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policy. 1

2

3

4

5

6



## I MMEDIATELY 

## D ANGEROUS TO 

## L IFE OR 

## H EALTH 

## (IDLH) V ALUE 

## P ROFILE 7

8

9

10



### FOR 11

12

13

14



## B UTANE 15

16

17

18



## [CAS N O



## . 106-97-8] 19

20

21

22

23

24

25

Department of Health and Human Services 26

Centers for Disease Control and Prevention 27

National Institute for Occupa tional Safety and Health 28

29

30External Review Draft

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policy. 

## Disclaimer 1

2

Mention of any company or product does not constitute endorsement by the National Institute for Occupational 3

Safety and Health (NIOSH). In add ition, citations to Web sites extern al to NIOSH do not constitute NIOSH 4

endorsement of the sponsoring organizations or thei r programs or products. Furthermore, NIOSH is not 5

responsible for the content of these Web sites. 6

7



## Ordering Information 8

9

To receive this document or information about other o ccupational safety and health topics, contact NIOSH: 10

11

Telephone: 1-800-CDC-INFO (1-800-232-4636) 12

TTY: 1-888-232-6348 13

E-mail: cdcinfo@cdc.gov 14

Or visit the NIOSH Web site: www.cdc.gov/niosh 15

16

For a monthly update on news at NIOSH, subscribe to NIOSH eNews by visiting www.cdc.gov/niosh/eNews. 17

18

DHHS (NIOSH) Publication No. XXX 19

20

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policy. 

## Foreword 1

Chemicals are a ubiquitous component of the modern wo rkplace. Occupational exposures to chemicals have the 2

potential to adversely affect the health and lives of workers. Acute or short-term exposures to high concentrations 3

of some airborne chemicals have the ability to quickly overwhelm workers, resulting in a spectrum of undesirable 4

health outcomes that may inhibit the ability to escape from the exposure envi ronment (e.g., irritation of the eyes 5

and respiratory tract or cognitive impairment), cause severe irreversible effects (e.g., damage to the respiratory 6

tract or reproductive toxicity), and in extreme cases, cause death. Airborne concentrations of chemicals capable 7

of causing such adverse health effects or of impeding escape from high-risk conditions may arise from a variety of 8

non-routine workplace situations , including special wo rk procedures (e.g., in confined spaces), industrial 9

accidents (e.g., chemical spills or explosions), and chemical releases into the community (e.g., during 10

transportation incidents or other uncontrolled-release scenarios). 11

12

The “immediately dangerous to life or health air concen tration values (IDLH values)” developed by the National 13

Institute for Occupational Safety a nd Health (NIOSH) characterize these high-risk exposure concentrations and 14

conditions [NIOSH 2013]. IDLH values are based on a 30-minute exposure duration and have traditionally 15

served as a key component of the decision logic for the selection of respiratory protection devices [NIOSH 2004]. 16

Occupational health professionals have employed these values beyond their initial purpose as a component of the 17

NIOSH Respirator Selection Logic to assist in developi ng Risk Management Plans for non-routine work practices 18

governing operations in high-risk envi ronments (e.g., confined spaces) and the development of Emergency 19

Preparedness Plans. 20

21

The approach used to derive IDLH values for high priority chemicals is outlined in the NIOSH Current 22

Intelligence Bulletin (CIB) 66: Derivation of Immediately Da ngerous to Life or Health Values [NIOSH 2013]. 23

CIB 66 provides 1) an update on the scientific basis a nd risk assessment methodology used to derive IDLH 24

values, 2) the rationale and derivati on process for IDLH values, and 3) a demonstration of the derivation of 25

scientifically credible IDLH values using available data resources. 26

27

The purpose of this technical report is to present the IDLH value for butane (CAS # 106-97-8). The scientific 28

basis, toxicologic data and risk assessment approach u sed to derive the IDLH valu e are summarized to ensure 29

transparency and scientific credibility. 30

31

John Howard, M.D. 32

Director 33

National Institute for Occupa tional Safety and Health 34External Review Draft

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policy. Centers for Disease Control and Prevention 1External Review Draft

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policy. 

