of

polystyrenes and could not be attributed to CO and COj since their

concentrations were too low. Some other toxicant, perhaps styrene, was

responsible.

• When compared to other common natural and synthetic building materials,

the thermal decomposition products of polystyrene appear to be among the

least toxic.

5.0 Acknowledgements

The authors gratefully acknowledge the helpful discussions with

Ms. Maya Paabo and the assistance of Ms. N. Jason, Ms. M. Diephaus, and

50
Ms. A. Durham and Ms. C. S. Bailey who performed the literature search and

compiled the references.

This work was performed under Contract CPSC-IAG-74-25, Task Order 84-8

from the U. S. Consumer Product Safety Commission, Dr. Rita Orzel, Project

Officer. The opinions expressed herein are those of the authors and not those

of CPSC.

51
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Tox. 4:533-555 (1977).

46. Hilado, C. J. and Machado, A. M. , Effect of char yield and specific

toxicants on toxicity of pyrolysis gases from synthetic polymers. Fire

Tech. M-.51-62 (1979).

47. Hilado, C. J. and Huttlinger, P. A., Toxicity of off-gases from thermal

insulation. J. Therm. Insul. 4:276-287 (1981).

48. Hilado, C. J., Huttlinger, P. A., and Shabdue, C. L., Smoke and toxic

gases from materials in healthcare facilities. J. Cons. Prod. Flamm.

8:65-76 (1981).

49. Hilado, C. J. and Huttlinger, N. V., Concentration-response data on toxicity of pyrolysis gases from six synthetic polymers. J. Comb. Tox.

5:81-100 (1978).

50. Hilado, C. J. and Brauer, D. P. Concentration-time data on toxicity tests

and resulting relationships. J. Comb. Tox. 6:136-148 (1979).

51. Hilado, C. J. and Huttlinger, N. V., Toxicity of pyrolysis gases from

phenolic, isocyanurate, and polystyrene rigid foam insulation. J. Therm.

Insul. 2:40-47 (1978).

55
52. Hllado,C. J., Olcomendy, E. M. , and Bauer, P. B., Effect of pyrolysis

temperature and air flow on toxicity of gases from a polystyrene polymer.

J. Comb. Tox. 6:13-19 (1979).

53. Hilado, C. J., Gumming, H. J., and Schneider, J. E. , Relative toxicity of

pyrolysis gases from materials: effects of temperature, air flow and

criteria. Fire & Matls. 3:183-187 (1979).

54. Kishitani, K. , Study of injurious properties of combustion products of

building materials in initial stage of fire. J. of the Faculty of

Engineering, University of Tokyo(B) 31^:1-35 (1979).

55. Kishitani, K. , and Yusa, S., Study on evaluation of relative toxicities

of combustion products of various materials. J. of the Faculty of

Engineering, The University of Tokyo, 35:1-17 (1979).

56. Nishimaru, Y. , Saito, F., Nakamura, K, Morikawa, T., and Yusa, S.,

Evaluation of acute toxicity of smoke and gases from smoldering and

burning plastic foams. Fourth Joint Meeting U.S. -Japan Panel on Fire

Research and Safety, UJNR, Tokyo, pp. 567-586, 1979.

57. Alarie, Y., Lin, C. K. , and Geary, D. L. , Sensory irritation evoked by

plastic decomposition products. Am. Indus. Hyg. Asoc. J. 35:654-668

(1974).

58. Alarie, Y., Irritating properties of airborne materials to the upper

respiratory tract. Arch. Environ. Health, J3::433-441 (1966).

59. Alarie, Y. and Barrow, C. S., Toxicity of plastic combustion products.

Toxicological methodologies to assess the relative hazards of thermal

decomposition products from polymeric materials. Nat. Bur. Stand. (U.S.)

NBS-GCR-77-85 (1976-1977).

60. Barrow, C.S., Alarie, Y., and Stock, M. F., Sensory irritation and

incapacitation evoked by thermal decomposition products of polymers and

comparisons with known sensory irritants. Arch, of Environ. Health

^'.79-88 (1978).

61. Anderson, R. C. and Alarie, Y. C. E., An attempt to translate toxicity of

polymer thermal decomposition products into a toxicological hazard index

and discussion on the approaches selected. J. Comb. Tox. 5:476-484

(1978).

62. Alarie, Y. C. and Anderson, R. C., Toxicologic and acute lethal hazard

evaluation of thermal decomposition products of synthetic and natural

polymers. Tox. & Appl. Pharm. ^:341-362 (1979).

63. Alarie, Y. and Anderson, R. C., Toxicologic classification of thermal

decomposition products of synthetic and natural polymers. Tox. & Appl.

Pharm. 57:181-188 (1981).

56
64. Dressier, D. P., Smoke toxicity of common consumer products. Report to

Consumer Product Safety Commission, Contract No. CPSC-C-74-212 (1975).

65. Robinson, R. S., Dressier, D. P., Dugger, D. L., and Cukor, P., Smoke

toxicity of fire-retardant television cabinets. J. Comb. Tox. 4:435-453

(1977).

66. Nelson, G. L. , Hixson, E. J., and Denine, E. P., Combustion product

toxicity studies of engineering plastics. J. Comb. Tox. 5:222-238

(1978).

67. Cornish, H. , Toxicity of thermal-degradation products of plastics. In:

Products of Combustion of (Plastics) Building Materials. Armstrong Cork

Co., Lancaster , PA, March 1973, p. 30.

