A11102 MtlbME

NAFL INST OF STAN0AB08 S TECH R.I.C.

„ A1 1102461642

QC100 U5S N0 85-32S8 V1988 C.1 NBS-PUB- >-3268

A Literature Review of the

Chemical Nature and Toxicity of

the Decomposition Products of

Polyethylenes

Reference

NBS

PUBLICATIONS

Maya Paabo

Barbara C. Levin

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

January 1986

Sponsored in part by;

QC ^e U.S. Consumer Product Safety Commission

2 QQ ithesda, MD 20207

U56

85-3268

1986

nESEA!lCH IN?OPJ.!ATI01f CEIfTEH

NBSIR 85-3268 '

I • •

' - A LITERATURE REVIEW OF THE 2

CHEMICAL NATURE AND TOXICITY OF q

THE DECOMPOSITION PRODUCTS OF

POLYETHYLENES

Maya Paabo

Barbara C. Levin

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

January 1986

Sponsored in part by:

The U.S. Consumer Product Safety Commission

Bethesda, MD 20207

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

5
iw: SWA«3TU A

YtiaiX0f«WA'3«aTA^^^

;i^o; aiJouaPw:

" ' wijftjs aw

’33jJ3^riT3yjOa''

: 2) Iirit4^i

•i,

30«)aiMMO3 TO ThS^RAiaO 8.U

W) ^im * • & l|K1^|*3fss*jP^-

fis’Tj' L'^s^ iBl' '^0^, a,M i|»t.<f«t||Hifi«l3i

f^9t v*i(iA»fiti.

.*«h«»l|-flr.><MinW io«aM^Wj:^^0 J*<3MT«A«»Sa,i.U

.80HA0{4ATS ^

(JA3 f>U*T

4’

i... •'•
TABLE OF CONTENTS

Page

List of Tables iv

Abstract 1

1. INTRODUCTION 2

2. THERMAL DECOMPOSITION 3

2.1 Thermal Degradation in the Absence of Oxygen 5

2.1.1 Vacuum Pyrolysis 5 2.1.2 Inert Atmospheres 7 2.2 Small-Scale Tests in Oxidative Atmospheres 9

2.2.1 Generation of CO and CO

2 10

2.2.2 Organic Combustion Products 15

2. 2. 2.1 Irritants 15

2. 2. 2.

2

Non-Irritant Organic Compounds 17

2. 2. 2.

3

Polycyclic Aromatic Hydrocarbons 21

2. 2. 2.

4

Free Radicals 22

3. TOXICOLOGY 23

3.1 DIN Toxicity Test Method 24

3.2 University of San Francisco (USF) Toxicity Test Method 29

3.3 Federal Aviation Administration (FAA/CAMI) Toxicity

Test Method 31

3.4 The Dow Chemical Company Test Method 33

3.5 Large-Scale Tests 36

3.6 Miscellaneous Tests 38

4. SUMMARY 40

5. ACKNOWLEDGMENTS 42

6. REFERENCES 42

-iii-
LIST OF TABLES

Page

Table 1. Thermal Degradation Products Produced from Polyethylenes 48

Table 2. Degradation Products Generated from Polyethylene During

Pyrolysis, Thermooxidation, and Combustion 52

Table 3. CO and CO2 Concentrations in the Combustion Products

from a Polyethylene 54

Table 4. Concentrations of Polycyclic Aromatic Hydrocarbons in

Smoke Particulates from Polyethylene 55

Table 5. Toxicological Effects on Rats Exposed to the Pyrolysis

Products from a Polyethylene Decomposed by the DIN

Method 56

Table 6 . Toxicological Effects on Rats Exposed to Combustion

Products from Polyethylene Decomposed According to the

DIN Toxicity Test Method 57

Table 7. Variation of Mean Respiration Frequency in Rats Exposed

to Polyethylene Decomposition Products 58

Table 8. Toxicity Results for Polyethylene Decomposed According to

the University of San Francisco Method Using the Rising

Temperature Mode 59

Table 9. Survival Times of Test Animals Exposed to Smoke from

Polyethylene Decomposed under Different University of San

Francisco Test Method Conditions 60

Table 10. Gas Analyses of the Combustion Products from Polyethylene

Examined via the University of San Francisco Test Method 61

Table 11. LC 5 Q Values Calculated for Different Polyethylene Foams

Decomposed by the Dow Chemical Company Test Procedures 62

Table 12. Influence of Heating Rates on the Toxicity of Combustion

Products from Polyethylene 63

-Iv-
A LITERATURE REVIEW OF THE CHEMICAL NATURE AND TOXICITY OF

THE DECOMPOSITION PRODUCTS OF POLYETHYLENES

Maya Paabo and Barbara C. Levin

Abstract

The literature on polyethylenes has been reviewed with an emphasis on the

identification of gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to

publications in English through 1984. The analytical chemical studies of the

thermal decomposition products generated under vacuum, inert and oxidative

experimental conditions are described. In oxidative atmospheres, which most

closely simulate real fire conditions, carbon monoxide (CO) was found to be

the predominant toxicant. Acrolein was another toxicant often noted in these

reviewed studies. More acrolein was generated under non-flaming than under

flaming conditions.

Results from seven different test procedures were considered in assessing

the acute inhalation toxicity of combustion products from various polyethylene

formulations. The combustion products generated from the polyethylenes

studied in the non-flaming mode appeared to be slightly more toxic than those

produced in the flaming mode. In the non-flaming mode, the LC^q values ranged

from 5 to 75 mg/il. In the flaming mode, the LC^q values ranged from 31 to

51 mg/A. The toxicity of the degradation products of polyethylenes appears to

be similar to that found for other common materials designed for the same end

uses

.

Keywords: combustion products, literature reviews, polyethylenes,

thermal decomposition, toxicity.

- 1 -
1 . INTRODUCTION

Polyethylene has been in comnercial production for over forty years.

With sales of about 6.25 x 10^ metric tons in 1983, polyethylenes compose the

largest fraction of plastic materials produced [1]^. Typical uses of polyethylenes include household goods (bottles, dishes and toys), packaging

materials, and coatings for tubing and cables in the building and electrical

Industries. This report reviews the literature on polyethylene published in

English through 1984 with special emphasis on the gaseous products generated

under various thermal decomposition conditions and the toxicity of those

products.

Polyethylenes are thermoplastic materials that are produced primarily by

the catalytic pol)onerization of ethylene gas (C2 H^) ^t elevated temperatures

(T) and pressures (P).

n(CH2 = CH^) (1)

ethylene polyethylene

The polyethylene molecules usually contain branches of various lengths. Of

all the hydrocarbon polymers, polyethylene has the simplest structure and the

highest ratio of hydrogen to carbon in its backbone. Most commercial polyethylene formulations also contain additives, such as stabilizers, antioxidants, crosslinking agents, slip and antiblock agents, and fire retardants.

^Numbers in brackets refer to the literature reference listed at the end of

this report.

-2 -
The molecular structure, molecular weight distribution, and density will

differ in various polyethylenes depending on the manufacturing process conditions. Low density polyethylene (LDPE) is of low crystallinity (< 60%) and

has a density in the range of 0.91-0.94 g/cm^ and a molecular weight of about

4 X 10^ g/mol. High density polyethylene (HDPE) is of high crystallinity

(~ 90%) and has a density in the range of 0.94-0.95 g/cm^ and a molecular

weight up to about 3 x 10^ g/mol. LDPE molecules are highly branched in

structure and may contain up to 30 branches with as many as 10 carbon atoms

each. HDPE molecules are almost linear in structure with only few short

branches. HDPE is more thermostable than LDPE since secondary carbon-hydrogen

bonds are stronger than tertiary carbon-hydrogen bonds [2,3].

2. THERMAL DECOMPOSITION

The combustion of polyethylenes can produce many gaseous products, the

nature of which depends mainly on the external conditions such as temperature

and oxygen availability. The final products formed during complete combustion

of polyethylenes are carbon dioxide (CO2 ) and water (H2 O). Under incomplete

flaming or non-flaming combustion conditions, many other low-molecular weight

hydrocarbons and oxygenated compounds (e.g. , carbon monoxide (CO), alcohols,

aldehydes, ketones, and esters) are also generated. The combustion products

that have been identified in the literature reviewed for this report are

presented in Table 1.

As all the C-C bonds in polyethylenes are of the same strength (except

those in the terminal positions or at the sites where branching occurs), polyethylenes decompose mostly by a random-chain scission type mechanism Involving

-3-
free-radical (R* ) reactions. The suggested decomposition mechanisms include

free radical formation by breakdown (eq. 2), free radical transfer within (eq.

3) or between molecules (eq. 4) with subsequent decompositions, and free

radical termination by disproportionation (eq. 5) or by combination (eq. 6)

[4-6].

Under oxidative conditions, additional reactions may occur. Oxygenated

free radicals are involved in these reactions as for example:

R - R ^ 2R ( 2 )

2R* - R - CH - - CH^ - R (3)

R* + CH^ = CH - CH^ - R

R* + R - CH^ - R -> R - CH - R + RH

2 (4)

I R - CH = CH^ + R

R + R - R - CH = CH^ + RH (5)

R + R -» R - R ( 6 )

R 0 + H^C - R R - CH^OH + R (7)

ROO’ + R - CH^OH ->• RCOOH + R - CHOH ( 8 )

RO + R -*-R-0-R (9)

-4 -
Fundamental studies of polyethylene degradation under various conditions have

been reviewed by Madorsky [A], Schwartz [7] and Cullis and Hirschler [3].

2.1 Thermal Degradation in the Absence of Oxygen

When polyethylenes are exposed to elevated temperatures under inert atmospheric conditions, saturated and unsaturated hydrocarbons of various chain

lengths are generated. Since polyethylenes do not contain any oxygen in their

molecular structure, no CO, CO2 or oxygen-containing organic compounds are

produced. The composition of the volatile compounds which are formed from

polyethylene products will reflect the presence of any additives present in

the formulation.

2.1.1 Vacuum Pyrolysis

Identification of the volatile compounds generated from polyethylenes

thermally decomposed under vacuum has been used in determining these degradation mechanisms. For example, a systematic mass spectrometric (MS) investigation by Madorsky et al. [4] found that a polyethylene (m.w. 20,000) pyrolyzed

in vacuum at temperatures up to 450 °C yielded 15 alkane and alkene type

compounds, each containing 2-7 carbon atoms (Table 1). Only a small portion

(4.3 mole %) of the fraction volatile at -80°C appeared as the monomer,

indicating the absence of a zip mechanism, in which the polymer degrades into

a monomer one unit at a time. Increasing the temperature increased the

percentage of the monomer found in the degradation products. In particular,

when a high-molecular-weight grade unbranched polyethylene (polymethylene) was

pyrolyzed at 500°C, 800°C and 1200°C, the weight percent of the monomer,

-5-
ethylene, in the total volatiles increased from 0% to 5.5% and to 26.4%,

respectively. Based on the amount of ethylene formed, Madorsky proposed that

two competing reactions occur when polyethylene decomposes. Below 800°C the

thermal degradation proceeds by a fragmentation process. At higher temperatures, degradation proceeds by formation of free radicals which unzip

producing the ethylene monomer.

Tsuchiya and Sumi also proposed that the main volatile degradation

products from a polyethylene were formed by a mechanism involving the intramolecular migration of free radicals [5]. When samples of a commercially

available HOPE were decomposed at fixed temperatures ranging from 375°C to

425°C, twenty-six compounds consisting mainly of normal alkanes and normal

1-alkenes containing 1 to 6 carbon atoms were identified by gas chromatography

(GC) (Table 1). As expected from eq. 3, the concentrations of these two

classes of compounds were similar. The concentrations of ethylene and other

hydrocarbons increased with increasing temperature. At 425“C, the monomer

yield was 11 mole percent in the fraction which was volatile at room temperature. These results agree reasonably with those of Madorsky [4] and other

degradation studies cited by Tsuchiya and Sumi [5]. Free radical transfer

Involving local coiling was considered responsible for the relatively large

amounts of propane and 1 -hexene found in the degradation products. The predominant decomposition product, propylene, as well as isobutylene and 2-butene

were all considered produced by a cleavage of the relatively weak C-C bond in

the 3-position to the terminal double bond.

- 6 -
2.1.2 Inert Atmospheres

The thermal degradation products of polyethylenes decomposed in inert

atmospheres are very similar to those generated under vacuum conditions. In a

study using Infrared spectrometry (IR) to characterize the pyrolysis and

combustion products of various pol)nners, Morimoto detected methane, ethylene,

acetylene and benzene when a commercially available polyethylene was decomposed at 700°C in a nitrogen atmosphere [8].

