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i

1

2

3

4

5

6

7 IMMEDIATELY DANGEROUS TO LIFE OR HEALTH (IDLH) VALUE PROFILE

8

9

10

11 FOR

12

13

14

15 FURAN

16

17

18 [CAS NO. 110-00-9] 

19

20

21

22

23

24

25 Department of Health and Human Services 

26 Centers for Disease Control and Prevention 

27 National Institute for Occupational Safety and Health 

28

29
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ii

1 Disclaimer

2

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

4 Safety and Health (NIOSH). In addition, citations to Web sites external to NIOSH do not constitute NIOSH 

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

6 responsible for the content of these Web sites. 

7

8 Ordering Information 

9

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

11

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

13 TTY: 1-888-232-6348 

14 E-mail: cdcinfo@cdc.gov 

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

16

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

18

19 DHHS (NIOSH) Publication No. XXX 
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iii

1 Foreword 

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

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

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

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

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

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

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

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

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

11 transportation incidents or other uncontrolled-release scenarios). 

12

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

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

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

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

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

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

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

20 Preparedness Plans. 

21

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

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

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

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

26 scientifically credible IDLH values using available data resources.

27

28 The purpose of this technical report is to present the IDLH value for furan (CAS # 110-00-9). The scientific 

29 basis, toxicologic data and risk assessment approach used to derive the IDLH value are summarized to ensure 

30 transparency and scientific credibility. 

31

32 John Howard, M.D. 

33 Director 

34 National Institute for Occupational Safety and Health 
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iv

1 Centers for Disease Control and Prevention
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v

1 Table of Contents

2 FOREWORD ................................................................................................................................................................ III

3 ABBREVIATIONS .......................................................................................................................................................VI

4 GLOSSARY .................................................................................................................................................................VII

5 ACKNOWLEDGMENTS .............................................................................................................................................XI

6 1.0 INTRODUCTION.............................................................................................................................................. 1

7 1.1 OVERVIEW OF THE IDLH VALUE FOR FURAN.........................................................................................................................1

8 1.2 PURPOSE .......................................................................................................................................................................1

9 1.3 GENERAL SUBSTANCE INFORMATION...................................................................................................................................1

10 2.0 ANIMAL TOXICITY DATA............................................................................................................................. 4

11 3.0 HUMAN DATA ................................................................................................................................................. 7

12 4.0 SUMMARY........................................................................................................................................................ 7

13 5.0 REFERENCES .................................................................................................................................................. 8

14

15

16

17

18
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vi

1 Abbreviations 

2

3 ACGIH American Conference of Governmental Industrial Hygienists 

4 AEGL Acute Exposure Guideline Levels 

5 AIHA American Industrial Hygiene Association 

6 BMC benchmark concentration 

7 BMCL benchmark concentration lower confidence limit 

8 C ceiling 

9 CAS chemical abstract service 

10 ERPG Emergency Response Planning Guidelines 

11 IDLH immediately dangerous to life or health 

12 LC50 median lethal concentration 

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

14 LEL lower explosive limit 

15 LOAEL lowest observed adverse effect level 

mg/m3 16 milligram(s) per cubic meter 

17 NAC National Advisory Committee 

18 NAS National Academy of Sciences 

19 NIOSH National Institute for Occupational Safety and Health 

20 NOAEL no observed adverse effect level 

21 OSHA Occupational Safety and Health Administration 

22 PEL permissible exposure limit 

23 ppm parts per million 

24 RD50 concentration of a chemical in the air that is estimated to cause a 50% decrease in the respiratory 

25 rate 

26 REL recommended exposure limit 

27 SCP Standard Completion Program 

28 STEL short term exposure limit 

29 TLV threshold limit value 

30 TWA time weighted average 

31 UEL upper explosive limit 

32 WEEL workplace environmental exposure level 
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vii

1 Glossary

2

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

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

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

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

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

8 effects [NAS 2001]. AEGLs are intended to be guideline levels used during rare events or single once-in-a9 lifetime exposures to airborne concentrations of acutely toxic, high-priority chemicals [NAS 2001]. The 

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

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

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

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

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

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

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

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

18 assessments [USEPA 2014]. 

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

20 to 96 hours. 

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

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

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

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

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

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

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

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

29 Bolus Exposure: A single, relatively large dose. 

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

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

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

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

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

35 [USEPA 2014]. 

36

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

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

39 ECt50: A combination of the effective concentration of a substance in the air and the exposure duration that is 

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

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

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

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

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

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

6 response to gross manifestations of clinical toxicity. 

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

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

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

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

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

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

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

14 specific exposure conditions. 

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

16 airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse 

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

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

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

20 minute exposure duration. 