68. Cornish, H. H. , Barth, M. L. and Hahn, K. L., Comparative toxicology of

plastics during thermodecomposition, presented at the International

Symposium on Toxicology and Physiology of Combustion Products, University

of Utah, March 22-26, 1976.

69. Standard Guide for Measurement of Gases Present or Generated During

Fires. ASTM E800-81, American Society for Testing Materials,

Philadelphia, PA (1984).

57
Table

1.

Volatile

Combustion

Products

of

Polystyrenes

Under

Varying

Experimental

Conditions

m

CNI

I CM

00 o rH m1 o 00 n CM

CM 0k 0k m 00 CM <T 00 ID CM

CM A fH CM CM 0k cs A CS C3N 1 CN ^H 00 A A CM CM <N ro (S CM CM CM m rH cn CM CM CM rH

•* CM rH A #1 CM A CM m, A 0k A CNJ oo 00 • 00 •h 0k •t vO cn

rH m *-H CN rH m rH 1-H m vO VO r-H i-H rH

3

o

tfl >

X X X X X X X X X X X X X X

u

a) x:

a,

(fl

cC4JM

z

z0k 0) m z

o CU oT 2 >H CU CU (U 6PC

CM

1 1 33 t '< * 33 33 N H N

X I I I I X

X X X X X

0) (1) K Z Z K

3 3

c C C o 3 3

•iH Cfl CX CX

4-1 4-1 CU O O

•r4 O rH CU •3 3 Xi H

Ul 3 o X) •H X3 cx cx o t3 CU 0) CU CU 43 •H X >» I-H I—

a, o c (U C 73 •r4 o X o 43 >v >v B >. o X) CU 5>s o O 43 o 3 3 13 C3 o 04 43 c (U40 M 43 cfl I-H CU •H O ”3 3 3 o 0) CU c C 43 c CU cU c CU •3 B rH 43 43

(U •o 43 CU •H (U CU t3 CU O CU (3 3 CX CX Q rH CX rH (U Ta x> rH c •H rH •H CU CU C C i 3 •H 'H 3

(0 o >> r-l rH rH Cfl (U o -o C3 4-1 o o Cfl (3 -3 -3 C

4J 4-1 4-1 o >> >> N N N N cfl cfl 3 43 43 3 3 1 1 3

(U 0) 0) IH M f—

(3 c c c 4-1 4J 43 P 3 3 B m cn 43 u u O u O rH CU CU 0) CU 3 3 1 Cfl 3 •H p A A 4-> cU CU cfl cfl Cfl 43 4i 43 43 ^H CJ 3 o 3 rH rH 3

58

ethylbenzene

x

He,N

x

3,13,14,16-19,22,23

ethylene

x

He,N

x

3,14,23,28

ethyl-methyl

benzene

-

N

x

17

formaldehyde

-

-

x

22
Table

1.

Volatile

Combustion

Products

of

Polystyrenes

Under

Varying

Experimental

Conditions

-

continued

cn

(U

CJc

0)

0)

i4-( 0) «

00

CNI

CM

cn

I VO

cs

r>- 00 cs cNimm 00 *>'3’oooo

CN| I—I »—1 t-H C'O »“H 1-H »-h oor^m<- moorxcs

T—t I—I T—H t—( f— t—( T—H (Vj

CN

CM

00 00

<j- CM

T—H *-H t-H t—

(U>

'H

4J

nJ t3

•HX

o

(Up

0)

cO CX P

M P

o (U a c p M

<

3o

CO >

X I I I X X I I

0) 0)

I s S Z Z I z z

XIII

I X X X

0) z z n; z

X X

0) w z I

X X X X X

I Z Z I I

0) p

c

(Ua1 c

1 rH (U o >> (U 0) c

•H CO 42 c c 0) p p P 0) (U p 0) 0) •H o (U p X C343 C3 S3 (0 3 a 3J O) 0) P (U o

o t3 43 43 a o P p

cx o CM 1 1 1 c a p •H CM ro 0) P p

o PL| CJ A 1 1 43 w (0 o CO (U rH rW rp »H Qn| rH rH

0) c 0) o >> >. >> >. Q O 0) 0) 0) c c 43 43 43 p 43 43 H c c X CO cO P P p p P

a CO 0) (U 43 43 CD (U 0) 43 0) 0) p X X 43 P P a a a p a a o 0) 0) 1 0) 0) 1 1 1 (U 1 1 p 4= 4= 1—

a a cn CM B 0 CQ.

0)c

0) (U C -P

(0 c P 0) c j:: c a 0) cu

0) I ^ •—I D< '

I

O (U N c

rH C (U o 0) N

c 43 C

cO P 0) 43 >»43 P CX P

0) o 0) iH P cx c

Q} a. o 0) C P

(0 ^ a.

cu o D. O OT O

M -H c P O

CL,s^ w' cii —

59

styrene
Table

1.

Volatile

Combustion

Products

of

Polystyrenes

Under

Varying

Experimental

Conditions -

continued

CScs

mm

CNi CM CM

0k 0k 0k

wm as o m as

0) (S CM CM o 1 0k 0k 1 c rH rv as as vO

0> <s p 0k * 0k 0) as o CP rH

0) 1 * A 1 a rH m m in (M CM CM

rH rH 0 0 * 0k o^ a\ ON cs 0 00 00 00 ro CO cn cn 1—

•H (N|

m

a)

(0o

i*ou

0)

0)M

0)

0)>

•H

•P'O

n)

0)M

0} rC

P4

UioB<

cdP

0)C

>iX >iXX

XX X!

