Technical Report Documentation Page 

1. Report No. 2. Government Accession No. 3. Reciptent's Cotolog No. I 

DOT/FAA/AM-86 /5 

4. Title and Subtitle 5. Report Dote 

- 

INHALATION TOXICOLOGY: VII. TIMES TO INCAPACITATION May 1986 

AND DEATH FOR RATS EXPOSED CONTINUOUSLY TO ATMOSPHERIC 6. Performing Organization Code 

ACROLEIN 

7. Author's) 

VAPOR 

Charles R. Crane, Donald C. Sanders, 

i 

Boyd R. Endocott, and John K. Abbott 

9. Performing Orgonitotion Name and Address 

FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, OK 73125 

12. Sponsoring Agency Name and Address 

Office of Aviation Medicine 

Federal Aviation Administration 

800 Independence Avenue SW. 

Washington, D.C. 20591 

This work was performed under task AM-B-83-TOX-43. 

15. Supplementory Notes 

AAM-114A 

8. Performlng Orgonizotion Report No. 

- 

DOT/FAA/AM-86/ 5 

10. Work Unit No. (TRAIS) 

11. Contract or Grant No. 

13. Type of Report ond Period Covered 

TECHNICAL REPORT 

Oct. 1982 to July 1983 

14. Sponsoring Agency Code 

16. Abstract 

~~ ~ ~~~~ 

Acrolein, an organic aldehyde (CH2=CH-CHO), is extremely irritating to the 

respiratory passages at very low concentrations. It is known to be present 

in the smoke from certain materials used in aircraft cabin interiors and 

could contribute, therefore, to an individual's failure to escape from a 

burning aircraft. In order to assess acrolein's ability to produce physical 

incapacitation in a mammal, laboratory rats were exposed continuously to measured 

atmospheric concentrations of acrolein vapor until they expired. The exposure 

time required to produce lethality was measured, as was the time at which physical 

incapacitation occurred. Incapacitation was defined operationally as loss of 

the ability to walk in a motor-driven wheel, which was enclosed in the exposure 

chamber. Dose-repsonse curves were generated by equating these two endpoints, 

time-to-incapacitation and time-to-death, to the atmospheric acrolein concentration 

via statistically derived regression equations. Experimental results suggest 

that the acrolein dose that will produce physical incapacitation could be 10 to 

100 times greater than has been predicted in the past. The possible relationship 

between the effective toxic doses of acrolein for rats, and those reported for 

humans, is discussed. 

I 

17. Key Words 18. Distribution Statement 

Combustion toxicology; smoke; irritant 

death; aircraft cabin fire. tion Service, Springfield, VA 22161. gas.; time-to-incapacitation; time-to- through the National Technical Informa- This document is available to the public 

19. Security Clossif. (of this report) 20. Security Clossif. (of this pogo) 21. NO. of Pages 22. Price 

Unclassified Unclassified 27 

form DOT F 1700.7 (8-72) Reproduction of completed page authorized 
INHALATION TOXICOLOGY: VII. TIMES TO INCAPACITATION AND DEATH 

FOR RATS EXPOSEP CONTINUOUSLY TC! ATMOSPHERIC ACROLEIN VAPOR 

--" I>NTRODUCT ION 

Acrolein, an unsaturated aliphatic aldehyde ICH,=CH-CHO) ~ is 

a 1::nown product of the thermal decomposition of certain materials 

used in aircraft cabin interiors, and a suspected component of 

the combustion products of others " '. Since lachrymation and the 

irritation of exposed mucous membranes have been reported for 

humans exposed to acrolein concentrations of less than 1 part per 

million ippm), the presence of even small quantities of this 

compound in smo1::e from an inflight. or postcrash fire could be 

postulated to at. least impede passenger escapezz'. . 

In a 1978 study conducted by the Harvard School of Public 

Health, and reported by Burgess4., acrolein was identified in 91 

percent of the 120 building fires that were monitored, and 

reached concentrations 98 times greater than the " tolerable " 

level in over half of these. Jacobs1z;: reported. that ac,ro!ein was 

used as a war gas in World War I. Cases of accidental poisoning 

have also been reported1"? but the possibility that more than one 

toxic gas was involved has precluded the estimation of timeconcentration effects from such data. 

