h is not lethal
concentrations
om the human

Blood carbo-
re made on
Itaneously-ex-
ts, using the
6 COHb data
|Also shown in
value for 24

in accordance
manufacturer
and optimum
solution flow
conversion of
taminant con-

yf atmospheric
mt using an
es were pre-
standard gas
indardization

most of the

exposed animals. In animals that died during
or shortly after exposure to concentrations above
the LC, value, pulmonary hemorrhage was a
common finding. Delayed deaths were routinely
seen with this compound in exposures below the
LCs. level, with peak mortality occurring about
24 hours postexposure, although occasional deaths
occurred three to four days later. The mor-
tality rates to inhaled HF for rats are presented
in Table 1; those rates for mice are in Table 2.
The LC; slopes for rats and mice are presented
in Figures 2 and 3, respectively, The slopes for
the HF and HF + CO exposures are not sta-
tistically different. There is no apparent effect
attributable to concurrent exposure to carbon
monoxide. Indeed, a single slope could be
plotted by combining the two sets of exposure
data, which would result in a more precise LCs.
value with narrower 95% confidence limits.
Exposure of rats to HCl resulted in LCs
values of 40,989 ppm for the pure compound, and
39,010 ppm for the combined exposure of HCl
and CO, as shown in Table 3. This difference
was not statistically significant; neither was the
greater difference found in mice as shown in
Table 4. The LC, slopes are plotted in Figure 4
for rats and in Figure 5 for mice. Hydrogen

Tapue 1.—7-Day Mortality Response of Rats Exposed
5 Minutes to HF Gas Singly and in Combination
with CO (28% Carboxyhemoglobin)

HF Concentration % Deaths
(ppm)
HF HF + CO
11, 550 0
12, 440 10 +
12,800 0
15, 990 10
17,615 30
17,750 40
18, 580 80
20, 730 70 .
21, 125 100
22, 355 90
22,740 100
23, 540 100
F 95,690 100
a
LCso 18, 200 ppm 18, 208 ppm
95% Confidence | 15, 965-20, 13, 698-24,
Limits 748 ppm 202 ppm

26,000 -

OHF+CO
@HF

24,000

22,000

20,000 +
ppm
HF 18,000

T

16,000 -

14,000

12,000 -

10,000 F

8,000 A . 4
10 50 90

% MORTALITY (Rats)

Fiaure 2. Five Minute LC» for Rats Exposed to HF
Singly and in Combination with CO.

11,000 - e
OD HF+CO a
@ HF 7

10,000 -

9,000

8,000 F

T

7,000
ppm
HFe,000 +

5,000

4,000 +

3,000 F

1 1

1
iT) 50 90
% MORTALITY (Mice)

2,000

Fravre 3. Five Minute LC» for Mice Exposed to HF
Stngly and in Combination with CO.



20459

References

. Aerospace Industry Association of America, Inc.:

Fire Suppression and Smoke and Fume Protection.
Crashworthiness Development Program Technical
Group Report AIA CDP-2, July 1968.

Civil Aeronautics Board: A Study of United States
Air Carrier Accidents Involving Fire 1955-1964:
Bureau of Safety Pamphlets. BOSP 7-6-3, March
1966.

. Snow, C. G., J. J. Carroll and M. A. Allgoood: Sur-

vival in Emergency Escapes From Passenger Air-
craft: The Experiment Perilous. FAA Office of
Aviation Medicine Report No. 70-16, in press.

. Hasbrook, A. H., J. D, Garner and ©. C. Snow:

Evacuation Pattern Analysis of a Survivable Com-
mercial Aircraft Crash, FAA Office of Aviation
Medicine Report No, AM-62-9, 1962.

. Marcey, J. F., and R. Johnson: Flaming and Self-

Extinguishing Characteristics of Aircraft Cabin In-
terlor Materials. NAFEC Report No. NA-68-30,
July 1968.

. Gross, D., J. J. Loftus, T. G. Lee, and V. E. Gray:

Smoke and Gases Produced by Burning Aircraft
Interior Materials. NAFEC Report No. NA-68-36,
June 1968.