0) s z z A A M 0) 0) 0) c a z » I I I I0) a0k h< X X X X I I I I X z z z

0)c

(d axi P 0) 0)

0) c

(d 0)

w 3 cu o X

X o a a rH (U (U cx o •H a a a a p p p p X o o o o a p cu (U p (U o •H rH iH u 1 cu p a a (U a o o

0) 0)

a

p cu o Cd

a Cd 0) 0) +J >» >>

Q c O 0)a

p P cd P c c u o

0) c a •Hp

C

X cx (U 0) CM iH rH

p o -3

p 0) 0) cu (U

p 3 A 5>^ >. s a a p p Pua a s rH fH C C p p o A •H «H w w p > > a cu • (U c 0) •H cu p

•H 0) •H a • a o cd (U a

0)p • P w

cx 3 0) 0) o

V)

cdc

Q)00OPP u

a0) a Haw o a o aweo P ep

cd

B

cd cd

•H ?W

0)c

0)ppw

>>

C -H O -H

OO (U p a cd c C -H

•H

a

a 0) 0) w

Q.

B 6 O

bO

O 0)a

pa cd w c: < cu c: cu p C (U 0 (u a 9 p ^ w >k a

0)p

a (U

p

w cu

p

cu >>

p CJ

a iH CJ (U (X o (U P w cx P CU o (U a B p a

(jp

cd cd P CJ cx u 3 P a a p •H a o

0) o p c C P cx

•H cu cx a

w

p ? w cu

(U (U

p

a

ap cd c c cd CJ 3 CJ •H O *H a a p a c

(U c •H W cn -H o p 0 cx CJ •> P a 3 C 3 o a o •H u O OOrH

0)

pp (U o cxi <; n p 0)

cd

a < a

C

0)00opp

•Hcc

•Ha

0)woou

0) asa

0) po

0) p

0) Po3aop

cxw

0) p

cdo

•H

'Oc

•>

ww COO)

QJpp

60 cd Cd o o o P *H *H p a a

•H c c Z M M

60

product

found.

product

not

found

or

no

analyses

performed.
Table 2. Flash Pyrolysis of Polystyrene at Different

Temperatures in Nitrogen Atmospheres [11]

Pyrolysis Temperature Styrene

Sample weight ( °C) (%)

1-5 yg 550 63+4

600 64+9

650 84+8

700 101 + 6

1-3 mg 700 75+5

61
Table 3. The Low-Boiling Point Volatile Products from

Radiant Pyrolysis of a Polystyrene in

Nitrogen or Air Atmospheres [19]

Relative Chromatogram Peak

Product Nitrogen Air

Toluene 0.8 1.2

Ethylbenzene < 0.2 0.2

Styrene 100.0^ 100.0

Benzaldehyde 0.0 0.9

a-methylstyrene 1.0 0.8

a Styrene yield is 33.2 + 3.1 wt %

b Styrene yield is 35.4 wt %.

62
Table A. Styrene Evolution During Thermal Decomposition of Polystyrenes

Sample

Temperature

(°c)

Mass

volatilized

(weight %)

Styrene evolved

(weight % of mass volatilized)

Vacuum Inert Oxidative Reference

PS 200 _ _ trace 22

IPS 224 1.0 - - 3.4 17

IPS 240 1.1 - 3.3 - 17

PS 240 0.6 - - 8.0 17

IPS 250 0.9 - - 3.8 17

PS 250 0.7 - - 7.0 17

PS 255 0.3 - 9.1 - 17

IPS 260 0.3 - 3.1 - 17

PS 260 0.6 - 13.0 - 17

PS 350 5-20 - 18-19 - 15

PS 350 7

- 37 - 15

PS 350 43-87 - - 14-22 15

PS 350 35 - - 18.5 15

PS/FR 350 40 - 1.5 - 15

PS/FR 350 40 - - 9.0^ 15

PS 350 - - - 5.2^ 22

PS 362 83 40.9 - - 27

PS 362 83 - 31.4 - 27

PS 400 99 47-50 - - 23

PS 437 67 - - 35.4 19

PS 447 46 - 33.2 - 19

PS 450 100 - 50-51 - 15

PS 450 100 - - 42-47 15

PS 500 - - - 5.8^ 22

PS 500 100 51-56 - - 23

PS 500 100 - 49-53 - 23

PS 800 100 47-48 - - 23

PS 800 99 - 9-13 - 23

PS 850 100 27.8 - - 27

PS 850 98 - 17.2 - 27

PS 1200 98 41-42 - - 23

PS 1200 95 - 0.6

Flash-Pyrolyzed Samples

23

PS - - - 93.7 - 12

PS 510 - - 79.1 - 18

PS/PB 510 - - 73.5 - 18

PS 550 - - 63+4 - 11

PS 600 - - 64+9 - 11

PS 650 - - 84+8 - 11

PS 700 - - 101+6 - 11

PS 700 - - 75+5 - 11

PS: Polystyrene; PS/FR: Polystyrene with flame retardants; IPS: Impact

polystyrene; PB: Polybutadiene; -: No data provided, a: Based on weight 7, of

total sample

63
Table

5.