Inhalation studies have been conducted with several animal 

species. Early studies were Lewin7s3." tut-n-of-the-century 

experiments with rabbits and guinea pigs, and Iwanoff7sJ.1 cat 

.studies in 1710. More recent work has utilized rats, mice, rabbi tsp and guinea pigs. SC::ogz2 exposed rats for 3:)- minute ;ser iods 

to acrolein concentrations of 0.1 to (3.7 mg/L (45 to 310 ppm) 

establishing a 3Ct-min LCml:, of 0.3 mg/L 1135 ppm). Salem and 

C~llumbine~.~ exposed mice, guinea pigs, and rabbits ko acrolein 

concentrations of 5,225 mg/m:" (2,330 ppm) and found the lethal 

doses ranged from 70, (:)(X) to 140, OOC) mg =min/m" (31 , 250 to 62, 50(5 

ppm=min). For the same three species, Pattle and Cullumbinel" 

reported the LC:!5tL, to be 24.4 mg/m" (10. 5 ppm) for a 6 - hour expo - 

sure. Other w~rkers~.~. ':!' have explored the biochemical effects 

on, and the adaptation of, rats exposed to extremely low levels 

of acrol ei n. 

Our primary interest was in acrolein .levels that cause irritation sufficient to incapacitate within SO min and that could be 

potentially lethal for persons attempting to escape from a fire 

situation. Our earlier workh with carbon monoxide (CO) and 

hydrogen cyanide (HCN) has shown that time - t o - incapacitation 

(ti 1, as measured with rats in a rotating cage assembly, is a 

useful tool for comparing the relative toxicity of combustion 

1 
MATERIALS AND METHODS 

Animals. Albino rats. a+ Sprague-Dawley origin were obtained 

+ram Charles River Breeding Laboratories? Wilmington, MA. They 

were ordered in a weight: range of 1OC) to 120 g and were held in 

isolation for 8 days prior ta use. Ali were maintained on drink - 

ing water containing 1.5 g/L of sulfathiazole for the first 4 

days, then normal tap water for the remaining 4 days' isolation. 

Rats were fasted avernight before testing in order to establish equivalent metabolic states; just before use, each animal 

was weighed and marked with an identifying color code. 

Exposure chamber desiqn. The animal exposure chamber utilized in this study di-ffers somewhat Qrom that used in previous 

studies; its design is detailed in Figure 1. It was constructed 

of 1/2-in polymethylmethacrylate (PMMA) with internal dimensions 

5i11.8 cm long by 26.2 c:m wide by 50.6 cm high. The twocompartment cylindrical rotatiny cage assembly, 40.6 cm in diameter by 25.0 cm wide, had a plastic mesh floor (perimeter) with a 

perforated internal divider. The cage was suspended across the 

width of the chamber by a central axle attached to the perforated 

divider; the outer chamber walls function a5 the end walls of the 

cage. A door (10 by 10 cm), equipped with gaskets, was installed 

in each side of the chamber at the level of the rotating cage 

floor, to allow rapid insertion or removal of test animals. The 

rotating cage was driven by a 4-rpm geared motor (Dayton model 

3M098) providing a linear (circumferential) velocity of 8.5 cm/s. 

Two plastic-bladed +an5 mounted on opposite sides of the chamber 

provided uniform mixing of the chamber- atmosphere. 

Test atmosphere qeneration. The amount of acrolein required 

for a given experiment was calculated from the desired atmospheric concentration and the enclosed chamber volume, 67.3.5 L. 

A side door was removed from the dry, empty chamber, and the calculated amount of freshly redistilled liquid acrolein was introduced by pipet into a 10-cm glass Petri dish centered on the 

chamber floor. The door was replaced and the fans turned on to 

hasten evaporation and atmospheric mixing; equilibration was 

considered to be complete when a1 1 1 iquid acrolein had evaporated, a period of 15 to 45 min depending on the quantity 

added. A sample of this preexposure atmosphere was then taken 

for analysis. 
1. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

Mixing fan assembly, consisting of DiaytQP model 221033 

motor, 1/15 hp, 5,000 rpm, 120 VQC, (50 Ha, fitted wj th a 

4-bladed, 7 - cm did nylon fan. 

