1 NAC Proposed 1: October 2009

2 

3 

4 

5 ACUTE EXPOSURE GUIDELINE LEVELS (AEGLs) 

6 FOR

7 AUTOMOTIVE GASOLINE (UNLEADED)

8 (CAS Reg. No. 86290-81-5; 8006-61-9) 

9 

10 

11 

12 

13 

14 PROPOSED 

15 

16 

17 

18 

19 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 2 of 41 

1 PREFACE 

2 

3 Under the authority of the Federal Advisory Committee Act (FACA) P. L. 92-463 of 

4 1972, the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous 

5 Substances (NAC/AEGL Committee) has been established to identify, review and interpret 

6 relevant toxicologic and other scientific data and develop AEGLs for high priority, acutely toxic 

7 chemicals. 

8 

9 AEGLs represent threshold exposure limits for the general public and are applicable to 

10 emergency exposure periods ranging from 10 minutes to 8 hours. Three levels – AEGL-1, 

11 AEGL-2 and AEGL-3 – are developed for each of five exposure periods (10 and 30 minutes, 1 

12 hour, 4 hours, and 8 hours) and are distinguished by varying degrees of severity of toxic effects. 

13 The three AEGLs are defined as follows: 

14 

15 AEGL-1 is the airborne concentration (expressed as parts per million or milligrams per 

cubic meter [ppm or mg/m3 16 ]) of a substance above which it is predicted that the general 

17 population, including susceptible individuals, could experience notable discomfort, irritation, or 

18 certain asymptomatic, non-sensory effects. However, the effects are not disabling and are 

19 transient and reversible upon cessation of exposure. 

20 

AEGL-2 is the airborne concentration (expressed as ppm or mg/m3 21 ) of a substance above 

22 which it is predicted that the general population, including susceptible individuals, could 

23 experience irreversible or other serious, long-lasting adverse health effects or an impaired ability 

24 to escape. 

25 

AEGL-3 is the airborne concentration (expressed as ppm or mg/m3 26 ) of a substance above 

27 which it is predicted that the general population, including susceptible individuals, could 

28 experience life-threatening health effects or death. 

29 

30 Airborne concentrations below the AEGL-1 represent exposure levels that could produce 

31 mild and progressively increasing but transient and nondisabling odor, taste, and sensory 

32 irritation or certain asymptomatic, non-sensory effects. With increasing airborne concentrations 

33 above each AEGL, there is a progressive increase in the likelihood of occurrence and the 

34 severity of effects described for each corresponding AEGL. Although the AEGL values 

35 represent threshold levels for the general public, including susceptible subpopulations, such as 

36 infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized 

37 that individuals, subject to unique or idiosyncratic responses, could experience the effects 

38 described at concentrations below the corresponding AEGL. 

39 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 3 of 41 

1 TABLE OF CONTENTS 

2 PREFACE.....................................................................................................................................................2

3 LIST OF TABLES........................................................................................................................................5

4 SUMMARY..................................................................................................................................................6

5 1. INTRODUCTION................................................................................................................................8

6 2. HUMAN TOXICITY DATA...............................................................................................................9

7 2.2.1. Odor Threshold............................................................................................................................9

8 2.2.2. Clinical Studies..........................................................................................................................10

9 3. ANIMAL TOXICITY DATA............................................................................................................12

10 3.1. Acute Toxicity ...........................................................................................................................13

11 3.2. Repeat-Exposure Studies...........................................................................................................14

12 3.3. Neurotoxicity.............................................................................................................................17

13 3.4. Developmental/Reproductive Toxicity......................................................................................18

14 3.5. Genotoxicity ..............................................................................................................................19

15 3.6. Chronic Toxicity/Carcinogenicity .............................................................................................19

16 3.7. Summary....................................................................................................................................20

17 4. SPECIAL CONSIDERATIONS ........................................................................................................20

18 4.1. Metabolism and Disposition......................................................................................................20

19 4.2. Mechanism of Toxicity..............................................................................................................21

20 4.3. Structure-Activity Relationships ...............................................................................................22

21 4.4. Other Relevant Information.......................................................................................................22

22 4.4.1. Species Variability ................................................................................................................22

23 4.4.2. Susceptible Populations ........................................................................................................22

24 4.4.3. Concentration-Exposure Duration Relationship ...................................................................22

25 4.4.4. Concurrent Exposure Issues..................................................................................................23

26 5. DATA ANALYSIS FOR AEGL-1 ....................................................................................................23

27 5.1. Summary of Human Data Relevant to AEGL-1........................................................................23

28 5.2. Summary of Animal Data Relevant to AEGL-1........................................................................23

29 5.3. Derivation of AEGL-1...............................................................................................................23

30 6. DATA ANALYSIS FOR AEGL-2 ....................................................................................................24

31 6.1. Summary of Human Data Relevant to AEGL-2........................................................................24
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 4 of 41 

1 6.2. Summary of Animal Data Relevant to AEGL-2........................................................................24

2 6.3. Derivation of AEGL-2...............................................................................................................24

3 7. DATA ANALYSIS FOR AEGL-3 ....................................................................................................25

4 7.1. Summary of Human Data Relevant to AEGL-3........................................................................25

5 7.2. Summary of Animal Data Relevant to AEGL-3........................................................................26

6 7.3. Derivation of AEGL-3...............................................................................................................26

7 8. SUMMARY OF AEGLs....................................................................................................................26

8 8.1. AEGL Values and Toxicity Endpoints......................................................................................26

9 8.2. Comparison with Other Standards and Guidelines....................................................................27

10 8.3. Data Adequacy and Research Needs .........................................................................................28

11 9. REFERENCES...................................................................................................................................28

12 APPENDIX A: Major Hydrocarbons found in Gasoline Vapor................................................................33

13 APPENDIX B: Derivation of Level of Odor Awareness...........................................................................34

14 APPENDIX C: Derivation of Gasoline AEGLs ........................................................................................35

15 APPENDIX D: Category Graph of AEGL Values and Toxicity Data for Gasoline..................................37

16 APPENDIX E: Derivation Summary for Gasoline AEGLs.......................................................................39
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 5 of 41 

1 LIST OF TABLES 

2 

3 TABLE S 1. Summary of AEGL Values for Gasoline ................................................................................7

4 

5 TABLE 1. Chemical and Physical Properties...............................................................................................9

6 TABLE 2. Odor Detection and Odor Recognition Thresholds for Gasoline..............................................10

7 TABLE 3. Clinical Study with Gasoline and Gasoline Vapor (Drinker et al. 1943)..................................11

8 TABLE 4. Clinical Study with Gasoline Vapor (Davis et al. 1960)..........................................................11

9 TABLE 5. Acute Toxicity of Gasoline Blending Stream Vapor to Rats ...................................................13

10 TABLE 6. Repeat-Exposure, Subchronic and Chronic Exposure, Developmental Toxicity, and 

11 Genotoxicity Studies with Gasoline Vapor........................................................................................15

12 TABLE 7. AEGL-1 Values for Gasoline Vapor........................................................................................24

13 TABLE 8. AEGL-2 Values for Gasoline Vapor........................................................................................25

14 TABLE 9. AEGL-3 Values for Gasoline Vapor........................................................................................26

15 TABLE 10. Summary of AEGL Values for Gasoline Vapor ....................................................................26

16 TABLE 11. Standards and Guidelines for Gasoline Vapor ........................................................................27

17 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 6 of 41 

1 SUMMARY

2 

3 Automotive gasoline (CAS No. 86290-81-5) is a clear, amber colored volatile and 

4 flammable liquid with a characteristic odor. The most serious immediate hazard from the 

5 accidental release of gasoline is the threat of fire or explosion. Gasoline is a complex substance 

6 made by blending various refinery streams containing many hydrocarbon components. The 

7 hydrocarbons consist of paraffins, cycloparaffins and aromatic and olefinic hydrocarbons having 

8 carbon numbers predominantly in the C3 to C11 range. Composition is variable depending on the 

9 crude oil or petroleum source, refining facilities, and total petroleum product demand. Carbon 

10 numbers in gasoline vapor range from C4-C6. The major hydrocarbon found in gasoline vapor is 

11 isopentane (C5H12, 34%). Automotive gasoline may also contain oxygenates such as ethanol or 

12 ethers and proprietary additives. 

13 

A level of distinct odor awareness (LOA) of 7.4 ppm (approximately 22 mg/m3 14 ) was 

15 calculated for a gasoline blend comprised of summer and winter blends. The LOA represents the 

16 concentration above which it is predicted that more than half of the exposed population will 

17 experience at least a distinct odor intensity, and about 10% of the population will experience a 

18 strong odor intensity. The LOA should help chemical emergency responders in assessing the 

19 public awareness of the exposure due to odor perception. 

20 

21 Relatively high concentrations of gasoline vapor may be irritating to the eyes. Data on 

22 sensory irritation were available from a clinical study. At sufficiently high vapor concentrations, 

23 gasoline is neurotoxic, inducing narcosis. Data were available on acute, repeat-exposure, 

24 subchronic exposure, neurotoxicity, reproductive and developmental toxicity, and chronic 

25 toxicity/carcinogenicity. Most of these studies used the rat as the animal model. Results of the 

26 available toxicity studies indicate that various blending streams of gasoline have similar toxicity. 

27 

28 The AEGL-1 is based on the sensory irritation study of Davis et al. (1960) in which 

29 volunteers were exposed to three different blends of gasoline vapor on separate occasions. Each 

blend was tested at approximately 880, 2200, and 4400 mg/m3 30 for 30 minutes. The 30-minute 

exposure to all three blends of gasoline vapor at 2200 mg/m3 31 produced subjective eye irritation 

32 at a higher incidence (15/30 subjects) than under control conditions (1/20 subjects). The 

33 incidence of objective eye irritation, although scored as slight (+1 on a scale of 1 to 4), was 

higher in the 2200 mg/m3 34 group (15/30) than in the control group (2/20). Incidences of ocular 

35 tearing were similar in this group (3/30) and the control group (2/20). Incidences of subjective 

36 and objective eye irritation, including tearing, were higher at the higher concentration of 4400 

mg/m3 37 . Because the eye irritation when measured objectively was slight (less than marked), an 

38 intraspecies uncertainty factor of 3 (instead of 10) was applied to protect sensitive subjects. 

39 There is adaptation to the slight irritation that defines the AEGL-1. Therefore, the same value of 

730 mg/m3 (2200 mg/m3 40 /3) was used across all exposure durations. 

41 

42 Although anecdotal human experience indicates acute inhalation of high concentrations 

43 can cause acute neurological effects (gasoline sniffers), tested concentrations in rodent studies of 

44 acute duration were not high enough to induce narcotic effects. The acute studies were 

conducted for 4 hours at the limit concentration of 5000 mg/m3 45 . The AEGL-2 values were based 

46 on the subchronic study of Schreiner et al. (2000) in which male and female Sprague-Dawley 

rats inhaled 22,500 mg/m3 47 gasoline vapor (whole-body) for 6 hours/day, 5 days/week for 13 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 7 of 41 

1 weeks. This concentration was the highest tested concentration in the subchronic studies. At 

2 this concentration, the rats failed to show clinical signs indicative of neurotoxicity during 

exposure. The point of departure, the 6-hour exposure to 22,500 mg/m3 3 , was divided by 

4 interspecies and intraspecies uncertainty factors of 1 and 3, respectively for a total uncertainty 

5 factor of 3. An interspecies uncertainty factor of 1 is sufficient because solvent uptake is 

6 generally greater in rodents than in humans based on higher blood:air partition coefficients for 

7 related hydrocarbons. In addition, the higher respiratory rate and greater cardiac output in 

8 rodents, on a body weight basis compared with humans, indicates faster uptake. Although 

9 humans differ in the rate at which they metabolize chemicals, the susceptibility of the general 

10 population to central nervous system depressants varies by no more than 2- to 3-fold as indicated 

11 by the minimum alveolar concentration, the concentration of an anesthetic that produces 

12 immobility in 50% of patients. Therefore, an intraspecies uncertainty factor of 3 is considered 

13 sufficient. Higher uncertainty factors would result in values inconsistent with the clinical study 

14 of Davis et al. (1960). Time scaling may not be relevant for hydrocarbons that act as anesthetics 

15 because blood concentrations of the major light components of gasoline rapidly approach steadystate. Therefore, the 6-hour value of 7500 mg/m3

 (22,500 mg/m3 16 /3) was used across all AEGL-2 

exposure durations. The 7500 mg/m3 17 value is supported by the study of Kuna and Ulrich (1984) 

in which no toxic signs were observed in squirrel monkeys exposed to 6350 mg/m3 18 for six 

19 hours/day for 13 weeks. Partially vaporized gasoline was not a reproductive or developmental 

toxicant following repeat exposures to 20,000 to 23,900 mg/m3 20 (McKee et al. 2000; Roberts et 

21 al. 2001).

22 

23 None of the concentrations tested in acute or subchronic studies with rodents resulted in 

24 mortality, and there are no reports of human fatalities from exposure to gasoline vapors. It is not 

25 apparent that concentrations high enough to cause death from inhalation of gasoline vapor can be 

26 attained. Based on the likelihood that lethal concentrations of gasoline vapor cannot be 

27 attained/sustained under ambient conditions, an AEGL-3 was not determined. 

28 

29 The calculated values are listed in the table below. 

30 

TABLE S 1. Summary of AEGL Values for Gasoline

Classification 10-min 30-min 1-h 4-h 8-h Endpoint (Reference)

AEGLB1 

(Nondisabling) 

730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3 Slight eye irritation in 

humans (Davis et al. 

1960) 

AEGLB2 

(Disabling) 

7500 mg/m3

* 

7500 mg/m3

* 

7500 mg/m3

* 

7500 mg/m3

* 

7500 mg/m3

* 

No clinical signs at 

highest tested 

concentration of 

22,500 mg/m3

 – rat 

(Schreiner et al. 2000) 

AEGLB3 

(Lethal) 

Not 

determined 

Not 

determined 

Not 

determined 

Not 

determined 

Not 

determined 

No data** 

*The AEGL-2 value is higher than 1/10 of the lower explosive limit (LEL) of gasoline in air (LEL = 14,000 ppm). 

Therefore, safety considerations against hazard of explosion must be taken into account. 

**A lethal concentration was not attained in the available acute, subchronic, and chronic toxicity studies. Automotive 

gasoline vapor may act as a simple asphyxiant in sensitive individuals at 990,000 mg/m3

. 

