Benzene

Agent Name
Benzene
CAS Number
71-43-2
Formula
C6-H6
Major Category
Solvents
Benzene formula graphical representation
Synonyms
(6)Annulene; Benzene; Benzin; Benzine; Benzol; Benzol 90; Benzole; Benzolene; Bicarburet of hydrogen; Carbon oil; Coal naphtha; Cyclohexatriene; Mineral naphtha; Motor benzol; Nitration benzene; Phene; Phenyl hydride; Polystream; Pyrobenzol; Pyrobenzole; [ChemIDplus] UN1114
Category
Aromatic Solvents
Description
Colorless to light-yellow liquid with an aromatic odor. Note: A solid below 42 degrees F; [NIOSH]
Sources/Uses
Benzene was used in the past as a solvent in inks, rubber, lacquers, and paint removers. Today, it is used mainly in closed processes to synthesize organic chemicals. Gasoline in some countries contains a high concentration of benzene (as high as 30%); the U.S. average is 1-3%. Workers who remove or clean underground storage tanks may be exposed to significant levels. [ACGIH] Gasoline in North America now contains about 1% benzene. [AIHAJ 2002;63(2):225-30] The European Union (EU) reduced in 2000 the maximum allowed benzene content in gasoline from 5% to 1% by volume. Mean exposures in the Swedish petroleum industry are well below the Swedish occupational exposure limits. [PMID 28578463]
Comments
"The final OSHA Benzene standard in 1910.1028 applies to all occupational exposures to benzene except some subsegments of industry where exposures are consistently under the action level (i.e., distribution and sales of fuels, sealed containers and pipelines, coke production, oil and gas drilling and production, natural gas processing, and the percentage exclusion for liquid mixtures);" [NIOSH Pocket Guide Appendix] As an organic solvent, benzene can induce narcosis and anesthesia acutely. After chronic exposure, it can cause aplastic anemia and leukemia. [ACGIH] "Exposure to benzene has been associated with development of a particular type of leukemia called acute myeloid leukemia (AML)." [ATSDR Public Health Statement: Benzene] “There is sufficient evidence in humans for the carcinogenicity of benzene. Benzene causes acute myeloid leukaemia/acute non-lymphocytic leukaemia.” [IARC Monograph Volume 100F (2012)] The WHO classification of AML includes “Acute erythroid leukemia” and “Acute monocytic leukemia.” [www.cancer.org] Significant benzene exposure increases the risk of leukemia during the 10 years following exposure. Risk is not related to exposures that occurred greater than 20 years prior to the onset of disease. [PMID 10861761] The highest exposures (mean of 11 ppm) in petroleum refinery workers occur in disconnecting cargo loading hoses, and respiratory protection is required. [PMID 20941467] Workers exposed to products containing <0.1% benzene are not likely to be exposed above the TLV of 0.5 ppm. [PMID 18615290] "Our results confirmed the association between high-level benzene exposures and leukemia risks, and provided further evidence of a threshold effect and relevant exposure window." [PMID 27058483] See "Hospital-Based Case-Control Study of MDS Subtypes and Benzene Exposure in Shanghai." [PMID 28146040] In high-dose animal reproductive studies, benzene increases sperm abnormalities, fetal loss, and delayed ossification. [Frazier]
Restricted
EPA restricts benzene emission from specific point sources; maximum contaminant level in drinking water is 5 ppb; FDA prohibits the use of benzene in food; [ATSDR Case Studies]
Reference Link #1
Biomedical References

Exposure Assessment

BEI
S-phenylmercapturic acid in urine = 25 ug/g creatinine; t,t-Muconic acid in urine = 500 ug/g creatinine; sample at end of shift;
Skin Designation (ACGIH)
Yes
TLV (ACGIH)
0.5 ppm
STEL (ACGIH)
2.5 ppm
PEL (OSHA)
1 ppm, STEL(OSHA) = 5 ppm (see CFR 1910.1028)
IDLH (NIOSH)
500 ppm
Excerpts from Documentation for IDLHs
Other human data: It has been stated that 3,000 ppm is endurable for 0.5 to 1 hour [Flury 1928]. It has also been stated that exposure at 19,000 to 20,000 ppm for 5 to 10 minutes is fatal; exposure at 7,500 ppm for 30 minutes is dangerous; exposure at 1,500 ppm for 60 minutes induces serious symptoms; exposure at 500 ppm for 60 minutes leads to symptoms of illness; exposure at 50 to 150 ppm for 5 hours produces headache, lassitude, and weakness; and exposure at 25 ppm for 8 hours has no effect [Gerarde 1960].
Vapor Pressure
94.8 mm Hg
Odor Threshold Low
34 ppm
Odor Threshold High
119 ppm
Lethal Concentration
LC50 (rat) = 10,000 ppm/7h
Explanatory Notes
Detection odor thresholds from AIHA; Flash point = 12 deg F; VP from HSDB; See 2022 "Notice of Intended Changes" for TLV; [ACGIH TLVs and BEIs]
Half Life
Whole body: 9-24 hours; however, up to 90 hours due to distribution in fat; [TDR, p. 154]
NFPA
may ignite at ambient temp
ERPG-1
50 ppm
ERPG-2
150 ppm
ERPG-3
1,000 ppm

Adverse Effects

Anemia
Aplastic anemia
Neurotoxin
Acute solvent syndrome
Reproductive Toxin
Yes
IARC Carcinogen
Established
NTP Carcinogen
Human carcinogen
ACGIH Carcinogen
Confirmed Human

Diseases, Processes, and Activities Linked to This Agent

Diseases

Occupational diseases associated with exposure to this agent:

Activities