Mlchal et al. studied the decomposition products of polyethylenes under

three different conditions: pyrolysis in inert atmospheres, thermo-oxidation,

and combustion in air [6]. When the p3rrolysls products generated from a

sample of a commercial polyethylene heated at 400 °C under a flow of helium

were analyzed by gas chromatography/mass spectrometry (GC/MS), forty-four

different hydrocarbons were identified (Table 2). These compounds contained 3

to 18 carbon atoms and consisted mainly of alkanes and 1-alkenes. In addition, three aromatic compounds, benzene, toluene and ethyl benzene, were also

detected.

A similar detailed study of the volatile products of an Industrial high

pressure type polyethylene decomposed at 510°C in an inert atmosphere was

conducted by Pacakova et al. using pyrolysis gas chromatography [9]. The

forty-eight compounds identified were mainly unsaturated hydrocarbons,

consisting of 1-alkenes containing 5 to 9 carbons, corresponding n-alkanes and

1,3-alkadienes (Table 1).

-7 -
The composition of the thermal degradation products of polyethylenes was

demonstrated to be partially dependent on the molecular structure of the

starting material by Hoff et al. [10]t They examined two samples of commercial polyethylenes ; an LDPE without any additives and a HOPE containing an

antioxidant and carbon black. The materials were decomposed In a Pyrex tube

with a movable furnace at 360 ®C under a helium atmosphere, and the gases were

analyzed by GC and GC/MS techniques. Among the 25 products identified, the

hydrocarbons were dominant in both cases (Table 1). During the initial stages

of thermal degradation, the degree of formation of C2 to C7 linear hydrocarbons was about the same for both samples. However, in final products,

short-chain branched hydrocarbons were relatively more abundant in the combustion products generated from the LDPE sample than from the HDPE sample, which

formed mostly linear hydrocarbons.

In addition to the usual decomposition products observed, polycyclic

aromatic hydrocarbons (PAHs) have also been detected among the degradation

products of polyethylenes [11]. Morikawa pyrolyzed a commercial grade of

polyethylene in a quartz furnace under a nitrogen atmosphere. Benzo(a)pyrene

(BaP), which was used as an indicator for PAHs, was determined by high

pressure liquid chromatography (HPLC). Evolution of BaP was found to increase

at 900°C and higher temperatures. At 1000°C, BaP was detected at a concentration of 1 mg/g of polyethylene; this amount is equivalent to that detected in

an air-flowing atmosphere (see Section 2. 2. 2. 3).

Since pure polyethylenes contain no oxygen, no oxygen-containing

compounds would be expected to be generated during their pyrolysis in inert

atmospheres. However, CO and CO2 have been detected in some studies [6,8].

-8 -
(Michal, who specifically set out to measure the CO produced during the

pyrolysis and thermooxidation of polymeric materials, detected no CO when a

high-pressure type polyethylene was decomposed in helium at 500 °C [12].) The

CO and CO2 reported by others must have originated from additives, air trapped

in the polyethylene formulation, or the inadvertent introduction of air or

water vapor into the inert experimental environment. The production of CO can

occur by the following reactions

C + H^O > CO + ( 10 )

C „ n 2n+2 + m'H^O -> C + m’CO + 2m'H«

2 m 2m+2 2

( 11 )

where m + m' = n.

Morikawa examined this last possibility and found that when a polyethylene was

decomposed in nitrogen, the evolution of CO due to the presence of added water

vapor was small [13]. At 1000°C, the amount of CO generated from a 500 mg

sample of polyethylene was about 0.05 g/g, which was an order of magnitude

less than that found for materials containing oxygen in their structure. No

CO generation was observed below 900°C.

2.2 Small-Scale Tests in Oxidative Atmospheres

In order to evaluate the toxic atmospheres produced by polyethylenes

decomposed in real fire situations, the thermal degradation of polyethylenes

has been studied under a wide range of oxidative conditions and temperatures.

Although large-scale tests can more closely simulate actual fire conditions,

-9-
almost all the experiments included In this review have been conducted as

small-scale laboratory tests. Non-flaming conditions, when used in smallscale tests, are considered to represent an early fire stage when a material

may be pyrolyzed some distance away from the combustion zone without being

ignited.

In both flaming and non-flaming tests performed under oxidative

conditions, a complex mixture of oxygen-containing organic compounds is formed

in addition to the saturated and unsaturated hydrocarbons that were noted

above to be generated in the absence of oxygen. CO and CO

2 are the principal

decomposition products generated. Certain oxygen-containing organic

compounds, such as acrolein, formaldehyde and volatile carboxylic acids

(formic acid, acetic acid and propionic acid), are also detected and may be of

toxicological importance, since these compounds are considered to be

irritants

.

2.2.1 Generation of CO and CO

2

Concentrations of CO and CO

2 have been measured in most of the combustion

studies of polyethylenes. The results of these studies have shown that the

evolution of CO and CO

2 is dependent on the air supply rate, the temperature

of decomposition, and residence time of fuel vapor in the combustion zone.

In order to simulate different real-fire conditions, Michal [12,14,15]

used different combustion systems for pyrolysis in helium, oxidative nonflaming and flaming tests. During combustion in air with depleted oxygen

content, the CO content in the thermal degradation products of a commercial

- 10-
polyethylene increased with increasing temperature. Under ventilated conditions, greater amounts of CO were detected in the non—flaming mode than in the

flaming mode. When the O

2 supply was limited, the concentration of CO was

greater in the flaming mode than in the non-flaming mode. As expected, the

CO

2 content was found to be greatest during well-ventilated flaming combustion

and was not temperature dependent.

In one study, Michal decomposed a high-pressure type polyethylene (Bralen

RB 03-23) in a quartz combustion tube at 550°C in various gas mixtures of

helium and oxygen [12]. Gas chromatography was used for determination of CO

in the thermal degradation products. The pyrolysis results in pure helium

atmospheres, described in Section 2.1.2, showed no CO production; whereas,

under thermooxidative conditions with unspecified O2 concentrations, the CO

yield was found to be 29.7 mg/g.

The same polyethylene was also decomposed under depleted O

2 atmospheres

in a 4.2 H combustion chamber (CAB 4.2) containing a crucible furnace under

the combustion chamber. The chamber was designed to simulate combustion in

air with depleted oxygen. As the atmospheric O

2 was decreased under

restricted flaming conditions, the CO concentration increased. The average CO

yield under limited flame combustion in five tests was 100.2 mg/g. Under

these conditions, the CO concentration increased as the temperature of the

crucible was raised from 500°C to 800°C [12].

In a second study, Michal decomposed the same high pressure type

polyethylene in another combustion chamber (CAB 4.5) and the gaseous products

were measured in an adjoining chamber [14]. This two chamber system was

- 11 -
designed in an attempt to model the natural flow of toxic combustion products.

The total volume of the system was 4.5 £, and samples (less than one gram)

were combusted in a crucible furnace under both non-flaming and flaming conditions. Table 3 indicates that more CO was formed in the non-flaming mode

(500°C) than in the flaming mode (600°C). By contrast, the CO

2 concentration

was considerably higher when the polyethylene was decomposed during flaming

combustion than in non-flaming combustion. When compared to other polymeric

materials (polypropylene, polystyrene, and polyamide) investigated under nonflaming conditions, the polyethylene was found to produce the most CO and

therefore was considered by the author to be the most dangerous of these

materials [14].

In a third study by Michal, a sample of a low density polyethylene

(Bralen 03-23) was decomposed in a 650 I combustion chamber (CAB 650) designed

to accommodate larger amounts of material (up to several grams) and provide

more variable conditions for thermal degradation [15]. This combustion

chamber was intended to simulate well-developed fires. Carbon monoxide and

carbon dioxide determinations were made after complete combustion of the

sample.

There were several differences between the CAB 650 and CAB 4.5 systems.

In the CAB 650 system, a fan was used for mixing the thermal degradation

products and for providing more air to the crucible furnace; whereas in the

CAB 4.5 system, since there was no forced air supply, the gases moved by

natural convection. The ratio of sample weight to the chamber size in CAB 650

was about an order of magnitude lower than that in CAB 4.5.

-12
Under the experimental conditions in CAB 650, polyethylene flamed at

500"C. In the presence of the increased amount of air supplied to the furnace

in this test, the CO production was relatively low, i.e., less than 0.5 mg/g

for all samples tested. However, more CO2 was generated in CAB 650 than that

observed under the restricted flame combustion in CAB 4.5, an indication that

more thorough thermooxidation occurs in the presence of the greater air

supply. Generation of CO2 under these flaming conditions was not found to be

temperature dependent since approximately the same amount was measured at

600°C, 800°C and 1000°C [15].

Morikawa studied the effect of oxygen and water vapor on the generation

of CO from polymeric materials including a polyethylene [13]. The results in

nitrogen were discussed in Section 2.1.2. In air, the thermal decomposition

of this polyethylene in the presence of water vapor was examined in a tube

furnace at three temperatures, 500°C, 600°C, and 700°C. The effluent gases

were analyzed by GC. The evolution of CO was generally greater in the

presence of water vapor and depended upon the air flow rate. The highest

concentration of CO was observed at 500°C at an air flow of 1 Jl/min and water

vapor flow of 1 g/min. In this case, the CO production in the presence of

water vapor and air was five times greater than in the absence of water vapor,

namely, 500 mg/g and 100 mg/g, respectively. When the CO generation in air

(500 mg/g at 500°C) was compared to that in nitrogen (0 mg/g at 900°C and

50 mg/g at 1000°C), it was concluded that the evolution of CO seems to be a

function of the atmospheric oxygen content, temperature, and water vapor.

The presence of CO and CO2 has been also determined in several other

studies on the oxidative degradation of polyethylenes [6,8,10,16,17]. For

- 13-
example, during studies of hazards generated in underground mines, Paciorek et

al. measured the amount of CO and CO 2 that was produced when a polyethylene

wire Insulation (cross linked, pigmented and containing about 0.5% amine antioxidant) was decomposed In a test designed to simulate the oxidative overheating and combustion that can occur in mines [16]. Gaseous products were

analyzed by MS. The major fraction (about one third) of the volatiles

detected was CO 2

. Only small amounts of CO were observed.

Morimoto et al. measured the toxic gaseous products generated by a series

of polymers and cellulosics decomposed under flaming conditions [8]. When a

polyethylene sample was burned in a tube furnace at 700°C under an air flow

of 100 ^./hr, both CO2 (738 mg/g) and CO (210 mg/g) were detected [8]. The

concentration of CO

2 , but not CO, was found to depend on the air supply rate.

When the air flow rate was reduced by 50%, the CO2 levels decreased to

502 mg/g, whereas the CO level remained about the same (195 mg/g).

Boettner et al. studied the products of incomplete combustion of

polyethylenes and other plastics which may be produced during waste incineration and could be toxic in real fire situations [17]. Three polyethylene

samples were studied : LDPE and HOPE powders and a HOPE in pellet form.

Samples were decomposed in a tube furnace under various controlled heating

rates and air and oxygen supplies. The major combustion products were identified by IR, minor ones by MS. Although the concentrations of CO and CO2 depended again upon the heating rates and air flow rates, CO2 and CO were the

major volatile products formed from all three polyethylene samples. For

example, at a heating rate of 5°C/mln and air flow rate of 100 mH/mln, the CO

and CO2 concentrations ranged from 255-312 mg/g and 88-213 mg/g, respectively.

- 14-
As the heating rate was Increased ten fold to 50°C/mln, the concentration of

CO decreased to 110-208 mg/g and that of CO2

increased somewhat to

178-388 mg/g. When oxygen (40 mH/min) was added to the air flow during the

5®C/min experiments, the CO concentration decreased slightly to 171-179 mg/g

and the CO2 concentrations considerably increased to 753-1842 mg/g.

2.2.2 Organic Combustion Products

2.2.2. 1 Irritants

When polyethylenes are thermally degraded under oxidative experimental or

real fire conditions, complex volatile organic chemical species are produced.

The reaction to form these organic volatiles occurs partially within the

heated polyethylene material, which has a restricted oxygen supply and

partially in the gas phase, which has a rich oxygen supply. Short-chain

compounds, such as aldehydes and ketones, are generated predominantly by the

gas-phase oxidation of the volatilized hydrocarbons.

In an attempt to Identify the volatile breakdown products of

toxicological concern, several studies have been performed to detect

irritants, such as acrolein, formaldehyde, and low molecular weight carboxylic

acids. Morikawa studied the irritant components of smoke from various

polymeric and cellulosic materials and found that the evolution of irritants

from a polyethylene was relatively large [18]. Polyethylene samples were

thermally decomposed in a quartz tube furnace in air. The concentrations of

carboxylic acids and acrolein in impinger samples were determined by a GC

technique. Formaldehyde was measured by a colorimetric technique using a

spectrophotometer.