21 LC01: The statistically determined concentration of a substance in the air that is estimated to cause death in 1% of 

22 the test animals. 

23 LC50: The statistically determined concentration of a substance in the air that is estimated to cause death in 50% 

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

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

26 percentage of the test animals. 

27

28 LD50: The statistically determined lethal dose of a substance that is estimated to cause death in 50% (one half) of 

29 the test animals; median lethal concentration. 

30 LDLO: The lowest dose of a substance that causes death, usually for a small percentage of the test animals. 

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

32 the presence of an ignition source. 

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

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

35 death. 

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

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

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

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

3 detailed understanding on a molecular level. 

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

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

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

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

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

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

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

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

12 MSHA (30 CFR 57.5001) for allowable occupational airborne exposure concentrations. PELs are legally 

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

14

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

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

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

18 a dose evaluated in a health effects or toxicology study. 

19 RD50: The statistically determined concentration of a substance in the air that is estimated to cause a 50% (one 

20 half) decrease in the respiratory rate. 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

36

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

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

39 further modification based on the overall database. 
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x

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

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

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

4 
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xi

1 Acknowledgments 

2

3 This document was developed by the Education and Information Division (Paul Schulte, Ph.D., Director). G. 

4 Scott Dotson, Ph.D., was the project officer and lead NIOSH author for this technical report. The basis for this 

5 document was a report contracted by NIOSH and prepared by Andrew Maier, Ph.D., Ann Parker, and Lynn 

6 Haber, Ph.D. (Toxicology Excellence for Risk Assessment [TERA]). 

7

8 Education and Information Division 

9 Devin Baker, M.Ed. 

10 Charles L. Geraci, Ph.D. 

11 Thomas J. Lentz, Ph.D. 

12 Richard Niemeier, Ph.D. 

13 Chris Sofge, Ph.D. 

14

15 NIOSH would like to acknowledge the contribution of the following subject matter experts for their critical 

16 technical review of this report. 

17

18 Michael S. Bisesi, Ph.D., R.E.H.S., C.I.H., Senior Associate Dean for Academic Affairs; Director, Center 

19 for Public Health Practice; Interim Chair & Associate Professor, Division of Environmental Health 

20 Science, College of Public Health, Ohio State University 

21

22 Mary A. Fox, Ph.D., Assistant Professor; Co-Director, Risk Sciences and Public Policy Institute; 

23 Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins 

24 University 
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1

1 1.0 Introduction 

2 1.1		 Overview of the IDLH Value for Furan

3

IDLH Value: 43 ppm (120 mg/m3 4 )

5

6 Basis for IDLH Value: The IDLH value for furan is based on a rat LOAEL of 1,014 ppm for a 1- hour exposure 

7 reported by Terrill et al. [1989] for potential escape- impairing effects, such as respiratory distress. The 30-

8 minute duration adjusted concentration for the LOAEL is 1,278 ppm. Applying a composite uncertainty factor of 

9 30 to account for extrapolation from a concentration that causes an escape- impairing effect in animals, animal to 

10 human differences, and human variability, results in an IDLH value of 43 ppm. 

11

12 1.2 Purpose

13

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

15 exposures to furan and (2) the rationale behind the Immediately Dangerous to Life or Health (IDLH) value for 

16 furan. IDLH values are developed based on the scientific rationale and logic outlined in the Current Intelligence 

17 Bulletin (CIB) 66: Derivation of Immediately Dangerous to Life or Health (IDLH) Values [NIOSH 2013]. As 

18 described in CIB 66, NIOSH performs in-depth literature searches to ensure that all relevant data from human and 

19 animal studies with acute exposures to the substance are identified. Information included in CIB 66 on the 

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

21 the establishment of an IDLH value. The information that is identified in the in-depth literature search is 

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

23 concentration and duration), health endpoint evaluated, and critical effect levels (e.g., NOAELs, LOAELs, LC50

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

25

26 1.3 General Substance Information		

27

28 Chemical: Furan 

29 CAS No: 110-00-9 

Synonyms: 1,4-Epoxy-1,3-butadiene; Axole; Oxole; Divinylene oxide* 30

Chemical category: Oxygen heterocycles† 31
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2

1 Structural formula: 

2

3

4

5

6

7 Table 1 highlights selected physiochemical properties of furan relevant to IDLH conditions. Table 2 provides 

8 alternative exposure guidelines for furan. Table 3 summarizes the Acute Exposure Guidelines Level (AEGL) 

9 values for furan. 

