Registration Dossier

Administrative data

Description of key information

After repeated dose exposure via oral or inhalation routes, benzene causes adverse effects on the haematopoietic system of animals and in humans.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, near guideline study, published as NIH publication, some limitations in design but fully adequate for evaluation
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Deviations:
yes
Remarks:
no clinical chemistry analysis, no ophthalmological examination, no neurobehaviour, no organ weights.
GLP compliance:
yes
Remarks:
assumed - audit of 2 year data documented
Limit test:
no
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Portage, MI)
- Age at study initiation: 6 weeks
- Weight at study initiation: mean weights per group males 110-137 g ; females 75-101 g
- Housing: 5 per sex per cage in polycarbonate cages
- Diet: Purina Lab Chow 5001 - pellets (Ralston-Purina Co., St. Louis, NJ) ad libitum
- Water: ad libitum
- Acclimation period: 15 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22±1°C
- Humidity: 40-65%
- Air changes: 15 per h
- Photoperiod: 12 h dark / 12 h light

IN-LIFE DATES: From: 14 October 1978 To: 13 February 1979
Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: A weighed amount of benzene was mixed with the appropriate amount of corn oil and stirred for 5 minutes. Rats were dosed at a rate of 5 mL/kg. Benzene in corn oil was found to be stable at 25º C for at least 7 days. Dose mixtures were used within 2 weeks of preparation.


Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
All benzene/corn oil mixtures analyzed by gas chromatography and were within ±10% of the target concentrations.
Duration of treatment / exposure:
120 days (17 weeks). Sub-group of animals from 0, 200, and 600 mg/kg groups killed after 60 days (8-9 weeks).
Frequency of treatment:
Once per day, 5 days/week.
Remarks:
Doses / Concentrations:
0, 25, 50, 100, 200, 400, 600 mg/kg bw/day
Basis:
other: nominal in corn oil
No. of animals per sex per dose:
10/sex/group for 0, 25, 50, 100 and 400 mg/kg; 15/sex/group for 0, 200 and 600 mg/kg
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: none
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: once per week

FOOD CONSUMPTION: Yes
- Time schedule: once per week

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule / number of animals for collection of blood: animals killed at day 0 and day 60 and on 5 animals/group at terminal kill and on any animals killed in a moribund condition.
- Method of collection: from the orbital sinus
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- Parameters examined: haemoglobin, haematocrit, white blood cell count, red blood cell count, mean corpuscular volume, reticulocyte count, coagulation time.

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes. Examinations on all animals except those with excessive autolysis or cannibalized.

HISTOPATHOLOGY: Yes. The following tissues were examined histologically in the predosing vehicle control, study vehicle control, and interim-kill animals and the 600 mg/kg animals at terminal kill: mandibular lymph node, salivary glands, femur, thyroid gland, parathyroid, small intestine, colon, liver, prostate/testes or ovaries/uterus, lungs and mainstem bronchi, mammary gland, heart, oesophagus, stomach, brain, thymus, trachea, pancreas, spleen, kidneys, adrenal glands, urinary bladder, pituitary gland; in addition, spleens were examined in all dose groups. Special histology studies performed on animals killed at days 0 and 60 and on 5 animals/group at 0, 200, and 600 mg/kg at terminal kill and on any animals killed in a moribund condition.
Statistics:
Tests of significance included pairwise comparisons of high dose and low dose groups with vehicle controls and tests for overall dose-response trends. Haematology data was initially screened for outliers and as the same animals were examined across time, a repeated measures analysis of variance (Winer, 1971) method was used to investigate temporal and dose-related variation.
Clinical signs:
not specified
Mortality:
not specified
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
BODY WEIGHT AND WEIGHT GAIN: Final mean bodyweights, relative to vehicle controls, were depressed: 4, 2, 7, 14, 20 and 22% for males and 6, 9, 6, 16, 15 and 20 % for females at dose levels of 25, 50, 100, 200, 400 and 600 mg/kg respectively.