Summary

of

Toxicity

Protocols

(A U > <

'T3

U

o

U -H§

W 'O

'TS *T3 *o

C

00c

4J

CA

:3 (A Xi >

B (A OO

0) O 0) O 0)

0) 0) O u O o U U a

o u u CO CO CO CO CO c c c

(0 CO CO c 3 c C c O o i-H o

c 3 c u u C M •H •H V4H C •H u U 3 3 3 3 3 4J 0) o 4J 0) 3 3 3 Mh UH H-4 4H (A O M U 4-» -H (A U

a.3

u a

u

0)DQ> Xx 3

4^

0)3

0) XX3

3 CO § E O 3

U 4-( &

M-t 0) O M

3

0) (A &gH X

0)

o

s

o

X

o

z g g 5 o

w

o

S3 oW

c c C c c u 3 3

o o o o O (0 O 0

•H •H •H •H •H rH •H •H

4J u 4J 4J 4-» 3 4J >> 4J

CO (0 CO CO (0 CJ CO U 3

fH 4J 4J o >» 4J 4J 4J (A 4J O 4J

CO 4J •H •H 4J u *H •H •H CO •H 4J u •H O c U u CO c U u u > U CO 3 L U

•H •H CO CO U 0) CO CO CO O CO 0) o >> 3

GO o cl4x: o,x: x: •H 3 <xx: 0« *H .3 O.Xi •H 3 4J u 0.4S O a CO 4J CO 4J 4J o* O' CO CO 4J CO 73 4J CO 4J CL* O’ CO 3 3 4J U <0 U CO CO (A 0) O CO U (0 U U cO o CO (A 0) 3 U 3

O c .c C 0) c o 0) 0» C 0) C 0) C CO 0) .3 c Q> <U 1.4 •H 3 3 0) •H 0) 4J H »o V4 Cm *H T3 •H *0 •H o T3 4J •H *3 CM a O’ 4J •H

PQ CO CO CO (A 0 3

0) \ /-*s /.“N /-«s 0) 0) 3 u 0) rH rM -H CN CN •M CN r-H (N rH <N m T3 •3 rH (N m u CM *3 *H (N

oro

ra

V)

4-1 raWi

3

o m

m ^

o o om

CN »-«

CO 0) 0) u u

•H *H e a

(A

4J

•H

CA ^ (A

4J ^ 4J

<0 cO CO U U M

0)U

•Ha

mooCM rs

0) (A (A U U U

•H <0 cO B u U

X 42

GO GO

Pu 0) CM 3 CM C CM CM 1-t C/i (A 0 3 0 3 0 3 O 3 •3

35 0) GO 00 X X

s

M

3 • .H • *H • (A • (A 3 < 3 > .3 > 42 > > 4J (/) a •H O •H O •H M •H M

3 3 *H C *H M js Z »-) 35 £ 5 £ 5 04 £ 04 O P2

4J • (A O -K «

0) Z ^ CN

4C m« •K»n sO

CO 00 GO

icCO O'

.o

O' o •K CO S

64

Described

by

Kaplan

et

al.

[26]

NO:

Nose

only

exposure

Animals

in

an

activity

wheel

during

exposure

HO;

Head-only

exposure
Table

6.

Results

from

the

Dow

Chemical

Co.

Test^

[31]

0)c ^ o o

0) e o o CM

a, <

o.

t-i

w

A

A

wc• H

0) e

I—1 Ol< o '3"

m o o cx

>-l 'w' o

(T3

CN

m

O 6 o o o CM

O o m o ex o m m o o CM 0< pH CN| m m

33 w'

VAA

inC

—\ m o X e > •H o ex <3" o m LO CM u z a f—

V

cO '

t-i 4JC

0)

O o o o o O o o o o S O o o o o o o o c CM cx 00 O' so in <r -cj- o o ex 00 o 00 VO vO m o o ^ m CNI m CO

in

ctJ O £ o o o o o o O o o ex o o o o o o O o o cx 00 O' CO mH m 00 O w ro m on CO CN| m

CM Js®

m 'O o o^ <yy a\

O

W 1-H t-H CM rH tH

nj u

fO

coB

•Hc<

cO 4JoH

0)X

tJ 0

in in o o

ex exX

0)

0) 00 Xi c 0

•H to X o 0 ex Q X

0) 0) (1) U Vj

(U 0) .C rC

t3 T3 0) 0) 4Jc c

a) 0) in in

<u 0) <x a

to

O o tu CO to • z • Z f-l 0) cu

i-H 33 f-H t/3 Xi 33 CO Xi ex

dd

to CM CM •H CM CM •H £ rH

•H CJc

O

p

O P p td CtJ cd

Xi '3- SO <T vO fu to > >

tu o CO

O to XI c: c p cd C B p CtJ o< 0) 0)

(0 o O

O rH o O o rH 00 00 z X Xi Xi 00 Xi Xi Xi 00 00 cd cd >> 0 B >> >, >M d e X Xi p p p O •H p P P o 0) 0) M

CO CO CO

Qa CO cn cn

Q o > >

•^T < < B rH»p ex-^ e o m LO o m B in o o o

a) o m 0 inm in

H

w '3' lO

m <r Z in

m (d P u

65

of

which

only

the

minimum

is

of

which

only

the

maximum

is
Table

7.