31 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 8 of 41 

1 1. INTRODUCTION

2 

3 Automotive gasoline (CAS No. 86290-81-5) is a clear, amber colored volatile and 

4 flammable liquid with a characteristic odor. Gasoline is a complex substance made by blending 

5 various refinery streams with many hydrocarbon components. The hydrocarbons consist of 

6 paraffins, cycloparaffins and aromatic and olefinic hydrocarbons having carbon numbers 

7 predominantly in the C3 to C11 range. Definitions and examples of these classes of chemicals are 

8 provided in Appendix A. Carbon numbers of the major components of liquid gasoline range 

9 from C5-C9. Composition is variable depending on the crude oil or petroleum source, refining 

10 facilities, and total petroleum product demand. Ranges of major hydrocarbons in gasoline 

11 (vol%) are paraffins and cycloparaffins (59-66%), aromatics (26-32%), and olefins (8-9%). 

12 Carbon numbers in gasoline vapor range from C4-C6; at room temperature the C4 hydrocarbons 

13 are gases. The major hydrocarbon found in gasoline vapor is isopentane (C5H12, 35%). 

14 Predominant components found in gasoline vapor and gasoline vapor containing 10% ethanol are 

15 listed in Appendix A. The lighter components, primarily isomers of butane and pentane are 

16 present in the vapor. 

17 

18 Various additives are blended into automotive gasoline (Appendix A). These include 

19 octane enhancers such as methyl t-butyl ether (MTBE; 15% v/v), t-amyl methyl ether (TAME), 

20 ethyl t-butyl ether (ETBE 17% v/v), t-butyl alcohol (TBA), ethanol (EtOH, 10%), and methanol; 

21 antioxidants such as butylated methyl, ethyl, and dimethyl phenols; metal deactivators; ignition 

22 controllers; icing inhibitors; corrosion inhibitors; and detergents/dispersants. These additives 

23 have low vapor pressures. Gasoline sold in the United States is unleaded and contains 10% 

24 ethanol. Ethanol is added at the marketing terminal (ATSDR 1995; API 2002; White 2009). 

25 Chemical and physical properties of automotive gasoline are listed in Table 1. 

26 

27 The commercial production of gasoline begins with crude oil which is refined into the 

28 following fractions: light naphtha, heavy naphtha, kerosene and light gas-oil, heavy gas-oil, and 

29 reduced crude. Each refinery stream has been assigned a CAS number. The light naphtha is 

30 used as a component of finished gasoline without further refining. Heavy oils can be treated by 

31 catalytic or thermal cracking which breaks down the higher boiling hydrocarbons into lower 

32 boiling ones; these can be used as components of gasoline. After various streams have been 

33 blended, sulfur compounds may be removed by hydrogenation. Additives and blending agents 

34 are added to improve the performance and stability of the gasoline. Typical retail gasoline 

35 contains 200-300 compounds. The benzene content of finished gasoline is 1-1.5% (ATSDR 

36 1995; White 2009). European blends of gasoline may contain up to 7.5% benzene (Dutch 

37 Intervention Values 2009). 

38 

39 Gasoline is a high volume commercial product (McKee et al. 2000). U.S. production 

40 volume of motor gasoline in 1989 was 306.6 million gallons/day (ATSDR 1995). Several 

41 million gallons/day are imported. Recent production data were not located. 

42 

43 The most serious immediate hazard from the accidental release of gasoline is the threat of 

44 fire or explosion (Anonymous 1989). The lower and upper flammability limits are 1.4 and 7.4% 

45 or 14,000 and 74,000 ppm. The autoignition temperature is between 280 and 486oC, and the 

46 flashpoint is -46oC (ATSDR 1995). 

47 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 9 of 41 

1 A review of monitoring studies of workplaces for a variety of jobs in the manufacture, 

2 transport, and sale of gasoline shows that C4 and C5 compounds represent 54-81% of the total 

3 hydrocarbons in industrial hygiene samples (Dalbey et al. 1996). Thus, although the 

4 hydrocarbons comprising gasoline are predominantly in the range of C3 to C11, exposure of 

5 humans would be to the more volatile components in the range of C4 to C6 (Bruckner et al. 2008; 

6 White 2009). The C4 to C5 hydrocarbons are generally regarded as less toxic than the higher7 molecular-weight counterparts (Reese and Kimbrough 1993). Studies that address the toxicity of 

8 both wholly vaporized gasoline and gasoline vapor containing the more volatile components are 

9 discussed in the following sections. 

10 

Because gasoline is a complex substance, concentrations are reported in mg/m3 11 . Many of 

12 the studies reviewed here reported concentrations in ppm. Concentrations are listed as they were 

13 reported. Appropriate conversions were made for calculation of AEGL values. 

14 

15 

TABLE 1. Chemical and Physical Properties 

Parameter Value Reference 

Synonyms Petrol; benzin; motor fuel; O’Neil 2001; ATSDR 1995 

Chemical formula Not applicable (mixture) 

Molecular weight 108 (avg. whole gasoline); 

72.6-80 (vapor) 

ATSDR 1995; AIHA 2008 

CAS Reg. No. 86290-81-5; 8006-61-9* 

Physical state liquid, clear, amber-colored AIHA 2008 

Solubility in water Insoluble 20oC O’Neil 2001 

Vapor pressure 275-475 mm Hg at 20oC Amerada Hess 2004 

Vapor density, saturated (air =1) 3 to 4 Amerada Hess 2004 

Liquid density (water =1) 0.7-0.8 g/cm at 21oC AIHA 2008; ATSDR 1995 

Melting point not relevant 

Boiling point 32-210 oC O’Neil 2001 

Flammability limits in air 1.4-7.4% ATSDR 1995 

Conversion factors Whole gasoline: 

 1 ppm = 4.42 mg/m3

 1 mg/m3

 = 0.23 ppm 

Gasoline vapor: 

 1 ppm = 2.99 mg/m3

 1 mg/m3

 = 0.33 ppm 

Calculated (based on average 

molecular weights of 108 and 73, 

respectively) 

16 * CAS No. 86290-81-5 is unleaded gasoline that meets 1990 industry average specifications. CAS No. 8006-61-9 is 

17 assigned to natural gasoline, a complex combination of hydrocarbons separated from natural gas by processes such 

18 as refrigeration or absorption. Individual refinery process streams have additional CAS numbers. 

19 

20 2. HUMAN TOXICITY DATA 

21 2.2.1. Odor Threshold 

22 

23 Gasoline has a characteristic odor. The odor threshold and odor recognition 

24 concentrations have been reported for gasoline and gasoline containing MTBE and TAME 

25 (Amerada Hess 2004). For non-oxygenated gasoline the odor detection and odor recognition 

26 thresholds were 0.5-0.6 ppm and 0.8-1.1 ppm. For gasoline with 15% MTBE, the respective 

27 thresholds were 0.2-0.3 ppm and 0.4-0.7 ppm, and for gasoline with 15% TAME, the respective 

28 thresholds were 0.1 ppm and 0.2 ppm. 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 10 of 41 

1 

2 The American Petroleum Institute (API 1994) reported odor threshold, recognition, and 

3 intensity thresholds for summer and winter blends of gasoline and for blends containing 

4 oxygenates (Table 2). Trained panelists participated in a forced choice sniff test by identifying 

5 which of three ports contained the odor. The lowest average odor detection and recognition 

6 thresholds were for the summer blend of gasoline containing 15% ETBE (97% purity). For 

7 MTBE, the odor detection threshold decreased with increases in MTBE concentration. Odor 

8 intensity values for gasoline blends without oxygenates ranged from 2.03-3.33. Odor intensity 

9 values for the blends ranged from 2.95-4.60. Most panelists described the odor for both the 

10 blends of gasoline as well as gasoline containing oxygenates as gasoline. 

11 

12 Using the data of API (1994) a level of distinct odor awareness (LOA) was calculated for 

gasoline. The LOA of 7.4 ppm (approximately 22 mg/m3 13 ) was calculated for gasoline based on 

14 the odor detection value of 0.474 ppm for a composite of summer and winter blends. The 

15 calculation is shown in Appendix B. The LOA represents the concentration above which it is 

16 predicted that more than half of the exposed population will experience at least a distinct odor 

17 intensity, and about 10% of the population will experience a strong odor intensity. 

18 

TABLE 2. Odor Detection and Odor Recognition Thresholds for Gasoline 

Gasoline blend Odor Detection Odor Recognition 

Gasoline – summer blend 0.576 ppm 0.802 ppm 

Gasoline – winter blend 0.479 ppm 1.121 ppm 

Gasoline – composite 0.474 ppm 0.765 ppm 

Gasoline – summer blend + 3% MTBE 0.500 ppm 0.696 ppm 

Gasoline – summer blend + 11% MTBE 0.275 ppm 0.710 ppm 

Gasoline – summer blend + 15% MTBE 0.264 ppm 0.686 ppm 

Gasoline – winter blend + 15% MTBE 0.219 ppm 0.398 ppm 

Gasoline – composite + 15% MTBE 0.085 ppm 0.185 ppm 

Gasoline – summer blend + 15% ETBE 0.064 ppm 0.139 ppm 

Gasoline – summer blend + 15% TAME 0.114 ppm 0.207 ppm 

MTBE (97% purity) 0.053 ppm 0.125 ppm 

19 Source: API 1994. 

20 

21 2.2.2. Clinical Studies 

22 

23 Drinker et al. (1943) conducted a clinical study with male and female volunteers exposed 

24 to various concentrations of straight lead-free commercial gasoline and the volatile fraction of 

25 gasoline distilled below 110oC. Except for two exposures with a face mask, the exposures took 

26 place in a 16x22x9-ft chamber. Gasoline was metered into the ventilating air at the top of the 

27 chamber and exited at the floor. Concentrations were computed from the volume of gasoline 

28 vaporized and checked by vapor pressure and charcoal adsorption methods. Male volunteers, 

29 ages 23 to 45 years, and female volunteers, ages 17-32 years, participated in the study as 

30 outlined in Table 3. At concentrations up to 900 ppm, only slight sensory irritation was reported. 

31 While no dizziness was reported during the exposure to 900 ppm, two of six men reported 

32 feeling unsteady following the exposure. One subject experienced nausea during the 1-hour 

33 exposure to 2600 ppm, and all subjects felt slightly lightheaded. The slight irritation reported at 

34 low concentrations of whole gasoline was not present during the exposure to the light fraction. 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 11 of 41 

1 The authors also noted that inhalation of gasoline causes slight gastrointestinal disturbance in 

2 about 10% of the population. 

3 

4 

TABLE 3. Clinical Study with Gasoline and Gasoline Vapor (Drinker et al. 1943) 

Concentration in ppm/Subjects Exposure Duration Response 

Whole Gasoline Vapor 

160 (8 females) 8 hours Odor detection for various periods of time; 

slight irritation of eyes and throat 

270 (13 males) 8 hours Odor detection throughout day, slight 

irritation of eyes and throat 

11,200 (3 males, 1 female) 

vapor delivered by face mask 

5-5.5 minutes Nose and throat irritation within 20 seconds; 

feeling of incoordination 

Gasoline Vapor Distilled below 110oC 

140 (10 females) 8 hours Odor detection; no definitive irritation 

150 (8 females) 8 hours Odor detection; very slight irritation of the 

eyes and throat 

500 (9 males) 1 hour Slight irritation of the eyes and throat 

900 (6 males) 1 hour Slight irritation of the eyes and throat; 

threshold for unsteadiness 

2600 (5 males, 1 female) 1 hour Strong odor; slight dizziness, transient eye 

irritation 

10,700 (4 men) 

vapor delivered by face mask 

4-7 minutes Unsteadiness (compared to euphoria from 

alcohol or ether) 

5 

6 

7 Ten healthy male volunteers, ages 23 to 40 years, were exposed to three varieties of 

8 unleaded vaporized gasoline for 30 minutes (Davis et al. 1960). The subjects were blind to the 

9 test material. The gasoline sample composition varied as follows: A: 25% paraffins, 30% 

10 naphthenes (cycloparaffins), 40% aromatics; B: 40% paraffins, 35% naphthenes, 20% aromatics; 

11 and C: 30% paraffins, 5% naphthenes, 65% aromatics. Volunteers were exposed individually in 

12 a 10x7x9.5-ft chamber. Gasoline was metered into the top of the chamber and exhausted near 

13 the floor. Chamber air samples were collected on silica gel, eluted with n-dodecane, and 

14 analyzed by gas chromatography. Concentrations averaged 200, 500, and 1000 ppm. Because 

15 three different blends were tested, it is assumed that the gasoline was almost wholly vaporized. 

Therefore, concentrations in mg/m3

 would be 880, 2200, and 4400 mg/m3 16 , respectively. Each 

17 subject filled out a 21-part questionnaire following exposure. The questionnaire addressed odor; 

18 irritation of the eyes, nose, and throat; headache, dizziness, drowsiness/fatigue, and headache. A 

19 photograph of each subject’s left eye was taken before and after exposure. The photographs 

20 showed conjunctival blood vessels in detail (graded over a range of 1-4, with 1 representing very 

21 slight change, 2 and 3 representing intermediate change, and 4 representing marked change). 

22 Total positive responses of the 10 subjects to 12 questions and the highest responses are 

23 summarized in Table 4. 

24 

25 

TABLE 4. Clinical Study with Gasoline Vapor (Davis et al. 1960)

Concentration in ppm 

(mg/m3

) 

Total Responsesa

 Highest Response (number of subjects)b

Control 1 

Control 2 

6 

4 

Transient cough (2); drowsiness (2) 

Responses evenly distributed 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 12 of 41 

Sample A 

 200 (880) 

 528 (2323) 

 1054 (4638) 

9 

15 

9 

Itching or burning of eyes (3); headache (3) 

Itching or burning of eyes (7); headache (2) 

Itching or burning of eyes (4) 

Sample B 

 186 (818) 

 497 (2187) 

 996 (4382) 

7 

12 

26 

Transient cough (2) 

Itching or burning of eyes (6); ocular tearing (2) 

Itching or burning of eyes (9); ocular tearing (4); 

 nose irritation, cough, nausea, drowsiness, fatigue (2) 

Sample C 

 164 (722) 

 501 (2204) 

 984 (4330) 

8 

11 

16 

Itching or burning of eyes (3); drowsiness (2) 

Itching or burning of eyes (5); headache (2) 

Itching or burning of eyes (9); ocular tearing (3) 

 itching of nose (2) 

1 n = ten subjects. 

2 All exposure durations were 30 minutes. 

a 3 Total responses of 10 subjects answering 12 questions (possible score of 120).

b 4 Single responses not recorded. 