HAEMATOLOGY: A dose-related leukopenia was observed for both male and female rats. Day 60 mean WBC counts were 6.4, 2.5 and 1.7 (males) and 4.3, 2.3 and 1.7 (females) at 0, 200 and 600 mg/kg respectively. Day 60 mean LYM counts were 5.8, 2.0 and 1.3 (males) and 3.8, 1.9 and 1.5 (females) for 0, 200 and 600 mg/kg respectively. Day 120 mean WBC counts were 5.0, 7.0, 5.7, 6.0, 5.2, 3.5 and 3.1 (males) and 8.1, 6.2, 4.9, 5.0, 4.8, 3.4 and 3.8 (females) for 0, 25, 50, 100, 200, 400 and 600 mg/kg respectively. Day 120 mean LYM counts were 4.1, 5.1, 3.9, 3.9, 3.4, 2.3, and 2.4 (males) and 6.6, 4.7, 3.9, 3.6, 3.7, 2.7 and 2.8 (females) for 0, 25, 50, 100, 200, 400 and 600 mg/kg respectively.

HISTOPATHOLOGY: NON-NEOPLASTIC: Lymphoid depletion in the B-cell of the spleen was observed in 3/5 male and 4/5 female rats at 200 mg/kg and 5/5 male and 5/5 female rats at 600 mg/kg at 60 days and in 1/10 male and 10/10 females at 600 mg/kg at 120 days. Increased extramedullary haematopoiesis was observed in the spleen of 4/5 male and 3/5 female rats that received 600 mg/kg for 120 days.

Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (nominal)
Sex:
male
Basis for effect level:
other: Based on effects observed at 200 mg/Kg bw/day dose level.
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (nominal)
Sex:
male
Basis for effect level:
other: decreased final body weight, white blood cell and lymphocyte counts and lymphoid depletion of B-cells in the spleen at 200 mg/kg and above
Dose descriptor:
LOAEL
Effect level:
25 mg/kg bw/day (nominal)
Sex:
female
Basis for effect level:
other: reduction in white blood cell and lymphocyte counts at 25 mg/kg (lowest dose tested)
Critical effects observed:
not specified
Conclusions:
Repeat oral administration of benzene to rats is associated with adverse effects in the haematopoietic system. NOAEL for males was 200 mg/kg. No NOAEL was established for females. LOAEL for females was 25 mg/kg/day (lowest dose tested).
Executive summary:

Groups of 10 or 15 rats/sex were administered 0, 25, 50, 100, 200, 400 or 600 mg/kg benzene in corn oil by gavage, 5 days/ week for 17 weeks. Five rats/sex were killed on days 0 and 60 from the 0, 200, and 600 mg/kg groups, remaining surviving animals were killed on day 120. Clinical observations, bodyweights, food consumption, haematological analyses and histopathological examinations were performed. No compound-related deaths occurred. Final mean body weights (relative to those of the vehicle controls) were depressed 14%-22% for male and female rats that received ≥200 mg/kg benzene. A dose-related leukopenia and lymphocytopenia was observed in males at ≥200 mg/kg and in females at ≥25 mg/kg. In the spleen, lymphoid depletion of B-cells was observed in both sexes at ≥200 mg/kg benzene and increased extramedullary haematopoiesis was observed 600 mg/kg.

NOAEL for males was 100 mg/kg/day. LOAEL for males was 200 mg/kg and for females was 25 mg/kg/day.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEL
25 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
Adequate information is available to characterise the repeated oral toxicity of benzene in animals.