Results

from

the

NBS

Test

[9] ^ o a

CU

p^ jj • w cd c

•H o a u on o o o o o o o o o o o o o o o o o o o o o o o p NO m m m ON rd d •d d A A A rd rd i-d •d m m m rd m o

hJ

u c

XJ C6 *H K a oo o

cn

C

•Ha

w ^oj o (d m -o too a O ,—

U) O +

t-J

C oi •Ha M omo

too a

cd

t>^ uo vj 4J 0)

td wQ ^ a o 3

XI c

cd X)

a o

a) o H

vOA

A

O CNO

00

VO

m vo ov

ON NO

r>. 00

NO

O 00

inm

NO 00

m NO 00

O NO

O CO Cv) 00

m 'd' <•m

m cn AAA O (S o in o ON

-<r (N

CN (N <N

ON ON

O

in ON ON < cN m

r-l NO 00

O NO o

in 'd- 'd' AAA O I O

in -d" A A

cN -d- NO

in

m in rd cs vo

-dm -dm

n 00

inm fo o

cn I 00

CN

rd -d- vo

moom <r

<t inm

1*1

rd dT ON d rd cs o O ON m m cn

rH o m o m CO

r-H Cd >—

m

00 I m .-I Cd

rd d" NO

moo d NO -d d d d

rd

d NO o m o f-H rd ON m m d

CO«2w

n)»

NO

>N

}-l OP

CdpoX

cd hJ

0)c

0)u

>> 4-)

>> rHo

cx

0) Pu

(U p

V)

0) •HpOp

cdPoX

cd Pc

0)p0) too ip c

IH -H

0) P C •H

C/l 0) 4d 1—

p ^ cd 5n --d cn

•rd P m cd P w X 1—

0) >>

O too

p rd V—0

cd

O o X Pd Q

73 cd too rd C

(U P *H

0) I g P O cd

jfiO rd

H Z P-d

PP

66

I.D:

Insufficient

data
Table

8.

Results

from

the

University

of

Utah

Test

[3A]

O 6 o o o O o W & m vO m 1 1 1 00 a o ro CM m o

4Jw (N CNl (N

m CN o e o o o o o o o o w a 00 in vO 00 a 00 00 cs rvi m CJ»

4-1 'w' t-H

V o CO mO S'? m V 1 4-) 1

(TJ vO

vO o ^ W Bn?

4-1 > c> eom W /—V >>

trJ

—t3 wje

(N

o> 00

vO 00 \o rH Ov

uo

14-4

m LD CM VO 'O' i-H <r ro m 'T m (1) c

(U

i-i

U)wo

ft

00 00 00 vO vO 0) • • • • • 0) m m o O O -cl- V4 CN m n CN •4f -O’ X A A A 4-1

0) X4-1 uo c o tH o4 m £ '

u 04 WOEro —'

d,^ e O

0) o H

W

wz

OV ro cs cyi 00 3 • • • • • • • 1—

in CNl cn o o <r cO »—

1-H CN

m 'O’ A >

»4Ho

0) • 00 c o o o o o o O in c 0) <r o o ON 00 < CN vO CO > m in m N- 'T <r 'O’ 'O’ J-4 *H

00

CT> rH 00 C3V 00

'O’ 'O’ in 0 u 'O’ 'O’m

d >-i s: z Z O -H s z Z O -H cO 1 U-i Oli o o o Q IH o o o Q M-I z

0) X4-1

V) X (0 H >

67

Flaming

Non-flaming
COHb

blood

content

(Z)

and

death

ratio*

of

rats

at

decomposition

temperatures

of;

300°C

A00°C

500°C

600*0

Material

Z

ratio

%

ratio

Z

ratio

Z

ratio

<s CM CM CM <M N CM CM CM N CM CM CM CM «

CM CM CM CM CM CM CM O O O o O o O CM +

+ + + 4- + •f + +

O -0“ 00 00 00 in O' >o O cn O' (M

00 00 00 r*. r- r**. 00 CM CM CM en <n 00 O'

CO ^

r4 cs

O' lO (N iD

-H r-t r>. 00 V

O'

rv r>. CM

00

in

00 m

V mV

in in o in m r-H 0*4 V V V V

r*> 00 00

00

x m A

68

The

ratio

of

dead

rats

to

the

total

number

of

rats

exposed

to

the

fumes.

Non-flaming

Flaming
Table 10. Concentration-Response Data from a Polystyrene Decomposed via

the NASA/USF Toxicity Test Method^ [A9]

Mass

Loaded

(r)

Number

of

Tests

Time to

Death

(.min)

Mortality

(%)

CO

(ppm)

CH^

(ppm)

0.1 1 26.6 + A.l 75 900

0.2 1 25.2 + 2.

100 AOOO

0.5 2 28.1 + 1.2 38 + 18 A600 + 1130

1.0 5 27.5 + 1.3 100 + 0 6900 + 2000 760 + 160

2.0 A 28.0 + A.62 + A3 A650 + 2250 1A50 + 7A0

5.0 2 2A.8 + 6.5 100 + 0 3500

a: Rising temperature program (200-800°C at A0°C/min)

69
Table

11.