5 

6 The data in Table 4 show that the response to itching or burning eyes was most frequent, 

7 with an apparent concentration-response relationship. An analysis of variance of the rescored 

8 data (corrected for control responses) showed that the responses as a group lacked significance. 

Incidences of drowsiness in the control and 4400 mg/m3 9 exposure were 3/30 and 2/20. Ocular 

tearing was similar in the control and 2200 mg/m3 10 groups (10%), but was higher (27%) in the 

group exposed to 4400 mg/m3 11 . Objective eye irritation was graded +1 (very slight) or +2 

(intermediate) with only one subject’s eye graded +3 (in one group exposed to 4400 mg/m3 12 ); this 

subject’s scores were +1 and 0 following the other two exposures to 4400 mg/m3 13 . In the 4400 

mg/m3 14 exposure group, objective eye irritation scores averaged 0.9 to 1.4 out of 4. Numerous 

15 negative scores of -1 and 0 were also recorded following exposure. Subjective eye irritation was 

16 concentration related, with the higher scores at the higher concentrations. Subjective eye 

17 irritation did not fully correlate with responses of objective (photographed) eye irritation. No 

18 differences in irritation were noted between the gasoline vapor samples at approximately the 

19 same concentrations. 

20 

21 Neurological effects have been observed in individuals that habitually sniff gasoline for 

22 its euphoric/hallucinogenic properties (ATSDR 1995). These effects include postural tremor, 

23 ataxia, abnormal gait, affected speech, fatigue, headaches, memory loss, and sleep problems. 

24 

25 Cytogenetic monitoring studies and cancer epidemiology studies of workers exposed to 

26 gasoline have produced inconclusive results (ATSDR 1995). Most of these studies were 

27 considered inadequate due to inherent limitations including unreported exposure concentrations, 

28 length of exposure, and concurrent exposure to other substances. Exposure of human 

29 lymphoblastoid cells to 0.6% and 1.2% unleaded gasoline, with or without metabolic activation, 

30 failed to induce mutations at the TK+ locus (Richardson et al. 1986). Assays for mutagenicity 

31 and sister chromatid exchange were also negative. 

32 

33 3. ANIMAL TOXICITY DATA 

34 

35 Using standard protocols, ARCO clear gasoline with MTBE was tested for acute oral and 

36 dermal toxicity and skin and eye irritation and sensitization (ARCO Chemical Co. 1984). The 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 13 of 41 

1 acute oral LD50 was >5.0 g/kg in rats. The acute dermal toxicity in rabbits was >2.0 g/kg. The 

2 ARCO gasoline was considered a moderate dermal irritant and was a minimal irritant to the 

3 rabbit eye (instillation of 0.1 mL). Gasoline was a weak sensitizing agent in the guinea pig. 

4 

5 3.1. Acute Toxicity 

6 

7 The acute inhalation toxicity of various blending streams of gasoline has been reported 

8 with the rat as the test species (Table 5). All exposure durations were for four hours. All studies 

9 followed the same methodology (provided in the following example). A group of five male and 

five female Sprague-Dawley rats inhaled a measured concentration of 5200 mg/m3 10 sweetened 

11 naphtha (API No. 81-08; CAS No. 64741-87-3), whole-body, for 4 hours (API 1982). A second 

12 group was exposed to air only and served as the control group. Exposures took place in 160-L 

13 glass and stainless steel chambers. The atmospheres were generated by delivering test material 

14 liquid to a glass bead column. Air, heated to 55oC and delivered in a counter-current manner 

15 relative to the liquid, vaporized the liquid. The vapor was diluted with air and piped to the 

16 exposure chamber. Concentrations were measured throughout the exposure period by a total 

17 hydrocarbon analytical method. Animals were observed for clinical signs during the exposure 

18 period, hourly for four hours following the exposure, and twice daily for 14 days post-exposure. 

19 Rats were weighed prior to exposure and on days 7 and 14. Surviving rats were sacrificed and 

20 organs and tissues were examined macroscopically. The lungs and trachea were examined 

21 microscopically. There were no deaths and no significant clinical signs observed during or 

22 following exposure. Two male rats and one female rat showed a slight clear nasal discharge 

23 during exposure. Females gained slightly less weight than expected over the 14-day recovery 

24 period. There were no microscopic changes in the lungs or trachea that could be attributed to 

25 treatment. 

26 

27 In some of the studies listed in Table 5, languid behavior (hypoactivity) was observed 

28 during exposure (light alkylate naphtha) and nasal discharge was observed in two animals on day 

29 2 post-exposure (light, catalytically cracked naphtha) (API 1995). Lower body weight gain, seen 

30 with API 81-08 was not observed in most of the studies. There were no significant gross 

31 observations at necropsy and no histological changes observed in the lungs in any study. 

32 

TABLE 5. Acute Toxicity of Gasoline Blending Stream Vapor to Rats

Blending Stream LC50 (mg/m3) 

Naphtha, light catalytic cracked (API 81-04) >5300 

Naphtha, heavy catalytic cracked (API 83-18) >5000 

Naphtha, light catalytic reformed (API 83-04) >5200 

Naphtha, heavy catalytic reformed (API 83-06) >5000 

Naththa, full range catalytic reformed (API 83-05) >5000 

Naphtha, sweetened (API 81-08) >5200 

Naphtha, light alkylate (API 83-19) >5000 

Naphtha, heavy thermally cracked (API 84-02) >5000 

All studies were conducted for four hours at the limit concentration of 5000 mg/m3 33 . 

34 Sources: API 2008a,b; CONCAWE 1992. 

35 

A group of five male and five female Sprague-Dawley rats inhaled 5200 mg/m3 36 of ARCO 

37 clear gasoline with MTBE for 4 hours (ARCO Chemical Co. 1984). Chamber atmospheres were 

38 generated by metering the test material to a flask maintained at 100oC and then mixing with 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 14 of 41 

1 room air. Rats were observed during exposure and at set intervals for 14 days post-exposure. 

2 Animals appeared unaffected during exposure. Upon removal from the chamber, lacrimation 

3 was noted in 2 of 10 animals, mucoid nasal discharge in 7 of 10 animals, red nasal discharge and 

4 dry rales in 2 of 10 animals, and reduced righting reflex in 4 of 10 animals. These signs 

5 continued into the next day, but generally abated during the 14-day observation period. There 

6 were no deaths, and rats gained weight during the post-exposure period. At necropsy, discolored 

7 kidneys were observed in 4 of 5 males and 2 of 5 females. 

8 

9 3.2. Repeat-Exposure and Subchronic Studies

10 

11 Groups of 5-6 B6C3F1 mice inhaled 0 (filtered air), MTBE (7814 ppm), API-91-01 

12 unleaded gasoline (2014 ppm), or PS-blend unleaded gasoline (2028 ppm) for 6 hours/day, 5 

13 days/week, for 3 or 21 days (Moser et al. 1996) (Table 6). Neither blend of gasoline contained 

14 significant amounts of MTBE. The API-91-01 blend contains a slightly greater percentage of 

15 aromatics and olefins than the PS-6 blend. Mice were sacrificed 18 hours after the last exposure. 

16 During exposure, abnormal gait, hypoactivity, decreased muscle tone, and increased lacrimation 

17 were observed in the group exposed to MTBE. Occasional hypoactivity was observed in mice 

18 exposed to the unleaded gasolines. Compared to the control, relative liver weight was increased 

19 in all groups after 3 and 21 days, and relative uterine weight was decreased for all groups after 3 

20 days and in the MTBE- and API-91-01-treated groups after 21 days. 

21 

22 Chu et al. (2005) exposed groups of 15 male and 15 female Sprague-Dawley rats to 

23 filtered air, 6130 ppm ethanol, 500 ppm gasoline, or a mixture of 85% ethanol and 15% gasoline 

24 (6130 ppm ethanol and 500 ppm gasoline) for 6 hours/day, 5 days/week for 4 weeks. Ten rats of 

25 each gender were sacrificed after 4 weeks, and the remaining rats were held for a 4-week 

26 recovery period. No clinical signs of toxicity were observed. Body weight gain was reversibly 

27 suppressed by 21% in female rats that inhaled the ethanol-gasoline mixture. Reversible 

28 inflammation of the upper respiratory tract was observed only in the gasoline-ethanol group. 

29 The authors concluded that treatment with gasoline and ethanol produced mild, reversible 

30 biochemical, hematological, and histological effects (adrenal cortical vacuolation), with some 

31 indication of interaction when the vapors were co-administered. 

32 

33 Halder et al. (1986) exposed groups of ten Sprague-Dawley rats/sex to 0, 120, 1150, or 

11,800 mg/m3 34 of the C4 and C5 hydrocarbons that comprise typical gasoline vapor. Atmospheres 

35 consisted of 25% each n-butane, n-pentane, isobutene and isopentane. Exposure was for 6 

36 hours/day, 5 days/week for 3 weeks. No adverse clinical signs were observed. No treatment37 related changes were found in body weight, serum chemistry, hematology, histopathology of 

38 tissues, or organ weight. 

39 

40 Groups of 20 male and 20 female Sprague-Dawley rats inhaled vapor of either unleaded 

gasoline at concentrations of 0, 1570 or 6350 mg/m3

 or leaded gasoline at 420 or 1530 mg/m3 41 for 

42 90 days (Kuna and Ulrich 1984). Groups of four male and four female squirrel monkeys inhaled 

43 the same concentrations. Exposures were for 6 hours/day, 5 days/week. Gasoline was wholly 

44 vaporized in an atomizer with heated nitrogen; and then mixed with the exposure chamber air 

45 inflow. Atmospheres were analyzed with a total hydrocarbon analyzer connected to an 

46 automatic sampling device. No “remarkable” changes were observed in body weight; 

47 hematology; CNS response (flash-evoked response time, tested in monkeys); pulmonary function 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 15 of 41 

1 tests (in monkeys); urinalysis; deposition of IgG in the renal glomerulus; lead levels in blood, 

2 urine, and tissue; organ weight; organ-to-body weight ratio; or histopathology. Minor changes in 

some parameters in rats are listed in Table 6. Male rats exposed to 6350 mg/m3 3 unleaded 

4 gasoline showed male-rat-specific changes in the kidney tubules. 

5 

6 Groups of 20 Sprague-Dawley rats (10/sex) and 20 CD-1 mice (10/sex) were exposed 

7 whole body to vapors of light catalytically cracked naphtha at measured concentrations of 0, 530, 

2060, or 7690 mg/m3 8 for 13 weeks (Dalbey et al. 1996). Exposure was for 6 hours/day, 5 

9 days/week. Atmospheres were analyzed by gas chromatography. No significant treatment10 related changes were found in clinical signs, body weight, serum chemistry, hematology, 

11 histopathology of 24 tissues, or organ weight. In rats, a marginal increase was noted in the 

number of sperm per gram of epididymis in the 7690 mg/m3 12 group, compared to sham-exposed 

13 controls, but not compared to untreated controls. 

14 

15 In a study conducted in the same manner, groups of 15 male and 15 female SpragueDawley rats inhaled 0, 410, 1970, or 8050 mg/m3 16 of partially vaporized full range catalytic 

17 reformed naphtha for 13 weeks (Dalbey and Feuston 1996). No significant treatment-related 

18 effects were found in clinical signs, serum chemistry, hematology, or histopathology of 24 

19 organs. Body weight and weights of liver and kidney were marginally increased in males in the 

8050 mg/m3 20 group. 

21 

22 Additional studies including neurotoxicity, developmental toxicity, and chronic 

23 toxicity/carcinogenicity are summarized in Table 6. 

24 

25 

TABLE 6. Repeat-Exposure, Subchronic and Chronic Exposure, Developmental Toxicity, and Genotoxicity 

Studies with Gasoline Vapor

Type of Study 

(species) 

Material 

Characterization 

Concentrations 

(mg/m3

) 

Effect Reference 

General toxicity 

3, 21 days 

(mouse) 

PS-6 blend 

API-91-01 

0, 2056 ppm 

0, 2014 ppm 

Occasional hypoactivity 

Occasional hypoactivity 

Moser et al. 1996 

General toxicity 

4 weeks 

(rat) 

ethanol 

gasoline 

ethanol+gasoline 

6130 ppm 

500 ppm 

6130+500 ppm 

No clinical signs 

No clinical signs 

Reversible body weight 

suppression in female rats; 

reversible nasal inflammation; 

biochemical changes 

Chu et al. 2005 

General toxicity, 

3 weeks 

(rat) 

Combination of 

25% n-butane, 

25% isobutene, 

25% n-pentane, 

25% isopentane 

0, 120, 1150, 

11,800 

No adverse clinical signs or 

effects 

Halder et al. 1986 

General toxicity, 

subchronic 

(rat, monkey) 

Wholly 

vaporized leaded 

and unleaded 

gasoline 

0, 1570, 6350 Alpha 2-microglobulin 

mediated nephropathy in male 

rats; slight increases in 

thrombocyte and reticulocyte 

counts and liver weight in male 

rats receiving 6570 mg/m3

; 

slight increase in tissue lead 

content in rats receiving leaded 

Kuna and Ulrich 

1984 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 16 of 41 

gasoline 

Monkeys – no significant toxic 

effect 

General toxicity, 

subchronic 

(rat, mouse) 

Partially 

vaporized light 

catalytically 

cracked naphtha 

0, 530, 2060, 

7690 

No treatment related clinical 

signs, or changes in body 

weight, serum chemistry, 

hematology, histopathology, 

organ weight; marginal 

decrease in sperm in male rats 

at 7690 mg/m3

Dalbey et al. 1996 

General toxicity, 

subchronic 

(rat) 

Partially 

vaporized full 

range catalytic 

reformed 

naphtha 

0, 410, 1970, or 

8050 

No treatment-related clinical 

signs, no effect on serum 

chemistry or male reproductive 

parameters; lower white blood 

cell count (up to 24% at highest 

concentration); increased liver 

and kidney weight; no 

microscopic lesions 

Dalbey and Feuston 

1996 

Neurotoxicity, 

subchronic 

(rat) 

Vapor from light 

catalytic 

reformed 

naphtha 

0, 750, 2500, 

7500 ppm (0, 

2250, 7500, 

22,500) 

No clinical signs during 

exposure; no change in motor 

activity other parameters during 

an FOB; transient decreases in 

hematology parameters 

Schreiner et al. 2000 

Neurotoxicity, 

subchronic 

(rat) 

Gasoline vapor 

condensate with 

or without 

additives: 

MTBE, ETBE, 

TAME, DIPE, 

ethanol, TBA 

0, 2000, 10,000, 

20,000 

No neuropathology; negative 

FOB; motor activity affected by 

gasoline containing TBA with 

effect resolving during recovery 

O’Callaghan et al. 