Ventilation holes, 1 2 - mm did, CU~ through em$.er dividtar 

of rotating cage. 

Petri dish, 9-cm did. 

Exposure chamber walls constru&M of %-in (12-mm) thick 

polymethylmethacrylate (PMMA) . Rotating cage assembly, center: dividap and outer rim 

constructed from %-in (6-mm) P"A. 

Gas sampling ports sealed with serum vial stoppers. 

Chamber access port for animal insertism and removgJ. 

Thumbscrew fasteners. 

Polyethylene mesh cover for rqtati ng cap; mesh openings 

are approximately 7-mm square. 

Center divider and support for rokating cgge, 

constructed from %-in (6-mm) thick IPMMA. 

Cage drive motor; Dayton mq#@.L 3m)C,?8, 4 rpm, 120 VAG, 

60 Hz. 

Cross supports for chambw- rims and' plastic mesh 

perimeter. 

3 
~crolein analysis. The routine measurement of dCfOlein 

concentration in the chamber was accomplished gas chromatograph - 

ically (GC). The accuracy of this GC technique was verified 

originally, and rechecked periodically, by analysis of duplicate 

standard and test gas samples using a second, independent spec - 

trophotometric analytical technique. The differences in results 

obtained by the two methods never exceeded S percent. 

The GC method cteilized a 12-ft by 1/8-in column of F'orapak 

Q, a nitrogen gas carrier flow of 3:) mL/min, an oven temperature 

of 2i(2 OC, and a hydrogen flame ionization detector. The reten - 

tion time for acrole.in ctnder these conditions was 4.95 min. 

Samples af chamt,er atmosphere were ta1::en for this analysis 

in a glass syv-i nge arid used i mmedi ate1 y to f 1 ussh and fi 11 a 2OcSmicroliter (pL) gas c.ample loop on the GC. The areas of the 

resulting ac'rolein peaks were measured with an electronic inte - 

grator and converted ta equivalent parts- per - million in the 5ampled atmosphere by means of a standard curve. 

The acrolein standard curve, consisting of three to five 

concentration points, was constructed daily using the following 

procedure. A 30- to 5;(:)-pL a1 iquot of freshly redistilled acrolein was cirawn int-.cl a Hamilton GC syringe and the needle tip 

inserted int,;~ a small cork:: disk to prevent evaporation. The 

corked syrinqe was ke(;ighed to the nearest 0.01 mg, the cork:: disk 

removed, and the acr-olein sample immediately injected into a 

plastic h9.g (saran f ilm) that had been previously evacuated and 

f i 1 led w1 th a known volume of air. The syringe - cork assembly was 

then r2weighed, and the quantity of acrolein that had been added 

to tkle bag was calcu Lated by difference, the concentration being 

eXpressed as ppm (voE~..!me/volume) at ambient temperature and 

Pr.ess;ure. 

A separate gas s;tmple bag was prepared by this procedure for 

each point on the starldard curve. Each bag was then 1::neaded 

gently to mi:.: the contents, and a syringe sample was removed and 

used to fill the 'Zlc:)C)-pL GC gas sample loop. The areas 04 the 

resulting acrolein peaks were quantified by an electronic inte - 

grator and plotted against concentration. The equation for the 

resulting standard CL\;rVE? was calculated by a linear least- squares 

regression, and the c,oncentrations of unknown samples were then 

calculated using that eqL!ation. 

The procedure tha'c was used to confirm the performance of 

the GC method is based on the quantitative conversion of acrolein 

to its 2,4-dinitrophenylhydrarone (2,4-DNP) followed by spectro - 

photometric assay of' this highly colored derivative " . One prob - 

lem associated with tPte quantitative Conversion of trace amounts 

(micromolar) of lov~ mcllecular weight aldehydes to theif corresponding 2,4-DNP dE!ri\latives is that the solubility of the 2,4- 

DNP in an aqueous medi um is sufficient to prevent the reaction 

4 
.from proceeding to completion. To force the reaction to completion, we employed a modification of the procedure suggested by 

derivative is continuously extracted into a nonaqueous (iso - 

octane) layer. The details of this analytical procedure are 

presented in the Appendix. 