- 15 -
Under non-flaming conditions, the amount of irritants from this polyethylene sample increased with oxygen concentration, whereas, under flaming

conditions, the concentration of irritants decreased (presumably due to

further oxidation and/or decomposition). Maximum evolution of acrolein

(350 Pmol/g), formaldehyde (2600 ymol/g) , and the volatile carboxylic acids

(380 ymol/g) was obtained when the samples of polyethylene were subjected to

smoldering combustion at 300-400 °C. Formic acid and acetic acid accounted for

the greatest fraction of the detected carboxylic acids.

A limited comparison of the above results to those from a few other nonoxygenated polymers studied by Morikawa showed that this polyethylene appears

to generate significant amounts of irritant gases. When compared to wood,

several times more acrolein and formaldehyde were generated from polyethylene.

Only the evolution of carboxylic acids from polyethylene was equivalent to

that generated from wood under similar smoldering conditions [18].

Hodgkin et al. also detected irritant volatile gases in the combustion

products of polyethylenes [19]. Four commercial polyethylene samples, LDPE

and HOPE pellets, and two LDPE foams, were decomposed in a muffle furnace

under a wide range of air flows at temperatures ranging from 500°C to 800°C.

The volatile products were analyzed by IR, nuclear magnetic resonance (NMR),

GC/MS and wet chemical techniques. The list of products identified Included

acrolein, formaldehyde, acetaldehyde, and acetic acid (Table 1). These

results differed somewhat from those of Morikawa [18] in that the only

carboxylic acid detected by Hodgkin et al. was acetic acid and only trace

amounts of acrolein were found. These differences may be attributed to the

higher experimental temperatures used by Hodgkin et al. , and the different

chemical sample collection and analysis methods.

- 16 -
Whereas Morikawa and Hodgkins et al. investigated the generation of

irritant gaseous products from polyethylenes exposed to elevated temperatures

(to simulate real fire conditions) [18,19], Hoff et al. studied the decomposition of polyethylenes at lower temperatures (to simulate industrial processing

conditions) [10] . Three different commercial LDPE and HDPE samples were

decomposed in a tube furnace at 280°C. Volatile products were detected by GC

and MS/GC techniques. At this temperature, the predominant products were the

carboxylic acids, formic and acetic, followed by the aldehydes, acrolein,

formaldehyde, and acetaldehyde.

The study of Hoff et al. also showed that processing polyethylenes under

real manufacturing conditions gives rise to the same volatile irritants as

those generated in the laboratory tests. For industrial hygiene purposes,

atmospheric measurements were made near machinery processing polyethylenes at

temperatures ranging from 140°C to 250°C. The average concentrations of

formaldehyde, acetaldehyde, acrolein, formic acid, and acetic acid, however,

were very low (< 1 mg/m^) and not considered hazardous [10].

2. 2. 2. 2 Non-Irritant Organic Compounds

To assess the toxic hazards associated with the combustion of

polyethylenes in fires, many laboratories have looked for volatile organic

compounds other than CO, CO 2 , and irritant gases in the smoke evolved during

thermal decomposition [6,8,14,16,17,19]. Both hydrocarbons and oxygencontaining compounds have been identified. Under non-flaming conditions, a

variety of aldehydes and ketones are produced; whereas under flaming conditions, hydrocarbons predominate and the evolution of aromatic compounds is

increased.

- 17 -
Michal et al. examined the thermal degradation products from a

polyethylene decomposed under three conditions: pyrolysis in helium, nonflaming thermooxidation and flaming combustion in air [6]. In addition to the

hydrocarbons observed during pyrolysis in helium (see Section 2.1.2), many

oxygen-containing compounds were identified in the studies conducted in air

(Table 2). In these studies, samples of a commercial polyethylene (Bralen

Z 1907-601) were thermally decomposed in a flow quartz micro-reactor at 350“C

(non-flaming thermooxidative mode). The volatile products were identified by

GC/MS. Under the thermooxidative conditions, the main products were 3-15

carbon aldehydes (48%). Other minor oxygen-containing products included

ketones, acetic acid, ethanol and epoxide. In addition to the oxygencontaining compounds, the volatile products included 25% olefins and 12%

paraffins. Under flaming conditions conducted under a glass funnel, hydrocarbons represented the most substantial fraction (~ 65%) of the identified

volatile products. The yield of aromatic compounds was also greater under

flaming than under non-flaming thermooxidative conditions. Among the numerous

organic products generated, acrylic acid was considered the most toxic

compound identified [6].

Hydrocarbons were found also to represent a substantial portion of the

combustion products when samples of a high-pressure type polyethylene (Bralen

RB 03-23) were decomposed under flaming combustion conditions in a two-chamber

combustion system (CAB 4.5) [14]. Propionaldehyde constituted only a minor

percentage of the total volatiles and no ketones were detected at all (see

Table 2).

- 18 -
Hodgkins et al. identified many combustion products of polyethylenes

decomposed under both flaming and non-flaming oxidative conditions [19]. The

organic products from the oxidative flaming experiments included saturated and

unsaturated hydrocarbons with a chain length ranging from two to twenty-three

carbons. Only a few of the low molecular weight hydrocarbons were actually

identified (Table 1). Most of the products identified were in the higher

molecular weight range and consisted of aldehydes, ketones and aromatic

compounds. Basically, the same product pattern was observed for four different samples of polyethylene decomposed under similar conditions. The composition of the hydrocarbons varied with changes in temperature but not with

changes in air flow rates. The major changes noted as the temperature

increased were the increase in the aromatic hydrocarbons, benzene and toluene,

and the large decrease in acetone production.

Boettner et al. also noted that the composition of the organic volatile

products was similar for different polyethylenes [17]. When three different

polyethylene samples (LDPE pellets, HDPE powder and HDPE pellets) were heated

in a tube furnace under various combustion conditions, the organic compounds

identified included mostly straight-chain saturated and unsaturated hydrocarbons containing one to six carbon atoms (Table 1). Unsaturated hydrocarbons predominated over saturated products. The only oxygen-containing

compounds detected were methanol and acetaldehyde.

The presence of low molecular weight hydrocarbons in the combustion

products of a polyethylene wire insulation was also observed by Paclorek et

al. [16]. Methane, ethylene, ethane, propane, and benzene were detected as

minor components of the smoke produced when a commercial polyethylene wire

- 19-
insulation was decomposed in a "stagnation" burner arrangement in which preheated air was passed over the test specimen.

Morimoto et al. [8] performed a detailed study on the low molecular

weight hydrocarbons generated from polyethylene decomposed under different

ventilation conditions at a constant temperature of 700®C. In air, the main

products detected by IR were methane, ethylene, and acetylene. At an air flow

rate of 50 £./hr, the concentrations for methane, ethylene, and acetylene were

65 mg/g, 187 mg/g and 10 mg/g, respectively. Only the concentration of

acetylene was found to be dependent on oxygen availability. When the air flow

through the combustion chamber was doubled from 50 l/hx to 100 A/hr, the

acetylene concentration increased from 10 mg/g to 34 mg/g, respectively.

In industrial processing, polyethylenes are subjected to temperatures

significantly lower than those used in the studies described above. During

tests to examine industrial processing hazards, Hoff et al. studied the decomposition of LDPE and HDPE type polyethylenes over a temperature range of 265

to 290°C using a tube furnace [10]. The volatile organics were analyzed by GC

and MS techniques. Hoff et al. identified a total of 44 products representing

hydrocarbons, alcohols, aldehydes, ketones, acids, lactones, cyclic ethers,

and cyclic esters. Essentially the same products were formed for both types

of polyethylene tested. This agrees with results of Hodgkin et al. [19] and

Paciorek et al. [16]. Contrary to the non-flaming and flaming studies

conducted at higher temperatures [6,14,19], the oxygen-containing organic

compounds constituted the majority and hydrocarbons the minority of compounds

detected.

-20-
2. 2. 2. 3 Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are not considered acute

toxicants; however, some have been shown to be carcinogens. Since generation

of PAHs is generally associated with smoke and soot particulates, PAHs may be

of importance in long term or repetitive exposures to fire gases (e.g., in the

case of fire fighters). The presence of PAHs in the smoke of polyethylenes

has been demonstrated in a number of studies [11,20,21]. Morikawa studied the

evolution of PAHs, especially benzo(a)pyrene during pyrolysis under inert

conditions (see Section 2.1.2 for details) and oxidative combustion of polyethylene and other materials [11,20]. Samples of a polyethylene were

decomposed in a tube furnace at several temperatures ranging from 600 to 900°C

under varying airflow rates [20]. PAHs were determined by GC analysis of the

extracts of the collected soot and solid products. Evolution of condensed

matter from this polyethylene was highest at 600 and 900 °C and lower at 700

and 800 °C. The corresponding yields of benzo(a)pyrene increased with

increasing temperatures (from 0.1 mg/g at 600°C to 1.3 mg/g at 900°C). In

addition to benzo(a)pyrene , five other PAHs, anthracene, fluoranthene, pyrene,

benzo(a)anthrathene, and benzo( c)pyrene , were detected in the soot and solid

products from this polyethylene.

The evolution of PAHs is normally associated with soot formation during

fires. However, Morikawa found that formation of benzo(a)pyrene is not always

accompanied by the formation of soot and solid products as the consistency of

the condensed matter may vary over the temperature range. More benzo(a)pyrene

was observed to evolve from a polyethylene than from a polystyrene, even

though the polystyrene produced three to four times more soot than the poly-

-21 -
ethylene [20]. In addition, when the polyethylene was decomposed at 900°C (a

non-sooting temperature) in nitrogen, benzo(a)pyrene was also produced [11].

PAHs in the smoke from samples of a polyethylene (containing additives 5%

by weight) exposed to radiant thermal fluxes of 4.3 W/cm^ (non-flaming) and

5.0 W/cm^ (flaming) were also detected by Zinn et al. [21]. Chemical characterization of the smoke particulates was performed by HPLC, GC, and MS/GC.

The PAH yields were 0.045 mg/g in the non-flaming tests and 0.025 mg/g in the

flaming tests. The principal compounds detected in the non-flaming combustion

of this polyethylene were anthracene and/or phenanthrene and pyrene; in the

flaming mode, the major product was pyrene (Table 4).

Compared to other polymers (polystyrene, polymethylmethacrylate and

polypropylene) studied by Zinn, and decomposed under similar conditions, the

polyethylene generated the greatest quantities of PAHs. Again, the generation

of PAHs did not correlate with soot formation as polystyrene generated the

most soot but only traces of PAHs [21]. These results agree well with those

of Morikawa [11,20].

2. 2.2.4 Free Radicals

When polyethylenes are decomposed in a fire or processed at elevated

temperatures in air, the heated polymer undergoes an oxidative thermal degradation which proceeds partly through alkyl, peroxy, and alkoxy radical formations. Free radicals from the combustion of polymers have been observed to

cause injuries to cells in tissue cultures [22] and are of toxicological

concern due to their high reactivity.

-22-
Two research groups have detected free radicals by electron spin

resonance (ESR) spectroscopy from the industrial processing of polyethylenes

[10,23]. These studies indicated that the detected species were alkoxy and

peroxy radicals formed by decomposing polyethylenes in oxygen. In addition to

free radicals, one of these groups also detected the presence of hydroperoxides [10]. The concentration of free radicals and peroxides in the environment were estimated roughly to be about the same as that found for the total

aldehydes (~ 2.2 mg/m^) [10]. Even though both these studies demonstrated

that processing of polyethylenes gives rise to free radicals, free radicals

are normally very short-lived species, and there is no clear evidence that the

free radicals constitute a hazard when polyethylenes are involved in real

f ires.

3. TOXICOLOGY

Several bioassay methods have been used to assess the acute toxicity of

fire gases. In these tests, animals are exposed to smoke and toxic gases and

either death or incapacitation serves as the biological endpoint. Most test

procedures include some chemical analysis of specific toxicants of interest.

The various toxicity test methods have been described in detail by Kaplan et

al. [28].

In the reviewed literature, seven different toxicity test procedures were

utilized to assess the toxicity of combustion products from polyethylenes. A

brief summary of the five main methods used and the biological endpoints that

have been evaluated is given below.