2004 

Reproductive 

toxicity, 

two generation 

(rat) 

volatile fraction 

from a gasoline 

terminal 

5076, 10,247, or 

20,241 

No significant effects other 

than male rat specific 

nephropathy 

McKee et al. 2000 

Reproductive 

toxicity, onegeneration; two 

generation 

(rat) 

GVC with or 

without 

additives: 

MTBE, ETBE, 

TAME, DIPE, 

ethanol, TBA 

0, 2000, 10,000, 

20,000 

No impact on reproduction Gray et al. 2004 

Developmental 

toxicity, 

GD 6-19 

(rat) 

Gasoline vapor 

condensate (API 

94-02) 

0, 2653, 7960, 

23,900 

No maternal toxicity; no 

developmental effects 

Roberts et al. 2001 

Developmental 

toxicity, GD 0-19 

(rat) 

Light 

catalytically 

cracked naphtha 

0, 2150, 7660 

GD 6-19 

No treatment-related clinical 

signs or effects on reproductive 

parameters other than increased 

resorptions at 7660 mg/m3

Dalbey et al. 1996 

Developmental 

toxicity GD 6-19 

(rat) 

Partially 

vaporized full 

range catalytic 

reformed 

naphtha 

0, 2160, 7800 Reproductive performance 

unaffected; no affect on body 

weight gain; serum glucose 

decreased and serum potassium 

increased 

Dalbey and Feuston 

1996 

Genetic toxicity GVC with or 

without 

additives: 

0, 2000, 10,000, 

20,000 

Assay results negative for 

micronuclei formation in bone 

marrow; sister chromatid 

Schreiner et al. 2004 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 17 of 41 

MTBE, ETBE, 

TAME, DIPE, 

ethanol, TBA 

exchange assay positive for 

gasoline vapor condensate and 

condensate containing MTBE 

Chronic toxicity/ 

carcinogenicity 

(rat, mouse) 

Wholly 

vaporized 

gasoline 

containing 2% 

benzene 

296, 1290. 9080 Survival unaffected; decreased 

body weight gain at 9080 

mg/m3

 both species; male rat 

nephropathy; liver tumors in 

sensitive strain of female mice 

MacFarland et al. 

1984 

Chronic toxicity/ 

carcinogenicity 

(rat) 

GVC with or 

without 

additives: 

MTBE, ETBE, 

TAME, DIPE, 

ethanol, TBA 

0, 2000, 10,000 

or 20,000 

Survival unaffected; reversible 

changes in body weight 

(gasoline +ethanol and gasoline 

+ ETBE); reversible FOB 

motor activity change (gasoline 

+ TBA); neuropathology 

negative; 

Benson et al. 2004 

1 Subchronic exposures are for 13 weeks, 6 hours/day, 5 days/week. 

2 Rat studies were conducted with male and female Sprague-Dawley rats; CD-1 mice were additionally tested in the 

3 toxicity study of Dalbey et al. (1996), and squirrel monkeys were additionally tested in the study of Kuna and Ulrich 

4 1984. 

5 FOB = functional observational battery. 

6 GVC = gasoline vapor condensate consisting of approximately 15-20% of starting gasoline which was slowly 

7 vaporized at near maximum gasoline in-use tank temperature (130oC) and condensed. 

8 GD = gestation day. 

9 

10 

11 3.3. Neurotoxicity

12 

13 Neurotoxicity assessments were not performed following acute exposures. Clinical signs 

14 were generally absent with the exception of languid behavior and hunched appearance exhibited 

during a 4-hour exposure of rats to 5000 mg/m3 15 light alkylate naphtha (API 1995). 

16 

17 In a subchronic (13 week) study, Schreiner et al. (2000) exposed groups of 16 male and 

18 16 female Sprague–Dawley rats (whole-body) to 0, 750, 2500, or 7500 ppm (approximately 0, 

2250, 7500, or 22,500 mg/m3 19 ) of vapors of a light catalytic reformed naphtha distillate (CAS No. 

64741-63-6).1 20 Standard parameters of subchronic toxicity were measured throughout the study. 

21 At necropsy, organs were weighed and tissues were examined microscopically. There was no 

22 mortality and no clinical signs such as tremors, ataxia, or lethargy were seem. Compared to the 

23 control group, there were no changes in motor activity or other parameters during a standard 

24 functional observational battery (FOB). Changes in some hematology parameters such as a 

decrease in white blood cell count in males in the 22,500 mg/m3 25 group generally abated during a 

four-week recovery period. In male rats that inhaled 22,500 mg/m3 26 , a small increase in relative 

27 kidney weight and decreases in absolute and relative spleen weight were reversible at the end of 

the recovery period. These parameters were unaffected in female rats. Rats in the 22,500 mg/m3 28 

29 group showed a male-rat specific light hydrocarbon nephropathy. 

30 

31 A 13-week neurotoxicity study was conducted with gasoline vapor generated by 

32 vaporizing gasoline at near-maximum in-use automotive fuel tank temperature conditions 

33 (O’Callaghan et al. 2004). The starting material, described in Daughtrey et al. (2004), was 

 

1

 Light catalytic reformed naphtha is comprised of hydrocarbons having carbon numbers predominantly in the C5-C11

range. It contains a relatively large proportion of aromatics and branched chain hydrocarbons and may contain as 

much as 10% benzene by volume. Finished gasoline contains 20-30% of this light catalytic reformed naphtha. 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 18 of 41 

1 slowly vaporized, separated, condensed and recovered. This fraction, termed gasoline vapor 

2 condensate (GVC) was used in multiple studies. Samples of GVC to which one of four ethers or 

3 one of two alcohols was added were also tested (See Appendix A for volume percent additives). 

Male and female Sprague Dawley rats were exposed to 0, 2000, 10,000 or 20,000 mg/m3 4 of each 

5 test material, 6 hours/day, 5 days/week for 13 weeks. A standard FOB and motor activity tests 

6 were administered at 3 weeks and several times thereafter. At study termination, brains were 

7 evaluated for glial fibrillary acidic protein (GFAP), a biomarker of brain damage. Except for 

8 vapor containing the oxygenate t-butyl alcohol, FOB and motor activity were unaffected. 

9 Behavioral effects (undefined change in motor activity) for the group exposed to gasoline vapor 

10 containing t-butyl alcohol resolved during a recovery period. Neuropathology was negative in 

11 all groups. Analysis of GFAP revealed a mild gliosis only in males exposed to gasoline vapor 

12 condensate containing ethyl alcohol. 

13 

14 3.4. Developmental/Reproductive Toxicity

15 

16 In a two-generation reproductive toxicity study, groups of 30 male and female Sprague17 Dawley rats inhaled gasoline vapor daily for 6 hours/day, 7 days/week, for 10 weeks prior to 

18 mating and throughout the mating period (up to 3 weeks) (McKee et al. 2000). Selected first 

19 generation pups were treated in the same manner. The study was conducted in accordance with 

20 United States and European guidelines (OECD Guideline 416). In order to assess vapor 

21 representative of the exposure of handlers and customers at gasoline service stations, the vapor 

22 consisted of the volatile fraction from a gasoline terminal vapor recovery unit at a distribution 

23 terminal in the Netherlands. The assigned CAS Reg. No. was 68514-15-8. Exposure took place 

in 1.5 m3 chambers; measured concentrations were 5076, 10,247, and 20,241 mg/m3 24 (the latter 

25 reported as 50% of the LEL). The vapor consisted of primarily C4 and C5 hydrocarbons. There 

26 were no treatment-related effects in parental animals. Microscopic changes were limited to 

27 males and involved hydrocarbon droplet nephropathy of the kidney, specific to male rats. There 

28 were no deleterious effects on offspring survival and growth. The potential for endocrine 

29 modulation was assessed by analysis of sperm count and quality as well as time to onset of 

30 developmental landmarks in females. No toxicologically significant effects were observed. The 

NOAEL for reproductive toxicity in this study was >20,000 mg/m3 31 . 

32 

33 In a one-generation study, groups of 26 male and 26 female Sprague-Dawley rats inhaled 

34 the evaporative emissions of gasoline or gasoline containing the ether or alcohol oxygenates, 

TAME, ETBE, DIPE, ethanol, or TBA, at 0, 2000, 10,000, or 20,000 mg/m3 35 , 6 hours/day prior to 

36 mating and up to weaning of the F1 on lactation day 28 (Gray et al. 2004). There were no 

37 differences in male or female fertility with any exposure. Reduced weight gain was observed in 

38 groups inhaling gasoline vapor and gasoline/MTBE, ethanol, ETBE, and TBA. All exposures 

39 caused increases in the kidney weight of male rats. Weight changes and discolorations in other 

40 organs were not accompanied by histopathological changes, and so were not considered adverse. 

41 

42 A developmental toxicity study was conducted according to U.S. EPA TSCA Guideline 

43 No. 798-4350 (Roberts et al. 2001). Groups of 21 to 24 pregnant Sprague-Dawley rats inhaled 

measured concentrations of 0, 2653, 7960, or 23,900 mg/m3 44 (the latter reported as 75% of the 

45 LEL), 6 hours/day, on days 6 to 19 of gestation. The test material was gasoline vapor 

46 condensate derived from unleaded gasoline that met 1990 industry average specification (the 

47 1990 Clean Air Act required increased oxygen content in gasoline). All rats were sacrificed on 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 19 of 41 

1 gestation day 20. No maternal toxicity was observed. Developmentally, there were no 

2 differences between treated and control groups in fetal malformations, total variations, 

3 resorptions, body weight or viability. Under conditions of this study, the developmental NOAEL 

was >23,900 mg/m3 4 . 

5 

6 Groups of 15 pregnant Sprague Dawley rats inhaled vapor of light catalytically cracked 

naphtha, whole-body, at concentrations of 0, 2150, or 7660 mg/m3 7 for 6 hours/day on gestation 

8 days 0-19 (Dalbey et al. 1996). Dams were sacrificed on gestation day 20. There were no 

9 skeletal or visceral effects in the fetuses. The only observed effect was an increase in resorptions 

in the dams that received 7660 mg/m3 10 . In a study conducted in the same manner, groups of 11-

12 pregnant Sprague-Dawley rats inhaled 0, 2160, or 7800 mg/m3 11 of partially vaporized full 

12 range catalytic reformed naphtha for 6 hours/day on gestation days 6-19 (Dalbey and Feuston 

13 1996). At sacrifice on day 20, no maternal or fetal effects were observed. 

14 

15 3.5. Genotoxicity

16 

17 The genetic toxicity of gasoline was reviewed by ATSDR (1995). The weight of 

18 evidence from in vivo animal studies suggests that unleaded gasoline is not genotoxic to rats and 

19 not strongly genotoxic to mice. In vitro rodent studies produced mixed results. Mutagenicity 

20 tests with Salmonella typhimurium TA1535, TA1537, TA1538, TA98, or TA100, with and 

21 without metabolic activation were largely negative. Mutations were observed only at toxic 

22 concentrations. Assays for gene mutation in rodent lymphoma cells were negative. Assays for 

23 unscheduled DNA synthesis in rodent primary hepatocytes were positive only as gasoline 

24 concentrations approached toxic levels. Results of an assay for unscheduled DNA synthesis in 

25 rat kidney cells were negative. 

26 

27 In a subchronic inhalation study with male and female Sprague-Dawley rats exposed to 0, 

2000, 10,000, or 20,000 mg/m3 28 of gasoline vapor concentrate, with and without oxygenates, all 

29 assays for micronucleus formation in bone marrow were negative (Schreiner et al. 2004). 

30 Statistically significant increases in sister chromatid exchange over several doses were observed 

31 in cultured lymphocytes of rats that inhaled gasoline vapor condensate or gasoline vapor 

32 condensate containing MTBE. Females appeared more sensitive than males. Gasoline vapor 

33 condensate containing TAME induced increased sister chromatid exchanges in both sexes at the 

34 highest dose only. 

35 

36 3.6. Chronic Toxicity/Carcinogenicity 

37 

38 Gasoline vapor with and without MTBE was tested for chronic toxicity and 

39 carcinogenicity in male and female F344 rats (Benson et al. 2004). Whole-body exposures were 

to 0, 2000, 10,000, or 20,000 mg/m3 40 , 6 hours/day, 5 days/week for 104 weeks. Survival to study 

41 termination was unaffected by either concentrate. Final body weight in males and females 

inhaling 20,000 mg/m3 42 gasoline vapor condensate was decreased by 9% and 8% respectively. 

43 Reductions in final body weight in male and females rats inhaling gasoline vapor containing 

44 MTBE were both 8%. Incidences of hepatic adenomas or carcinomas were unaffected by either 

45 exposure compared with the respective control groups. Male-rat specific nephropathy was 

46 observed in both control and treated rats. 

47 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 20 of 41 

1 In an earlier study, chronic inhalation of unleaded gasoline vapor resulted in increased 

2 hepatocellular adenomas and carcinomas in B6C3F1 female mice (MacFarland et al. 1984). 

3 Tumors appeared in female mice between 18 months and terminal sacrifice in the highest 

4 exposure group, 2056 ppm, 6 hours/day. This increase may have been due to the promotion of 

5 spontaneously initiated cells that occur with unusually high frequency in this mouse strain 

6 (Bruckner et al. 2008). Male rats also exhibited male-rat-specific nephropathy. Inhalation of 

7 unleaded gasoline vapor promoted the development of N-nitrosodiethylamine initiated tumors in 

8 male but not female B6C3F1 mice (Standeven et al. 1995). 

9 

10 In addition to increased hepatocellular adenomas and carcinomas in B6C3F1 mice, 

11 gasoline has been shown to induce P450 activity and produce hepatomegaly and a transient 

12 increase in hepatocyte proliferation, all considered relevant to tumor-promoting activity 

13 (Bruckner et al. 2008). However, based on epidemiological evidence, an association between 

14 gasoline exposure and cancer in humans is inconclusive (IARC 1989). 

15 

16 3.7. Summary

17 

18 Acute toxicity is similar for all blending streams of gasoline. No deaths were reported in 

male and female rats that inhaled the limit concentration of 5000 mg/m3 19 of various blending 

20 streams of gasoline for 4 hours (API 2008a,b). No mortality was reported in male and female 

rats that inhaled 20,000 mg/m3 21 gasoline for more than 10 weeks (McKee et al. 2000) or in male 

and female rats that inhaled 22,500 mg/m3 22 of a blending stream for 13 weeks (Schreiner et al. 