Sel i m2r-s , which utilized a two-phase reaction medium in which the 

The concentration of acrolein in the chamber atmosphere was 

plotted as a function of exposure time for each experiment. The 

areas under this curve, from time=(:) to t, and to td, were inte - 

grated to obtain C=t products (concentration X exposure time) for 

both incapacitation and death, C=ti and C.ta. An average concentration for each exposure was then calculated as the quotient of 

C=t divided by the appropriate response time; e.g., the average 

concentration for incapacitation equals C=t, divided by ti. 

Animal exposure procedure. Once the test atmosphere had 

reached equilibrium, a chamber air sample was collected and analyzed gas chromatographically for acrolein concentration. The 

cage rotation and fan motors were turned off , and a fasted, 

weighed rat was inserted into the cage. The chamber door was 

immediately sealed, the exposure timer activated, and the cage 

and fan motors restarted. 

After an elapsed time of 1 min, a second chamber air sample 

was withdrawn for GC analysis to determine the new equilibrium 

concentration. Additional samples were collected for analysis at 

9- to 10-min intervals throughout the exposure, this being the 

time required for all major peaks from the previous injection to 

clear the EC column. 

Time-to-incapacitation was recorded as the elapsed time at 

which the rat could no longer perform the coordin,ated act of 

wall.::iny in the rotating cage--the animal would begin stumbling, 

sliding, or tumbling. Cage rotation was stopped at ti, and the 

rat was observed until visible signs of breathing ceased; this 

time interval (from initiation of exposure) was called t,. A 

final chamber atmosphere sample wa5 collected f.ollowing the rat's 

death to provide a complete time- concentration record for the 

e:.: posure per i od. 
RESULTS AND DISCUSSION 

A total of 22 rats were exposed, one at a time, to selected 

concentratlons of acrolein in air. The observed response times, 

t, and ta, are listed in Table 1 along with the Ct-product calcu - 

lated for each response time, and the average concentration calculated as the area under the Ct-curve divided by the response 

time. 

Visual ly observed behavioral responses, in addition to t, 

and t,.:., can be summarized best as general observations made at 

different acrolein levels. 

At conc,entrations between 500 and 750 ppm, the rats exhib - 

ited immediate agitation and rubbing of the nose (with forepaws) 

when inserted into the chamber, followed by normal wa1k:ing in the 

rotating cage. Gasping was noted at about 15 min, and abnormal 

walking (crawling, sliding, etc.) began at about 30 min. The 

t., ‘5 ranged +ram 27 to 36 min. Convulsions preceded death by 1 

to 2 min; no cyanosis of the extremities was observed, 

At concentrati on5 around 1 , (:)(X) ppm, gasping began at 3 to 6 

min, becoming severe by 6 to 11 min. Wa1C::ing appeared normal for 

the first 6 to 10 min, after which there would be alternating 

periods of crawling and wa1l::ing--this crawling was a sufficiently 

coordinated type of locomotion that it was not scored as incapac - 

itation. The t3.’S occurred in the range 14 to 20 min, and severe 

convulsions began about 1 min before death. 

At the 10: 000-ppm level , yaspi ng began by I. 5 to 2.5 mi n. 

Between 4 and 5 min the animals became hyperactive (running, 

climbing, frantic grooming, etc.) and occasional tremors or mild 

convulsions were noted during this period of heightened. activity. 

One or more severe convulsions f ol lowed soon after the 5- to 6- 

min t,, with cyamosir; occ~u-ring in a few animals in the interval 

between t, and t.:. Death occurred at 7 to 10 min. 

In the 2C),60(:)-ppm range, the rats became hyperactive immediately on being placed in the chamber; they were gasping by 1.5 

min and cyanotic by 2.C) to 2.5 min. Muscle tremors either pre - 

ceded or coincided with t, , which occurred at 3 to 4 minutes. 