7. Leach, L. J., C. J. Spiegel, R. H. Wilson, G. EB. Syl-
vester, and K. E. Lauterback: A Multiple Chamber
Exposure Unit Designed for Chronic Inhalation
Studies, AMER, IND. HYG. ASSOC. J., 20:18, 1959.

8. Forbes, W. H., F. Sargent, and F. J. W. Roughton:
The Rate of Carbon Monoxide Uptake by Normal
Men, AMER. J. PHYSIOL., 143 :594, 1945,

9. Goldbaum, L. R., E. L. Schloegel and A. M, Domin-
gues: Application of Gas Chromatography to Toxi-
cology in Progress in Chemical Toxicology, New
York, Academic Press (A. Stolman, Ed.), 1963, pp 26.

10. Saltzman, B. B.: Modified Nitrogen Dioxide Reagent
for Recording Air Analyzers, ANAL, CHEM., 82 :135,
1960.

11. O'Keeffe, A. E., and G. C. Ortman: Primary Stand-
ards for Trace Gas Analysis, ANAL, CHEM., 38 :760,
1966.

12, Litchfield, Jr, J. T., and F, Wilcoxon: A Stmpli-
field Method of Evaluating Dose-Effect Experiments,
J. PHARMACOL, EXPTL, THERAP., 96:99, 1949.

18. Gray, E. LeB., F. M. Patton, 8. B. Goldberg, and
E. Kaplan: Toxicity of the Oxides of Nitrogen II,
ARCH. IND, HYG. & OCC. MED., 10:418, 1954.



b of Rats Exposed TaBLE 4.—7-Day Mortality Response of Mice Exposed nary hemorrhage. Again, as shown in Tables
ind in Combination 5 Minutes to HCl Gas Singly and in Combination 5 and 6, there was no significant difference be-
with CO (25% Carboxyhemoglobin) tween exposure to NO, alone and exposure to
NO, in combination with CO. Simultaneous ex-
eaths HCI Concentration % Deaths posure of rats to CO and NO, resulted in a
_ (ppm) slightly higher LC,,, an indication of a slightly
less toxic response. The results of these LC,
HCl + CO . wg °
+ HCL HCl + CO studies of NO, on rats are almost identical to
those reported by Gray, e¢ al."*; the latter found
3, 200 7 a 5-minute LC, value of 832 ppm which com-
10 4,920 10 pares well with our value of 831 ppm.
5,060 7 . + +
80 6,145 18 In HCN exposures, either singly or in com-
6,410 0 bination with CO, all deaths occurred during
100 7,525 40 the exposure period or within 20 minutes post-
90 8,065 13 exposure. There were no delayed deaths. The
100 2 ae 38 70 results of the experiments are given in Tables 7
Jo 13.655 40 and 8 for rats and mice, respectively. Carbon
39,010 ppm 21, 010 80 monoxide at the 25% carboxyhemoglobin level
35, 049-43, 26, 485 87 had no effect on the acute toxicity of HON.
419 ppm 27,386 87 90 Because the primary effect of HCN intoxication
80,000 is the blocking of intracellular oxygen transport
LCso 13,745 ppm 10,663 ppm through the cytochrome system, the slightly de-
e 95% Confidence 10, 333-18, 6, 921-16, ereased extra-cellular oxygen transport was not
Limits 283 ppm 428 ppm
of
Tasie 6.—7-Day Mortality Response of Mice Exposed
Zz 5 Minutes to NO? Singly and in Combination with
4“ CO (25% Carboxyhemoglobin)
Tapue 5.—7-Day Mortality Response of Rats Exposed j
5 Minutes to NO2 Singly and in Combination with | NOz Concentration % Deaths
a CO (25% Carboxyhemoglobin) (ppm)
NOz NOz + CO
NO: Concentration % Deaths
m,
(ppm) 260 7
NO NO: + CO 550 27
580 0
a 590 0
90 260 10 849 7
YY (Mice) 270 , 0 850 °
550 40 950 7
le Exposed to HCl 580 0 1,200 40
ith CO. 590 30 1,250 13
750 20 1,380 AT
840 30 1,500 53.
icity of HCl is 850 30 . . 1,990 20
of HF. The 1,000 40 2, 280 74
using death in 1,200 50 2, 560 67
0% deaths were 1,250 90 2,950 74
ntration tested 1,380 100 208 100 98
r of magnitude 1,660 80 ?
LCs . 831 ppm 1,140 ppm LCso 1,880 ppm 1,644 ppm
s resulted from 95% Confidence 556-1, 240 720-1, 707 95% Confidence 1, 845-2, 1, 203-
within 12 hours Limits ppm ppm Limits 626 ppm 2,247 ppm

hibited pulmo-



chloride is definitely less toxic to rats than is HF,
but, in mice, the effective range of lethal response
to HCl overlaps that of HF. It should be noted
that the range of HCl concentrations which had
to be used was much wider than that with HF.