Toxicity

of

Pyrolysis

Gases

from A

Polystyrene

Rigid

Foam

Insulation

Decomposed

under

the

NASA/USF

Toxicity

Test

Method

[51] co

•H

4J•H>

0) QW

TJc

CO -u

C/DC

CO0) o w

u • . X 42

N o o 4J

U c

+1 +1

CO cO •H o; 0) e ts tj fM• • 0 0

vO to c c

cs fH

0)w ^a c

CO *H

'—I s

rH w- oaco

•HW

C

C/D

mo+ 1

rTMH

CNI o

+1

vOO

O'

cs+1

O'

C3'

vO CN • . CNi o O o O ON +1 +1 • • 00

'O' CXD o O' CN c

•Hao

oo 'O'

m to 0 c . • • o

•H vO o u -O' C in

0) -H + 1 -H +1 • 4J 00 a

vO CM

m CO

cO . . • a 4-> m vO SO 0

C/D f-HOo

(X) oo

CN

4-1 42 ^ a 4-4 00 0( o O o o o to •H • » • • >-l (U

0) rH t-H rH rH >H 4-) :s 73 (U

0) c a o 5 V) >> o 4J V4 rH

0) (0 c

>-i iw

O 0) (0 o 0 43 43 V4 r-i 4-1 •H

4J 0) 'O o 73

O •H >4-4

a

CO XJ (U 0 a) 0 cO V4 o 0) o u o (X o a. o •H ? >-l 0) S o P o x3 cO 4-* d >4-1 a. (X) 00 (U 4-J a u O c >4-4 CO CO (D V4 •H O V4 4-1 H o a 0) rH

>4-1 c o.

d

o? cO

a CO o 0) 0) 0) z rH s H OS

(U

V4 o u o CJ CO 4D CJ d 0) o o •H H •H •H « -o •H •H P p 4J P o o 4-1 4-J CD (v CO

CO 10 c 4J

4-1 4-» s C/D

C/D C/D

Q

Q

a

70
Table 12. Toxicity of Pyrolysis Gases from a Polystyrene Foam

Decomposed Under the NASA/USF Toxicity Test Method [42]

Air flow Mean Time^ — Standard Deviation

rate

( 2,/ min)

Temperature

Mode

Incapacitation

(min)

Death

(min) Mortality

0 ramped 19.0 + 0.4 26.2 + 0.1 8/8

0 600°C 10.3 + 6.7 26.0 + 0.7 5/8

0 800°C 6.0 + 4.2 21.8 + 6.6 11/12

1 600°C 4.1 + 0.9 12.0 + 1.4 3/8

3 600°C 3.1 + 0.3 7.0 + 1.5 4/8

1 800°C 3.9 + 2.3 n. d. 0/12

3 800°C 6.1 + 2.9 n.d. 0/8

a : mean of 2-3 tests.

71
Table 13. Relative Toxicological Comparisons of a Polystyrene Foam

and Other Materials in the Test of Kishitani and Yusa [55]

Heating

Temp. Sample W(g)

850°C Japanese cedar

Lauan

Hardboard

Untreated plywood

Fire retardant- treated plywood

Melamine resin- impregnated sheet //I Melamine resin- impregnated sheet ifl Polyacrylonitrile

Polyamide

Wool

Urea resin foam

Polystyrene foam

Polyurethane foam

Polyvinyl chloride foam

Polyvinyl chloride A

3.72-5.83

3.47-5.21

3.09-4.46

1.31-2.19

2.20-3.55

0.60-1.00

0.64-0.97

0.24-0.33

0.17-0.25

0.41-0.60

0.24-0.33

17.7-24.6

0.58-0.87

2.61-4.02

34.5-48.6

550°C Japanese cedar

Lauan

Untreated plywood

Fire retardant- treated plywood

Melamine resin- impregnated sheet iH

Polyacrylonitrile

Polyamide

Urea resin foam

Polystyrene foam

Polyvinyl chloride foam

5.50-8.32

6.13-9.11

4.35-6.98

3.42-4.91

2.47-3.72

0.61-0.88

0.38-0.55

0.25-0.39

10.7-15.2

3.45-5.45

W: Specimen weight which produced an average time to incapacitation between

2. 5-3.

min.

NOTE: Heating at 550°C of untreated plywood, polystyrene and polyvinyl

chloride A were compared at a time of 3. 5-4.min.

72
Table

14.

Results

from

the

Nishimaru

Test

[56]

/~s o o 00 o CN 'O'

m c 0) 00 CN. CNI CN| NO CN| CNl o o . • . . • 9 • o •H •H cs < CNI o 00 CNI cn in

4-1 4-) e

CO c

0) 4-1 OO -H +1 + 1 + 1 +1 + 1 + 1 + 1 + e •H 6

•H o ' / o ON NO

m t-H 1-H ON 00

H CO . 00 40- o 00

m <• 00 ON

a

Q • « • • • • • • C CO • CNJ CNI in CNl 'O' cn in in

cO o CO 1—

f—

cn .-H t-H cs

0) c S M +1

/-—

00 NO in NO 00 o m fN

C^

C . • • . . • . . O -H ON 00 o o CJN 00 o o c S'? e f—

t-H cs CN 1-H rH cs cs

•H

V—

Vw' c V4 o 0) *H 43

4J E

nJ CO C3Nmm

O C3N in o in

4= cjX NO cn CNI f'- cn o

4-1

O

O CO . . . . . • . • c o e o f—

o o O t-H o o

0) 0) o u c0 « o oa w X .-H C3N CN| NO rH C3N f-H M O X .-H CNI O o CM o o o O CO . . . • • • . . s o o o o o O o o •w' m o o o c vO m NO

bO o . • . • C •H /—

.-4

m o 0) f-H

m 0) 0) •H 4-) C 1 1 c c 1 1 c c P cO *H o m o o 00 cn o o

c3 ^4 e CNI 00 c c o c c • • • • Q o o o f—

co

•H

44 44

C o o o o o o in o w CO 'H NO NO Nf C" NO NO 'O' NO

0) l-i E H ^ wQ

l-i 0) 44 r*H t-H C3N rH rH

C/1 44

W • • • . • • • M 14-1 (U o o o o o o o m

CO < H S /-

s (U u

r—1 '—

01 O.§

|4 44 O W in in

m

mm inm

m IH 0) rH iH tH rH

cn 0)