Following incapacitation the cyanosis became more pronounced, 

muscular fasciculation became generalized, and sporadic wholebody convulsions preceded death, which occurred at 6 to 7 min. 

At the highest concentrations, 35,OC)O to 4C),C)(X) ppm, gasping 

was severe by I to 2 min, and even an occasional short convulsion, with recovery, was noted prior to incapacitation. Although 

t, , 2.8 min, was shorter than for the 20,000- ppm exposures, 

behavior was not appreciably different. Cyanosis and fairly 

continuous convulsive activity occurred from t, until death -- 

which was at 4.7 to 4.9 min. 
TABLE 1 

RESFONSE TIMES AND ACROLEIN CONCENTRATIONS* 

Along with the expected decreases in t,, and td that were 

observed with exposure to increasing concentrations of acrolein, 

certain other response patterns became apparent. At concentrations of 1,000 ppm or less, convulsions were noted only just 

prior to death, while at higher concentrations, tremor and convulsions appeared before incapacitation. A surface muscle tremor 

or fasciculation, which differed from the whole-body convulsions, 

was noted at the lC),(:)c:)(:)-pprn level following periods of extreme 

physical activity and was a common observation at the higher 

concentrations, independent of physical exertion. One unexpected 

result was the absence of any evidence of severe eye irritation. 

While "grooming" motions about the nose were common on all experiments, only at the X),c:)(:10-ppm level did any abnormally rapid eye 

b1inl::ing occur, and then only in a single experimental animal. 

7 
All rats' eyes remalned open during the exposure periods, and we 

observed none of the profuse lachrymation that we have noted 

previously in rats exposed to other irritant gases, such as 

hydrogen chloride, or smoke from halogen - containing polymers. 

Figure 2 is a combination scattergraph of the twa measured 

response times, t, and ta as a function of act - olein concentra - 

tion. In this and a11 subsequent figures? response times are in 

minutes and acrolein cancentrations are in parts per thousand 

(ppt). The relationship between time - t o - effect and magnitude of 

the noxious agent is, once again, the familiar rectangular hyper - 

bola that. we have obtained for all toxic gases studied to date 

and al. so for the measure of time-to-cull apse as the result of 

exposure to hyperthermic atmospheres. 

An equation was derived, for each response, that relates - 

time-tu-effect and concentration; this curve fitting was accomplished with the aid of a nonlinear least squares regression 

algorithm proposed by Marq~tardt"~. When the model equation for 

the regression was of the form, 

where y represents response time and :.; represents acrolein con - 

centration, the resulting curves fit the data acceptably well, as 

can be seen in Figures 3 and 4. The log - log, linearized versions 

of these same equations are presented as Figures; 5 and 6. For 

these two equations, the values for the parameters, a, k, and b, 

are a5 follows, 

filthough these equations are acceptably descriptive of the 

experimental data and obviously useful in predicting the con - 

tinuum of response - time versus concentration relationships, and 

despite the fact that the form of the equation is the toxicologically meaningful one of a rectangular hyperbola with nonzero 

asymptotes, the negative sign of the derived values for the 

parameter, b, does present a modeling problem. 

Equation 1 can be rewritten as follows, 

where t... is response time in minutes, and C is acrolein concen - 

tration in ppt. In the biophysical interpretation of this equa - 

tion model, the parameters, a and b, represent the asymptotic 

values for the two ends of the hyperbola; i.e., "a" is the shortest possible response time that can be achieved from exposure to 

an overwhelming concentration and "b" is the lowest acrolein 

concentration that can incapacitate (or k::ill) as the result of an 

8 
60 

58 

40 

30 

20 

18 

+ 

i' 

+ 

o+ + 

0*0+ 

++ + 

000 00 

++ + + 

0 0 

10 20 30 40 50 

Acrolein Concn., ppt 

Figure 2. Times-to-incapacitation (0) and times-to-death (+I 

plotted against the average chamber concentration of acrolein. 

Each point represents one rat, exposed individually; N=22. 