## Table of Contents 1

FOREWORD

............................................................................................................................... ................................. III 2

ABBREVIATIONS

............................................................................................................................... ........................ VI 3

GLOSSARY

............................................................................................................................... .................................. VII 4

ACKNOWLEDGMENTS

............................................................................................................................... ............... X 5

1.0 INTRODUCTION

............................................................................................................................... ............... 1 6

1.1 O VERVIEW OF THE IDLH V ALUE FOR B UTANE

........................................................................................................... 1 7

1.2 P URPOSE

............................................................................................................................... ...................................... 1 8

1.3 G ENERAL S UBSTANCE I NFORMATION

...................................................................................................................... 1 9

2.0 ANIMAL TOXICITY DATA

............................................................................................................................. 4 10

3.0 HUMAN DATA

............................................................................................................................... .................. 7 11

4.0 SUMMARY

............................................................................................................................... ......................... 7 12

5.0 REFERENCES

............................................................................................................................... .......................... 8 13

14

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policy. 

## Abbreviations 1

2

ACGIH American Conference of Gove rnmental Industrial Hygienists 3

AEGL Acute Exposure Guideline Levels 4

AIHA American Industrial Hygiene Association 5

BMC benchmark concentration 6

BMCL benchmark concentra tion lower confidence limit 7

C ceiling 8

CAS chemical abstract service 9

ERPG Emergency Response Planning Guidelines 10

IDLH immediately dangerous to life or health 11

LC 50 median lethal concentration 12

LC Lo lowest concentration of a chemical that caused death in humans or animals 13

LEL lower explosive limit 14

LOAEL lowest observed adverse effect level 15

mg/m 3 milligram(s) per cubic meter 16

NAC National Advisory Committee 17

NAS National Academy of Sciences 18

NIOSH National Institute for O ccupational Safety and Health 19

NOAEL no observed adverse effect level 20

OSHA Occupational Safety and Health Administration 21

PEL permissible exposure limit 22

ppm parts per million 23

RD 50 concentration of a chemical in the air that is estimated to cause a 50% decrease in the respiratory 24

rate 25

REL recommended exposure limit 26

SCP Standard Completion Program 27

STEL short term exposure limit 28

TLV threshold limit value 29

TWA time weighted average 30

UEL upper explosive limit 31

WEEL workplace environmental exposure level 32External Review Draft

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Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. 

## Glossary 1

2

Acute Exposure : Exposure by the oral, dermal, or inhalation route for 24 hours or less. 3

Acute Exposure Guideline Levels (AEGLs) : Threshold exposure limits for the general public applicable to 4

emergency exposure periods ranging from 10 minutes to 8 hours. AEGL-1, AEGL 2, and AEGL-3 are 5

developed for five exposure periods (10 and 30 minutes, 1 hour, 4 hours, and 8 hours) and are distinguished 6

by varying degrees of severity of toxic effects ranging fro m transient, reversible effects to life-threatening 7

effects [NAS 2001]. AEGLs are intended to be guideline levels used during rare events or single once-in-a8

lifetime exposures to airborne concentrations of ac utely toxic, high-priority chemicals [NAS 2001]. The 9

threshold exposure limits are designed to protect the ge neral population, including the elderly, children or 10

other potentially sensitive groups that are generally not considered in the development of workplace exposure 11

recommendations (additional information av ailable at http://www.epa.gov/oppt/aegl/). 12

Acute Reference Concentration (RfC) : An estimate (with uncertainty spa nning perhaps an order of magnitude) 13

of a continuous inhalation exposure for an acute duration (24 hours or less) of the human population 14

(including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a 15

lifetime. It can be derived from a NOAEL, LOAEL, or benchmark concentration, with uncertainty factors 16

(UFs) generally applied to reflect limitations of the data used. Generally used in USEPA noncancer health 17

assessments [USEPA 2014]. 18

Acute Toxicity : Any poisonous effect produced within a short period of time following an exposure, usually 24 19

to 96 hours. 20

Adverse Effect : A substance-related biochemical change, functional impairment, or pathologic lesion that affects 21

the performance of an organ or system or alters the ab ility to respond to additional environmental challenges. 22

Benchmark Dose/Concentration (BMD/BMC) : A dose or concentration that produces a predetermined change 23

in response rate of an effect (called the benchmar k response, or BMR) compared to background [USEPA 24

2014] (additional information available at http://www.epa.gov/ncea/bmds/). 25

Benchmark Response (BMR) : A predetermined change in response rate of an effect. Common defaults for the 26