-23 -
Lethality

Method

LC50 No. Animals Time to

Affected Death

Incapacitation

IC 50

Incapacitation

DINa

USPb

FAA/CAMic

Dow^

CMIR6

X

X X

X X

X

X

X

X

X

aMethod developed in response to the German Commission of Standards

^University of San Francisco

^Federal Aviation Administration

*^Dow Chemical Company

^Carnegie Mellon Institute of Research

3.1 DIN Toxicity. Test Method

The toxicity of the combustion products from various materials, including

polyethylenes , has been evaluated by two groups of workers using several

variations of the DIN method. Briefly, the DIN Draft 53436 test method uses a

dynamic flow system in which materials of equal volume or equal weight per

unit length are decomposed in a quartz tube. The tube is heated by an

externally moving (1 cm/min) furnace at fixed temperatures between 200°C and

600°C. The decomposition products are diluted with air at chosen flow rates.

Chambers of various designs have been used to expose animals in the head-only

or whole-body mode. These exposures usually last for 30 minutes and lethality

is the usual biological endpoint.

An early version of the DIN method was used by Hoffmann and Oettel to

compare the toxicity of the thermal decomposition products of building

materials [29]. They demonstrated that ranking materials based solely on the

chemical analyses of a few of the decomposition products may be misleading and

does not correspond with results from toxicological experiments on animals.

-24-
In these experiments, a polyethylene (without a filler) was decomposed at

100° increments between 200 and 600°C with an air flow rate of 100 H/h. The

pyrolysis products were further diluted with an 100 £/h air supply. Rats were

exposed in the whole-body mode for 30 minutes. The blood carboxyhemoglobin

(COHb) levels in the experimental animals were determined i.mmediately after

the exposure. The results of these experiments showed that when five gram

samples of a polyethylene were pyrolyzed, 100% mortality occurred at temperatures of 400°C and greater, whereas no deaths were observed at lower temperatures (Table 5). Since COHb concentrations in the dead animals ranged from 79

to 85%, the lethalities were attributed by Hoffmann and Oettel to CO [29].

Hoffmann and Oettel also compared the toxicity produced by the thermal

degradation of the same polyethylene to that of other conventional building

materials tested at the same sample weight under similar conditions. The

toxicity of these materials, cellulose, rigid poly(vlnyl chloride) (PVC), and

pine, were classified 1, 2, and 3, respectively, according to a Swiss classification (where 1 indicates the most toxic case). The polyethylene that was

tested was assigned a toxicity classification of 4. Based on animal test

results, temperatures above 400°C generated decomposition products with the

same toxicity from all four materials. However, at 300°C, the decomposition

products from the polyethylene were less toxic than those from the other three

materials. At 200°C, cellulose was the only material to produce toxic

combustion products [29].

In another study, Hoffmann and Sand investigated the toxicity of the

decomposition products from two types of polyethylene (HDPE and LDPE) and

compared the results to those from pine wood [30]. Conditions were set such

-25-
that sublethal concentrations of CO were generated. In these experiments, ten

grams of the polyethylenes were decomposed at 600°C. The air supply through

the furnace was 450 A/h and an additional air supply of 450 A/h was used for

dilution of the pyrolysis products in the exposure chamber. The CO concentrations were determined by Draeger tubes^ and were less than 1000 ppm. The COHb

levels in the blood at the end of the 30 minute exposures were 27 percent and

33 percent for the LDPE and HOPE, respectively, and no deaths occurred. Under

the same test procedure, pine wood generated about 2000 ppm CO, COHb levels of

51%, and also no deaths. The authors concluded that under these test conditions, the combustion products from these polyethylenes appear to be no more

toxic than those from pine wood and that in a real fire, the toxicological

risk from the fire gases of polyethylenes is no greater than that of pine

wood.

Herpol et al. used the DIN toxicity test method to investigate whether

synthetic materials are more dangerous when involved in fires from a toxicological point of view than natural materials [32-34]. The polyethylene samples

included in this study are listed below:

No. 5 and K9 - Low density sheets

No. 6 or KIO - High density sheet A

No. 7 - High density sheet B

No. 8 - Low density granules

Kll - Tubing (treated with fire retardant)

2 It should be noted that the use of colorimetric tubes, such as Draeger tubes,

provides unreliable and, at best, semlquantitative results, primarily because

other combustion gases may interfere in the analysis. The temperature of the

gas being sampled also has been noted to have an effect on the results [31].

-26-
These materials were decomposed at three temperatures, 400, 600 and

800®C, in a furnace through which an air flow of 200 il/h was passed. The

combustion products were further diluted by an additional air flow of 200 £/h

before entering the exposure chamber in which rats were exposed in a whole

body mode for 30 minutes. Lethality (as measured by the cessation of respiration) was the biological endpoint.

The polyethylene samples flamed in all except a few tests at 400 °C. At

600 °C, all of the polyethylene samples were about equally toxic and caused

92-100% mortality. At 400 and 800 °C, samples 5 and K9 were more toxic than

samples KIO and Kll (FR) (Table 6). The COHb levels in the blood of dead rats

ranged between 48 and 79 percent. The CO concentration-time products for 30

minutes ranged from 29,000 to 189,000 ppm'min in those experiments in which

deaths occurred. In an earlier study of lethalities from pure CO in air,

Herpol et al. found that no deaths occurred at CO concentration-time products

up to 120,000 ppm’mln and 100 percent of the animals did not die until

210,000 ppm'min was reached [35]. In the pure CO experiments in which all the

animals died, the mean COHb ranged from 58-71%. In the experiments on polyethylenes, most of the CO concentration-time products are lower than the

lethal CO concentration-time products seen in the pure CO tests, an indication

of the presence of other toxicants.

The CO 2 concentration-time products in Table 6 ranged from 26.0 to 191.8

percent *min except for sample Kll(FR) which had an CO2 concentration-time

product of 0.5 percent»min at 400°C. A CO2 concentration— time product greater

than 75 percent’min will increase the rate of respiration [35]

.

In these

experiments, however, the respiration of rats decreased drastically even when

-27-
CO

2 concentration-time products were above 100 percent*rain (Table 7). This

reduction suggests the presence of irritants in the combustion products.

Comparison of results (shown below) obtained with two wood products

decomposed in the DIN test method showed that some of the samples of polyethylene (not fire retarded) appeared to be more toxic at 800°C, but had about

the same degree of toxicity at 400 and 600°C [33].

Percent Mortality at

Sample 400°C 600 °C 00 00

0

5, K9 94 94 100

6, KIO 67 100 39

7 92

8 100

beech 72 54 17

poplar 100 28

To assess the hazard produced from the decomposition of a material,

Herpol proposed the use of a "toxicity index" (TX) based on a mathematical

expression which takes into consideration the observed mortality and exposure

time under the most toxic conditions [34,36,37]. A good correlation was shown

to exist between the TX and LT^q values (time necessary to kill 50 percent of

the rats). The maximum TX values for the three polyethylenes tested (K9, KIO,

Kll(FR)) ranged from 30 to 48. These values indicated a higher overall

toxicity for the polyethylene samples than for the poplar and beech wood

samples (results shown below) [34].

-28 -
Maximum TX

K9

KIO

Kll (FR)

beech

poplar

48.00

29.53

30.93

8.80

16.93

3.2 University of San Francisco (USF) Toxicity Test Method

The USF test method has been used by Hilado et al. to evaluate the

toxicity of the thermal decomposition products from a great number of commercial materials, including polyethylene. The test method involves exposing

four mice in the whole-body mode to the thermal degradation products from one

gram samples decomposed in a tube furnace. The temperature is either

increased from 200 to 800°C at a rate of 40°C/min or fixed at a temperature

ranging from 200 to 800°C. The experiments are conducted with or without a

forced air supply. Animals are exposed for 30 minutes or until the time of

death of the last surviving animal. Biological endpoints are average times to

incapacitation (T^) as indicated by staggering, prostration, convulsions, and

collapse, and time to death (T^) as indicated by cessation of movement and

lack of respiration.

The results of the evaluation of several samples of polyethylene

decomposed in the USF furnace set in the rising temperature mode without any

added air supply are presented in Table 8. The average times to incapacitation ranged from 11.54 ± 0.62 to 15.52 ± 4.44 minutes and average times to

death ranged from 13.99 ± 0.85 to 24.69 minutes. In most tests, death

occurred two to six minutes after incapacitation (as indicated by staggering).

The average times and standard deviations were calculated from the mean of two

-29-
or more experiments and are not indicative of the variability of the animals

within any one test.

The relative toxicity of polyethylenes is highly dependent on the

conditions of combustion (temperature and air flow rate). Changing from the

rising temperature program to a fixed temperature mode at 800®C results in

shorter times to animal responses, i.e., higher toxicity [39]. This effect is

attributed to the more rapid generation of toxicants from polyethylenes when

decomposed at 800°C as compared to the rising temperature program.

Progressive increases in toxicity were also observed in the fixed temperature

mode as the temperature was increased [40].

When the polyethylenes were decomposed under a forced air supply, the

times to death and times to incapacitation were generally shorter than when

the polyethylenes were decomposed in the static mode [41]. The effects of the

temperature regime and ventilation conditions on the times-to-death from the

exposures to the combustion products from a polyethylene are summarized in

Table 9 [42].

In a study on the lethal effects of CO in air, Hilado and Cummlng found

that the tlme-to-death from 10,000 ppm CO was about five minutes [43]. When

polyethylene samples were decomposed with the USF test method using either of

the two temperature modes, GC gas analysis of the chamber atmospheres at the

time of death of the last surviving animal showed the presence of relatively

high concentrations of CO, methane, and ethylene (Table 10). The CO concentrations ranged from 9,155 to 15,050 ppm (rising temperature mode) and from

565 to 16,560 ppm (fixed temperature mode). From the results in Table 10, it

-30-
appears that CO could be the principal toxicant in the combustion gas mixture

from the polyethylenes decomposed in the rising temperature mode and in the

experiments in the fixed mode at 500, 600, and 800°C without forced air. At

300 and 400°C, where the CO concentrations were below 3000 ppm, other gases

most likely contributed to the observed deaths.

The role of CO in the combustion gas mixture was estimated by a concentration-time relationship or "death product" (DP), which was defined as

t DP = / Cdt

o

where C is the concentration of CO at time t [44]. Hilado and Cumming

determined the critical DP for CO to be 47,240 ± 14,980 ppm*min [43]. Tests

were terminated upon death of the last surviving animal or 30 min. The DP

values for CO from five polyethylene samples decomposed with the rising

temperature mode were found to range from 41,880 to 74,650 ppm'min [44].

For three other polyethylene samples decomposed at 800 °C, the DP values ranged

from 60,290 to 95,390 ppm’min [45]. The range of DP values calculated for

these polyethylenes suggest that CO was probably the principal toxicant.

3.3 Federal Aviation Administration (FAA/CAMI) Toxicity Test Method

The toxicity of the thermal degradation products from various aircraft

cabin materials, including a fire retarded polyethylene flotation cushion, has

been evaluated by Crane et al. using the FAA toxicity test method [46]. This

test method utilizes a static system consisting of a tube furnace connected to

an exposure chamber in which three rats are exposed in the whole-body mode for

-31 -
30 minutes. The combustion products, generated from 0.75 g samples decomposed

at 600°C, are recirculated between the furnace and the animal chamber during

the exposure. Separate rotating activity wheels in which the rats are forced

to run or walk continuously are used to determine the time to incapacitation

(T^) and time to death (T^)* Rats are considered incapacitated when they

start to slide or tumble in the rotating cages and dead when visible respiration ceases. When the animals were exposed to the combustion products from a

fire retarded rigid polyethylene foam, the mean observed response times for

and were 6.66 ± 0.85 minutes and 10.26 ± 0.62 minutes, respectively.

For comparison purposes. Crane et al. converted the observed response times to

"standard" response times (i.e., the values were normalized to a 200 gram rat

and 1.000 gram fuel load). The normalized values were 5.25 minutes for T^ and

8.08 minutes for T^. That the "standard" T^ value for this polyethylene foam

was within the range of T^ values (4,29 to 5.55 min) determined for 6 other

commercial foams is an indication that the toxicity of this polyethylene was

about equal to that of other foams used for the same end purpose [46].

The FAA/CAMI screening test method was also used by Hilado et al. to

evaluate a series of materials and to compare the test results with those

obtained by the USF test method [47]. The sample evaluated was a low density

polyethylene (referred to as PE 1 in section 3.2). All animals died when a

0.75 g sample of the polyethylene was decomposed at 600°C. The average times

to incapacitation and to death were 4.88 ± 0.29 min and 8.03 ± 0.08 min,

respectively. About 10,000 ppm of CO were detected in the exposure atmosphere. This polyethylene produced the most toxic degradation products when

compared to three other materials tested according to the FAA/CAMI method

(i.e., in degree of toxicity, polyethylene > polycarbonate > ABS >

-32-
polystyrene). In contrast, this polyethylene ranked third when tested with

the USF method using the rising temperature program (40‘*C/min from 200 to

800“C) with no forced air flow [47].