9 
50 

c 

40 

C 

0 

+, 30 

20 c 

I 

0 

+, 

I 

10 20 30 40 50 

Rcrolein Concn., ppt 

Figure 3, Time-to-incapacitation as a function of the average 

chamber concentration of acrolein. Fitted regression equation: 

ti = 1.5 + 40/(C+0.5)3 RSSQ = 238. 

10 
60 

50 

i 

0 

+., 

I 

L 20 

10 

V V 

10 20 30 40 50 

Rcrolain Concn., ppt 

Figure 4. Time-to-death as a function of the average chamber 

concentration of acrolein. Fitted regression equation: 

td = 3.75 + 50/ (C+0.5), RSSQ = 473- 

11 
4 

3 

2 

1 

1 2 3 

Ln(C+B.S) 

4 

Figure 5. Loq-log plot of (ts-l.5) versus (C+O.5), a linearized 

transformation of Fig. 3. Fitted regression equation: 

ln(t-1.5) = ln(40) - ln(C+0.5). 

12 
Figure 6. Log-log plot of (t,-3.75) versus (C+0.5), a linearized 

transformation of Fig. 4. Fitted regression equation: 

ln(t,-3.75) = ln(50) - ln(C+0.5). 

13 
exceedingly long exposure time. Logically, both of these parameters should have positive values, since there could hardly be a 

physiological e+fect from a zero concentration and, correspond - 

ingly, no effect: could result from an exposure of zero minutes. 

The f a.tt that the model equat.i on, [ZI could not be fit to 

thE acrolein data using a positive value for the parameter, b, 

suggests that the specific farm of that equation may be inappro - 

priate, for describing the toxicokinetics of acrolein. A 1il::ely 

possibility is that acrolein is exerting its toxic effect differ - 

entially at two or more specific biological sites and, as a con - 

sequence, the overall effect on response time is a function of 

something other than the first power of the effective concentra - 

tion, (C-b). If the Concentration is functioning at some power 

other than one --that is, if the effective concentration is (Cb) r' where n i 5. not equal to one --then n must have a value that 

lies between zero and one; otherwise the fit with the data gets 

worse rather than better. 

If response time were related to the square root of the 

effective acrolein concentration, the value of n would be 0.5. 

The model equation would then be: 

Fitting this equation to the data resulted in reasonable and 

positive values for the three parameters (a, I::, and b) and a 

residual 5um of squares (RSSQ) that was smaller than with equa - 

tion C27. (The RSSQ is a measure of the "goodne~s of fit " 

between the data and the model equation: the smaller RSSQ repre - 

senting the better fit.) The values for the three parameters in 

equation [SI are as follows, 

Figure 7 is the plot, for equation C33, of t3. as a function of 

concentration, and Figure 8 is that for ta. The corresponding 

log - log transformations are shown in Figures 9 and 10. 

Reasonable predictions of response time for a given acrolein 

concentration can be made using either equation E21 or equation 

C31, provided one does not exceed the concentration limits utilized in the study. However, the values obtained for the coefficients in equation E31 should be more meaningful in the physio - 

logical sense. Comparison of the values from the two equations 

suggests, for example, that the limiting (asymptotic) response 

times are more likely to be 0.1 and 1.0 minutes rather than 1.50 

and 3.75 minutes (for t, and td respectively), and the limiting 

effective concentration for infinite exposures is milch more 

1 i kel y to be 300 ppm than a neqative 50(3 ppm. 

14 
. . . I 

0 

. 10 20 30 40 50 

Acrolein Concn., ppt 

Figure 7. Time-to-incapacitation as a function of the square 

root of the effective acrolein concentration. Fitted regression 

equation: e, = 0-1 + 18/J(C--0.3), RSSQ = 141. 

15 
h, 

Acrolefn Concn., ppt 

Figure 8. Time-to-death as a function of the square root of the 

effective acrolein concentration. Fitted regression equation: 

td = 1 .O + 25/J(C-0.3), RSSQ = 533. 

16 
4 

3 

2 

1 

. . . . . 

Figure 9. Log-log plot of (t%-O=l) versus J(C-0.31, a linearized 

transformation of Fig. 7. Fitted regression equation: 

ln(t*-O,l) = ln(18) - %ln(C-0-3). 