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records
Reference
Endpoint:
chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP-status unknown, non-guideline, animal experimental study, published in peer-reviewed literature, notable limitations in design and reporting but contributing to a weight of evidence
Qualifier:
no guideline followed
Principles of method if other than guideline:
Eight to twelve-week old male and female C57B1/6 BNL mice were exposed to air or benzene vapour in air. At various times during and after the exposure period, five to ten mice were removed from both the treated and control groups and the blood, bone marrow and spleens removed and examined for evidence of haematotoxicity.
GLP compliance:
not specified
Limit test:
no
Species:
mouse
Strain:
C57BL
Sex:
male/female
Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: details on construction and design reported elsewhere
- Generation of vapour: No details reported
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
2-16 weeks
Frequency of treatment:
6 h/day, 5 days/week or 3 consecutive days/week
Remarks:
Doses / Concentrations:
0, 10, 25, 100, 300, 400 ppm (0, 32, 80, 320, 960, 1280 mg/m3)
Basis:
other: target concentration - (6h/d, 5d/wk for 2-16 wks)
Remarks:
Doses / Concentrations:
0, 300 ppm (960 mg/m3)
Basis:
other: target concentration - (6h/day, 3 d/week for 8 weeks)
No. of animals per sex per dose:
No specific detail. At 300 ppm for 16 weeks 88 control and 89 exposed females
Control animals:
yes, concurrent no treatment
Details on study design:
Post-exposure period: 16 weeks
Dose descriptor:
NOAEC
Effect level:
10 ppm
Sex:
male/female
Basis for effect level:
other: lymphocytopenia after 10 expousres at 25 ppm
Dose descriptor:
NOAEC
Effect level:
32 mg/m³ air (nominal)
Sex:
male/female
Basis for effect level:
other: lymphocytopenia after 10 expousres at 80 mg/m3
Critical effects observed:
not specified

Benzene (100 ppm or higher for 6 h/day, 5 days/week for 2 weeks) produced a reduction in bone marrow cellularity and the number of pluripotent stem cells in the bone marrow. There was also as increase in the fraction of stem cells in DNA synthesis. At 25 ppm lymphocyte concentration in peripheral blood was decreased. Exposure to 300 ppm 6 h/day, 5 days/ week for 2, 4, 8, and 16 weeks produced a diminution in the stem cell levels in bone marrow. Stem cells returned to control levels 2 weeks after the end of benzene exposure for 2 and 4 weeks, 16 weeks after exposure for 8 weeks, and to 92% of controls 25 weeks after 16 weeks of exposure. Blood lymphocytes showed a more rapid return to the control level.

Conclusions:
Repeated inhalation exposure to benzene at 6h/day, 5 days/week produces haematotoxicity in mice. The NOAEC was 10 ppm (32 mg/m3).
Executive summary:

Haematotoxicity was examined in male and female C57Bl/6 BNL mice exposed to benzene vapour at concentrations of 0, 10, 25, 100, 300 or 400 ppm benzene for 2 -16 weeks. At various times during and after the exposure period, five to ten mice were removed from both the treated and control groups and the blood, bone marrow and spleens removed and examined.

At ≥100 ppm for 10 exposures benzene produced a reduction in bone marrow cellularity and the number of pluripotent stem cells in the bone marrow. The fraction of stem cells in DNA synthesis was also increased. At 25 ppm lymphocyte concentration was decreased. 16 weeks of exposure to 300 ppm benzene, 6 h/day, 5 days/week, produced a diminution in the haemopoietic stem cells with incomplete recovery 16 weeks after termination of exposure although full recovery was seen with shorter exposure durations (2, 4 or 8 weeks). There was a more rapid return of blood lymphocytes to control levels.

The NOAEC for haematotoxicity was 10 ppm (32 mg/m3).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
11.2 mg/m³
Study duration:
chronic
Species:
other: human (epidemiological findings)
Quality of whole database:
Adequate information is available to characterise the repeated inhalation toxicity of benzene in animals and humans.

Repeated dose toxicity: inhalation - local effects

Link to relevant study records
Reference
Endpoint:
chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP-status unknown, non-guideline, animal experimental study, published in peer-reviewed literature, notable limitations in design and reporting but contributing to a weight of evidence
Qualifier:
no guideline followed
Principles of method if other than guideline:
Eight to twelve-week old male and female C57B1/6 BNL mice were exposed to air or benzene vapour in air. At various times during and after the exposure period, five to ten mice were removed from both the treated and control groups and the blood, bone marrow and spleens removed and examined for evidence of haematotoxicity.
GLP compliance:
not specified
Limit test:
no
Species:
mouse
Strain:
C57BL
Sex:
male/female
Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: details on construction and design reported elsewhere
- Generation of vapour: No details reported
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
2-16 weeks
Frequency of treatment:
6 h/day, 5 days/week or 3 consecutive days/week
Remarks:
Doses / Concentrations:
0, 10, 25, 100, 300, 400 ppm (0, 32, 80, 320, 960, 1280 mg/m3)
Basis:
other: target concentration - (6h/d, 5d/wk for 2-16 wks)
Remarks:
Doses / Concentrations:
0, 300 ppm (960 mg/m3)
Basis:
other: target concentration - (6h/day, 3 d/week for 8 weeks)
No. of animals per sex per dose:
No specific detail. At 300 ppm for 16 weeks 88 control and 89 exposed females
Control animals:
yes, concurrent no treatment
Details on study design:
Post-exposure period: 16 weeks
Dose descriptor:
NOAEC
Effect level:
10 ppm
Sex:
male/female
Basis for effect level:
other: lymphocytopenia after 10 expousres at 25 ppm
Dose descriptor:
NOAEC
Effect level:
32 mg/m³ air (nominal)
Sex:
male/female
Basis for effect level:
other: lymphocytopenia after 10 expousres at 80 mg/m3
Critical effects observed:
not specified