10

11 Table 1: Physiochemical Properties of Furan 

Property Value 

Molecular weight 68.07‡

Chemical formula C4H4O

Description Colorless liquid 

Odor Strong ethereal; chloroform-like

Odor Threshold Not available 

UEL 14.3%†

LEL 2.3%†

Vapor pressure 600 mmHg at 25°C (77°F)‡

Flash point -35.56°C (-32°F)‡

Ignition temperature 390°C (734°F)†

Solubility Sparingly soluble in water†

12 Abbreviation: °C – Celsius; °F – Fahrenheit; mmHg – millimeter mercury; LEL – lower explosive limit; UEL – upper explosive limit * 13 NLM [2014] 

† 14 IFA [2014] 

‡ 15 HSDB [2014] 

16

17 Table 2: Alternative Exposure Guidelines for Furan 

Organization Value 

Original (SCP) IDLH value [NIOSH 2014] None 

NIOSH REL [2014] Not available 

OSHA PEL [2014] Not available 

ACGIH TLV [2014] Not available 

AIHA ERPG [2013] Not available 

AIHA WEEL [2013] Worker exposure by all routes should be minimized to the 

fullest extent possible. 

18 Abbreviation: ACGIH – American Conference of Governmental Industrial Hygienists; AIHA – American Industrial Hygiene 

19 Association; ERPG – Emergency Response Preparedness Guidelines; IDLH – immediately dangerous to life or health; NIOSH – National 

20 Institute for Occupational Safety and Health; OSHA – Occupational Safety and Health Administration; PEL – permissible exposure limit; 

21 REL – recommended exposure limit; SCP – Standards Completion Program; WEEL – workplace environmental exposure level 

O
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1 Table 3: AEGL Values for Furan 

2

Classification 10-min 30-min 1-hour 4-hour 8-hour Endpoint [AEGL-1 NR NR NR NR NR Not applicAEGL-2 12.0 ppm 

33.0 mg/m3

8.5 ppm 24.0 mg/m3

6.8 ppm 19.0 mg/m3

1.7 ppm 4.7 mg/m3

0.85 ppm 2.4 mg/m3

1,014 ppm adverse efalthough tdistress anresponse nbody weig(Terrill et 

AEGL-3 35.0 ppm 

97.0 mg/m3

24.0 ppm 67.0 mg/m3

19.0 ppm 53.0 mg/m3

4.8 ppm 13.0 mg/m3

2.4 ppm 6.7 mg/m3

2,851 ppm lethality in 

Abbreviation: AEGL – acute exposure guideline levels; mg/m3 3 – milligrams per cubic meter; min – minute; NR – not recommended due to insufficient da* 4 References: NAS [2010]
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4

1 2.0 Animal Toxicity Data 

2 Lethality studies were conducted in three different species. Koch and Cahan [1926] exposed a single rat and 

3 rabbit via inhalation of furan from saturated cotton held over the nose. Both animals struggled; the rat died the 

4 following day and the rabbit died shortly after collapsing from the exposure. There was no information available 

5 on the exposure concentration because of the nonstandard exposure method. Egle and Gochberg [1979] reported 

6 a 1-hour LC50 of 42 ppm in mice exposed to furan vapor; no individual concentrations were reported and hypoxia 

7 contributed to the mortality observed. In addition to the evaluation of lethality data, Terrill et al. [1989] also 

8 evaluated non-lethal effects and reported a LOAEL of 1,014 ppm for a 1-hour exposure in rats, based on observed 

9 respiratory distress. Symptoms of intoxication were seen at concentrations between the LOAEL and reported 

10 lethal concentrations. These symptoms included increased respiratory rate, decreased blood pressure, 

11 convulsions, complete anesthesia and death from asphyxia. In a 2-year NTP [1993] study, there was clear 

12 evidence of carcinogenic activity in rats (based on liver neoplasms and leukemia) and in mice (based on liver and 

13 adrenal gland tumors). However, no cancer potency values have been developed for furan. 

14

15 Table 4 summarizes the LC data identified in animal studies and provides 30-minute equivalent derived values for 

16 furan. Table 5 provides non-lethal data reported in animal studies with 30-minute equivalent derived values. 