H

PQs o o o o o o o o o

0> 0 mmm

m

mmmm

H

w C'.

m 'O' cn C'-

m 'O' cn

0) 0) c c

i—i 0) 0)

cO

u i-i •r4 >N in M 44 44 CM

0) cn cn 44 >N P >N P

CO rH Co rH Cu s o O o O

04 04 IH

73
Table 15. Comparison of Results From Various Materials

Under the Nishimaru Test [56]

Material

Temperature

(°c)

Sample Mass

(8)

Before After

Test Test

Test

Duration

(min)

Flaming

Duration

(min)

Mean Time to

Incapacitation + S .D. (min)

Polystyrene

foam 1

Polyvinyl

550 15 0.1 10 0.90-3.83 4/6 NI

chloride

foam

550 7.5 1.9 10 1.93- 4.62 + 1.94

Urea resin

foam

550 1 0.1 10 0.43-0.75 3.18 + 0.81

Polyurethane

foam

550 5 0.3 10.5 none 5/6 NI

Lauan 550 15 3.1 10 0.50-3.50 5.60 + 1.17

S.D.: Standard deviation of average time to incapacitation of 6 mice

NI: Not incapacitated

7A
Table 16. Toxicological Evaluation of GM 47 and GM 49 Polystyrene Foams

Under the University of Pittsburgh Toxicity Test Method [62]

^5 0 LLg 0 LTso LLTso TP ^

^'^5 0 TP ^

'-‘^5 0 Material (mg/ 2.) i&) (min) (g*min) (mg/ Z) (mg/ 2,)

GM47 22 5.8 11 64 9.7 48.3

GM49/FR 14 10.0 9 90 16.7 62.5

FR: Fire

a: based

b; based

retardant

on a 30 minute concentration average

on the actual time to complete loss of sample mass

75
Table

Loading

(mg/ £,)

32

128

3 TUF =

17. Results From Polystyrene Television Cabinets Tested Under the

Harvard Medical School Tests [65]

Temp. Flame Mortality Tupa

retarded (%) (min)

450 yes 0 20 no 10 20

350 yes 0 20 no 0 20

400 yes 0 20 no 82 2

450 yes 51 12 no 93 5

Time of useful function

76
Table 18. Analysis of Gases in the Animal Chamber from

Thermal Decomposition of Polystyrene in the

Harvard Medical School Test [65]

Flame Time Gas Concentration (%)

Retarded (min) CO 0, CO,

yes 3 0 14.50 2.25

12 0 17.50 1.00

no 3 0.45 11.50 4.00

12 0.40 15.00 2.50

Fuel load: 128 mg/ 8, Decomposition Temperature: 450 °C

77
Table

19

.

Amount

of

Material

Necessary

to

Produce

Mortality

in

50%

of

the

Rats

Under

the

GE/SRI

Test

166 ]

0 0 0 0 0 0 0 0 0 0 0 0 0 c CM E 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 a cn r-^ 0 0 vO ON ON LTi <f in NO ON

•H 0 a 0 CJ <3

" m rH »H n in 00 in m rH

•U 1^ rH rH rH rH rH f-H m 1 CM

0 0 ON 0 0 0 0 0 0 0 0 0 0 ON n rH 0 ON ON CM m 0 NO CM 00

NO m m ON m r> CM m ON p>. CM CM rH CM CM rH CM CM 1-H tH rH o

o

CNl o^ O fS

CS CM <N

ro m 00 o

LO m vc cs

1-H .—4 CN m NO NO 00 m

CM 00 NO

CM rH m CM m

• 00 NO rH sr CJN ro CJN m CM r>. hJ • • • ON cn ro r>. ON ^r CM 00 0

j j rH ' rH rH rH rH CM CM CM

NO NO

' 0 rH m CM CJN m in « • • • • • • • • • C3N m 00 ON 0 m ro CM CM NO CM

s—

rH rH rH rH CM rH CM

(fl 00 ON 0 CN m m CJN m in 00 00 m

u NO 00 ON C3N tH rH 0 CM NO NO m ro CJN m oc rH rH rH rH rH rH rH CM tH CM

NO 0 rH NO NO CJN CJN 00 in rH in CM

eUc rH CM CsJ m NO 00 00 0 CM CM m m 00

61 rH rH rH rH rH t—

rH CM CM CM CM < m NO

* 00 0 C3N m 00 00 '3

- NO ro

• «

• C3N 0 NO CM CJN CJN 00 ro 00 ro u 1 1 rH rH CM rH rH rH m in

cn NO CJN m NO rH in NO 00 00

in • « • • • • • • « C?N 00 0 00 CM m m 0 NO rH

N—/ rH rH rH rH rH ro ro '3

-

C/1 i

NO CJN 4- CM ro 00 0 in 00 CJN '3- CJN ro in

00 00 C3N rH CN m m NO NO r>. rH ro

cud rH rH rH rH rH iH rH rH ro '3' 'Ot + i

'O l4-( M •H •rM • rH rH M X M X 00 C3 c3 M 0 cu M M CU 0 >M U

4-J 4-» 0) 0) f—

0) (U CU (U (3 CU CU CU 0) (3 (U (U C G

fO 4-1 c C C rH 4J 4-» 4J c rH S3 44 .H 0) •H (3 4-1 0) CU CU (3 c3 c3 C3 (U c3 (U (3 6 00