23 (2000). In the latter study, no clinical signs were noted during exposure. Studies of subchronic 

24 and chronic duration and studies that addressed developmental and reproductive toxicity showed 

25 no significant toxic effects. Genotoxicity studies were generally negative. 

26 

27 4. SPECIAL CONSIDERATIONS

28 4.1. Metabolism and Disposition

29 

30 There are no relevant studies of rates or extent of absorption, distribution, metabolism, or 

31 excretion of gasoline in humans. The metabolic pathways of many of the components of 

32 gasoline have been studied in animal models, but information on the toxicokinetics of complex 

33 substances is sparse. Individual hydrocarbons such as pentane are hydroxylated by hepatic 

34 cytochrome P-450 enzymes to pentanol, conjugated with glucuronic acid and excreted. 

35 Dennison et al. (2003) used physiologically-based pharmacokinetic (PBPK) modeling to 

36 characterize the pharmacokinetics of gasoline in rats. Most gasoline components are 

37 metabolized or oxidized primarily in the liver by cytochrome P-450/2E1. It was assumed that 

38 essentially all of the components of gasoline serve as competitive inhibitors of oxidation of the 

39 other components. Therefore, a lumped approach was used to model the pharmacokinetics of 

40 whole gasoline. Selected target components of gasoline were n-hexane, benzene, toluene, 

41 ethylbenzene, and o-xylene. Male F344 rats were exposed in a closed chamber for 6 hours to the 

42 single chemicals at concentrations between 500 and 2000 ppm, to various mixtures of all five 

43 chemicals at 50 to 1000 ppm each, to mixtures of the chemicals at the same concentration of 

44 100-500 ppm each, and to winter and summer blends of gasoline at 500, 1000, and 1500 ppm. 

45 The experimental data from all combinations of chemicals and computer simulation results from 

46 the model matched well. The PBPK model analysis indicated that metabolism of individual 

47 components was inhibited up to 27% during the 6-hour experiments of gasoline uptake. 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 21 of 41 

1 

2 4.2. Mechanism of Toxicity

3 

4 Automotive gasoline is a complex substance consisting of many hydrocarbon 

5 components. Although gasoline components vary within limits with octane number and engine 

6 requirements, the acute toxic effects do not differ significantly (ACGIH 1992; Niemeier 2001). 

7 Some gasoline additives are of toxic interest, but their generally low concentration and low 

8 volatility make a negligible contribution to the vapor phase. 

9 

10 Exposure to very high concentrations of hydrocarbons may cause excitement, loss of 

11 equilibrium, stupor, and coma (Cavender 1994a, 1994b, 1994c; Bruckner et al. 2008). The 

12 effectiveness of the individual components of gasoline as CNS depressants is related to their 

13 volatilization, potency, and blood/air partition coefficients. Recovery from CNS effects is rapid 

14 and complete in the majority of cases. Death is postulated to be due to either central nervous 

15 system depression due to asphyxia leading to respiratory failure, or cardiac sensitization to 

16 circulating catecholamines leading to a fatal arrhythmia (ATSDR 1995). 

17 

18 Because hydrocarbons are lipophilic, they partition into and accumulate in neuronal 

19 membranes and myelin. The more lipophilic the hydrocarbon (i.e., the higher its neuronal 

20 tissue:blood partition coefficient), the more potent a CNS depressant it is. The mere presence of 

21 hydrocarbons has generally been thought to disrupt the ability of the neuron to propagate an 

22 action potential and repolarize. Recent research has revealed that hydrocarbons might act by 

23 more specific mechanisms and might affect specific neurotransmitters and membrane receptors 

24 (i.e., by enhancing gamma-aminobutyric acidA receptor function, or activating dopaminergic 

25 systems). 

26 

27 Many volatile hydrocarbons are of low acute toxicity. Concentrations that cause CNS 

28 depression are generally non-injurious to the lung. Exposure of rats to gasoline vapor at 20,000 

mg/m3 29 for more than 10 weeks was without effect (McKee et al. 2000). The aromatic 

30 hydrocarbons are more toxic than the aliphatic and alicyclic hydrocarbons but, due to their lower 

31 boiling point, are present to a much smaller extent in gasoline vapor. 

32 

33 Long-term exposure to some hydrocarbons results in α2u-globulin nephropathy and 

34 associated renal carcinogenicity specific to male rats (Bruckner et al. 2008). The nephropathy is 

35 characterized by hyaline droplet formation and necrosis of kidney cells. The toxic affect is 

36 attributed to the α2u-microglobulin protein which is unique to the male rat. The α2u37 microglobulin protein is synthesized in the liver of male rats and is readily excreted in the 

38 glomerular filtrate. Select hydrocarbons combine with the protein to form poorly digestible 

39 complexes and prevent efficient catabolism of the protein following resorption from the 

40 glomerular filtrate. The tubular epithelial cells become engorged with the protein, resulting in 

41 metabolic disturbances followed by cell death and exfoliation. Exfoliated necrotic cells form 

42 tubular casts which plug the nephron near the corticomedullary junction. The casts become 

43 mineralized and may be flushed into the medullary segments where they may remain. α2u44 Microglobulin nephropathy is unique to male rats. This protein is not synthesized in humans 

45 (U.S. EPA 1991). Therefore, this adverse effect is not considered relevant to human exposure to 

46 gasoline vapor. 

47 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 22 of 41 

1 4.3. Structure-Activity Relationships

2 

3 Gasoline vapor is a complex substance composed of volatile hydrocarbons, primarily in 

4 the C4 to C6 range. The predominant hydrocarbons in vapor such as butane and pentane, have 

5 high vapor pressures, low blood/air partition coefficients (Dahl et al. 1988) and are practically 

6 nontoxic (Galvin and Marashi 1999). Individual components of gasoline vapor are not addressed 

7 in detail in this document. 

8 

9 4.4. Other Relevant Information

10 4.4.1. Species Variability

11 

12 All acute toxicity studies were conducted with the rat as the test species. Therefore, no 

13 information on species variability during acute inhalation exposure could be ascertained. 

Subchronic studies with rats, mice (up to 7690 mg/m3

), and monkeys (up to 6570 mg/m3 14 ) failed 

15 to provide data on relative sensitivity. Although data were available only for a few 

16 hydrocarbons, the C7 hydrocarbon n-heptane and xylene components, in vitro studies of 

17 blood/air partition coefficients show that uptake of hydrocarbons is greater by rat blood than 

18 human blood (Gargas et al. 1989). Human and rat blood to air partition coefficients for n19 heptane were 2.9 and 4.8, respectively, and human and rat blood to air partition coefficients for 

20 m-xylene were 33 and 46. Greater chemical uptake by rats than humans is also due to the more 

21 rapid respiration rate and greater cardiac output in rodents compared with humans on a body 

22 weight basis. 

23 

24 4.4.2. Susceptible Populations

25 

26 No information was available on susceptible human populations. No information was 

27 located on age-related sensitivity. Children and the elderly may be more or less sensitive to the 

28 toxic effects of solvents and vapors, but age-dependent susceptibility to acute effects of such 

29 vapors usually differs by no more than two- to threefold (Bruckner et al. 2008). Although 

30 humans differ in the rate at which they metabolize chemicals, the susceptibility of the general 

31 population to central nervous system depressants varies by no more than 2- to 3-fold as indicated 

32 by the minimum alveolar concentration, the concentration of an inhaled anesthetic that produces 

33 immobility in 50% of patients (Kennedy and Longnecker 1996; Marshall and Longnecker 1996). 

34 

35 4.4.3. Concentration-Exposure Duration Relationship

36 

37 No data were located that provided information on the concentration-exposure duration 

38 relationship for either the slight eye irritation experienced at gasoline vapor concentrations 

≤4400 mg/m3 39 (Drinker et al. 1943; Davis et al. 1960) or the vapor’s effect on the central nervous 

40 system. For the endpoints of both sensory irritation and depression of the central nervous system 

41 by solvents, there is generally a concentration threshold. For neurotoxicity, time to steady state 

42 for individual components depends on lipophilicity as well as chemical interactions. Once 

43 steady-state is attained, the CNS effect observed with exposure to high concentrations is most 

44 likely a concentration-dependent effect with exposure duration of lesser importance. For 

45 example, for n-nonane, inhaled by F344 rats at 100, 500, or 1000 ppm for 4 hours, steady-state 

46 was approached in the blood within two hours at the two higher concentrations (Robinson 2000). 

47 The blood:air partition coefficient was 5.13. 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 23 of 41 

1 

2 4.4.4. Concurrent Exposure Issues

3 

4 Gasoline is a complex substance of hydrocarbon components. The effect of inhalation of 

5 multiple similar hydrocarbons appears to be additive (Dennison et al. 2003). The highly volatile 

6 “light ends” which include hydrocarbons such as isopentane (C5H12), are practically non-toxic. 

The 4-hour LC50 for isopentane is 280,000 mg/m3 7 (Matheson Tri-Gas, Inc. 2009). The aromatics 

such as toluene are more toxic, with a 3-hour LC50 value in the mouse of 32,250 mg/m3 8 (U.S. 

9 EPA 2002). 

10 

11 5. DATA ANALYSIS FOR AEGL-1

12 5.1. Summary of Human Data Relevant to AEGL-1

13 

14 Drinker et al. (1943) exposed male and/or female subjects to whole gasoline vapor 

15 (unleaded) at concentrations of 160 and 270 ppm and to gasoline vapor distilled below 110oC at 

16 concentrations of 140 and 150 ppm for 8 hours. Male and/or female subjects were also exposed 

17 to the distillate vapor at 500, 900 or 2600 ppm for 1 hour. Additional exposures via face masks 

18 and lasting only a few minutes utilized concentrations of 11,200 ppm (whole gasoline vapor) and 

19 10,700 ppm (distillate vapor). Odor detection and very slight irritation were reported at 

20 concentrations up to and including 900 ppm. At this concentration, a slight neurotoxic effect 

21 was apparent only after the exposure. Unfortunately, the study employed a 17-year-old female 

22 college student and thus does not meet the U.S. EPA ethical criteria for human exposure. 

23 

24 On separate occasions, Davis et al. (1960) exposed 10 male subjects to three different 

25 samples of unleaded gasoline vapor for 30 minutes. Target concentrations were 880, 2200, and 

4400 mg/m3 26 . Concentration-related itching or burning of the eyes was the primary reported 

27 symptom. Objective irritation of the eye, as measured by redness, was negative or slight at 880 

and 2200 mg/m3

 (score range of -2 to +1) and intermediate at 4400 mg/m3 28 (score range of -1 to 

29 +3 in the three exposures). The scores in the control groups ranged from -1 to +1, but the eyes of 

more subjects in the 880 and 2200 mg/m3 30 groups were assigned a +1 than in the control groups. 

Incidences of ocular tearing in the control, 880, 2200, and 4400 mg/m3 31 groups were 2/20, 1/30, 

3/30, and 8/30, respectively. Drowsiness was reported by two subjects inhaling 4400 mg/m3 32 and 

33 as well as by two control subjects. 

34 

35 5.2. Summary of Animal Data Relevant to AEGL-1 

36 

37 All acute inhalation studies were conducted with rats as the test animal. A 4-hour 

exposure to 5000 mg/m3 38 vapor of various gasoline blending streams was generally without a 

39 significant toxic effect (API 2008a,b). In subchronic studies, the highest concentrations tested, 

20,000 and 22,500 mg/m3

 (rat), 7690 mg/m3 (mouse), and 6570 mg/m3 40 (monkey) were without 

41 toxic effects (Schreiner et al. 2000; O’Callaghan et al. 2004; Dalbey et al. 1996; Kuna and Ulrich 

42 1984). 

43 

44 5.3. Derivation of AEGL-1

45 

46 The AEGL-1 is based on the sensory irritation study of Davis et al. (1960). The 30-

minute exposures to three different blends of gasoline vapor at approximately 2200 mg/m3 47 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 24 of 41 

(measured concentrations of 2323, 2187, and 2204 mg/m3 1 ) produced subjective eye irritation at a 

2 higher incidence (15/30) than under control conditions (1/20). The incidence of objective eye 

irritation, although scored as slight (+1 on a scale of 1 to 4), was higher in the 2200 mg/m3 3 group 

4 (15/30) than in the control group (2/20). Incidences of subjective and objective eye irritation, 

including ocular tearing were higher at the higher concentration of 4400 mg/m3 5 . Incidences of 

ocular tearing were similar in the 2200 mg/m3 6 group (3/30) and the control group (2/20). 

7 Because the eye irritation when measured objectively was slight (less than marked), an 

8 intraspecies uncertainty factor of 3 was applied to protect sensitive subjects. There is adaptation 

to the slight irritation that defines the AEGL-1. Therefore, the same value of 730 mg/m3 9 (2200 

mg/m3 10 /3) was used across all exposure durations. AEGL-1 values are summarized in Table 7. 

11 Calculations are in Appendix C and a category graph of the toxicity data in relation to AEGL 

12 values is in Appendix D. 

13 

TABLE 7. AEGL-1 Values for Automotive Gasoline Vapor

10-min 30-min 1-h 4-h 8-hour 

730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3

14 

15 

16 6. DATA ANALYSIS FOR AEGL-2

17 6.1. Summary of Human Data Relevant to AEGL-2

18 

19 Davis et al. (1960) exposed 10 male subjects to three different samples of unleaded 

gasoline vapor for 30 minutes. Target concentrations were 880, 2200, and 4400 mg/m3 20 . 

Drowsiness was reported by two subjects inhaling 4400 mg/m3 21 and in two control subjects. 

22 

23 6.2. Summary of Animal Data Relevant to AEGL-2

24 

25 All acute inhalation studies were conducted with rats as the test model. A 4-hour 

exposure to 5000 mg/m3 26 of vapor of various gasoline blending streams was generally without a 

27 toxic effect (API 2008a,b; ARCO Chemical Co. 1984). No higher concentrations were tested in 

acute studies. In subchronic studies, the highest concentrations tested, 20,000 and 22,500 mg/m3 28 

(rat), 7690 mg/m3

 (mouse), and 6570 mg/m3 29 (monkey) were also without apparent toxic effects 

30 (Schreiner et al. 2000; O’Callaghan et al. 2004; Dalbey et al. 1996; Kuna and Ulrich 1984), 

31 although clinical signs were specifically addressed only in the study of Schreiner et al. (2000). 