17 Information in these tables includes species of test animals, toxicological metrics (i.e., LC, NOAEL, LOAEL), 

18 adjusted 30-minute concentration, and the justification for the composite uncertainty factors applied to calculate 

19 the derived values. 
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1 Table 4: Lethal Concentration Data for Furan

2

Reference Species 

(sex) 

LC50

(ppm) 

LCLo(ppm) 

Time (min) 

Adjusted 30-minute Concentration* (ppm) 

Composite Uncertainty Factor 

Derived Value (ppm)†

Terrill et al. [1989] Rat 

(males) 

3,398 -- 60 4,281 100‡ 43 

Terrill et al. [1989] Rat 

(females) 

3,550 -- 60 4,473 100‡ 45 

Terrill et al. [1989] Rat 

(both sexes) 

3,464 -- 60 4,364 100‡ 44 

34 Abbreviation: LC – lethal concentration; LC50 – median lethal concentration; LCLo – lowest concentration of a chemical that caused death in humans or a5 per million 6

*For exposures other than 30 minutes the ten Berge et al. [1986] relationship is used for duration adjustment (Cn 7 x t = k); no empirically esti

8 therefore the default values were used, n = 3 for exposures greater than 30 minutes and n = 1 for exposures less than 30 minutes. 

† 9 The derived value is the result of the adjusted 30-minute concentration divided by the composite uncertainty factor. 

10 ‡ Composite uncertainty factor to account for adjustment of LC50 values to LC01 values, use of lethal concentration threshold in animals, int11 human variability. 121314151617181920212223242526
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1 Table 5: Non-lethal Concentration Data for Furan 

2

Reference Species 

(reference) 

NOAEL (ppm) 

LOAEL (ppm) 

Time (min) 

Adjusted 30-minute Concentration* (ppm) 

Composite Uncertainty Factor 

Derived Value (ppm)†

Terrill et al. [1989] + Rat (both sexes) -- 1,014 60 1,278 30‡ 43 

3 Abbreviation: NOAEL – no observed adverse effect level; min – minute; LOAEL – lowest observed adverse effect level; ppm – parts per million4

*For exposures other than 30 minutes the ten Berge et al. [1986] relationship is used for duration adjustment (Cn 5 x t = k); no empirically esti

6 therefore the default values were used, n = 3 for exposures greater than 30 minutes and n = 1 for exposures less than 30 minutes. 

† 7 The derived value is the result of the adjusted 30-minute concentration divided by the composite uncertainty factor. + 8 Identified study is the primary basis of the IDLH value for furan. ‡ 9 Composite uncertainty factor assigned to account for adjusting from a LOAEL to NOAEL, interspecies differences and human variability.
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7

1 3.0 Human Data 

2 No human studies for furan were found.

3 4.0 Summary 

4 A single acute lethality study in the rat provides the only adequate toxicity data for development of an IDLH 

5 value. The study reports a 1-hour LC50 value of 3,464 ppm for both sexes combined [Terrill et al. 1989]. This 

6 study also identified a LOAEL of 1,014 ppm for a 1-hour exposure for potential escape-impairing effects, such as 

7 respiratory distress. This LOAEL is more appropriate as the basis of the IDLH value because it protects against 

8 potential escape-impairing effects such as respiratory distress. The 30-minute duration adjusted concentration for 

9 the LOAEL is 1,278 ppm. Applying a composite uncertainty factor of 30 to account for extrapolation from a 

10 concentration that causes an escape-impairing effect in animals, animal to human differences, human variability 

11 and potential cancer risks, results in an IDLH value of 43 ppm. 

12

13 It should be noted that the IDLH value for furan differs by more than an order of magnitude from the AEGL-2 30-

14 minute value, which is intended to represent an airborne concentration of a substance above which it is predicted 

15 that the general population, including susceptible individuals, could experience irreversible or other serious, long16 lasting adverse health effects or an impaired ability to escape [NAS 2001]. The AEGL-2 value for furan is based 

17 on a threshold effect (i.e., respiratory distress and increased secretory response) in male and female rats exposed 

18 at 1,014 ppm for 1 hour [Terrill et al. 1989, NAS 2010]. NIOSH based the IDLH value for furan on the same data 

19 set and endpoint. The differences between the AEGL-2 value for 30-minute and the IDLH value can be attributed 

20 to the use of a much larger uncertainty factor during the derivation of the AEGL values. A total uncertainty factor 

21 and modifying factor of 150 were applied to account for limited data, interspecies variability and human 

22 variability to derive the AEGL-2. In comparison, NIOSH applied a composite uncertainty factor of 30 to account 

23 for adjusting from a LOAEL to NOAEL, interspecies differences and human variability. 

24
External Review Draft Document 

May 2015 

   

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

information quality guidelines. It has not been formally disseminated 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. 

8

1 5.0 References 

2

3 ACGIH (American Conference of Governmental Industrial Hygienists) [2014]. Annual TLVs® (Threshold Limit 

4 Values) and BEIs® (Biological Exposure Indices) booklet. Cincinnati, OH: ACGIH Signature Publications. 

5

6 AIHA (American Industrial Hygiene Association) [2006]. AIHA Emergency Response Planning (ERP) 

7 Committee procedures and responsibilities. Fairfax, VA: American Industrial Hygiene Association, 

8 https://www.aiha.org/get9 involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERP-SOPs2006.pdf. 