3.4 The Dow Chemical Company Test Method

Potts et al. studied the toxicity of several polyethylene formulations

decomposed under non-flaming (oxidative pyrolysis) and flaming conditions

[26]. The test method employed was developed by the Dow Chemical Company

specifically to evaluate smoke toxicity [48]. Rats were exposed for 30

minutes in a whole-body mode to degradation products generated in a quartz cup

furnace located within the exposure chamber. All the smoke generated in the

furnace was kept in the exposure chamber (i.e. , static system). The rats were

observed for any abnormal symptoms (e.g. , irritation, breathing irregularity,

and nasal discharges) and mortality. ^^50 values (the concentration of

material consumed (mg/A) that caused 50% of the animals to die) were calculated for deaths that occurred during the 30 minute exposure and a 14 day

post-exposure period. The chamber atmosphere was analyzed for CO, CO2 , and O 2 by GC and for acrolein by GC/MS and colorimetric methods using a spectrophotometer.

Toxicity experiments were performed on three commercial samples of

polyethylene [ETHAFOAM 220 foam, XFS4101 foam (which was fire retarded), and

DOW 520 pellets] [26]. Three to six gram samples decomposed in the flaming

mode produced signs of abnormal behavior and deaths during the 30 minute

exposures (no rats died during the 14 day post-exposure period). In these

experiments, the average CO concentrations ranged from 1500 ppm to 4100 ppm,

-33-
02 levels from 11% to 15%, and acrolein concentrations from 3 to 23 ppm. The

lethalities were attributed to CO poisoning together with marked oxygen

depletion.

The non-flaming experiments, which were carried out at temperatures just

below the auto-ignition temperatures of the polyethylene samples (0.35 to 2

grams), produced signs of breathing difficulties and eye irritation.

Lethalities occurred only during the post-exposure period (in most cases,

within 16 to 48 hrs). In these experiments, the average CO concentrations

ranged from 100 to 2200 ppm, acrolein concentrations were between 19 to

155 ppm, while 0£ levels remained above 19%. Gross pathologic examinations of

the animals showed lesions in the upper and lower respiratory system. The

lethalities were attributed principally to the concentrations of acrolein in

the exposure atmosphere. To verify that the levels of acrolein measured in

these experiments can cause deaths as a result of a 30 minute exposure, Potts

et al. conducted control exposures to acrolein in air. Since the LC^q for

acrolein was determined to be in the range of 45-95 ppm and most of the

lethalities occurred within 24-48 hours following the exposure, it seems

reasonable to assume that the acrolein played a major role in the deaths of

the rats [26].

The polyethylene foams examined by Potts et al. were found to be more

toxic in the non-flaming mode than in the flaming mode (Table 11). (No LC^q

values were calculated for exposures with polyethylene sample DOW 520). When

compared to cellulosic materials tested by the same method in the flaming

mode, the decomposition products from these polyethylenes [LC^q (30 min +

14 day) values of 35 and 31 mg/i] were found to be about as toxic as those

-34-
from wood [LC^q (30 min + 14 days) = 35.0 mg/l]’, whereas, in the non-flaming

mode, the decomposition products from these polyethylenes [LC^q (30 min + 14

day) values of 6 and 5 mg/H] were more toxic than those from wood [LC^q (30

min + 14 days) = 22 mg/^.]. In contrast, the toxicity of a polyethylene wire

insulation in the non-flaming mode as determined by Levin et al. using the

National Bureau of Standards (NBS) toxicity test method [49] appeared to be

much less toxic than that found by Potts et al. The results of Levin et al.

showed a non-flaming LC^g (30 min + 14 day) value greater than 75 rng/i. [50].

The difference in the results of Levin et al. and those of Potts et al.

indicate that the high toxicity of the foams examined by Potts et al. are not

necessarily characteristic of polyethylenes in general.

Potts et al. also found that the acrolein concentrations from the nonflaming decomposition of wood were lower than those formed from these polyethylenes (e.g., 43 ppm for a 6 gram sample of wood vs 155 ppm for a 2 gram

sample of polyethylene) [48]. Therefore, acrolein may be contributing to the

post-exposure deaths from these polyethylenes.

Polyethylenes produce high concentrations of acrolein only over a narrow

temperature range. Decreasing the pyrolysis temperature 40 °C below the autoignition temperature reduced the acrolein concentrations from a five gram

sample of polyethylene to < 2 ppm and produced no deaths. Closer to the autoignition temperature, 65 to 97 ppm of acrolein were generated and all the test

animals died. Potts et al. point out that since polyethylenes are lethal over

the very narrow pyrolysis temperature range of approximately 40°C, the time in

which lethal effects can be produced in real fire situations is probably very

short.

-35-
3.5 Large Scale Tests

The hypothesis of Potts et al. was examined in large-scale tests where

approximately the same sample weight of polyethylene per room volume ratio

(13.6 mg/il) noted to produce 100% rat mortality in the Dow small-scale test

was decomposed [24]. In the first series of experiments, blocks of the same

polyethylene foams, ETHAFOAM 220 and XFS-4101 (FR), were decomposed by radiant

2 heat fluxes (_^ 25 kW/m ) either under flaming or non-flaming conditions in a

3 70 m room. Rats were exposed to the smoke in rooms adjacent to the burn

room. In the large-scale non-flaming tests, only 5% of the foam was consumed

and in the flaming experiments, only about one third of the foam was

decomposed. The concentration of acrolein in the vicinity of the rats was

less than 10 ppm for the flaming tests and less than 5 ppm for the non-flaming

tests. The exposed rats showed no ill effects in either case.

In a second series of tests, approximately 18 kg (40 lbs) of the same two

polyethylene foams were burned in the flaming mode in a building of about

3 1000 m in volume. Rats were placed in the building and were exposed to the

combustion products from the fire for a total time of 30 minutes. The small

amount of acrolein (less than 15 ppm) produced no ill effects in the rats.

Heat blisters were noted at the edges of rats' ears due to temperatures which

briefly reached 60 to 80°C [24]. The investigators concluded that the

acrolein concentrations produced in certain "real" fires involving polyethylenes would probably not constitute a significant hazard.

To evaluate whether polyethylene-based materials pose an unreasonable

hazard in a "real" fire, Kuhn et al. studied the production of the toxic

-36 -
gases, CO and acrolein, from polyethylene foams decomposed under both nonflaming and flaming conditions in full-scale fire tests not involving animals

[2A]. In the first series of experiments about 320 kg (710 lbs) of the same

two brands of polyethylene, ETHAFOAM 220 and XFS-4101 (FR), were burned in a

3 building of about 1000 m in size. The fire, after becoming well developed,

was extinguished with water. The concentration of acrolein, which was

measured in the burn room prior to the extinguishment, was estimated to be

less than 15 ppm for both foams. (The presence of soot may have interfered

with the spectrophotometric colorimetric technique used.)

In the second series of tests, the relative hazard of acrolein in fullscale tests was compared to that of CO. One to nine cartons (each containing

approximately 50 lbs) of the same two brands of polyethylene were burned in a

3 34 m room connected to a corridor. The maximum concentrations of CO and

acrolein detected in the corridor were 14000 ppm and 15 ppm, respectively.

The LC^q (30 min and 14 day) value for CO as determined for CO in rats is

4600 ppm [25] and that for acrolein is in the range of 45-95 ppm [26]. Other

studies of five minute exposures of baboons to acrolein in air showed that

500 ppm produced no deaths either during or following the exposures; whereas,

concentrations of about 1000 ppm produced some post-exposure deaths [27].

Therefore, the large-scale test results suggest that the acrolein concentrations generated in "real” fires involving polyethylene foams were not toxicologically significant; whereas the levels of CO are of toxicological concern.

-37 -
3.6 Miscellaneous Tests

Gad and Smith used a test method developed at the Carnegie Mellon

Institute of Research (CMIR) to evaluate the influence of heating rates on the

toxicity of the decomposition products from a HDPE [51]. The experimental

procedure involved exposing the whole-bodies of rats to the thermal degradation products generated in a furnace heated by a radiant IR source. The

furnace and the exposure chamber were interconnected so that the animals

received a static exposure. CO and CO

2 were monitored during the exposure by

IR and the total hydrocarbons were measured by flame photometry. A motordriven rotating activity wheel was used to determine incapacitation and

lethality. The LC^q and IC^q values (the concentrations that killed or

incapacitated 50% of the test animals exposed for 30 minutes) were based on

the weight of the polyethylene sample volatilized.

Six rats were exposed for 30 minutes to the decomposition products from

HDPE samples heated at rates of 20, 30, 40 and 50°C/mln starting from an

ambient temperature of 25°C. The polyethylene flamed early when exposed to

the higher heating rates (40 and 50°C/min). The experimental results were

influenced by the change in heating rate as well as by the mode of combustion.

The production of CO increased as the heating rate Increased (e.g., the

maximum CO concentration from a two gram sample increased from 800 ppm at

20°C/min to 7300 ppm at 50°C/min). However, much more of the sample was

decomposed at the higher heating rates. A similar trend was observed for

total hydrocarbons.

-38-
The LC^q and IC^q results calculated for 30 minute exposures at different

heating rates in both the flaming and non-flaming modes are summarized in

Table 12. In the non-flaming mode, the toxic effect of the combustion

products from the polyethylene Increases slightly (lower value indicates

Increased toxicity) at the higher heating rates. In the flaming mode, the

combustion products from the polyethylene appear to be less toxic as the LC^q

values increased by almost a factor of two over the non-flaming results at the

lower heating rates. In most cases, the lethalities appear to be attributable

to the CO concentrations. Comparing the polyethylene results and those of

Douglas fir. Gad and Smith concluded that over the range of experimental

conditions, the combustion toxicity of this HDPE was not greater than that of

Douglas fir, a reference material commonly used for comparison.

Kishitani and Nakamura used a dynamic system and time based animal model

(similar to that employed by other Japanese research groups) to evaluate the

toxicity of combustion products of building materials [52]. A polyethylene

was decomposed in a tube furnace at 350, 500 and 750°C (temperatures to which

materials would be subjected during the initial stages of a fire). Flaming

occurred at 750 °C. One mouse at a time in a whole-body mode was exposed to

the combustion products in an adjacent chamber for 15 minutes, a time period

which was estimated as the time required to evacuate a multi-storied building.

Surviving mice were kept and observed for one week following the tests. A

vibration sensor during the exposures was used to detect movement of the

mouse. Time of death in minutes or days, as Indicated by the cessation of

respiration, was the biological endpoint.

- 39 -
The maximum concentrations of CO generated by the degradation of ten gram

samples of a polyethylene were 6500 ppm at 350°C, 3900 ppm at 500°C, and

1800 ppm at 750°C. No deaths occurred from the exposure to the 750°C

(flaming) combustion products, but all mice died from the non-flaming combustion products generated at 350°C and 500°C. All those deaths, except one,

occurred 1 to 3 days following the exposure. The one lethality occurred at

14 min during the exposure at 350°C. The authors proposed that the postexposure deaths were caused by various hydrocarbons known to be generated from

polyethylene decomposed in the temperature range of 350-500°C [52].

4. SUMMARY

In this report, a review has been made of the chemical nature and

toxicity of the volatile products generated during combustion of polyethylenes. The thermal degradation products from polyethylenes are largely

dependent upon the temperature and oxygen availability. In the absence of

oxygen, a mixture of primarily n-alkanes and 1-alkenes are produced. In the

presence of oxygen, additional oxygen-containing organic compounds (mostly low

molecular weight aldehydes and carboxylic acids) are formed. Among the great

number of gaseous products identified, CO appears to be the predominant

toxicant. Non-flaming combustion also favored the production of acrolein and

other irritant gases. Flaming combustion favored the production of CO

2

,

hydrocarbons, and aromatics. Under restricted flaming with limited O

2 content, production of CO increased with increasing temperature.

The toxicity of the combustion products from polyethylenes has been

examined by seven different test procedures. Most of these test methods

-40-
evaluated the toxicity by determining the numbers of animals affected and

times to incapacitation and death without developing quantitative concentration-response relationships. In general, polyethylenes are more toxic in the

non-flaming mode than in the flaming mode. The toxicity in the non-flaming

mode increases with temperature and air supply. It is also greater when the

material is decomposed with a high constant temperature than with a rising

temperature program.