32 Schreiner et al. (2000) reported an absence of neurotoxicity (tremors, ataxia, lethargy) in rats 

during subchronic exposure to 22,500 mg/m3 33 . 

34 

35 6.3. Derivation of AEGL-2

36 

37 The study of Davis et al. (1960) does not address effects helpful in determining an 

38 AEGL-2. For substances with anesthetic effects, the threshold for neurotoxicity is the point of 

39 departure. In a series of studies of the acute inhalation toxicity of blending streams of gasoline, 

the limit concentration of 5000 mg/m3

 (range, 5000-5300 mg/m3 40 ) was generally without effect. 

41 Clinical signs of slight nasal discharge, lacrimation in a few animals, and reduced righting reflex 

42 were observed in some of the studies (API 2008a,b; ARCO Chemical Co. 1984). 

43 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 25 of 41 

1 Because acute studies do not address endpoints consistent with the definition of the 

2 AEGL-2, observations from longer-term studies are relevant. Male and female Sprague-Dawley 

rats exposed to 22,500 mg/m3 3 of a gasoline blending stream failed to show neurotoxic signs 

4 during a 6 hour/day exposure over 90 days (Schreiner et al. 2000). Rats were observed 

specifically for tremors, ataxia, and lethargy. The point of departure, 22,500 mg/m3 5 , was divided 

6 by interspecies and intraspecies uncertainty factors of 1 and 3, respectively, for a total of 3, 

giving an AEGL-2 value of 7500 mg/m3

 (22,500 mg/m3 7 /3). An interspecies uncertainty factor of 

8 1 is sufficient because solvent uptake is generally greater in rodents than in humans (based on 

9 higher blood:air partition coefficients for related hydrocarbons (Bruckner et al. 2008; Gargas et 

10 al 1989)]. In addition, chemical uptake is faster in rodents than in humans based on higher 

11 respiratory rate and greater cardiac output on a body weight basis. Although humans differ in 

12 the rate at which they metabolize chemicals, the susceptibility of the general population to 

13 central nervous system depressants varies by no more than 2- to 3-fold as indicated by the 

14 minimum alveolar concentration, the concentration of an inhaled anesthetic that produces 

15 immobility in 50% of patients (Kennedy and Longnecker 1996; Marshall and Longnecker 1996). 

16 Therefore, an intraspecies uncertainty factor of 3 (rather than the default of 10) is considered 

17 sufficient. Higher uncertainty factors would result in values inconsistent with the clinical study 

18 of Davis et al. (1960). Time scaling may not be relevant for hydrocarbons that act as anesthetics 

19 as blood concentrations rapidly approach steady-state. Therefore, the 6-hour value of 7500 

mg/m3 20 was used across all exposure durations. AEGL-2 values are summarized in Table 8. 

21 Calculations are in Appendix C and a category graph of the toxicity data in relation to AEGL 

22 values is in Appendix D. 

23 

24 

TABLE 8. AEGL-2 Values for Automotive Gasoline Vapor

10-min 30-min 1-h 4-h 8-h 

7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 

*The AEGL-2 value is higher than 1/10 of the lower explosive limit (LEL) of gasoline in air (LEL = 14,000 ppm 

or 42,000 mg/m3

). Therefore, safety considerations against hazard of explosion must be taken into account. 

25 

26 The subchronic study of Kuna and Ulrich (1984) in which squirrel monkeys inhaling 

6350 mg/m3 27 for 6 hours/day showed no toxic signs supports the calculated AEGL-2 value, and 

28 by extension, the interspecies uncertainty factor of 1. Lack of toxicologically significant effects 

29 in reproductive and developmental repeat-exposure studies at concentrations of 20,000 to 23,900 

mg/m3 30 (McKee et al. 2000; Roberts et al. 2001; Gray et al. 2004) support the key study. 

31 

32 The toxicity of individual hydrocarbons comprising gasoline vapor may also be 

33 supportive of the values derived for gasoline vapor. In a subchronic study of n-pentane toxicity 

with male and female Sprague-Dawley rats, 20,000 mg/m3 34 /day for 6 hours/day, 5 days/week for 

35 13 weeks was a NOAEL for lethality and changes in body weight gain, hematology parameters, 

36 clinical chemistry, gross findings, ophthalmology, and histopathology of major tissues and 

37 organs (McKee et al. 1998). This value is similar to the NOAEL for a blending stream in the 

38 AEGL-2 key study. 

39 

40 7. DATA ANALYSIS FOR AEGL-3

41 7.1. Summary of Human Data Relevant to AEGL-3

42 

43 No human data relevant to calculation of AEGL-3 values were located. 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 26 of 41 

1 

2 7.2. Summary of Animal Data Relevant to AEGL-3

3 

4 None of the acute or subchronic studies with gasoline vapor or gasoline vapor plus 

5 additives resulted in mortality in rats. The highest exposures for 4-hour acute and 6 hour/day 

subchronic studies were approximately 5000 mg/m3 (API 2008a,b) and 22,500 mg/m3 6 (Schreiner 

7 et al. 2000), respectively. There was no mortality in these studies. The 4-hour LC50 for 

isopentane is 280,000 mg/m3 8 (Matheson Tri-Gas, Inc. 2009). 

9 

10 7.3. Derivation of AEGL-3

11 

12 It is not apparent that concentrations high enough to cause death from inhalation of 

13 automotive gasoline vapor can be attained except in occasional accidental or misuse cases. 

14 Based on the likelihood that lethal concentrations of gasoline vapor cannot be attained/sustained 

15 under ambient conditions, an AEGL-3 was not determined (Table 9). 

16 

17 At sufficiently high concentrations, toxicologically inert chemicals may act as simple 

18 asphyxiants by displacing atmospheric oxygen (Leikauf and Prows 2001). For the sensitive 

19 population of people with pulmonary diseases (edema or emphysema) or cardiovascular 

20 diseases, an arterial oxygen saturation of 65% may be the threshold for a life threatening 

21 condition. Using the SatCur model (2009), 65% oxygen saturation in a sensitive subject 

22 performing light exercise corresponds to 14% atmospheric oxygen. This corresponds to a 33% 

atmosphere of a simple asphyxiant (330,000 ppm or 990,000 mg/m3 23 ). 

24 

TABLE 9. AEGL-3 Values for Automotive Gasoline Vapor

10-min 30-min 1-h 4-h 8-h 

Not determined* Not determined* Not determined Not determined Not determined 

25 * AEGL-3 values were not determined due to insufficient data. Automotive gasoline vapor may act as a simple 

asphyxiant in sensitive individuals at 990,000 mg/m3 26 . 

27 

28 8. SUMMARY OF AEGLs

29 8.1. AEGL Values and Toxicity Endpoints 

30 

31 AEGL values are summarized in Table 10. Derivations summaries are in Appendix E. 

32 

TABLE 10. Summary of AEGL Values for Gasoline Vapor

Exposure Duration

Classification 10-min 30-min 1-h 4-h 8-h

AEGL-1 

(Nondisabling) 

730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3

AEGL-2 

(Disabling) 

7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 

AEGL-3 

(Lethal)** 

Not determined Not determined Not determined Not determined Not determined 

33 *The AEGL-2 value is higher than 1/10 of the lower explosive limit (LEL) of gasoline in air (LEL = 14,000 ppm). 

34 Therefore, safety considerations against hazard of explosion must be taken into account. 

35 **AEGL-3 values were not determined due to insufficient data. Automotive gasoline vapor may act as a simple 

asphyxiant in sensitive individuals at 990,000 mg/m3 36 . 

37 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 27 of 41 

1 8.2. Comparison with Other Standards and Guidelines 

2 

3 Standards and guidelines for automotive gasoline are listed in Table 11. The American 

4 Conference of Government Industrial Hygienists (ACGIH) Threshold Limit Value of 300 ppm 

(890 mg/m3 5 ) is based on Runion (1975). Runion (1975) cites the study of Drinker et al. (1943) 

6 as showing eye irritation at 160-270 ppm during 8-hour exposures. The ACGIH short-term 

exposure limit is 500 ppm (1480 mg/m3 7 ). 

8 

 The Emergency Response Planning Guideline-1 (ERPG-1) of 200 ppm (654 mg/m3 9 ) is 

10 based on the study of Drinker et al. (1943) in which eye irritation was reported at 140 ppm 

11 during an 8-hour exposure. It is believed that the threshold for eye irritation would be 200 ppm 

for shorter exposure periods. The ERPG-2 of 1000 ppm (3270 mg/m3 12 ) was based on the onset of 

mild central nervous system depression in workers. The ERPG-3 of 4000 ppm (13,080 mg/m3 13 ) 

14 was considered non-life-threatening. The ERPG values used the conversion factor of 3.27 

(molecular weight of 80 for gasoline vapor) to convert from ppm to mg/m3 15 . 

16 

TABLE 11. Standards and Guidelines for Automotive Gasoline Vapor 

Exposure Duration

Guideline 10 min 30 min 1 h 4 h 8 h 

AEGL-1 730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3

AEGL-2 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 

AEGL-3** Not determined Not determined Not determined Not determined Not determined 

ERPG-1 (AIHA)a 654 mg/m3 

ERPG-2 (AIHA) 3270 mg/m3 

ERPG-3 (AIHA) 13,080 mg/m3 

Dutch VRWb 2 mg/m3 

Dutch AGW 1000 mg/m3 

Dutch LBW 5000 mg/m3

IDLH 

(NIOSH)c 

─Ca 

REL-TWA 

(NIOSH)d 

 Ca 

OSHA PEL 

(NIOSH)e

 ─

TLV-TWA 

(ACGIH)f 

 890 mg/m3; 

1480 mg/m3

(15-min STEL) 

MAK (Germany)g ─

MAC (The 

Netherlands)h

 240 mg/m3

; 

480 mg/m3

 (15-

min excursion) 

17 *The AEGL-2 value is higher than 1/10 of the lower explosive limit (LEL) of gasoline in air (LEL = 14,000 ppm or 

42,000 mg/m3 18 ). Therefore, safety considerations against hazard of explosion must be taken into account. 

** Automotive gasoline vapor may act as a simple asphyxiant in sensitive individuals at 990,000 mg/m3 19 . 

20 VRW = Voorlichtingsrichtwaarde, threshold at which the general public needs to be informed (based on odor). 

21 AGW = Alarmeringsgrenswaarde, threshold for irritation. 

22 LBW = Levensbedreigende waarde, neurotoxicity. 

23 Ca = potential occupational carcinogen. 

24 a 25 ERPG (Emergency Response Planning Guidelines, American Industrial Hygiene Association (AIHA 2008). 

26 The ERPG-1 is the maximum airborne concentration below which it is believed nearly all individuals could be 

27 exposed for up to one hour without experiencing other than mild, transient adverse health effects or without 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 28 of 41 

1 perceiving a clearly defined objectionable odor. 

2 The ERPG-2 is the maximum airborne concentration below which it is believed nearly all individuals could be 

3 exposed for up to one hour without experiencing or developing irreversible or other serious health effects or 

4 symptoms that could impair an individual=s ability to take protective action. 

5 The ERPG-3 is the maximum airborne concentration below which it is believed nearly all individuals could be 

6 exposed for up to one hour without experiencing or developing life-threatening health effects. 

7 

b 8 Dutch Intervention Values are similar to the ERPG values and the 1-hour AEGL values, but are based on slighter 

9 effects – odor, irritation, and neurotoxicity, respectively. 

10 c 11 IDLH (Immediately Dangerous to Life and Health, National Institute of Occupational Safety and Health)

12 (NIOSH 2005) represents the maximum concentration from which one could escape within 30 minutes without any 

13 escape-impairing symptoms, or any irreversible health effects. 

14 d 15 NIOSH REL-TWA (National Institute of Occupational Safety and Health, Recommended Exposure Limits - 

16 Time Weighted Average) (NIOSH 2005) is defined analogous to the ACGIH-TLV-TWA. 

17 e 18 OSHA PEL-TWA (Occupational Safety and Health Administration, Permissible Exposure Limits - Time 

19 Weighted Average) (NIOSH 2005) is defined analogous to the ACGIH-TLV-TWA, but is for exposures of no more 

20 than 10 hours/day, 40 hours/week (no value assigned). 

21 f 22 ACGIH TLV-TWA (American Conference of Governmental Industrial Hygienists, Threshold Limit Value - 

23 Time Weighted Average) (ACGIH 1992) is the time-weighted average concentration for a normal 8-hour workday 

24 and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse 

25 effect. 

26 

27 gMAK (Maximale Arbeitsplatzkonzentration [Maximum Workplace Concentration]) (Deutsche 

28 Forschungsgemeinschaft [German Research Association 2008] is defined analogous to the ACGIH-TLV-TWA (no 

29 value assigned). 

30 

31 hMAC (Maximaal Aanvaarde Concentratie [Maximal Accepted Concentration]) (SDU Uitgevers [under the 

32 auspices of the Ministry of Social Affairs and Employment], The Hague, The Netherlands is defined similar to the 

ACGIH TLV. The 15-minute ceiling is 480 mg/m3 33 . Note: automotive gasoline is called benzene.

34 

35 8.3. Data Adequacy and Research Needs

36 

37 The data base for gasoline is rich. Clinical studies addressed subjective and objective eye 

38 irritation. Studies with laboratory rodents addressed acute and subchronic toxicity, chronic 

39 toxicity/carcinogenicity, neurotoxicity, reproductive and developmental toxicity and 

40 genotoxicity. 

41 

42 9. REFERENCES

43 

44 ACGIH (American Conference of Government and Industrial Hygienists). 1992. Documentation of the 

45 Threshold Limit Values and Biological Exposure Indices. Cincinnati, OH: ACGIH. 

46 

47 AIHA (American Industrial Health Association). 2008. Emergency Response Planning Guidelines: 

48 Gasoline. Fairfax, VA (Preprint). 

49 

50 Amerada Hess Corporation. 2004. Material Safety Sheet: Gasoline, All Grades. MSDS No. 9950, 

51 Amerada Hess, Woodbridge, NJ. 

52 

53 Anonymous. 1989. Toxicology update. J. Appl. Toxicol. 9:203-210. 

54 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 29 of 41 

1 API (American Petroleum Institute). no date. Gasoline Blending Streams Test Plan. Submitted to the 

2 US EPA by The American Petroleum Institute, Petroleum HPV Testing Group. Consortium 

3 Registration #1100997. 

4 

5 API (American Petroleum Institute). 1982. LC50 Acute Inhalation Toxicity Evaluation in Rats (API-No. 

6 81-08). API Medical Research Publication 30-31990. Study conducted by the International Research 

7 and Development Corporation for the American Petroleum Institute, with amendment dated February 

8 14, 1983. Washington, DC: American Petroleum Institute. 