BMR are 10% or 5%, reflecting study design, da ta variability, and sensitivity limits used. 27

BMCL : A statistical lower confidence limit on th e concentration at the BMC [USEPA 2014]. 28

Bolus Exposure : A single, relatively large dose. 29

Ceiling Value (“C”) : U.S. term in occupational exposure indicati ng the airborne concentration of a potentially 30

toxic substance that should never be exceeded in a worker’s breathing zone. 31

Chronic Exposure : Repeated exposure for an extended period of time. Typically exposures are more than 32

approximately 10% of life span for humans and >90 days to 2 years for laboratory species. 33

Critical Study : The study that contributes most significantly to the qualitative and quantitative assessment of risk 34

[USEPA 2014]. 35

36

Dose : The amount of a substance available for interactions with metabolic processes or biologically significant 37

receptors after crossing the outer boundary of an organism [USEPA 2014]. 38

ECt 50 : A combination of the effective concentration of a s ubstance in the air and the exposure duration that is 39

predicted to cause an effect in 50% (one half) of the experimental test subjects. 40External Review Draft

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information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. Emergency Response Planning Guidelines (ERPGs) : Maximum airborne concentrations below which nearly all 1

individuals can be exposed without experiencing health effects for 1-hour exposure. ERPGs are presented in a 2

tiered fashion with health effects ranging from mild or transient to serious, irreversible, or life threatening 3

(depending on the tier). ERPGs are developed by the Am erican Industrial Hygiene Association [AIHA 2006]. 4

Endpoint : An observable or measurable biological event or sign of toxicity ranging from biomarkers of initial 5

response to gross manifestations of clinical toxicity. 6

Exposure : Contact made between a chemical, physical, or biological agent and the outer boundary of an 7

organism. Exposure is quantified as the amount of an agent available at the exchange boundaries of the 8

organism (e.g., skin, lungs, gut). 9

Extrapolation : An estimate of the response at a point outside the range of the experimental data, generally 10

through the use of a mathematical model, although qualitative extrapol ation may also be conducted. The 11

model may then be used to extrapolate to res ponse levels that cannot be directly observed. 12

Hazard : A potential source of harm. Hazard is distinguished from risk, which is the probability of harm under 13

specific exposure conditions. 14

Immediately Dangerous to Life or Health (IDLH) condition : A situation that poses a threat of exposure to 15

airborne contaminants when that e xposure is likely to cause death or imme diate or delayed permanent adverse 16

health effects or prevent escape from such an environment [NIOSH 2004, 2013]. 17

IDLH value : A maximum (airborne concentration) level above which only a highly reliable breathing apparatus 18

providing maximum worker protection is permitted [NIOSH 2004, 2013]. IDLH values are based on a 30- 19

minute exposure duration. 20

LC 01 : The statistically determined concentr ation of a substance in the air that is estimated to cause death in 1% of 21

the test animals. 22

LC 50 : The statistically determined concentration of a substa nce in the air that is estimated to cause death in 50% 23

(one half) of the test animals; median lethal concentration. 24

LC LO : The lowest lethal concentration of a substance in the air reported to cause death, usually for a small 25

percentage of the test animals. 26

27

LD 50 : The statistically determined lethal dose of a substance that is estimated to cause death in 50% (one half) of 28

the test animals; median lethal concentration. 29

LD LO : The lowest dose of a substance that causes death, usua lly for a small percentage of the test animals. 30

LEL : The minimum concentration of a gas or vapor in air, below which propagation of a flame does not occur in 31

the presence of an ignition source. 32

Lethality : Pertaining to or causing death; fatal; referring to the deaths resulting from acute toxicity studies. May 33

also be used in lethality threshold to describe the point of sufficient subs tance concentration to begin to cause 34

death. 35

Lowest Observed Adverse Effect Level (LOAEL) : The lowest tested dose or con centration of a substance that 36

has been reported to cause harmful (adverse) health effects in people or animals. 37External Review Draft

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information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. Mode of Action : The sequence of significant events and processes that describes how a substance causes a toxic 1

outcome. Mode of action is distinguished from the more detailed mechanism of action, which implies a more 2

detailed understanding on a molecular level. 3

No Observed Adverse Effect Level (NOAEL) : The highest tested dose or concen tration of a substance that has 4

been reported to cause no harmful (adverse) health effects in people or animals. 5