The HDPE LC^q values for 30 minute exposures (no post-exposure period)

were about 25 mg/i in the non-flaming mode and about 50 mg/il in the flaming

mode according to the Carnegie Mellon Institute of Research test method [51].

The LC^q values of the polyethylene foams calculated for 30 minute exposures

and 14 day post-exposure periods was about 5 mg/2. in the non-flaming mode and

about 35 mg/2, in the flaming mode according to results obtained by the Dow

Chemical Company test method [26]. The 30 min and 14 day post-exposure LC^q

value for polyethylene wire insulation in the non-flaming mode was greater

than 75 mg/2 when determined by the NBS toxicity test method [50]. Since

acrolein is produced in the non-flaming mode and most deaths are postexposure, many studies have examined the production of acrolein. However, it

is not clear whether the post-exposure deaths are due to acrolein alone or if

additional irritant gases ought to be examined. The difference in the LC^q

values in the non-flaming mode probably reflects the differences in the test

methods and sample variability.

The only available comparative study of full-scale versus bench-scale

experiments suggests that small-scale testing may produce toxicity results

which overestimate those found under full-scale testing. Since numerous full-

-41 -
scale scenarios may be envisioned and only one has been studied, these

findings may have only limited applicability.

The results presented in this review show that the toxicity of the

combustion products from various samples of polyethylenes are not highly or

unusually toxic.

5 . ACKNOWLEDGMENTS

The authors gratefully acknowledge the help of Ms. N. Jason,

Ms. M. Diephaus, Ms. A. Durham, and Ms. C.S. Bailey who performed the literature search and compiled the references. This study was supported in part by

the Consumer Product Safety Commission. Dr. Rita Orzel was project officer

under NBS contract no. 753-1386 (CPSC Task Order No. 84-8).

6. REFERENCES

1. Materials '84. A Modern Plastics Special Report. Modern Plastics

^:45-67 (1984).

2. Henkel, R.N. , Polyethylene and ethylene copolymers. In "Modern Plastics

Encyclopedia", J. Agranoff, ed. , Volume 59, McGraw Hill, Inc., New York,

1982, pp. 73-98.

3. Cullis, C.F. and Hirschler, M.M. , The Combustion of Organic Polymers.

Clarendon Press, Oxford, England, 1981, pp. 320-345.

4. Madorsky, S.L. , Thermal Degradation of Organic Polymers. Interscience

Publishers, John Wiley & Sons, Inc., New York, 1964, pp. 93-126.

5. Tsuchiya, Y. and Sumi , K. , Thermal decomposition products of

polyethylene. J. Poly. Sci. Part A-1 ^:415-424 (1968).

6. Michal, J. , Mitera, J. , and Tardon, S. , Toxicity of thermal degradation

products of polyethylene and polypropylene. Fire and Matls. J_:160-168

(1976).

-42-
7. Schwartz, R.J., Fire retardation of polyethylene and polypropylene. In

"Flame Retardency of Polymeric Materials", W. Kuryla and A.J. Papa, eds..

Volume 2, Dekker Publ. , New York, 1973, pp. 83-133.

8. Morimoto, T. , Takeyama, K. , and Konishi, F., Composition of gaseous

combustion products of pol}nners. J. Appl. Sci. 2^:1967-1976 (1976).

9. Pacakova, V., Nogatz, M. , and Novak, V., Pyrolysis capillary gas

chromatography of some polymeric materials. Collect. Czech. Chem.

Commun. 47:509-517 (1982).

10. Hoff, A., Jacobsson, S. , Pfaffli, P. , Zitting, A., and Frostling, H. , Degradation products of plastics. Scand. J. of Work, Environ, and Health

^:l-60 (1982).

11. Morikawa, T. , Evolution of soot and polycyclic aromatic hydrocarbons from

combustion and pyrolysis of polymers and low molecular weight

hydrocarbons. Fire Sci. and Tech. ^:27-35 (1984).

12. Mlchal, J. , Determination of carbon monoxide in thermal degradation

products of polymeric materials. Fire and Matls. ^:149-152 (1981).

13. Morikawa, T. , Effects of water vapor on evolution of carbon monoxide in

combustion and pyrolysis. J. Comb. Tox. ^:85-96 (1982).

14. Michal, J., Combustion products of polymeric materials. I Test Chamber

CAB 4.5. Fire and Matls. ^:163-166 (1983).

15. Michal, J. , Combustion products of polymeric materials. II Test Chamber

CAB 650. Fire and Matls. ^:169-172 (1983).

16. Paciorek, K.L. , Kratzer, R.H. , and Kaufman, J., Coal mine combustion

products identification and analysis. Final Report No. BuMines-OFR-1-73

under Contract No. HO 122009 of Ultrasystems, Inc., Irvine, CA,

July 1972, 165 p.

17. Boettner, E.A. , Ball, G.L., and Weiss, B. , Combustion products from the

incineration of plastics. Report #EPA-670/2-73-049 prepared under Grant

#EP-00386 for the Office of Research and Development, U.S. Environmental

Protection Agency, Washington, DC by the University of Michigan, Ann

Arbor, Michigan, July 1973, 140 p.

18. Morikawa, T. , Acrolein, formaldehyde, and volatile fatty acids from

smoldering combustion. J. Comb. Tox. 135-150 (1976).

19. Hodgkin, J.H. , Galbraith, M.N. , and Chong, Y.K. , Combustion products from

burning polyethylene. J. Macromol. Sci. Chem. A17 :35-44 (1982).

20.

Morikawa, T. , Evolution of soot and polycylic aromatic hydrocarbons in

combustion. J. Comb. Tox. 5:349-360 (1978).

-43 -
21. Zinn, B.T. , Browner, R.F., Powell, E.A., Joseph, K.T., Pasternak, M.

,

Gardner, R.O. , and Ndubizu, C. , Investigations of smoke formation by

polymeric materials : Smoke reduction methods and chemical

characterization of particulates. Final Report on Nat. Bur. Stand.

(U.S.) Grant No. G8-9003, for the period Oct. 1, 1978 to Sept. 30, 1979,

36 p.

22. Einhorn, I.N. , Physiological and toxicological aspects of smoke produced

during the combustion of pol5nmeric materials. Environ. Health Perspect.

jj_:163-189 (1975).

23. Westerberg, L.M., Pfaffli, P., and Sundholm, F. , Detection of free

radicals during processing of polyethylene and polystyrene plastics. Am

Ind. Hyg. Assoc. J. 4_3:544-546 (1982).

24. Kuhn, R.L. , Potts, W. J. , and Waterman, T. E., A study of the inhalation

toxicity of smoke produced upon pyrolysis and combustion of polyethylene

foams. Part II: Full scale fire studies. J. Comb. Tox. _5:434-464

(1978).

25. Levin, B.C., Paabo, M. , Bailey, C. , Harris, S.E., and Gurman, J.L.,

Toxicological effects of the interactions of fire gases and their use in

a toxic hazard assessment computer model. The Toxicologist _^:127 (1985)

26. Potts, W.J., Lederer, T.S., and Quast, J.F., A study of the inhalation

toxicity of smoke produced upon pyrolysis and combustion of polyethylene

foams. Part I: Laboratory studies. J. Comb. Tox. ^:408-433 (1978).

27. Kaplan, H.L. , Grand, A.F., Rogers, W.R., Switzer, W.G. , and

Hartzell, G.E., A research study of the assessment of escape impairment

by irritant combustion gases in postcrash aircraft fires. Report

#D0T/FAA/CT-84/l 6 prepared under Grant //DTFA 03-81-00065 for the Federal

Aviation Administration, Atlantic City, NJ , by the Southwest Research

Institute, San Antonio, TX, September 1984, 65 p.

28. Kaplan, H.L., Grand, A.F., and Hartzell, G.E. , A critical review of the

state-of-the-art of combustion toxicology. Final Report 01-6862,

Southwest Research Institute, San Antonio, TX, June 1982.

29. Hofmann, H. Th. and Oettel, H. , Comparative toxicity of thermal

decomposition products. Modern Plast. 4^:94-100 (1969).

30. Hofmann, H. Th. and Sand, H. , Further Investigations into the relative

toxicity of decomposition products given from smoldering plastics.

JFF/Comb. Tox. J_:250-257 (1974).

31. Standard Guide for Measurement of Gases Present or Generated During

Fires. ASTM E 800-81, American Society for Testing Materials,

Philadelphia, PA (1984).

32. Herpol, C., Biological evaluation of the toxicity of products of

pyrolysis and combustion of materials. Fire and Matls. J_:29-35 (1976).

-44 -
33 . Herpol, C. and Minne , R. , Biological evaluation of the toxicity of gases

produced under fire conditions by synthetic materials. Part 2: Behavior

of synthetic materials in definite combustion conditions as compared to

the behavior of traditional materials in same conditions. Comb. Sci. and

Tech. ^:229-24A (1976).

34. Herpol, C., Biological evaluation of toxicity caused by combustion of

building materials. Fire and Matls. _^:127-143 (1980).

35. Herpol, C., Minne, R. , and Van Outryve, E. , Biological evaluation of the

toxicity of gases produced under fire conditions by synthetic materials.

Part 1 : Methods and preliminary experiments concerning the reaction of

animals to simple mixtures of air and carbon dioxide and carbon monoxide.

Comb. Sci. and Technol. 12 ;217-228 (1976).

36. Herpol, C. and Vandevelde, P., Calculation of a toxicity index for

materials based on a biological evaluation method. Fire and Matls. ^:l-4

(1978).

37. Herpol, C. and Vandevelde, P., Note on the non-existence of correlation

between toxicity and other reaction to fire characteristics of materials.

J. Comb. Tox. ^.*135-142 (1981).

38. Hilado, C.J. and Huttlinger, N.V., Toxicity of pyrolysis gases from some synthetic polymers. J. Comb. Tox. ^:361-369 (1978).

39. Hilado, C.J., Soriano, J.A. , and Kosola, K.L. , Effect of heating rate on toxicity of pyrolysis gases from S 3mthetic polymers. J. Comb. Tox.

_4:533-555 (1977).

40. Hilado, C.J. and Brauer, D.P., Polyethylene: effect of pyrolysis

temperature and air flow on toxicity of pyrolysis gases. J. Comb. Tox.

^:63-67 (1979).

41. Hilado, C.J. and Smouse, K.Y. , The effect of temperature and air flow on

the relative toxicity of polymeric materials by the USF/NASA Toxicity

Screening Test Method. J. Comb. Tox. ^:305-336 (1976).

42. Hilado, C.J. and Huttlinger, P.A. , The use of rising temperature to

integrate fixed temperature effects in off-gas toxicity. J. Comb. Tox.

_7:201-206 (1980).

43. Hilado, C.J. and Cumming, H.J., Effect of carbon monoxide on Swiss albino

mice. J. Comb. Tox. ^:216-230 (1977).

44. Hilado, C.J., Carbon monoxide as the principal toxicant in the pyrolysis

gases from materials. J. Comb. Tox. _6:177-184 (1979).

45. Hilado, C.J. and Brauer, D.P., Concentration-time data in toxicity tests

and resulting relationships. J. Comb. Tox. ^:136-149 (1979).

-45-
46 . Crane, R.C., Sanders, D.C., Endecott, B.R., Abbott, K.J., and

Smith, P.W. , Inhalation toxicology: I Design of a small animal test

system. II. Determination of the relative toxic hazards of 75 aircraft

cabin materials. Prepared for Dept, of Trans., FAA, Washington, DC,

Report No. FAA-AM-77-9, March 1977, 59 p.

47. Hilado, C.J., Cumming, H.J., Machado, A.M. , Schneider, J.E., Crane, C.R.

,

Sanders, D.C., Endecott, B.R. , and Abbott, J.K., Comparison of animal

responses to the combustion products generated by two test procedures,

the USF/NASA methodology and the FAA/CAMI system. J. Comb. Tox.

_4 :325-359 (1977).

48. Potts, W.J. and Lederer, T.S., A method for comparative testing of smoke

toxicity. J. Comb. Tox. _4;114-162 (1977).

49. Levin, B.C., Fowell, A.J. , Birky, M.M. , Paabo, M. , Stolte, A., and

Malek, D. , Further development of a test method for the assessment of the

acute inhalation toxicity of combustion products. National Bureau of

Standards, Gaithersburg, MD, NBSIR 82-2532 (June 1982).

50. Levin, B.C., unpublished data.

51. Gad, S.C. and Smith, A. C., Influence of heating rates on the toxicity of

evolved combustion products: Results and a system for research. J. Fire

Sci. J^:465-479 (1983).