10

11 AIHA (American Industrial Hygiene Association) [2013]. Emergency response planning guidelines (ERPG) and 

12 workplace environmental exposure levels (WEEL) handbook. Fairfax, VA: American Industrial Hygiene 

13 Association Press, https://www.aiha.org/get14 involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Pages/default.aspx. 

15

16 Egle JL, Gochberg BJ [1979]. Respiratory retention and acute toxicity of furan. Am Ind Hyg Assoc J 40:310–314. 

17

18 HSDB (Hazardous Substances Data Bank) [2014]. HSDB. National Library of Medicine, Bethesda, MA, 

19 http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB. 

20

21 IFA (Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung) [2014]. GESTIS: Database on 

22 hazardous substances, 

23 http://gestis24 en.itrust.de/nxt/gateway.dll/gestis_en/000000.xml?f=templates$fn=default.htm$vid=gestiseng:sdbeng$3.0. 

25

26 Koch EM, Cahan MH [1926]. Physiologic action of furane. J Pharmacol Exp Ther 26:281–285. 

27

28 NAS (National Academy of Sciences) [2001]. Standing operating procedures for developing acute exposure 

29 guideline levels for hazardous chemicals. National Academy of Science, Committee on Toxicology, Board of 

30 Environmental Studies and Toxicology, National Research Council. Washington, DC: National Academy Press, 

31 http://www.nap.edu/. 

32

33 NAS [2010]. Acute Exposure Guideline Levels (AEGLs) for selected airborne chemicals. Vol. 9. - Chapter 3: 

34 Furan. National Academy of Science, Committee on Toxicology and Committee on Acute Exposure Guideline 

35 Levels, Board on Environmental Studies and Toxicology, National Research Council. Washington, DC: National 

36 Academy Press, http://www.epa.gov/oppt/aegl/pubs/furan_final_volume9_2010.pdf. Data accessed: August 1, 

37 2014.

38

39 NIOSH (National Institute for Occupational Safety and Health) [2004]. NIOSH respirator selection logic. 

40 Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

41 National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2005-100, 

42 http://www.cdc.gov/niosh/docs/2005-100/pdfs/05-100.pdf. 

43

44 NIOSH [2013]. NIOSH Current Intelligence Bulletin 66: Derivation of Immediately Dangerous to Life or Health 

45 (IDLH) Values. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control 

46 and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2014-

47 100, http://www.cdc.gov/niosh/docs/2014-100/. 
External Review Draft Document 

May 2015 

   

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

information quality guidelines. It has not been formally disseminated 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. 

9

1

2 NIOSH [2014]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health and 

3 Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and 

4 Health, DHHS (NIOSH) Publication No. 2005-149, http://www.cdc.gov/niosh/npg/. 

5

6 NLM (National Library of Medicine) [2014]. ChemIDplus lite. National Library of Medicine, Bethesda, Md, 

7 http://chem.sis.nlm.nih.gov/chemidplus/ProxyServlet?objectHandle=DBMaint&actionHandle=default&nextPage

8 =jsp/chemidlite/ResultScreen.jsp&TXTSUPERLISTID=0000110009. 

9

10 NTP (National Toxicology Program) [1993]. Toxicology and carcinogenesis studies of furan (CAS No. 110-00-9) 

11 in F344/N rats and B6C3F1 mice (gavage studies). Research Triangle Park, NC: U.S. Department of Health and 

12 Human Services, National Toxicology Program, NIH Publication No. 93-2857, NTP TR 402. 

13

14 OSHA (Occupational Safety and Health Administration) [2014]. Occupational Safety and Health Standards. 29 

15 CFR 1910. Subpart Z -- Toxic and Hazardous Substances. OSHA; Washington, DC, 

16 http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9992. 

17

18 ten Berge WF, Zwart A, Appelman LM [1986]. Concentration-time mortality response relationship of irritant and 

19 systematically acting vapors and gases. J Haz Mat 13:301–309. 

20

21 Terrill JB, Van Horn WE, Robinson D, Thomas DL [1989]. Acute inhalation toxicity of furan, 2 methylfuran, 

22 furfuryl alcohol, and furfural in the rat. Am Ind Hyg Assoc J 50:A359–A361. 

23

24 USEPA (United States Environmental Protection Agency) [2014]. Integrated Risk Information System (IRIS): 

25 glossary. Washington, DC: U.S. Environmental Protection Agency, National Center for Environmental 

26 Assessment, http://www.epa.gov/iris/ index.html.