Occupational Exposure Limit (OEL) : Workplace exposure recommendations developed by governmental 6

agencies and non-governmental organizations. OELs ar e intended to represent the maximum airborne 7

concentrations of a chemical substance below wh ich workplace exposures should not cause adverse health 8

effects. OELs may apply to ceiling, short-term (STELs), or time-weighted average (TWA) limits. 9

Peak Concentration : Highest concentration of a substance record ed during a certain period of observation. 10

Permissible Exposure Limit (PEL) : Occupational exposure limits deve loped by OSHA (29 CFR 1910.1000) or 11

MSHA (30 CFR 57.5001) for allowable occupational air borne exposure concentra tions. PELs are legally 12

enforceable and may be designated as ceiling, STEL, or TWA limits. 13

14

Point of Departure (POD) : The point on the dose–response curve from which dose extrapolation is initiated. 15

This point can be the lower bound on dose for an estima ted incidence or a change in response level from a 16

concentration-response model (BMC), or it can be a NOAEL or LOAEL for an observed effect selected from 17

a dose evaluated in a health e ffects or toxicology study. 18

RD 50 : The statistically determined concentration of a substa nce in the air that is est imated to cause a 50% (one 19

half) decrease in the respiratory rate. 20

Recommended Exposure Limit (REL) : Recommended maximum exposure limit to prevent adverse health 21

effects based on human and animal studies and establishe d for occupational (up to 10-hour shift, 40-hour 22

week) inhalation exposure by NIOSH. RELs may be designated as ceiling, STEL, or TWA limits. 23

Short-Term Exposure Limit (STEL) : A worker’s 15-minute time-weighted average exposure concentration that 24

shall not be exceeded at any time during a work day. 25

Target Organ : Organ in which the toxic injury manifests in terms of dysfunction or overt disease. 26

Threshold Limit Values (TLVs®) : Recommended guidelines for occupational exposure to airborne 27

contaminants, published by the American Conference of Governmental Industrial Hygienists (ACGIH). TLVs 28

refer to airborne concentrations of chemical subs tances and represent conditions under which it is believed 29

that nearly all workers may be rep eatedly exposed, day after day, over a working lifetime, without adverse 30

effects. TLVs may be designated as ceiling, short-term (STELs), or 8-hr TWA limits. 31

Time-Weighted Average (TWA) : A worker’s 8-hour (or up to 10-hour) time-weighted average exposure 32

concentration that shall not be exceeded during an 8-hour (or up to 10-hour) work shift of a 40-hour week. 33

The average concentration is weighted to take into ac count the duration of different exposure concentrations. 34

Toxicity : The degree to which a substance is able to ca use an adverse effect on an exposed organism. 35

36

Uncertainty Factors (UFs) : Mathematical adjustments applied to th e POD when developing IDLH values. The 37

UFs for IDLH value derivation are determined by consid ering the study and effect used for the POD, with 38

further modification based on the overall database. 39External Review Draft

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information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. Workplace Environmental Exposure Levels (WEELs) : Exposure levels developed by the American Industrial 1

Hygiene Association (AIHA) that provide guidance for protecting most workers from adverse health effects 2

related to occupational chemical expos ures expressed as a TWA or ceiling limit. 3

4

5

6

7



## Acknowledgments 8

9

This document was developed by the Education and Info rmation Division (Paul Schulte, Ph.D., Director). G. 10

Scott Dotson, Ph.D., was the project officer and lead NIOS H author for this technical report. The basis for this 11

document was a report contracted by NIOSH and prepar ed by Andrew Maier, Ph.D., Ann Parker, and Lynn 12

Haber, Ph.D. (Toxicology Excellen ce for Risk Assessment [TERA]). 13

14



### Education and Information Division 15

Devin Baker, M.Ed. 16

Charles L. Geraci, Ph.D. 17

Thomas J. Lentz, Ph.D. 18

Richard Niemeier, Ph.D. 19

Chris Sofge, Ph.D. 20

21

NIOSH would like to acknowledge the contribution of th e following subject matter experts for their critical 22

technical review of this report. 23

24

Mary A. Fox, Ph.D., Assistant Professor; Co-Direct or, Risk Sciences and Public Policy Institute; 25

Department of Health Policy and Management, Bl oomberg School of Public Health, Johns Hopkins 26

University 27

28

Richard B. Schlesinger, Ph.D., Fellow A.T.S., Senior Associate Dean for Academic Affairs and Research 29

Professor of Biology, Dyson College of Arts and Sciences, Pace University 30

31External Review Draft

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information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. 