Benzene (100 ppm or higher for 6 h/day, 5 days/week for 2 weeks) produced a reduction in bone marrow cellularity and the number of pluripotent stem cells in the bone marrow. There was also as increase in the fraction of stem cells in DNA synthesis. At 25 ppm lymphocyte concentration in peripheral blood was decreased. Exposure to 300 ppm 6 h/day, 5 days/ week for 2, 4, 8, and 16 weeks produced a diminution in the stem cell levels in bone marrow. Stem cells returned to control levels 2 weeks after the end of benzene exposure for 2 and 4 weeks, 16 weeks after exposure for 8 weeks, and to 92% of controls 25 weeks after 16 weeks of exposure. Blood lymphocytes showed a more rapid return to the control level.

Conclusions:
Repeated inhalation exposure to benzene at 6h/day, 5 days/week produces haematotoxicity in mice. The NOAEC was 10 ppm (32 mg/m3).
Executive summary:

Haematotoxicity was examined in male and female C57Bl/6 BNL mice exposed to benzene vapour at concentrations of 0, 10, 25, 100, 300 or 400 ppm benzene for 2 -16 weeks. At various times during and after the exposure period, five to ten mice were removed from both the treated and control groups and the blood, bone marrow and spleens removed and examined.

At ≥100 ppm for 10 exposures benzene produced a reduction in bone marrow cellularity and the number of pluripotent stem cells in the bone marrow. The fraction of stem cells in DNA synthesis was also increased. At 25 ppm lymphocyte concentration was decreased. 16 weeks of exposure to 300 ppm benzene, 6 h/day, 5 days/week, produced a diminution in the haemopoietic stem cells with incomplete recovery 16 weeks after termination of exposure although full recovery was seen with shorter exposure durations (2, 4 or 8 weeks). There was a more rapid return of blood lymphocytes to control levels.

The NOAEC for haematotoxicity was 10 ppm (32 mg/m3).

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Non-human data

Oral

Benzene toxicity following sub-chronic and chronic oral (gavage) exposure was investigated in studies using F344/N rats and B6C3F1 mice conducted as part of the National Toxicology Program (NTP, 1986). Animals were dosed 5 days per week for 17 or up to 103 weeks. The most significant findings in rats were a dose-related leukopenia and lymphocytopenia observed in males at ≥ 200 mg/kg and in females at ≥ 25 mg/kg in the 17 week study and in all groups dosed for one and two years. No NOAEL could be determined in the 2-year study. The LOAEL was 50 mg/kg/day for male rats and 25 mg/kg/day for female rats, i.e. the lowest doses administered.

In mice, tremors were observed intermittently at 400 and 600 mg/kg throughout the 17 week study. White blood cell and lymphocyte counts were decreased in males at 50 mg/kg bw or more and in females white blood cells were decreased at 600 mg/kg and lymphocytes were decreased at 400 mg/kg or more. In the chronic toxicity study weight gain reductions occurred in male and female mice at 100 mg/kg. Haematotoxic effects were limited to lymphocytopenia and associated leukocytopenia in all dose groups (males from 3 to 18 months, female mice from 12 to 18 months). Benzene increased the frequency of micronucleated normochromatic peripheral erythrocytes in male and female mice of all dose groups, males were more sensitive than females. Haematopoietic hyperplasia in the bone marrow and splenic haematopoiesis was observed in all dosed mice groups. The LOAEL was 25 mg/kg bw/day for male and female mice. A NOAEL was, therefore, not achieved.