Tante 2.—7-Day Mortality Response of Mice Exposed
5 Minutes to HF Gas Singly and in Combination with
CO (25% Carboxyhemoglobin)

HF Concentration
(ppm)

% Deaths

HF HF + CO

2,430 0
4, 480 7
4, 500 33
6, 220 33
7,410 60
7,615 67
8,140 53
8,760 93
10, 190 100
11,010 100

LCio 6,247 ppm 6,670 ppm
95% Confidence | 4, 789-8, 149 5, 690-7, 807
Limits ppm ppm

60,000

Oo HCI +CoO e a
@ Hcl Oo

50,000

ppm
HCI

40,000

30,000 F

10% 50 90
Y% MORTALITY (Rats)

Fioure 4. Five Minute LCs for Rats Exposed to HCl
Singly and in Combination with CO.

Tape 3—7-Day Mortality Response of Rats Exposed
5 Minutes to HCl Vapors Singly and in Combination
with CO (25% Carboxyhemoglobin)

HCI Concentration % Deaths
(ppm)
HCI HCl + CO
30, 000 0
32, 000 10
33, 980 10
39, 850 60
42, 460 80
45, 200 70
49, 580 100
56,046 | 90
57,290 90
59, 280 100
LCss 40,989 ppm 39,010 ppm
95% Confidence | 34, 803-48, 35, 049-43,
Limits 272 ppm 419 ppm
30,000 OHCI+co
@ Hcl oof

L 1
lo 50 90

% MORTALITY (Mice)

Fievbe 5. Five Minute LC» for Mice Exposed to HCl
Singly and in Combination with CO.

Consequently, the 5-minute toxicity of HCl is
much less predictable than that of HF. The
lowest. concentration of HCl causing death in
mice was 3,200 ppm; however 100% deaths were
not achieved at the highest concentration tested
(30,000 ppm), which was an order of magnitude
greater.

Most. NO,-induced animal deaths resulted from
pulmonary edema and were seen within 12 hours
postexposure; a few animals exhibited pulmo-

Le
95



lowing exposure to CO. The exposure to CO
resulted in 25% COHb for one group of rats and
50% COHb for the second group. The results
of these exposures were no different from those
in which the CO and HCN were used simulta-
neously, The data are presented graphically in
Figure 8 for rats, and in Figure 9 for mice.

0 HCN+CO
@ HCN

600} © 25% Pre COHb
4 50% Pre COHb Y

500 + e VE:

oO.
“eon
400 +
J °
Wii

300F

7
200 i 30 30

% MORTALITY (Rats)

Fiavre 8. Five Minute LC» for Rats Exposed to HON
Singly and in Combination with CO,

The CO exposure superimposed on the indi-
vidual contaminant exposures might have re-
sulted in more rapid responses, i.e., a decrease
time to death. Such a response would be im-
portant in consideration of potential hazards
for aircraft passengers. We compared the mor-
tality time data o. single and combined exposures
and found no significant differences or trends.

These acute studies show that the toxicity
ranking of the four materials tested is HCN,
NO., HF, and HCl, in decreasing order. How-

*

O HCN+ CO
@ HCN

400-

300

Ppm
HCN

200

1 1
10 50 90

100 y

% MORTALITY (Mice)

Fioure 9. Five Minute LC» for Mice Exposed to HCN
Singly and in Combination with CO.

ever, the hazard rating of various plastic formu-
lations would require experimental determina-
tion of the amounts of these materials produced
by pyrolysis of comparable quantities (ie., al-
though the combustion of 100 pounds of a
eyanide-containing plastic might produce con-
centration of 200 ppm HCN in an aircraft cabin,
it is possible that the combustion of some chlo-
ride-producing plastic might yield cabin con-
centrations as high as 50,000 ppm; in this event
the chloride-containing plastic would present the
greater hazard).