## 1.0 Introduction 1



### 1.1 Overview of the ID LH Value for Butane 2

3

IDLH Value: 1,400 ppm (>10% LEL) 4

5

Basis for IDLH Value: Despite the availability of toxicity data capab le of being used to calculate health-based 6

estimates for butane (see Tables 4 and 5), these estimates ar e all greater than 10% of the lower explosive limit 7

(>10% LEL). NIOSH has adopted a threshold of 10% LEL as a default basis for the IDLH value based on 8

explosivity concerns [NIOSH 2014]. Safe ty considerations related to the po tential hazard of explosion must be 9

taken into account and the IDLH value is set at the 10% LEL for butane of 1,400 ppm

. 10



### 1.2 Purpose 11

12

This IDLH Value Profile presents (1) a brief summary of technical data associated with acute inhalation 13

exposures to butane and (2) the rationale behind the Immedi ately Dangerous to Life or Health (IDLH) value for 14

butane. IDLH values are developed based on the scientific rationale and logic outlined in the NIOSH Current 15

Intelligence Bulletin (CIB) 66: Derivation of Immediately Dangerous to Life or Health (IDLH) Values [NIOSH 16

2013]. As described in CIB 66, NIOSH performs in-depth lite rature searches to ensure that all relevant data from 17

human and animal studies with acute exposures to the subs tance are identified. Information included in CIB 66 on 18

the literature search includes pertinent databases, key terms, and guides for evaluating data quality and relevance 19

for the establishment of an IDLH valu e. The information that is identified in the in-depth lite rature search is 20

evaluated with general considerations that include description of studies (i.e., species, study protocol, exposure 21

concentration and duration), health endpoint evaluated, and critical eff ect levels (e.g., NOAELs, LOAELs, LC 50 22

values). For butane, the in-depth literature search was conducted through February 2014. 23

24



### 1.3 General Substance Information 25

26

Chemical ; Butane 27

CAS No: 106-97-8 28

Synonyms: Butane, pure; n-Butane; Methylethylmethane; Diethyl; Liquefied petroleum gas (LPG); Butyl 29

hydride* 30

Chemical category: Aliphatic, saturated hydrocarbons; Organic gases † 31External Review Draft

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Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. 1

Structural formula: 2

3

4

5

Table 1 highlights selected physiochemical properties of butane relevant to IDLH conditions. Table 2 provides 6

alternative exposure guidelines for butane. Table 3 summaries the Acute Exposure Guidelines Level (AEGL) 7

values for butane. 8

9

Table 1: Physiochemical Properties of Butane 10

11

Property Value

Molecular weight 58.12 ‡

Chemical formula C 4 H 10 Description Colorless gas

Odor Gasoline-like; Natural gas

Odor Threshold none §

UEL 9.4% †

LEL 1.4% †

Vapor pressure 1820 mmHg at 25°C (77°F) ‡

Flash point -60°C (-76°F) ‡

Ignition temperature 287.78°C (550°F) ‡

Solubility Practically insoluble in water †

Abbreviation: o C – Celsius; o F – Fahrenheit; mmHg – millimeter mercury; LEL – lower explosive limit; UEL – upper explosive limit 12

* AIHA [1989] 13

† IFA [2013] 14

‡ HSDB [2013] 15

16

17

Table 2: Alternative Exposure Guidelines for Butane 18

19

Organization Value

Original (SCP) IDLH value None

NIOSH REL 800 ppm (1,900 mg/m 3 ), TWA

OSHA PEL [2011] 800 ppm (1,900 mg/m 3 ), TWA

ACGIH TLV [2014] 1,000 ppm (2,370 mg/m 3 ), STEL

AIHA ERPG [2010] Not available

AIHA WEEL [2010] Not available

Abbreviation: ACGIH – American Conference of Governmental I ndustrial Hygienists; AIHA – Am erican Industrial Hygiene 20

Association; ERPG – Emergency Re sponse Preparedness Guidelines; IDLH – immediatel y dangerous to life or health; NIOSH – Nationa l 21