52. Kishitani, K. and Nakamura, K. , Study on toxicities of combustion

products of building materials at initial stage of fire. Proceedings of

the Second Joint Meeting, U.S. Japan Panel on Fire Research and Safety,

UJNR, Tokyo, Oct. 19-22, 1976, 31 p.

53. Hilado, C.J. and Solis, A.N., Some possible reference materials for fire

toxicity tests. J. Comb. Tox. ^:163-172 (1977).

54. Hilado, C.J. and Cumming, H.J., Studies with the USF/NASA toxicity

screening test method: Carbon monoxide and carbon dioxide

concentrations. J. Comb. Tox. ^:376-384 (1977).

55. Hilado, C.J. and Huttlinger, N.V., Concentration-response data on toxicity of pyrolysis gases from six synthetic polymers. J. Comb. Tox.

^:81-100 (1978).

56. Hilado, C.J. , Olcomendy, E.M. , and Schneider, J.E., Toxicity of pyrolysis

gases from seat cushion materials. J. Cons. Prod. Flamm. _^:189-196

(1979).

57. Hilado, C.J., Cumming, H.J. , and Schneider, J.E. , Relative toxicity of

pyrolysis gases from materials: Effects of temperature, air flow and

criteria. Fire and Matls. J^:183-187 (1979).

58. Hilado, C.J., Cumming, H. J. , and Casey, C.J., Relative flammability and

toxicity of pyrolysis gases from cellular plastics. J. Cell. Plast.

15:205-210 (1979).

-46-
.r, - 59. Hilado, C.J., Huttlinger, P;A. , and Shabdue, C.L. , Smoke and toxic gases*

from materials In health care facilities., J. Cons.*^ Prod. Flamm. 8:65-76^-“

(1981). ‘

' o

i -:..

lU

^J.Ol

r.81.01

81,01 *1 -

^ TK..r '•

l^rwtc

hit*."

t -? nvt l!^.i)|

t2f*Alv»€lvO,8 =iiwf» ^vfaf&t5S^»S£,0t

’

* f

tflt,

»^.&ah

^ «na,|i[i«»oA

niaiOTa^A,

(^,t3iS*l8i%«

(lA 10 finas/xfiO

^ ^o»id^i|4srwfl - i nJ

p§^^'; «cu»^QiU^6giin&S'-'€.t.ik

'®''"‘^®li f'if- 0 art)»itM;:}u6

3 iin&^uS

#naJud

*0 |9ni»4i/a-l ^ am >^fia3«a-S

iwfcs’), '^«iKb3wa-£

oltfyj’ttH

BrtdOrD«loi^Jw£l

bi%B oio:?q*D

abiX^Jtb ffOdvfO

. ^9

b

%l)9c id^A^ dIM laO

>0

.Ml- 5,6*7.V.J0,'

•nsey^'xrtO

bia& oJaojoiO

ifUiMdoIaY^

A0i»iciu1qI;>XO

»AfiqosqpJax!^

7 liin*aa<I

. _ 1®

** BnrnoaO'l

BiMlu(}X^.tAaiOi"£ , S

•naxad^ C " 41 a " BotX J~ 0« .C anajqadi Kt'C , C

•naxad i A #I

- tAkw i‘wbofl

iO tMianahtsC

a
Table 1

Thermal Degradation Products Produced from Polyethylenes

Compound Atmosphere Reference

Acetaldehyde 0 10,19

Acetic acid 0 10,18,19

Acetone 0 10,19

Acetylene 0,1 8

Acrolein 0 10,18,19,24,26

Acrylic acid 0 6,10

Anthracene 0 20,21

Benzene 0,1 6,8,9,10,16

Benzoanthracene 0 20,21

2 , 13 -Benzofluoranthene 0 21

1 , 2-Benzof luorene 0 21

2 , 3-Benzof luorene 0 21

Benzo(a)pyrene 0,1 11,20

Benzo ( c ) pyrene 0 20

Butadiene 0,1 6,7

Butanal 0 6,10

Butane 0,I,V 4,5,6,7,10,17

Butene 0,1 4,6,10

1 -Butene O.I.V 5,7,9,10,17

2-Butene, cis 0 ,v 5,17

2 -Butene, trans o,v 5,17

Butyric acid 0 10

Butyrolactone 0 10

Caproic acid 0 10

Carbon dioxide O.I 6,8,9,10,14,15,17,

24,26,30,32,33,34,

47,53,54,55

Carbon monoxide 0,1 8,9,13,14,15,17,24,

26,30,32,33,34,39,40

44,45,47,51,52,53,

54,55,56,57,58

Chrysene 0 21

Crotonic acid 0 10

Cyclohexane 0,1 6,9

Cyclohexene 0 6

Cyclopropane 0 10

Decanal 0 6

Decane 0,1 6,7

1-Decene 0,1 6,7,10

2 , 2-Dimethylbutane I 9

2, 2-Dimethy-cis-3-hexene I 9

3 , 3-Dimethylheptane I 10

2 , 4-Dimethylhexane I 9,10

2, 3-Dimethyl- 1 -hexene I 9

2 , 3-Dimethylpentane I 9

Dodecanal 0 6

Dodecane 0,1 6

48
Table 1 (continued)

1- Compound Atmosphere Reference

Dodecene

Epoxide

Ethane

Ethanol

Ethyl benzene

Ethyl cyclopentene

Ethylene

2

Ethyl -

1 -hexene

Fluoranthene

Formaldehyde

Formic acid

Furan

Heptadecane

1-

Heptadecene

1 .

3-

Heptadiene

1 ,6-Heptadiene

Heptanal

Heptane

2-

Heptanone

Heptene

1-Heptene

Hexadecane

1-

Hexadecene

Hexadiene

1 . 3

Hexadiene

1 , 5 -Hexadiene

Hexanal

Hexane

2-

Hexanone

Hexene

1

Hexene

2

Hexene

3

Hexene

Hydrogen chloride

Hydroperoxide

Hydroxyvaleric acid

Isobutene

Isobutanal

Isobutylene

Isodecane

Isononane

Isooctane

Isovaleric acid

Methane

Methanol

0,1

0

0,l,v

0

0,1

I

6,10

6

4,5,7,9,10,16,17,

19,47,53,55

10

6

6

o,i,v

I0

0

0

0

I 0,1

I

I0

0,1

0

0,1

0,1

0,1

0,1

I

I

I0

0,l,v

0

0,1

0,I,V

0

I0

0

0

I

0

V

II

I0

0,I,V

0

4,5,7,8,9,10,16,17

19,47,53,55

10

20,21

10,18

10,18

10

6

6

9

9

6

4,6,7,9,10

10

4,20

6,7,9,10

6

6

4

9

9

6

4,5,6,7,9,10

10

4,10

5,6,7,9,10,17

17

9

16

10

10

7 10

5

7

7

7 10

5,7,8,9,16,17,39,

40,44,45,47,53,55

56,58

10

49
Table 1 (continued)

Compound Atmosphere Reference

2-Methylbutane

2-

Methyl- 1 -butene

3-

Methyl- 1-butene

Methylcyclohexane

Methylcyclohexene

MethyIcyc lopentene

4,5-Methylene phenanthrene

2 -Methyl -4-ethylhexane

Methyl ethyl ketone

2-Methyl-3-ethylpentane

2-Methyl- 3 -ethyl- 2 -pentene

2 -MethyIhept ane 2-Methyl- 1-heptene

2

Methy1- 3 -hep tene

3

Methyl- 1-heptene

2-

Methyl- 1 -hexene

3-

Methyl- 1 -hexene

4

Methyl -2-hexene

Methyl -4 , 5 -methylene phenanthrene

2-Methylpentane

2 -Methyl -

1

- pentene

2 -Methyl- 2 -pentene

4 -Methyl- 1 -pentene

Methyl - phenanthrene

2-Methylpropane

2-Methyl-2-propenal

2-Methylpropene

Methylpyrene

Methyl vinyl ketone

1 .

3-

Nonadiene

Nonanal

Nonane

1-Nonene

Octadecane

1-Octadecene

1 .

3-

Octadiene

Octanal

Octane

Octene

1-Octene

Pentadecanal

Pentadecane

1-

Pentadecene

Pentadiene

1 .

3-

Pentadiene

1 .

4-

Pentadiene

Pentanal

Pentane

2-

Pentanone

Pentene

V

V

I,V

I

I0

0

I0

I

III

I

II

II

0

V

V

I I.v

0

V

0

V

0

0

I0

0,1

0,1

I 0,1

0

0

0,1

0

0,1

0

0,1

0,1

I I.v

I.v

0

O.i.v

0

0,1

55

5.9

9

10

6

21

10

10,19

9

9

9

9

9

10

9

9

9

21

55

9

5.9

21

510

5

21

10

9

6

6,7,9,10

6,7,9,10

6

6

9

6

6,7,9,10

20

6,7,9,10

6

6

6

4

5.9

5.9

6.10

4,5,6,7.9,10,17

10

4,6,9

50
Table 1 (continued)

Compound

1-

Pentene

2-

Pentene

Phenanthrene

Propadiene

Propane

Propanol

Propionaldehyde

Propionic acid

Propylene

Pyrene

Tetradecanal

Tetradecane

1-Tetradecene

Tetrahydrofuran

Toluene

Tridecanal

Tridecane

1-Tridecene

2 . 3 . 3

Trimethyl- 1 -butene

2.2.3-

Trimethyl-l-pentane

Trimethylcyclopentane

2 , 2 , 5-Trimethylhexane

2. 3

.4-

Trimethylpentane

Triphenylene

Undecanal

Undecane

1-Undecene

Valerolactone

Water

0: oxidative atmosphere

I: inert atmosphere

V : vacuum

Atmosphere Reference

o,i.v

V

0

I 0.1,v

0

0,1

0

0,l,v

0

0

0,1

0,1

0

0,1

0

0,1

0,1

I

I

I

I

I

0

0

0,1

0,1

0

0

5,7,10,17

5

22

4

4,5,7,9,10,17,19

10

6,10,14,19

10,18

4,5,6,7,9,10,16,17,19

20,21

6

6

6

10

6,19

6

6

6

9

9

10

9

9

21

6

6

6,10

10

9,10

51
Table 2

Degradation Products Generated from a Polyethylene During Pyrolysis,

Thermooxidation, and Combustion [6]

Pyrolysis

Thermooxidation Combustion

Product (%)^ (%) (%)

Carbon dioxide 0.1 0.4 N

Propylene 0.1 0.35 0.5

Butylene 1.5 3.7 2.7

Butane 1.5 - 2.3

1,3 Butadiene 0.75 4.1 1.1

Pentene + Propanal 6.5 7.5 6.7

- 7.4 - n- Pentane - 6.2 3.9

Butyra Idehyde - 14.5 5.8

Cyclohexane - 4.5 3.3

Hexene1

9.9 - 10.8

n-Hexane 4.8 - 4.9

Cyclohexene - 0.27 2.2

Benzene 2.6 0.65 5.9

Methylcyclopentene - 2.5 0.8

Valeraldehyde - 11.5 5.6

Heptene-1 5.6 1.4 3.0

n-Heptane 6.2 1.3 1.6

Toluene 0.8 0.9 3.3

EthyIcyc lopentene 0.5 - - Methyl isobutyl ketone - 2.2 1.7

(or allyl acetate)

Hexanal _ 5.6 2.7

Octen-1 5.7 - 3.9

n-Octane 4.6 - 2.0

Acrylic acid - 0.9 0.8

Ethyl benzene 1.3 0.89 2.5

Heptanal - 3.1 3.1

Nonene15.4 0.7 2.7

n-Nonane 3.5 1.4 1.2

Epoxide - 0.3 0.2

Keto-aldehyde - 0.6 0.3

Octanal - 2.5 0.2

Decene-1 5.8 - 0.7

n-Decane 3.0 0.6 0.3

Undecene-1 4.3 - 0.9

n-Undecane 3.0 - 0.3

Nonanal - 1.9 - Decanal - 0.8 - Tridecene-1 1.9 - 0.2

n-Tridecane 1.5 - 0.4

Undecanal - 0.4 - Silicone - 0.1 - Tetradecene1

2.0 - 0.15

52
Table 2 (continued)

Thermo

Pyrolysis oxidation

Product (%)^ (%)

n-Tetradecane 1.2 - Dodecanal - 0.2

Pentadecene-1 1.8 - n-Pentadecane 0.7 - Tridecanal - 0.1

Hexadecene-1 1.3 - n-Hexadecane 0.9 - Tetradecanal - 0.1

Heptadecene-1 0.5 - + n-Heptadecane 0.4 - Pentadecanal - 0.1

Octadecene-1 0.6 - + n-Octadecane 0.5 -

Pyrolysis: thermal degradation in inert atmospheres

Thermooxidation: thermal degradation in oxidative atmosphere

Combustion: flaming degradation

volume percent calculated from the total chromatogram area.