9 

10 API (American Petroleum Institute). 1994. Odor threshold studies performed with gasoline and gasoline 

11 combined with MTBE, ETBE and TAME, with cover letter dated 02/22/95. API Publication 4592, 

12 prepared by TRC Environmental, Windsor, CT. OTS0557644, available from the National Technical 

13 Information Service, Springfield, VA. 

14 

API (American Petroleum Institute). 1995. Index and Abstracts of API Health-Related Research, 13th 15 

16 ed., 1959-1994. American Petroleum Institute, Health and Environmental Sciences Department, 

17 Publication Number 4534. 

18 

19 API (American Petroleum Institute). 2002. Robust Summary of Information on Gasoline. API, 

20 Washington, DC. 

21 

22 API (American Petroleum Institute). 2008a Gasoline Blending Streams Category: Robust Studies 

23 Summary. File provided by R. White, API, Washington, DC: 

24 2008_aug21_gasoline_catanalysis_final_robust_study_summaries. 

25 

26 API (American Petroleum Institute). 2008b Gasoline Blending Streams Category Assessment 

27 Document. Submitted to the U.S. EPA by the American Petroleum Institute, Petroleum HPV Testing 

28 Group, Consortium Registration #1100997. 

29 

30 ARCO Chemical Co. 1984. Toxicology Report: Acute Toxicity Studies of ARCO Clear Gasoline with 

31 MTBE (1984) and Submission of Inhalation Studies Done on Rats with MTBE with Cover Letter 

32 Dated 021987. Studies performed by Bio/dynamics Inc., for the Atlantic Richfield Company, Los 

33 Angeles, CA. 

34 

35 ATSDR (Agency for Toxic Substances and Disease Registry). 1995. Toxicological Profile for 

36 Automotive Gasoline. U.S. Department of Health & Human Services, Public Health Service, Atlanta, 

37 GA. 

38 

39 Benson, J., C.R. Clark, E.B. Barr, A.P. Gigliotti, T.H. March, C.A. Elliot, A.P. Gomez, B.M. Tibbetts, 

40 and R. White. 2004. Inhalation Toxicity of Gasoline & Fuel Oxygenates: Chronic Toxicity. Poster 

presented at the 43rd 41 Annual Meeting of the Society of Toxicology held in Baltimore, MD. 

42 

43 Bruckner, J.V., S. S. Anand, and D. A. Warren. 2008. Chapter 24: Toxic Effects of Solvents and Vapors. 

 Pp. 981- 1051 in Casarett & Doull’s Toxicology: The Basic Science of Poisons, 7th 44 ed. New York: 

45 McGraw Hill Medical. 

46 

47 Cavender, F. 1994a. Chapter 19: Aliphatic hydrocarbons. In: Patty=s Industrial Hygiene and 

48 Toxicology, 4th ed., vol. II, Part B. John Wiley & Sons, New York, pp. 1221-1266. 

49 

50 Cavender, F. 1994b. Chapter 20: Alicyclic hydrocarbons. In: Patty=s Industrial Hygiene and 

51 Toxicology, 4th ed., vol. II, Part B. John Wiley & Sons, New York, pp. 1267-1299. 

52 
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1 Cavender, F. 1994c. Chapter 21: Aromatic hydrocarbons. In: Patty=s Industrial Hygiene and 

2 Toxicology, 4th ed., vol. II, Part B. John Wiley & Sons, New York, pp. 1301-1442. 

3 

4 Chu, I., R. Poon, V. Valli, A. Yagminas, W.J. Bowers, R. Seegal, and R. Vincent. 2005. Effects of an 

5 ethanol-gasoline mixture: results of a 4-week inhalation study in rats. J. Appl. Toxicol. 25:193-199. 

6 

7 CONCAWE (Conservation of Clean Air and Water in Europe). 1992. Gasolines. Product Dossier No. 

8 92/103. Brussels: CONCAWE. 

9 

10 Dahl, A.R., E.G. Damon, J.L. Mauderly, S.J. Rothenberg, F.A. Seiler, and R.O. McClellan. 1988. 

11 Uptake of 19 hydrocarbon vapors inhaled by F344 rats. Fund. Appl. Toxicol. 10:262-269. 

12 

13 Dalbey, W.E. and M.H. Feuston. 1996. Partially vaporized full range catalytic reformed naphtha: 

14 subchronic and developmental toxicity studies in rats. Inhal. Toxicol. 8:271-284. 

15 

16 Dalbey, W.E., M.H. Feuston, and J.J. Yang. 1996. Light catalytically cracked naphtha: subchronic 

17 toxicity of vapors in rats and mice and developmental toxicity screen in mice. J. Toxicol. Environ. 

18 Health 47:77-91. 

19 

20 Daughtrey, W.C., D.M. Burnett, P. Podhasky, M. Henley, and R.D. White. 2004. Inhalation Toxicity of 

Gasoline & Fuel Oxygenates: Test Sample Preparation. Poster presented at the 43rd 21 Annual Meeting 

22 of the Society of Toxicology held in Baltimore, MD. 

23 

24 Davis, A., L. Schafer, and Z. Bell. 1960. The effects on human volunteers of exposure to air containing 

25 gasoline vapor. Arch. Environ. Health 1:545-554. 

26 

27 Dennison, J.E., M.E. Andersen, and R.S.H. Yang. 2003. Characterization of the pharmacokinetics of 

28 gasoline using PBPK modeling with a complex mixtures chemical lumping approach. Inhal. Toxicol. 

29 15:961-986. 

30 

31 Drinker, P., C. Yaglou, and J. Warren. 1943. The threshold toxicology of gasoline vapor. J. Ind. Hyg. 

32 Toxicol. 25:225-232. 

33 

34 Dutch Intervention Values. 2009. Gasoline. Published by the Ministry of Housing, Spatial Planning and 

35 Environment, The Hague, The Netherlands. 

36 

37 Galvin, J.B., and F. Marashi. 1999. 2-Methylbutane (isopentane). J. Toxicol. Environ. Health, Part A, 

38 58:23-33. 

39 

40 Gargas, M.L., R.J. Burgess, D.E. Voisard, G.H. Cason, and M.E. Andersen. 1989. Partition coefficients 

41 of low-molecular-weight volatile chemicals in various liquids and tissues. Toxicol. Appl. Pharmacol. 

42 98: 87-99. 

43 

44 German Research Association (Deutsche Forschungsgemeinschaft). 2008. List of MAK and BAT 

45 Values 2007. Report No. 44, Commission for the Investigation of Health Hazards of Chemical 

46 Compounds in the Work Area. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. 

47 

48 Gray, T.M., K.P. Haxelden, D.R. Steup, J.P. O’Callaghan, G.M. Hoffman, and L.G. Roberts. 2004. 

49 Inhalation toxicity of gasoline & fuel oxygenates; reproductive toxicity assessment. Poster presented 

at the 43rd 50 Annual Meeting of the Society of Toxicology held in Baltimore, MD. 

51 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 31 of 41 

1 Halder, C.A., G.S. van Gorp, N.S. Hatoum, and T.M. Warne. 1986. Gasoline vapor exposures. Part II. 

2 Evaluation of the nephrotoxicity of the major C4/C5 hydrocarbon components. Am. Ind. Hyg. Assoc. 

3 J. 47:173-175. 

4 

5 IARC (International Agency for Research on Cancer). 1989. IARC Monographs on the Evaluation of 

6 Carcinogenic Risks to Humans. Some Chemicals that Cause Tumors of the Kidney or Urinary 

7 Bladder in Rodents and Some Other Substances. Vol. 73, Lyons, France, World Health Organization. 

8 

9 Kennedy, S.K. and D.E. Longnecker. 1996. History and Principles of Anesthesiology. P. 302 in 

10 Goodman & Gilman=s The Pharmacological Basis of Therapeutics, 9th Ed., J.G. Hardman et al., eds. 

11 New York: McGraw-Hill. 

12 

13 Kuna, R.A. and C.E. Ulrich. 1984. Subchronic inhalation toxicity of two motor fuels. J. Am. Coll. 

14 Toxicol. 3:217-230. 

15 

16 Leikauf, G.D. and D.R. Prows. 2001. Chapter 47: Inorganic Compounds of Carbon, Nitrogen, and 

17 Oxygen. In Patty’s Industrial Hygiene and Toxicology, Vol. 3. John Wiley & Sons, New York, pp. 

18 657-661. 

19 

20 MacFarland, H.N., C.E. Ulrich, C.E. Holdsworth. 1984. A chronic inhalation study with unleaded 

21 gasoline vapor. J. Am. Coll. Toxicol. 3:231-248. 

22 

23 Marshall, B.E. and D.E. Longnecker. 1996. General Anesthetics. P. 307 in Goodman & Gilman=s The 

24 Pharmacological Basis of Therapeutics, 9th Ed., J.G. Hardman et al., eds. New York: McGraw-Hill. 

25 

26 Matheson Tri-Gas, Inc. 2009. Material Safety Data Sheet for Isopentane. Matheson Tri-Gas, Inc. 

27 Basking Ridge, NJ. 

28 

29 McKee, R., E. Frank, J. Heath, D. Owen, R. Przygoda, G. Trimmer, and F. Whitman. 1998. Toxicity of 

30 n-pentane (CAS No. 109-66-0). J. Appl. Toxicol. 18:431-442. 

31 

32 McKee, R.H., S. Dally, B.A. Dmytrasz, J.F. Gonnet, R.E. Hagermann, C. Mackerer, C.S. Nessel, R.A.J. 

33 Priston, A.J. Riley, and J.H. Urbanus. 2000. An Assessment of the Reproductive Toxicity of 

34 Gasoline Vapor. CONCAWE report no. 00/53. Available online: 

35 http://www.concawe.org/DocShareNoFrame/docs/2/CAAIBNPACFICDAJIDIEHJBOHPDBY9DBY

36 AY9DW3571KM/CEnet/docs/DLS/2002-00232-01-E.pdf. 

37 

38 Moser, G.J., B.A. Wong, D.C. Wolf, O.R. Moss, and T.L. Goldworthy. 1996. Comparative short-term 

39 effects of methyl tertiary butyl ether and unleaded gasoline vapor in female B6C3F1 mice. Fund. 

40 Appl. Toxicol. 31:173-183. 

41 

42 Niemeier, R.W. 2001. Chapter 22; Petroleum, Coal Tar, and Related Products. Pp. 786-789 In Patty’s 

Toxicology, 5th 43 ed., Vol. 1. New York: John Wiley & Sons, Inc. 

44 

45 NIOSH. 2005. NIOSH Pocket Guide to Chemical Hazards. Online data base, U.S. Department of Health 

46 and Human Services: http://www.cdc.gov/niosh/npg. 

47 

48 O’Callaghan, J.P., C.M. Felton, B.K. Billig, W.C. Daughtrey. 2004. Inhalation Toxicity of Gasoline & 

Fuel Oxygenates: Neurotoxicity. Poster presented at the 43rd 49 Annual Meeting of the Society of 

50 Toxicology held in Baltimore, MD. 

51 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 32 of 41 

1 O’Neil, M.J., A. Smith, and P.E. Heckelman. 2001. Gasoline. The Merck Index. Whitehouse Station, 

2 NJ: Merck & Co., Inc., p. 4382. 

3 

4 Reese, E. and R.D. Kimbrough. 1993. Acute Toxicity of gasoline and some additives. Environ. Health 

5 Persp. 101(Suppl. 6):115-131. Available online: 

6 http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1520023&blobtype=pdf. 

7 

8 Richardson, K.A., J.L. Wilmer, D. Smith-Simpson, and T.R. Skopek. 1986. Assessment of the genotoxic 

9 potential of unleaded gasoline and 2,2,4-trimethylpentane in human lymphoblasts in vitro. Toxicol. 

10 Appl. Pharmacol. 82:316-322. 

11 

12 Roberts, L., R. White, Q. Bui, W. Daughtrey, F. Koschier, S. Rodney, C. Shreiner, D. Steup, R. Breglia, 

13 R. Rhoden, R. Schroeder, and P. Newton. 2001. Developmental toxicity evaluation of unleaded 

14 gasoline vapor in the rat. Reprod. Toxicol. 15:487-494. 

15 

16 Robinson, P.J. 2000. Pharmacokinetic Modeling of JP-8 Jet Fuel Components. I. Nonane and C9-C12 

17 Aliphatic Components. AFRL-HE-WP-TR-2000-0046, Wright Patterson AFB, OH. 

18 

19 Runion, H.E. 1975. Benzene in gasoline. Amer. Ind. Hyg. Assoc. J. 36:338-350. 

20 

21 SatCur. 2009. A Program Teaching the Hemoglobin Oxygen Saturation Curve. Available online: 

22 http://www.baloh.nl. 

23 

24 Schreiner, C., Q. Bui, R. Breglia, D. Burnett, F. Koschier, E. Lapadula, P. Podhasky, and R. White. 2000. 

25 Toxicity evaluations of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity 

26 study of a light catalytic reformed naphtha distillate in rats. J. Toxicol. Environ. Health, Part A, 

27 60:489-512. 

28 

29 Schreiner, C., G. Hoffman, C. Mason, and R. Gudi. 2004. Inhalation toxicity of gasoline and fuel 

oxygenates: micronucleus and sister chromatid exchange tests. Poster presented at the 43rd 30 Annual 

31 Meeting of the Society of Toxicology held in Baltimore, MD. 

32 

33 SDU Uitgevers. 2000. Nationale MAC List. Under the auspices of the Ministry of Social Affairs and 

34 Employment. The Netherlands: The Hague. 

35 

36 Standeven A.M., D.C. Wolf, and T.L. Goldsworthy. 1995. Promotion of hepatic preneoplastic lesions in 

37 male B6C3F1 mice by unleaded gasoline. Environ. Health Persp. 103:696-700. 

38 

39 U.S. EPA (U.S. Environmental Protection Agency). 1991. Alpha-2-globulin: Association with 

40 chemically-induced renal toxicity and neoplasia in the male rat. EPA/625/3-91/019F, Risk 

41 Assessment Forum, U.S. Environmental Protection Agency, Washington, DC. 

42 

43 U.S. EPA (U.S. Environmental Protection Agency). 2002. Interim AEGL Values for Toluene. Available 

44 online: http://www.epa.gov/oppt/aegl/pubs/results32.htm. 