Institute for Occupational Safety and Hea lth; OSHA – Occupational Safety and Health Administration; PEL – permissible exposure limit; 22

REL – recommended exposure limit; SCP – Standards Completion Progr am; STEL - short term expos ure limit; WEEL – workplace 23

environmental exposure level 24 H 3 C

CH 3External Review DraftMarch 20153This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by the National Institute for Occupational Safety and Health. It does not represent and should not be construed to represent anyagency determination or policy.Table 3: AEGL Values for Butane12Classification 10-min 30-min 1-hour4-hour 8-hour Endpoint [reference]AEGL-1 * 6,900 ppm†16,000 mg/m35,500 ppm†13,000 mg/m35,500 ppm†13,000 mg/m35,500 ppm†13,000 mg/m3Drowsiness in humans[Patty and Yant 1929]AEGL-2 *** * * *Dazed appearance in guinea pigs[Nuckolls 1933]AEGL-3**********LC01in mice[Shugaev 1969]Abbreviation: AEGL – acute exposure guideline levels; mg/m3– milligrams per cubic meter; min – minute; ppm – parts per million3References: NAS [2008]4† = >10% LEL5* = >50% LEL; ** = >100% LEL6External Review Draft

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information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. 

## 2.0 Animal Toxicity Data 1

2

The available toxicokinetic data on butane [Gill et al. 1991] and propane [Stewart et al. 1977] indicate steady3

state plasma concentrations for butane are achieved with in 30 minutes of exposure. By analogy to other CNS 4

depressants, concentration is expected to be the primary de terminant of the observed effects, consistent with the 5

choice of n = 3 for extrapolation from durations longer than 30 minutes. 6

7

Lethal concentrations of butane were evaluate d in rats and mice. Shugaev [1969] reported LC 50 values of 278,000 8

ppm in rats exposed to butane for 4 hours, and 287,000 ppm in mice exposed for 2 hours. No other signs of 9

toxicity were reported. Several studies evaluated acute toxicity under static conditions; these studies were not 10

considered appropriate for deri vation of an IDLH value. 11

12

Non-lethal animal data of classical endpoints were limite d to a single study. In guinea pigs, Nuckolls [1933] 13

observed irregular and rapid breathing in animals exposed to 21,000 ppm for 2 hours, which escalated to retching 14

and a dazed appearance at 50,000 ppm for 2 hours. Alt hough the animals were able to walk, this exposure was 15

considered potentially escape-impairing. Furthermore, a lthough this is an older stud y, exposure concentrations 16

were monitored and adjusted to maintain the nominal exposure levels. Other studies found that butane is a 17

cardiac sensitizer [Chenowith 1946; Krantz et al. 1948] and can cause hemodynamic effects (decr eased cardiac 18

output, decreased ventricular or aortic pressure) [Zakhari 1977], but these studies were not considered appropriate 19

for IDLH value derivation due to the limite d details and exposure under anesthesia. 20

21

Table 4 summarizes the LC data identified in animal st udies and provides 30-minute equivalent derived values for 22

butane. Table 5 provides non-lethal data reported in an imal studies with 30-minute equivalent derived values. 23

Information in these tables includes species of test an imals, toxicological metrics (i.e., LC, BMCL, NOAEL, 24

LOAEL), adjusted 30-minute concentration, and the justifi cation for the composite uncertainty factors applied to 25