17 
4 

3 

P 

0L 

-2 

. e L a . -1 0 1 2 3 4 

Figure 10. Log-log plot of {t--l.C)) versus -J(C-O.3), a linearized trans+ormation of Fig. 8. Fitted regression equation: 

ln(tcr-l.O) = ln(25) - Yln(C-0.3). 

18 
We have been unable to locate in the scientific literature 

any other studies of the incapacitating effects of acute exposures to acrolein using rats as subjects. However, since this 

study was completed (in 1981) there has been a report by Kaplan 

et a1 . x of acute exposures using baboons as subjects. In this 

study, baboons were exposed to known concentrations of acrolein 

far 5 min and then given the opportunity to physically escape 

from the exposure chamber. For all acrolein concentrations 

tested, up to a maximum of 2.78 ppt, the subjects escaped 

successfully; i.e., there were no instances of physical incapacitation. If equation C31, derived for rats, can be applied to 

baboons, it would predic.t a time-to-incapacitation of 11.5 min 

for baboons exposed to 2.78 ppt acrolein. 

Salem and Cull~tmbine~.~ found that lethal exposure times 

ranged from 13 to 27 min when mice, guinea pigs, and rabbits were 

exposed to an acrolein concentration of 5,225 mg/m", .whic'h ,would 

be equivalent to approximately 2,300 ppm acrolein depending on 

the ambient atmospheric pressure and temperature. This is reasonable agreement with a t, of 18.7 min predicted from equation 

C33 for a rat exposed to 2.9 ppt. 

Since the acrolein concentration-response time relationship 

derived from our experimental data can predict, within an acceptable margin, the response times for three other rodent species, 

andr since it is not inconsistent with data obtained from baboon 

exposures, it would seem reasonable that it could be used to 

approximate human exposure responses. 

There are no documented dosages for lethal or truly incapaci tating human expos~tres; however , Alarie et dl. J. have suggested 

that human exposure to 20 ppm would be lethal-- or at least would 

result in extremely severe injury to the respiratory tract. The 

most common statement in the literature, however, seems to be 

that exposure to IC) ppm or more would prove lethal for humans " in 

a few minutes" or "in a short time"x*r3e These predictions 

that 10 to 20 ppm could be incapacitating or lethal in a few 

minutes are not reconciled easily with the reported animal experiments in which concentrations 1CKI times greater are required to 

achieve a response time of about 10 min. 4 possible explanation 

is that the acrolein toxicity previouely predicted for humans is 

an overly conservative estimate based on (dis)com+ort indices as 

endpoints rather than on actual incapacitation or mortality -- as 

we suspect is also the case for hydrogen chloride gas-/. 

19 
SUMMARY AND CONCLUSIONS 

Rats were exposed in the Civil Aeromedical Institute (CAM11 

Inhalation toxicity assay system to selected atmospheric concentrations of acrolein vapor in air; these concentrations ranged 

from 53C) ppm to over 40,(:)00 ppm. The CAM1 system uti1 ires an 

enclosed rotating wheel that allows the measurement of a physical 

incapacitation endpoint as well as the traditional one of mortality. These two endpoints were measured as time-to-incapacitation 

(t,') and time-to-death (tal; the measured response times ranged 

from. 2.8 to 56.2 min. Results were graphed as scatterplots 

(response time vcrsc~s acrolein concentration) and regression 

equations were fitted to each data set using a nonlinear least 

squares technique. The resulting response equations are: 

t, = 0. 1 c 18/(C-0.3)':.'-m +or incapacitation and 

t, = 1.0 + 25/ (C-C:).~)'::'-- +or lethality, 

where response times are in minutes and acrolein concentrations, 

C, are in parts per thousand. 

These results suggest that acrolein, an almost universal 

component of smol.::e, is not so incapacitating a5 had been previously thought. Concentrations necessary to produce incapacitation in 10 min are 1ik:ely to be 10 to 100 times greater than 

those suggested by the scientific literature. 
REFERENCES 

1. Alarie Y, t!:'.ane L, Barrow C. Sensory Irritation: The Use of 

an Animal Model to Establish Acceptable Exposure to Airborne 

Chemical Irritants. In: Reeves AL, ed. Toxicoloav: F'rinciples and Practice, Vol. I. New York: John Wiley and Sons, 

1981: 48-92. 