We have shown in these experiments that car-
bon monoxide concentrations which are not
hazardous to life do not enhance the toxic re-
sponse to the four substances tested. Some LOso
values for CO combined with another toxic com-
pound are slightly lower than those of the com-
pounds alone . However, the series of exposures
of rats to NO, with 25% carboxyhemoglobin
established prior to exposure indicates that there
is neither a trend toward enhancement of tox-
icity, nor a protective value, but that the results
vary randomly to the extent which one would
expect from repeated series of 5-minute LCso
values for the various compounds.



—

TECHNICAL REPORT STANDARD TITLE PAGE

T. Report No. 2. Government Accession No. 3, Recipient's Catalog No.
FAA-AM-71-41
4. Title ond Subtitle 3, Report Date

THE ACUTE TOXICITY OF BRIEF EXPOSURES TO HF, HC1, NOo November 1971
AND HCN SINGLY AND IN COMBINATION WITH CO

6. Performing Orgonizotion Code

7. Author(s) 8. Performing Organization Report No.

E, Arnold Higgins, Ph.D.; Vincent Fiorica, Ph.D. ;
A, A. Thomas, M.D.; Harvey V. Davis, Ph.D.

9. Performing Organization Nome and Address 10. Work Unit No.
FAA Civil Aeromedical Institute
P. 0. Box 25082 11. Contrect or Grant No.
Oklahoma City, Oklahoma 73125 14C-60027-D

13. Type of Report and Period Covered

12. Sponsoring Agency Name ond Address

Office of Aviation Medicine OAM Report
Federal Aviation Administration
800 Independence Avenue, S.W, T4.” Sponsoring Agency Code

Washington, D.C. 20591

15. Supplementary Notes
The work reported in this manuscript was done under task No. AM-B-71-PHY-41,

Contract No. 1AC-60027-D.

16. Abstract
Experiments were conducted with animals to determine the toxic effect of short-term
exposures to some of the products produced in aircraft fires; the products were
tested both singly and in combination with carbon monoxide, These studies show
the toxicity rankings of the four materials tested to be HCN, NO2, HF and HC1,
in decreasing order. Carbon monoxide concentrations which alone are not
hazardous to life do not enhance the toxic response to these substances.

|
| 47. Key Words 18. Distribution Statement
Aircraft Figgs, Pyrolysis Products, Availability is unlimited. Document may
Toxic Gases, Lethal Concentration be released to the National Technical
( (LC5q) Information Service, Springfield, Virginia
| 22151, for sale to the public.
| 5 Seconty Clessits (ot his report) 2D. Security Classif. (of this page) 2. No. of Pages | 22, Price
Unclassified Unclassified 8 $3.00

Form DOT F 1700.7 (8-69)



Tasix 7.—7-Day Mortality Response of Rats Exposed
5 Minutes to HON Singly and in Combination with
CO (25% Carboxyhemoglobin)

HCN Concentra- % Deaths
tion (ppm)
HCN HCN + CO
280 i}
283 i)
334 10
357 10
368 20
497 20
504 70
557 70
583 80
690. 100
LOg0 503 ppm 467 ppm
95% Confidence 403-626 ppm 395-553 ppm
Limits

TaBLE 8.—7-Day Mortality Response of Mice Exposed
5 Minutes to HCN Singly and in Combination with
CO (25% Carboxyhemogiobin)

HCN Concentra- . % Deaths
tion (ppm)
HON HCN + CO
188 0
200 9
283 27
288 61
300 40
319 87
357 80
360 87
368 67 "
414 80
427 100
LCs 323 ppm 289 ppm
95 % Confidence | 276-377 ppm 245-340 ppm
Limits

important factor. In aircraft fires, it is pos-
sible that the build up of CO will be faster than
the build up of Sher toxic gases. In order to
determine the effect of prior exposure to CO on
mortality rates of HCN, two separate groups
of rats were exposed to HCN immediately fol-

1800
1600
1400
1200

1000
ppm

“00

600
400

200

Fiaure 6.