45 

46 van Doorn, R., M. Ruijten and T. van Harreveld. 2002. Guidance for the Application of Odor in 

47 Chemical Emergency Responses, Unpublished report, Version 2.1, August 29, 2002. 

48 

49 White, R. 2009. Gasoline: Composition and Toxicology. Presentation to the National Advisory 

50 Committee for Acute Exposure Guideline Levels, April 15, 2009. 

51 

52 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 33 of 41 

1 

2 APPENDIX A: Major Hydrocarbons found in Gasoline Vapor Condensate 

3 (representative composition) 

4 

Hydrocarbon Gasoline Vapor Condensate (%) Gasoline Vapor Condensate 

containing 10% Ethanol (%) 

Isobutane (C4H10) 2.8 2.2 

n-Butane (C4H10) 13.1 11.6 

Isopentane (C5H12) 34.8 34 

n-Pentane (C5H12) 13.7 10.2 

trans-2 Pentene (C5H10) 2.6 2.1 

2-Methylpentane (C6H14) 6.8 5.1 

n-Hexane (C6H14) 3.1 2.4 

Benzene (C6H6) 2.2 1.6 

3-Methyl hexane (C7H16) 1.4 1.2 

Isooctane (C8H18) 1.5 1.3 

Toluene (C7H8) 3.3 2.4 

Ethanol (C2H6O) 0.0 13.3 

5 Note: as measured by % gas chromatography area. 

6 Source: White (2009). 

7 

8 Typical Oxygenate Levels (v/v) 

9 (only one used in any gasoline) 

10 

Methyl t-butyl ether (MTBE) 21.3 

t-Amyl methyl ether (TAME) 11.9 

Ethyl t-butyl ether (ETBE) 16.3 

Diisopropyl ether (DIPE) 17.8 

Ethanol 13.3 

t-Butyl alcohol (TBA) 16.8 

11 Source: Daughtrey et al. (2004). 

12 

13 

14 Petroleum Chemistry Definitions (Source: API n.d.): 

15 

16 Paraffins: CnH2n+2: carbon atoms are joined by a single bond; may be linear or branched 

17 example: n-pentane 

18 Olefins: CnH2n: contain at least one double bond; may be linear, branched, or cyclic 

19 example: cyclohexene 

20 Cycloparaffins (naphthenes): 5-6 carbon atoms arranged in a ring, saturated 

21 example: cyclohexane 

22 Aromatics: carbon atoms arranged in a ring, unsaturated 

23 examples: benzene, toluene 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 34 of 41 

1 

2 APPENDIX B: Derivation of Level of Odor Awareness 

3 

4 The level of distinct odor awareness (LOA) represents the concentration above which it 

5 is predicted that more than half of the exposed population will experience at least a distinct odor 

6 intensity, and about 10% of the population will experience a strong odor intensity. The LOA 

7 should help chemical emergency responders in assessing the public awareness of the exposure 

8 due to odor perception. The LOA derivation follows the guidance given by van Doorn et al. 

9 (2002). 

10 

11 The lowest odor detection threshold (OT50) for gasoline without additives was for the summer 

12 and winter composite blend, 0.474 ppm. (API 1994). 

13 

14 The concentration (C) leading to an odor intensity (I) of distinct odor detection (I=3) is derived 

15 using the Fechner function: 

16 

17 I = kw x log (C /OT50) + 0.5 

18 

19 For the Fechner coefficient, the default of kw = 2.33 will be used due to the lack of chemical20 specific data: 

21 

22 3 = 2.33 x log (C /0.474) + 0.5 which can be rearranged to 

23 log (C /0.474) = (3 - 0.5) / 2.33 = 1.07 and results in 

C = (101.07 24 ) x 0.474 = 5.6 ppm 

25 

26 The resulting concentration is multiplied by an empirical field correction factor. It takes 

27 into account that in every day life factors such as sex, age, sleep, smoking, upper airway 

28 infections and allergy, as well as distraction, may increase the odor detection threshold by up to a 

29 factor of 4. In addition, it takes into account that odor perception is very fast (about 5 seconds) 

30 which leads to the perception of concentration peaks. Based on the current knowledge, a factor 

31 of 1/3 is applied to adjust for peak exposure. Adjustment for distraction and peak exposure lead 

32 to a correction factor of 4 / 3 = 1.33 

33 

34 LOA = C x 1.33 = 5.57 ppm x 1.33 = 7.4 ppm 

35 

The LOA for gasoline is 7.4 ppm (approximately 22 mg/m3 36 ). 

37 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 35 of 41 

1 

2 APPENDIX C: Derivation of Gasoline AEGLs 

3 

4 Derivation of AEGL-1 Values 

5 

6 Key Study: Davis, A., L. Schafer, and Z. Bell. 1960. The effects on human volunteers 

7 of exposure to air containing gasoline vapor. Arch. Environ. Health 1:545-

8 554. 

9 

10 Toxicity endpoint: Slight to subjective and objective eye irritation in human subjects at 2200 

mg/m3 11 for 30 minutes 

12 

13 Time scaling None; there is adaptation to the slight irritation that defines the AEGL-1 

14 

15 Uncertainty factors: Interspecies: not applied to human subjects 

16 Intraspecies: 3, generally applied to slight to mild sensory irritation studies 

17 to protect sensitive individuals; adaptation to irritation was demonstrated 

18 

Calculations: 2200 mg/m3/3 = 730 mg/m3 19 

20 

10-min AEGL-1: C = 730 mg/m3 21 

22 

30-min AEGL-1: C = 730 mg/m3 23 

24 

1-h AEGL-1: C = 730 mg/m3 25 

26 

4-h AEGL-1: C = 730 mg/m3 27 

28 

8-h AEGL-1: C = 730 mg/m3 29 

30 

31 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 36 of 41 

1 Derivation of AEGL-2 Values

2 

3 Key Study: Schreiner, C., Q. Bui, R. Breglia, D. Burnett, F. Koschier, E. Lapadula, P. 

4 Podhasky, and R. White. 2000. Toxicity evaluations of petroleum blending 

5 streams: inhalation subchronic toxicity/neurotoxicity study of a light catalytic 

6 reformed naphtha distillate in rats. J. Toxicol. Environ. Health, Part A, 

7 60:489-512. 

8 

Toxicity endpoint: No clinical signs in rats at highest chronic exposure, 22,5000 mg/m3 9 for 6 

10 hours/day, 5 days/week, subchronic 

11 

12 Time scaling None applied; steady-state in the blood is rapidly approached by 

13 hydrocarbon solvents 

14 

15 Uncertainty factors: Interspecies: 1, rodents have higher blood:air partition coefficients for many 

16 chemicals; in addition they have higher respiratory rates and cardiac output 

17 resulting in greater chemical uptake than in humans 

18 Intraspecies: 3, for hydrocarbon solvents the minimum alveolar concentration 

19 at which narcosis occurs differs by no more than two- to threefold among 

20 humans. 

21 

Calculations: 22,500 mg/m3/3 = 7500 mg/m3 22 

23 

10-min AEGL-2: C = 7500 mg/m3 24 

25 

30-min AEGL-2: C = 7500 mg/m3 26 

27 

1-h AEGL-2: C = 7500 mg/m3 28 

29 

4-h AEGL-2: C = 7500 mg/m3 30 

31 

8-h AEGL-2: C = 7500 mg/m3 32 

33 

34 

35 

36 Derivation of AEGL-3 Values

37 

38 Not determined. None of the rodent studies reported lethality at the highest concentrations tested. 

39 Therefore, AEGL-3 values cannot be determined. Gasoline vapor may act as a simple asphyxiant in 

sensitive individuals at a concentration of 990,000 mg/m3 40 . 

41 

42 

43 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 37 of 41 

1 APPENDIX D: Category Graph of AEGL Values and Toxicity Data for Gasoline 

2 

100 

1000 

10000 

100000 

mg/m3

0 60 120 180 240 300 360 420 480 

Minutes

Human - No Effect

Human - Discomfort

Human - Disabling

Animal - No Effect

Animal - Discomfort

Animal - Disabling

Animal - Some Lethality

Animal - Lethal

AEGL

AEGL-1

AEGL-2

3 

4 

5 

6 Data: 

 For Category: 0 = No effect, 1 = Discomfort, 2 = Disabling, SL = Some Lethality, 3 = Lethal 

 Source Species mg/m3 Minutes Category 

 

 NAC/AEGL-1 730 10 AEGL 

 NAC/AEGL-1 730 30 AEGL 

 NAC/AEGL-1 730 60 AEGL 

 NAC/AEGL-1 730 240 AEGL 

 NAC/AEGL-1 730 480 AEGL 

 

 NAC/AEGL-2 7500 10 AEGL 

 NAC/AEGL-2 7500 30 AEGL 

 NAC/AEGL-2 7500 60 AEGL 

 NAC/AEGL-2 7500 240 AEGL 

 NAC/AEGL-2 7500 480 AEGL 

 

 NAC/AEGL-3 Not determined 10 AEGL 

 NAC/AEGL-3 Not determined 30 AEGL 

 NAC/AEGL-3 Not determined 60 AEGL 

 NAC/AEGL-3 Not determined 240 AEGL 

 NAC/AEGL-3 Not determined 480 AEGL 

 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 38 of 41 

 Drinker et al. 1943 Human 420 480 0 (no irritation) 

 Human 450 480 0 (very slight irritation) 

 Human 480 480 0 (slight irritation) 

 Human 810 480 0 (slight irritation) 

 Human 1500 60 0 (slight irritation) 

 Human 2700 60 1 (slight irritation; threshold 

for unsteadiness) 

 Human 7800 60 1 (slight dizziness) 

 Human 32,100 5 2 (unsteadiness) 

 Human 33,600 5 2 (feeling of incoordination)

 

 Davis et al. 1960 Human 880 30 0 (minor irritation) 

 Human 2200 30 1 (slight eye irritation) 

 Human 4400 30 1 (slight to intermediate eye 

irritation) 

 

 API 2008a Rat 5000 240 0 (no effect) 

 Rat 5200 240 0 (no effect) 

 Rat 5300 240 0 (no effect) 

 

 ARCO Chemical Co. 

 1984 

 Rat 5200 240 0 (no effect) 

 Multiple studies: 

 McKee et al. 2000 

 Benson et al. 2004 

 Rat 20,000 360 0 (no effect) 

 Schreiner et al. 2000 Rat 22,500 360 0 (no effect) 

The 360-minute data points (20,000 and 22,500 mg/m3) are repeat-exposure (McKee et al. 2000), chronic 

exposure (Benson et al. 2004), and subchronic exposure (Schreiner et al. 2000) studies. 

1 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 39 of 41 

1 

2 APPENDIX E: Derivation Summary for Gasoline AEGLs 

3 Acute Exposure Guideline Levels For Gasoline 

4 (CAS Reg. No. 86290-81-5) 

5 

AEGL-1 VALUES

10-min 30-min 1-h 4-h 8-hour 

730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3 730 mg/m3

Key Reference: Davis, A., L. Schafer, and Z. Bell. 1960. The effects on human volunteers of exposure to air 

containing gasoline vapor. Arch. Environ. Health 1:545-554. 

Test Species/Strain/Sex/Number: Human/males/10 

Exposure Route/Concentration/Duration: Inhalation/0, 880, 2200, 4400 mg/m3 for 30 minutes 

Effects: Slight subjective and objective eye irritation at 2200 mg/m3 

Endpoint/Concentration/Rationale: Slight subjective and objective eye irritation at 2200 mg/m3) 

Uncertainty Factors/Rationale: 

Total uncertainty factor: 3 

Interspecies: None, human subjects 

Intraspecies: 3, generally applied to slight irritation in sensory irritation studies; adaptation to the irritation 

Modifying Factor: None 

Animal to Human Dosimetric Adjustment: Not applicable 

Time Scaling: None; there is adaptation to the slight irritation that defines the AEGL-1. 

Data Adequacy: The study was well-conducted and reported. Older clinical studies reported in several reviews 

support the derived values. 

6 

7 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 40 of 41 

1 

AEGL-2 VALUES

10-min 30-min 1-h 4-h 8-h 

7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 7500 mg/m3* 

Key Reference: Schreiner, C., Q. Bui, R. Breglia, D. Burnett, F. Koschier, E. Lapadula, P. Podhasky, and R. 

White. 2000. Toxicity evaluations of petroleum blending streams: inhalation subchronic 

toxicity/neurotoxicity study of a light catalytic reformed naphtha distillate in rats. J. Toxicol. 

Environ. Health, Part A, 60:489-512. 

Test Species/Strain/Number: Rat/Sprague-Dawley/15/sex/group 

Exposure Route/Concentration/Duration: Inhalation/0, 2250, 7500, 22,500 mg/m3/6 hours/day, 5 days/week, 

for 13 weeks 

Effects: No clinical signs of lethargy 

Endpoint/Concentration/Rationale: Although no lethargy/narcosis was observed, 22,500 mg/m3 was the 

highest exposure in any study 

Uncertainty Factors/Rationale: 

Total uncertainty factor: 3 

Interspecies: 1, for many hydrocarbons, rodents have higher blood:air partition coefficients; in addition 

they have higher respiratory rates and cardiac output resulting in greater chemical uptake than in humans 

Intraspecies: 3, for hydrocarbon solvents the minimum alveolar concentration at which narcosis occurs 

differs by no more than two- to threefold among humans. 

Modifying Factor: None applied 

Animal to Human Dosimetric Adjustment: Not applicable 

Time Scaling: None; 

Data Adequacy: The data base for gasoline is rich with studies at similar concentrations (20,000 mg/m3) and 

using different blending streams addressing general toxicity, neurotoxicity, reproductive and developmental 

toxicity and chronic toxicity/carcinogenicity. 

2 *The AEGL-2 value is higher than 1/10 of the lower explosive limit (LEL) of gasoline in air (LEL = 14,000 ppm). 

3 Therefore, safety considerations against hazard of explosion must be taken into account. 

4 

5 
AUTOMOTIVE GASOLINE NAC Proposed 1: October 2009/ Page 41 of 41 

1 

AEGL-3 VALUES

10-min 30-min 1-h 4-h 8-h 

Not determined Not determined Not determined Not determined Not determined 

Key References: 

Test Species/Strain/Number: 

Exposure Route/Concentration/Duration: 

Effect: 

Endpoint/Concentration/Rationale:. 

Uncertainty Factors/Rationale: 

Total uncertainty factor: 

Interspecies: 

Intraspecies: : 

Modifying Factor: 

Animal to Human Dosimetric Adjustment: 

Time Scaling: 

Data Adequacy: No studies were available that reported the threshold for lethality 

2