Inhalation

In the rat, the key study is considered to be that of Ward et al, 1985. Animals were exposed to concentrations of 0, 1, 10, 30 or 300 ppm (0, 3.2, 9.6, 960 mg/m3) benzene vapour, 6 h/day, 5 days/week, for 13 weeks. Decreased blood lymphocyte counts, relative increase in neutrophil percentages and slightly decreased femoral marrow cellularity were the only significant treatment-related parameters noted in animals exposed to 300 ppm. The NOAEC for toxicity at 28 and 90 days was 30 ppm (96 mg/m3) for both male and female rats.

In mice haematotoxic effects following repeated inhalation exposure to benzene include: decreases in haematocrit, total haemoglobin, erythrocyte count, leukocyte count, platelet count, myeloid/erythroid ratios, and percentage of lymphocytes at 300 ppm (960 mg/m3) (Ward et al, 1985); depressed bone marrow and splenic Multipotential Haematopoietic Stem cells (CFU-S) and Granulocyte/Macrophage Progenitor cells (GM-CFU-C) at benzene concentrations ≥103 ppm (Green et al, 1981a, b); bone marrow erythroid progenitor cell numbers were depressed 1 day after exposure to concentrations ≥ 10 ppm (32 mg/m3) (Dempster and Snyder, 1990); significant depression in femoral lipopolysaccharide (LPS) -induced B-colony-forming ability and splenic phytohaemagglutinin (PHA) -induced blastogenesis at 31 ppm (Rozen et al, 1984); a reduction in bone marrow cellularity and the number of pluripotent stem cells in the bone marrow at ≥ 100 ppm for 10 exposures (Cronkite et al, 1985).

On the basis of these studies the LOAEC for haematotoxicity in mice is 10 ppm (32 mg/m3). A NOAEC could not be defined.

Dermal

No published data are available

 

Human data

For updated Human data (see section 7.10 Endpoint Summary). This section will be revised in the next the next dossier update.

References

Agency for Toxic Substances and Disease Registry (ATSDR) (2007). Toxicological profile for Benzene, Department of Health and Human Services, Public Health Service.

Collins JJ, Ireland BK, Easterday PA, Nair RS and Braun J (1997). Evaluation of lymphopenia among workers with low-level benzene exposure and the utility of routine data collection. J Occup Environ Med 39, 232-237.

Cronkite EP, Drew RT, Inoue T and Bullis JE (1985). Benzene hematotoxicity and leukemogenesis. Am. J. Ind. Med. 7, 447-456.

Dempster AM, Snyder CA. (1990). Short term benzene exposure provides a growth advantage for granulopoietic progenitor cells over erythroid progenitor cells. Arch Toxicol 64(7):539-544.

EU RAR (2008). European Union Risk Assessment Report for Benzene. http://ecb.jrc.ec.europa.eu/documents/Existing-chemicals/RISK_ASSESSMENT/REPORT/benzenereport063.pdf.

Green JD, Snyder CA, LoBue J, Goldstein BD, Albert RE (1981a). Acute and chronic dose/response effects of inhaled benzene on multipotential hematopoietic stem (CFU-S) and granulocyte/macrophage progenitor (GM-CFU-C) cells in CD-1 Mice. Toxicol. App. Pharmacol. 58, 492-503.

Green JD, Synder CA, LoBue J, Goldstein BD and Albert RE (1981b). Acute and chronic dose/response effect of benzene inhalation on the peripheral blood, bone marrow, and spleen cells of CD-1 male mice. Toxicol. Appl. Pharmacol. 59, 204-214.

Lan Q, Zhang L, Li G, Vermeulen R, Weinberg RS, Dosemeci M, Rappaport SM, Shen M, Alter BP, Wu Y, Kopp W, Waidyanatha S, Rabkin C, Guo W, Chanock S, Hayes RB, Linet M, Kim S, Yin S, Rothman N and Smith MT (2004). Haematotoxicity in workers exposed to low levels of benzene. Science 306, 1774-1776.