3600
3200
2800
2400

2000
ppm

NO;
F600

1200

600 F

400

Figure 7.

—-

F 0 NO,t CO

e No, 7

ni L 1
10 50 30

% MORTALITY (Rats)

Five Minute LC» for Rats Exposed to NO,
Singly and in Combination with CO.

f  GNo,+co a

@ No, e e

L
10 50 90
% MORTALITY (Mice)

Five Minute LC» for Mice Exposed to NO;
Singly and in Combination with CO.

Ic
re
5

ir

mS

nN

Sot he te



The animals were exposed in a dynamic flow
system using a standard Rochester chamber’
modified to present the animals with a precisely-
timed 5-minute inhalation challenge. The modi-
fication consisted of a cage constructed with
gasketed solid ends mounted on a slide track
which ~was installed in one of the plastic panels
on the Rochester chamber. When the desired
contaminant concentration was achieved in the
chamber, the cage containing animals was rapidly
pushed into the chamber and the sealing clamps
were secured. After five minutes of exposure the
procedure was reversed and another experiment
was started by readjusting the contaminant con-
centration.

The animals were observed closely for seven
days following exposure in order to include
among the observations any delayed deaths which
were due to pulmonary edema.

A series of animal exposures was conducted to
determine the concentration of CO required to
produce 25% COHb (a level which produces

TOP
60r
sol

40F

Q Pooled Rats
@ Singie Rats
@ Mice 2

30.-

20

L on
00“ 1000-2000
a 1500

n

200 4000

3000 5000
ppm CO

Fiaure 1. Carboxyhemoglobin Formation in Rodents

Exposed to CO for 5 Minutes.

minor ONS effects in maa but which is not lethal
per se). Initial experimental CO concentrations
were based on calculations made from the human
CO uptake data of Forbes, e¢ al.2 Blood carbo-
xyhemoglobin measurements were made on
pooled blood samples from simultaneously-ex-
posed groups of three or four rats, using the
method of Goldbaum, eé a/.2 The COHb data
for rats are shown in Figure 1. Also shown in
this figure is the average COHb value for 24
mice exposed to a single carbon monoxide con-
centration. Since all animal species have from
0.5 to 1.0% endogenous COHb from hemoglobin
catabolism, this is essentially a 2-point plot show-
ing that the 25% COHb level is achieved in mice
during five minutes of exposure to 1,500 ppm
CO. The 5-minute CO concentration required to
achieve 25% COHb in rats is 2,100 ppm.

All contaminant exposure concentrations were
controlled by continuous monitoring. Hydrogen
fluoride, HCl, and HCN concentrations were
monitored using specific ion electrodes. Air sam-
ples were absorbed into a constant flow of
aqueous reagent solutions made in accordance
with the directions of the electrode manufacturer
for pick-up of the contaminant and optimum
measurement of the ion, Air and solution flow
rates were measured precisely for conversion of
ion concentration to airborne contaminant con-
centration. Calibration curves were prepared by
sampling known concentrations of the specific
ions made from primary standards. The stand-
ards used were NaF, NaCN, and NaCl.

Nitrogen dioxide was analyzed by continuous
spectro-photometric measurement of atmospheric
samples absorbed in Saltzman reagent using an
AutoAnalyzer.°, Calibration curves were pre-
pared by arialytical measurement of standard gas
bag concentrations backed up by standardization
with permeation tubes.”

The LC; values for each series of exposure to
the compounds tested, either singly or in com-
bination with CO, were calculated by the method
of Litchfield and Wilcoxon” using computer pro-
gram techniques. This method results in a slope
calculated by the method of least squares which
results in the lowest Chi square value possible.

Ill, Results and Discussion.