2. American Conference of Governmental Industrial Hygienists. 

Threshold Limit Values for Chemical Substances and Physical 

CSaents in the Workroom Environment. Cincinnati, OH: ACGIH, 

1977. 

9. Pouley 6, Dubreuil A, Godin J, Eoisset M, Boudene CL. Phenomena of Adantation in Rats Continuously Exoosed to LowConcentrations of Acrolein. Ann. Occr-rp. Hyg. 1976; 

19:27-32. 

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AFF'END I X 

Spectrophotometric Assay 04 Acrolein As Its 

2,4--Rinitrophenylhydrazone 

Acrolein that was to be used in the preparation of aqcreo~rs 

standards was purified daily by distillation. Its significant 

volatility required special handling during the preparation of 

liq~id standards; therefore, the approxima.te required volumes 

(0.i to 0.2 ml) were transferred by pipet to tared, glass weighing bottles (with ground-glass stoppers) and reweighed to the 

nearest. 0.01 mg. These small--diameter weighing bottle.; were of- a 

size that would al. low them to drop freel y dawn the neck of a 500- 

mL volumetric 1: 1asC::. The volconetric flask was f i 1 led to the 

calibration mark with deionized water and a volume of water equal 

to the volume of acrolein ta be added was withdr- awn by pipet. 

The weighing bottle was held over the 41asl:: mouth, the cover was 

loosened, and the bottle, contents, and cover were dropped into 

the water. The 41ask wa.5 str~ppered immediately and the contents 

mixed by repeated inversion. Wori::ing standards were prepared by 

dilution from this solution into additional 500-mL Qlasks; this 

approach allowed relatively large volumes (10 to 25 mL) of stock:: 

standard to be transferred, which minimized the relative magnitude of: pipetting errors. These transfers and subsequent dilu - 

tions to volume were accomplished quickly to minimize acrolein 

loss due to vaporization. 

The 2,4-dini trophenyl hydrar ine reagent. was prepared dai 1 y 3.5 

a saturated solution in 2N aqueous hydrochloric acid (HC1); the 

solution was filtered immediately prior to use. 

IEjooctame (2,2,4-trimethylpentane) used to extract the 2,4- 

DNF', was chromatagraphic quality analytical reagent grade (Mal-- 

1 inci::rod% Chr-amARS = 

The spectrophotometric analysis of aqueous acrolein standards was accompl ished by mixing, in a screw-cap glass centrifuge 

tube, 3 mL of the standard with 1 mL a4 saturated 2,4-dinit.r0- 

phenylhydrazine (in 2N HC1) and adding 10 mL of isooctane. The 

reaction tube was capped and shaken vigorouf;ly at S-min intervals 

over a 20-min period. A+ter the final sha\::ing, the tube was 

allowed to stand until the two layers Rad separated, then allowed 

to stand for an additional 5 min. The isooctane layer was then 

removed from the aqueous layer and centrifuged to remove the last 

trace of suspended water droplets,. Absorbance of the isooctane 

solution was measured in a quartz cuvette at 350 nm against a 

reagent blank::. The resulting absorbances were used to construct 

a standard curve by plotting absorbance against acrolein concentration. 
Gaseour; samples;, either of known concentration from the 

Saran bags or of unk:nown concentration from the e:.:posctre chamber, 

were obtained by withdrawing a 15-mL aliquot of the appropriate 

atmosphere into a 30-mL glass syringe, followed immediately by 15 

mL of deionized water. The syringe needle was replaced with a 

cap and the syringe shaken intermittently for 30 min. All samples'were kept in the capped syringes until they could be analyzed for acrolein using the spectrophotometric procedure 

described above for aqueous standards. Acrolein concentrations 

equivalent to the measured absorbances were calculated using the 

eqctati c3n derived' from the aqueous standard curve. 

A2