Vu C a rH rH ^ C C C iH X tH S3 ' '—

cu 0 (3 So So >. 4J 0 0 0 -p So 0 CU

4-1 Xi (X 4-) C 4-1 43 X> X X 4-1 43 S3 43 0 0 CO

n) V4 6 w cu 0 Or u V4 u M a O. (U P *H 0) •H 0 S c3 •H So .a (U i3 c3 c3 c3 X 0) 43 c3 tH iH rH PM 0 rH O.W M 0 0 0 0 s—

V4 PM 0 0 fH 0 M

>n 4= 0 r-i So So (U So >> So So CU SO SO S3 •H c S3 r-H 00 a. 0 rH rH 4-* rH rH rH •a tH 44 tH tH 3) M-l cu CM 0 •H 0 0 0 0 0 0 0) 0 0 0 43 43

P4 ca 3 Ph Pli PM P4 PM pp P4 P4 PM PM PM

78

I.C50:

Amount

of

test

material

needed

to

cause

50%

of

the

animals

to

die

F.R.:

Fire

retardant

C.L.

:

Confidence

limits

g.f.:

Glass

filled
Table 20. Results from the University of Michigan Test [67]

Static Chamber^ Relative

Toxicity

Dynamic 1Chamber‘d

Material LL 5 0 (g)LCg 0 (mg/ 2,) Ranking Material LL 5 0 (g)

LCg 0 (mg/e,)

Polyurethane

foam (FR) 18 12.0 1 Polypropylene 1.0 2.4

ABS 18 12.0 2 Polyurethane

foam (FR)

1.4 3.3

ABS (FR) 20 13.3 3 Polyurethane foam 1.5 3.6

SAN 760 23 15.3 4 PVC 1.7 4.1

Polypropylene 26 17.3 5 ABS 1.7 4.1

Polystyrene 29 19.3 6 SAN 760 2.1 5.0

Nylon knit 33 22.0 7 ABS (FR) 2.2 5.2

Nylon 43 28.7 8 Nylon 2.6 6.2

Polyurethane foam 44 29.3 9 Nylon knit 3.0 7.1

Nylon Yarn 47 31.3 10 Nylon yarn 4.3 10.2

PVC 54 36.0 11 Polystyrene 4.3 10.2

LL 50 : Amount of material loaded in the furnace that causes 50% of the rats to

die in 4 hours in the static system and 140 minutes in the dynamic

system.

LC 50 : The LL 50 divided by the volume of the exposure chamber or the total air

flow.

FR: Fire retarded,

a: Temperature approximately 700°C

b: Temperature ramped from ambient to 700-800°C at 3-5°C/min.

79
Styr«n«

80

Fi

guTe

1.

StructufG

of

styrGne

and

polystyr
NBS-114A 'REV. 2 -eci O.S. OEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR-85/3277

2. Performing Organ. Report No. 3.

TITLE AND SUBTITLE

PubI ication Date March 1986

POLYSTYRENES: A REVIEW OF THE LITERATURE ON THE PRODUCTS OF

THERMAL DECOMPOSITION AND TOXICITY

5 . AUTHOR(S)

Joshua L. Gurman, Laura Baier, and Barbara C. Levin

6. PERFORMING ORGANIZATION (If joint or other than NBS. see in struction s)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

MJkSH HCGX BK.XK0CX30ZMX

Gaithersburg, MD 20899

7 . Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

U. S. Consumer Product Safety Commission

Bethesda, MD 20207

10. SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it her^

The current English literature through 1984 on the products of pyrolysis

and combustion from polystyrenes and the toxicity of those products is

reviewed. Among 57 compounds detected by chemical analyses of the thermal

decomposition products produced under various atmospheric conditions (vacuum,

inert, and oxidative), the main volatile component is the styrene monomer. Evidence is provided that the mass fraction of styrene increases with furnace

temperatures at least through 500°C. At 800°C and above, the concentration of

styrene decreases. In oxidative atmospheres, carbon monoxide (CO), carbon

dioxide (COj) and oxidative hydrocarbons are formed. The concentrations of CO

and CO 2 are a function of temperature and combustion conditions, i.e., greater

amounts are produced in the flaming than in the non-flaming mode. Eleven

different test procedures were used to evaluate the toxicity of the pyrolysis

and combustion atmospheres of polystyrenes. The more toxic environments

produced under flciming conditions appear to be mainly attributable to CO and

CO 2. Incapacitating effects observed during exposures to non-flaming effluents

are not due to CO and CO 2 but rather to some other toxicant, probably the

styrene monomer. When compared to other common materials used in buildings and

residences, polystyrenes, in general, are among the least toxic.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Combustion products; fire data; literature reviews; polystyrene;

pyrolysis products; test methods; toxicity.

13. AVAILABILITY

Uni imited

1 1 For Official Distribution. Do Not Release to NTIS

rn Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

[77^ Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

15. Price

v^SCOMM.r,r. = - '
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