N: not determined

Combustion

(%)

0.2

0.15

0.15

0.07

0.07

0.15

0.15

53
Table 3

CO and CO 2 Concentrations in the Combustion

Products from a Polyethylene [14]

Combustion

mode

Temp.

(°c)

Sample

weight

(mg)

CO

(%) ^ CO 2 (%)

NF 500 100 0.238 1.24

200 0.472 1.95

300 0.738 2.71

F 600 100 0.126 2.60

200 0.297 3.72

300 0.513 3.66

a: Volume % as measured in the animal test chamber

NF: Non- flaming

F; Flaming

54
Table A

Concentrations of Polycyclic Aromatic Hydrocarbons in

Smoke Particulates from a Polyethylene [21]

PAH Species NF F

Phenanthrene, Anthracene A8.16^ 12. A7

A, 5-Methylene Phenanthrene 2.A5

Methyl - Phenathrene 0.6A

Fluoranthene 18.98

Pyrene 51. 8A A6.38

Methy 1 - A , 5 -Methylene Phenanthrene 0.61

1 , 2-Benzof luorene 1.77

2,3- Benzof luorene 1.33

Methy 1 - Pyrene I.IA

2,13-Benzofluoranthene 5.6A

Chrysene, Benzoanthracene, Triphenylene 8.59

mole %

PAH; Polynuclear aromatic hydrocarbon

NF: Non-flaming

F; Flaming

55
Table 5

Toxicological Effects on Rats Exposed to the Pyrolysis Products

from a Polyethylene^ Decomposed by the DIN Method [29]

Temperature

(°C)

COHb

(%)

Number of deaths

Number of exposed animals

200 <15 0/12

300 <15 0/12

AOO 79 12/12

500 85 12/12

600 82 12/12

sample weight 5 grams
Table 6

Toxicological Effects on Rats Exposed to Combustion Products

from Polyethylenes^ Decomposed According to the DIN

Toxicity Test Method [32-34]

Temp.

(°c) Sample

CO

(ppm»min)^

CO 2 (%-min)^

Mean COHb (%)

D A

Mortality

Number of

rats %

400 5, K9 131690 30.1 59 35 17/18 94

6, KIO 84300 26.0 65 24 12/18 67

Kll (FR) 1610 0.5 - 0.3 0/18 0

600 5, K9 115500 127.4 62 23 34/36 94

6, KIO 124220 113.0 63 - 24/24 100

7 118970 154.3 48 64 11/12 92

8 146630 191.8 65 - 12/12 100

Kll (FR) 188890 103.2 58 72 17/18 94

800 5, K9 117550 109.2 64 - 30/30 100

KIO 29000 40.9 79 48 7/18 39

Kll (FR) 126460 100.9 73 37 17/30 57

a.

b!

D:

A:

lOg samples

Accumulated concentration for 30 minutes

Dead animals

Alive animals

57
Table 7

Variation of Mean Respiration Frequency^ in Rats Exposed

to Polyethylenes Decomposition Products [32,33]

Mean respiratory frequency at:

Temp. Sample 6 12 18 24 30

(°c) No. min min min min min

400 5 89 73 34 28 9

6 97 96 100 53 26

600 5 76 46 28 9 4

6 82 43 20 8 0

7 63 31 53 33 8

8 55 36 13 0 0

800 5 37 14 4 1 0

^ expressed as percent of the mean normal value before the test.

58
Table 8

Toxicity Results for Polyethylenes^ Decomposed According to the

University of San Francisco Method Using the

Rising Temperature Mode^

Sample Ti

Designation (min) (min) Reference

PEI • 15.52 +

4.44C 22.60 + 0.45 47,53,54,55

PE2 11.54 + 0.62 13.99 + 0.85 41

11.74 + 0.29 19.84 + 0.29 53,54,55

PE foam 20.68 + 0.36 56,58

PE foam 20.93 + 0.47 58,59

PE microfoam 20.42 + 0.26 58,59

PE solid 1 19.84 44

PE solid 2 22.66 44

PE solid 3 24.69 44

PE solid 5 (LDPE) 12.80 + 1.34 18.60 + 0.30 38,44

PE solid 6 (HDPE) 13.82 + 2.53 18.29 + 1.22 38,44

sample weight 1 gram

b: A0°C/min from 200 to 800°C

c: standard deviation of average times from 2 or more experiments

Tj^; average time to staggering

Tjj: average time to death

PE: Polyethylene

59
o'

S3

Table 9

Survival Times of Test Animals Exposed to Smoke from a Polyethylene^ Decomposed Under Different University of

San Francisco Test Method Conditions [42]

Temperature

mode

Temperature

(°c)

Mean Time- to

No air flow

-death (min)

Air flow^

Fixed 300 31.0 30^

400 29.3 7.0

500 21.5 6.8

600 15.8 8.2

700 13.8 30^

800 11.7 30^

Rising 200 to 800°C

at 40°C/min

22.7 13.8

: sample designation PI

: air flow rate 18,/min

when no deaths occurred during the 30 minute exposure,

a survival time of 30 minutes is indicated

60
Table 10

Gas Analyses of the Combustion Products from Polyethylenes^

Examined via the University of San Francisco Test Method^

Temp. Sample Temp. CO COo CH4 C2H4 C2H6

Mode Designation (°c) (ppm) (%) (ppm) (ppm) (ppm) Referenc

Rising‘s PEI 11250 3.36 8550 6200 1250 47,53

PE2 15050 2.36 8900 8200 1500 39,54

PE solid 5 11075 9440 38

PE solid 6 9155 8205 38

Fixed PEI 300 565 0 40

PEI 400 2798 0 40

PEI 500 4320 2185 40

PEI 600 10578 9052 40

PE2 800 16560 40

sample weight 1 gram

without forced air flow

40°C/min from 200 to 800“C

61
Table 11

LC^q Values Calculated for Different Polyethylene Foams

Decomposed by the Dow Chemical Company Test Procedure [26]

95%

Sample

Combustion

mode

Confidence limits

(mg/ Jl)

ETHAFOAM 220 F %35 34 - 41

XFS4101 (FR) F 31.3 29.3 - 33.3

ETHAFOAM220 NF 5.3 4.4 - 6.6

XFS4101 (FR) NF 'v- 6.1 5.3 - 6.9

F: flaming

NF: non- flaming

62
Table 12

Influence of Heating Rates on the Toxicity of Combustion

Products from a Polyethylene [51]

Polyethylene Douglas Fir

Heating T^'^5 f 0 Tr ^ J-^5 0 LCg 0 IC 50

rate^ (mg/ H) (mg/ S,) (mg/ 2,) (mg/2,)

20 25.2 10.6 43.0 33.5

30 24.7 9.6 38.5 19.9

40 48.4* <12.4* 39.3 19.6

50 51.2* <19.6* 21.5 14.8

a: °C per minute from 25°C

b: value calculated on basis of material volatilized

during the 30 minute exposures

*: flaming experiments

63
'!^i^ ^ss»

%;

»lial\

.'ll A .11

’'ifj; Uf

, :?m'

sfMr-^l

L ^4u^\

. ^ ’ rtfeaw^ag

'j>'4S lO

ic.ec

«/ii& Lm

iiA' * W BT'.

[iPai ^ M

04

;va/.

iiity.' Mdf *

a

$3 _ , *(',' ' A%

r *M'i^W8raHlBiP" “ ^

iLm^y n . f^lb--'

"' “' »oti^»^«flJtii' Ta^ 1*

b»«Ull*l&v m »isl»W |^|d;

" ' " »»w»o43t» »ii;xii9i OC aHi gni-rurb ’

'' 'l^' '’>^^^’T^^

w sifiaoim^xii gniiuXl. :*'''^'il ti- m?., M:

., m

'.'•

• - ••ffi'fi''‘,jV •>”

' t

"'^^ ' ''^ •»• vt4n

p!

-,jr
NBS-114A tuEv -i-BCi U.S. DEPT. O'- COMM.

BIBLIOGRAPHIC DATA

SHEET (See instruction s)

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

NBSIR-85/3268 January 1986

4.

TITLE and subtitle

A LITERATURE REVIEW OF THE CHEMICAL NATURE AND TOXICITY OF

THE DECOMPOSITION PRODUCTS OF POLYETHYLENES

5.

AUTHOR(S)

Maya Paabo and Barbara C. Levin

6.

PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

Gaithersburg, MD 20899

7. Contract/Grant No.

8. Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State, ZIP)

The U. S. Consumer Products Safety Commission

Bethesda, MD 20207

10.

SUPPLEMENTARY NOTES

Q21 Document describes a computer program; SF-i85, 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 here) The literature on polyethylenes has been reviewed with an emphasis on the

identification of gaseous products generated under various thermal

decomposition conditions and the toxicity of those products. This review is

limited to publications in English through 1984, The analytical chemical

studies of the thermal decomposition products generated under vacuum, inert and

oxidative experimental conditions are described. In oxidative atmospheres,

which most closely simulate real fire conditions, carbon monoxide (CO) was found

to be the predominant toxicant. Acrolein was another toxicant often noted in

these reviewed studies. More acrolein was generated under non-flaming than

under flaming conditions.

Results from seven different test procedures were considered in assessing the

acute inhalation toxicity of combustion products from various polyethylene

formulation. The combustion products generated from the polyethylenes studied

in the non-flciming mode appeared to be slightly more toxic than those produced

in the flaming mode. In the non-flaming mode, the LC^.- values ranged from 5 to

75 mg/H. In the flaming mode, the LC-p. values ranged from 31 to 51 mg/t. The

toxicity of the degradation products or polyethylenes appears to be similar to

that found for other common materials designed for the same end uses.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon

Combustion products, literature reviews, polyethylenes, thermal

decomposition, toxicity.

13. AVAILABILITY 14. NO. OF

PRINTED PAGi S fxl Unlimited 1

1 1 For Official Distribution. Do Not Release to NTIS 60

1 1 Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. , 20402. 15. Price

(x^l Order From National Technical Information Service (NTIS), Springfield, VA, 22161
mi

I#?

'2TtiRKMl:;

Sff'S

®-y4i

J1 <1 ImI|||||| iH)|!0'TAi

ta«Aa»ATt fO JAM4M91M1 % ^

"SOtJIDtep ilO ' U3MTW.

,vi.

urUiW^’' ' ,, ^ ^ —

^y :rioi

^ ,*8-„ »0 ' «.<fr. «-*4 „

.. rOH T*A1

i£Sl

1^

'l!uSWft'

1-r "«*N»i‘s*y :jii6eui4M>^«jAflAt aoX3»Oilti3n»bt !^

.jfkl Wilvrz' ' I a4'9»i^^' ;»«<’«< 't to oooliJttyiod rmlJi'lo^|[R09ii6'.

' ^ dgiKrx«l;t smoiioolitfwq o4 bAiiflttt. ,'

.|>«iay«(»At: 94oob03'«|' lunmls «di io

•vlioi^ixo

bOKJtol ii|tiioft<xSi /vedYso «iiuiotiifM^ oy|) X«o*t yX«»oJu9 iiMii Wotiiw

«|^;J6hi»io« SliriL^onA^_«w' iii,lliX'^^^ ^ fbtm vitm: ntoio-roA b<<^

iiX9' '” (tovoo M^,S: «iJuMi«S ^ Afk '

, ,1 ' • ' ;. , -iv* I ~ir J(wu ,«i .

' .. A\

‘W*

--.iieiP" liAwit miodU

'^' &0^hi^' 'Wt *i»Q.U*Xuvyo) ,'"

’'ifc 5o»(u*<|4» ^^)m^ frtjaMl^l•rf<m swU' «ob«W' .ol>o<tt, loXmXi *rf4 ni ','%

titif' 'Ji^M\$0t |.S .4l^|;XC l^'3'f~bOitiAOX MUllAV ,Q«.^. 94J* /ll 0^1/1)034 ' A«i lp,^XJ!X^:x€0'r

m OB>»i tot ,Wof5S»«fc animo9 ,’'T^fo%'ol'

^

' ifiys* y»t ,*w!boTf*i , ooiioir*i«o^ _

: Jt:j|Oq«oo#b

Mijfw'SiBSsi

HA'*!

it', . 1^11

v./il. .

' “”^J}B!^vlaSK0SP" ta. yiwpMwnfim ur VI

rJbLui. .

" mli

tjs, '^lntfifaMfiU r^

im‘.

6?^'1