Hydrogen fluoride produced pulmonary edema
of varying degrees of severity in most of the

| a

expose
or sho
the L
comm
seen ¥
LCs.
24 hor
oceurl
tality
in Ta
The I
in Fi;
the F
tistice
attrib
mono:
plotte
data,
value
Ex
value:
39,01
and ¢
was I
great:
Table
for r

TABLE

LCso

95% 1
Lin



THE ACUTE TOXICITY OF BRIEF EXPOSURES TO HF, HCi, NO) AND
HCN SINGLY AND IN COMBINATION WITH CO

I. Introduction.

Recent studies made within the aviation com-
munity illustrate the importance of fire, smoke,
and fumes in the survivability and escape from
aircraft accidents. For example, the Aerospace
Industries Association (AIA)* examined the im-
portance of fire in 539 fatalities which occurred
in 16 impact-survivable accidents. They con-
cluded that fatalities in 12 of these accidents
were the result of the ensuing fire. Another re-
port? showed that during the period 1955-1964,
12 survivable U. S. Air Carrier accidents oc-
curred in which 68 crew members and 596 pas-
sengers either died by fire or received severe
injuries attributable to fire. The same study
also showed that 25 crew members and 269 pas-
sengers died by fire in other accidents which
had some fatalities at impact; the deaths by fire
occurred post-impaét. Snow, eé ai.,? made an ex-
haustive analysis of the human factors data from
three aircraft accidents involving emergency
evacuation, All three accidents were impact-
survivable but 105 of the 261 passengers died by
fire or smoke during attempts to escape the air-
craft after impact. Hasbrook, et a/.,* examined,
in some detail, the evacuation pattern of a sur-
vivable accident in which 16 passengers died
from smoke inhalation and fire.

Comprehensive aircraft safpty necessitates the
rapid evacuation of passengers immediately fol-
lowing impact-survivable crashes. Many such
crashes result in aircraft fires. Since inhalation
of the combustion products of aircraft compo-
nents may present a general toxicity hazard, it
would be wise to select totally nonflammable
materials or, lacking such materials, to select
those having the least toxic combustion products.

¥ Marcey and Johnson of NAFEC have con-
ducted studies’ pf the burning characteristics of
a total of 140 different materials divided into
two groups; one group comprised materials now
in use in air transport, the other, materials which

have been proposed for future use and which dis-
play superior resistance to fire. Also, the Fire
Research Section of the National Bureau of
Standards conducted research for NAFEC on the
smoke and gases produced by burning materials
used in the interior of aircraft.° Neither test,
however, examined the biological effects of the
toxic combustion products found.

Of the interior materials presently in use,
many formulations contain halogen, cyanide, and
nitrogenous moieties which can react during com-
bustion or pyrolysis to form the corresponding
halogen acid gases (HCl and HF), hydrogen
cyanide gas (HCN), and nitrogen dioxide
(NO.). Information has been needed concerning
the toxicity of these materials when exposure is
for a short period of time as might be ex-
perienced in the evacuation of a burning air-
craft. The present study was conducted to
provide this specific information for the gases
HCl, HF, HCN and NO,. In addition, other
experiments were performed to explore the toxic
effects of a simultaneous exposure to each of the
above gases in combination with carbon monoxide
(CO).

This study is not an exhaustive evaluation of
the toxicity of pyrolysis products. It was de-
signed to establish some criteria for evaluating
material in use, or proposed for use, in terms of
some of the more commonly produced, easily
identifiable toxic gases.

IL Experimental Approach.

Ten rats (Wistar) and 15 mice (ICR) per
group were exposed to a series of atmospheric
concentrations of each test material to determine
LCs (Lethal Concentration for 50% of the test
animals) values. Exposed rats weighed from
250 to 275 grams, while mice ranged from 30 to
35 grams. Quality control examinations were

conducted on each shipment of rats and mice
received to assure that healthy animals were used
in the toxicity studies.



AUTHORS

E. Arnold Higgins, Ph.D., Civil Aeromedical Institute, Federal Aviation
Administration, Oklahoma City, Oklahoma.

Vincent Fiorica, Ph.D., Civil Aeromedical Institute, Federal Aviation Ad-
ministration, Oklahoma City, Oklahoma.

A. A. Thomas, M.D., Toxic Hazards Division, 6570th Aerospace Medical Re-
search Laboratory, Wright-Patterson Air Force Base, Ohio 45433.

Harvey V. Davis, Ph.D.,* Toxic Hazards Division, 6570th Aerospace Medical
Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433,

*Harvey V. Davis, Ph.D., now employed with Standard Oil Company of Ilinois,

partment of Industrial Hygiene and Toxicology, 910 S. Michigan Ave., Chicago,
Tilinois 60680.