NTP (1986). Toxicology and carcinogenesis studies of benzene (CAS No. 71-43-2) in F344/N rats and B6C3F1 mice (gavage studies). NIH publication number 86-2545. Testing laboratory: Battelle Columbus Laboratories. Report no.: TR 289. Study number: NTP TR 289.

Pesatori AC, Garte S, Popov T, Georgieva T, Panev T, Bonzini M, Consonni D, Carugno M, Goldstein BD, Taioli E, Fontana V, Stagi E, Bertazzi PA and Merlo DF (2009). Early effects of low benzene exposure on blood cell counts in Bulgarian petrochemical workers. Med Lav, 100, 83-90.

Qu Q, Shore R, Li G, Jin X, Chen LC, Cohen B, Melikian AA, Eastmond D, Rappaport SM, Yin S, Li H, Waidyanatha S, Li Y, Mu R, Zhang X and Li K (2002). Hematological changes among Chinese workers with a broad range of benzene exposures. Am J Ind Med. 42, 275-285.

Qu Q, Shore R, Li G, Jin X, Chen LC, Cohen B, Melikian AA, Eastmond D, Rappaport S, Li H, Rupa D, Waidyantha S, Yin S, Yan H, Meng M, Winnik W, Kwok ESC, Li Y, Mu R, Xu B, Zhang X and Li K (2003). Validation and evaluation of biomarkers in workers exposed to benzene in China. Research Report 115, Health Effects Institute, Boston, MA.

Rothman N, Li GL. Dosemeci M, Bechtold WE, Mart GE, Wang YZ, Linet M, Xi L, Lu W, Smith MT, Titenko-Holland N, Zhang LP, Blot W, Yin SN and Hayes RB (1996). Hematotoxicity among Chinese workers heavily exposed to benzene. American Journal of Industrial Medicine, 29, 236-246.

Rozen MG, Snyder CA, Albert RE. (1984). Depression in B- and T-lymphocyte mitogen-induced blastogenesis in mice exposed to low concentrations of benzene. Toxicology Letters 20, 343-349.

Schnatter AR, Kerzic P, Zhou Y, Chen M, Nicolich M, Lavelle K, Armstrong T, Bird M, Lin l, Hua F and Irons R (2010). Peripheral blood effects in benzene-exposed workers. Chem Biol Interact (2009) doi:10.1016/j.cbi.2009.12.020

Swaen GMH, van Amelsvoort L, Twisk JJ, Versraeten E, Slootweg R, Collins JJ and Burns CJ (2010). Low level occupational benzene exposure and hematological parameters. Chem Biol Interact (2010).

Tsai SP, Fox EE, Ransdell JD, Wendt JK, Waddell LC and Donnelly RP (2004). A hematology surveillance study of petrochemical workers exposed to benzene. Reg Toxicol Pharmacol 40, 67-73.

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Ward E, Hornung R, Morris J, Rinsky R, Wild D, Halperin W and Guthrie W (1996). Risk of low red or white blood cell count related to estimated benzene exposure in a rubberworker cohort (1940-1975). Am J Ind Med 29, 247 -257.



Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Sub-chronic and chronic studies indicate that benzene causes adverse effects on the haematopoietic system of rats and mice following repeated oral exposure.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
In the rat, decreased blood lymphocyte counts and slightly decreased femoral marrow cellularity were the only significant treatment-related parameters noted in animals exposed to 300 ppm with a sub-acute and sub-chronic NOAEC of 30 ppm (96 mg/m3). In mice, reductions in a range of haematological parameters were recorded with a LOAEC of 10 ppm (32 mg/m3). Human data show haematological changes in neutraphil counts with a NOAEC of 3.5 ppm (11.2 mg/m3).

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: bone marrow

Repeated dose toxicity: inhalation - systemic effects (target organ) cardiovascular / hematological: hematopoiesis

Justification for classification or non-classification

After repeated dose exposure via oral or inhalation routes, benzene causes adverse effects on the haematopoietic system of animals and in humans. Consequently, benzene is classified as T, Cat 1 (H372) according to Regulation (EC) No 1272/2008 of the European Parliament.