calculate the derived values. 26

27

28External Review DraftMarch 20155This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by the National Institute for Occupational Safety and Health. It does not represent and should not be construed to represent anyagency determination or policy.Table 4: Lethal Concentration Data for Butane12Reference Species(reference)LC50(ppm)OtherLethality(ppm)Time(min)Adjusted30-minConcentration*(ppm)CompositeUncertaintyFactorDerivedValue(ppm)†Shugaev [1969]Mouse287,000--120382,6673012,755Shugaev [1969]Mouse278,000--240741,33330 24,7113Abbreviation:LC – lethal concentration; LC50– median lethal concentration; LCLo– lowest concentration of a chemical that caused death in humans or animals; min – minute; ppm – parts4per million56*For exposures other than 30 minutes the ten Berge et al. [1986] relationship is used for duration adjustment (Cnx t = k); no empirically estimated n values were7available, therefore the default values were used, n = 3 for exposures greater than 30 minutes and n = 1 for exposures less than 30 minutes.8†The derived value is the result of the adjusted 30-minute concentration divided by the composite uncertainty factor.9±Composite uncertainty factor to account for adjustment of LC50values to LC01values, use of lethal concentration threshold in animals, interspecies differences and10human variability.11^Composite uncertainty factor to account foruse of lethal concentration threshold inanimals, interspecies differences and human variability.121314External Review DraftMarch 20156This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by the National Institute for Occupational Safety and Health. It does not represent and should not be construed to represent anyagency determination or policy.Table 5: Non-lethal Concentration Data for Butane12Reference Species(reference)NOAEL(ppm)LOAEL(ppm)Time(min)Adjusted30-minConcentration*(ppm)CompositeUncertaintyFactorDerivedValue(ppm)†Nuckolls [1933]Guinea Pig--50,00012066,667106,667Patty and Yant [1929]Human10,000--103,33313,333Abbreviation:NOAEL – no observed adverse effect level;min – minute; LOAEL – lowest observed adverse effect level; ppm– parts per million34*For exposures other than 30 minutes the ten Berge et al. [1986] relationship is used for duration adjustment (Cnx t = k); no empirically estimated n values were5available, therefore the default values were used, n = 3 for exposures greater than 30 minutes and n = 1 for exposures less than 30 minutes.6†The derived value is the result of the adjusted 30-minute concentration divided by the composite uncertainty factor.7±Composite uncertainty factor to account forinterspecies differences and human variability.8‡Composite uncertainty factor to account for adjustment froma severe effect threshold in humans and human variability.9External Review Draft

March 2015

7

This information is distributed solely for the purpose of pre-dissemination peer review under applicable

information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. 

## 3.0 Human Data 1

2

Although there are a number of case reports on lethality in humans from exposure to butane, none of the available 3

studies provided information on exposure levels. In th e only human study reporting exposure concentrations, 4

Patty and Yant [1929] reported no symptoms except drowsi ness in individuals that were exposed up to 1% butane 5

concentrations (10,000 ppm) for 10 minutes. 6



## 4.0 Summary 7

8

Despite the availability of toxicity data capable of be ing used to calculate health -based estimates for butane (see 9

Tables 4 and 5), these estimates are all are greater than 10% of the lower explosive limit (>10% LEL). NIOSH 10

has adopted a threshold of 10% LEL as a default basis for the IDLH values based on explosivity concerns 11

[NIOSH 2014]. Safety considerations related to the pote ntial hazard of explosion must be taken into account and 12

the IDLH value is set at the 10% LEL for butane of 1,400 ppm

. 13

14

If the explosive hazards of butane are controlled or toxici ty issues are the primary co ncern, a health-based IDLH 15

value could be derived from numerous datasets. The lowest LC 50 value identified was 287,000 ppm for 2 hours in 16

mice [Shugaev 1969]. The duration adjusted LC 50 value for a 30-minute exposure is 382,700 ppm. An 17

uncertainty factor of 30 would be applied to account for extrapolation from a concentration that is lethal to 18

animals, animal to human differences and human variabilit y, resulting in a potential IDLH value of 13,000 ppm. 19

However, a more appropriate study from which to base the IDLH value is available. A LOAEL for signs of 20

disorientation and toxicity was identified in guinea pigs exposed to 50,000 ppm for 2 hours [Nuckolls 1933]. The 21

duration adjusted LOAEL for a 30-minute exposure is 66,700 ppm. An uncertainty factor of 10 is applied to 22

account for extrapolation from a concentration that causes escape impairing effects in animals, animal to human 23

differences and human variability, resulting in an IDLH value of 6,700 ppm. This value is supported by the 24

human data [Patty and Yant 1929], which indicated dr owsiness following exposure to 10,000 ppm for 10 minutes, 25

although there were uncertainties with the study. The IDLH value is a health-based value and may not protect 26

from physical hazards associated with butane exposure. For example, safety concerns may result when butane 27

exposures exceed 1,400 ppm, which is 10% of the LEL. 28

29External Review Draft

March 2015

8

This information is distributed solely for the purpose of pre-dissemination peer review under applicable

information quality guidelines. It has not been formally di sseminated by the National Institute for Occupational

Safety and Health. It does not represent and should not be construed to represent any agency determination or

policy. 

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