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EC number: 270-658-3 | CAS number: 68475-70-7 A complex combination of hydrocarbons obtained by the fractionation pyrolysis at 816°C (1500°F) of naphtha and raffinate. It consists predominantly of aromatic hydrocarbons having carbon numbers predominantly in the range of C6 through C8, including benzene.
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
![](https://poisoncentres.echa.europa.eu/o/diss-blank-theme/images/factsheets/A-REACH/factsheet/print_toxicological-information.png)
Toxicological Summary
- Administrative data
- Workers - Hazard via inhalation route
- Workers - Hazard via dermal route
- Workers - Hazard for the eyes
- Additional information - workers
- General Population - Hazard via inhalation route
- General Population - Hazard via dermal route
- General Population - Hazard via oral route
- General Population - Hazard for the eyes
- Additional information - General Population
Administrative data
Workers - Hazard via inhalation route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 3.25 mg/m³
- Most sensitive endpoint:
- carcinogenicity
- Route of original study:
- By inhalation
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 1
- Modified dose descriptor starting point:
- other: BOELV for benzene
- Value:
- 3.25 mg/m³
- Explanation for the modification of the dose descriptor starting point:
None applied
- AF for dose response relationship:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for differences in duration of exposure:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for other interspecies differences:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for intraspecies differences:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for the quality of the whole database:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for remaining uncertainties:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Workers - Hazard via dermal route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 23.4 mg/kg bw/day
- Most sensitive endpoint:
- carcinogenicity
- Route of original study:
- By inhalation
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 1
- Modified dose descriptor starting point:
- other: BOELV for benzene
- Value:
- 23.4 mg/kg bw/day
- Explanation for the modification of the dose descriptor starting point:
The BOELV (mg/m3) was converted into a human dermal DNEL (mg/kg bwt/d) by adjusting for differences in uptake between the two routes of exposure (REACH Guidance, Appendix R.8-2, Example B.4).
- AF for dose response relationship:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for differences in duration of exposure:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for other interspecies differences:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for intraspecies differences:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for the quality of the whole database:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
- AF for remaining uncertainties:
- 1
- Justification:
- The BOELV (8-hr) was used without modification (ECHA Guidance, Appendix R.8-13)
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- low hazard (no threshold derived)
Workers - Hazard for the eyes
Local effects
- Hazard assessment conclusion:
- low hazard (no threshold derived)
Additional information - workers
Compositional information:
These hydrocarbon streams meet the regulatory definition of UVCB substances, with inherent variations in composition present due to differences in manufacturing history. This variability is documented in the Category Justification (appended to IUCLID section 13), which lists the chemical marker substances present along with an indicative concentration range for each e.g.:
· Benzene: ≥ 0.1 - 90%
· Buta-1,3-diene: 0 - 1%
· Isoprene: 0 - 10%
· Ethylbenzene: 0 - 32%
· Styrene: 0 - 24%
· DCPD: 0 - 21%
· 2-methyl-2-butene: 0 - 12 %
· Toluene: 0 - 78%
· n-Hexane: 0 - 22%
· Xylenes: 0 - 14%
· Naphthalene: 0 - 9%
· Anthracene: <0.1%
The approach developed by the ExWG on the selection of category constituents for use in human health exposure assessments was implemented for Category H. The primary constituents used are benzene and DCPD. A full description of this approach is available in Section 13.
Uses:
These hydrocarbon streams are used as intermediates, in manufacture and as fuels. These DNELs address concerns linked to the CMR properties of the marker substances or their potential to cause other long-term health effects leading to an equivalent level of concern.
Substance selection for risk characterization:
In general, risk characterization will be based on the premise that a marker substance with a low DN(M)EL present at high concentration in a stream will possess a greater relative hazard potential than a marker substance with a higher DN(M)EL present at the same or lower concentration.
Against this background, the most hazardous marker substances present in these streams are highlighted in the following table (details of the DN(M)EL derivations follow this table):
Marker Constituent |
CAS Number |
EC Number |
DNEL Value (mg/mg3) |
Source/Rationale |
Benzene |
71-43-2 |
200-753-7 |
3.25 |
To be revised in Q1 2020. |
DCPD |
77-73-6 |
201-052-9 |
2.31 |
Value from LOA REACH registration dossier. |
Isoprene |
78-79-5 |
201-143-3 |
8.4 |
Value from LOA REACH registration dossier. |
Naphthalene |
91-20-3 |
202-049-5 |
25 |
Non-LOA substance. Derived from repeated dose toxicity. |
N-hexane |
110-54-3 |
203-777-6 |
72 |
Non-LOA substance. Derived from neurotoxicity. |
Ethylbenzene |
100-41-4 |
202-849-4 |
77 |
Non-LOA substance. Derived from repeated dose toxicity. |
Styrene |
100-42-5 |
202-851-5 |
85 |
Non-LOA substance. Derived from repeated dose toxicity. |
Toluene |
108-88-3 |
203-625-9 |
192 |
Value from LOA REACH registration dossier. Derived from neurotoxicity. |
Xylenes |
1330-20-7 |
215-535-7 |
221 |
Value from LOA REACH registration dossier. Derived from neurotoxicity. |
2-methyl-2-butene |
513-35-9 |
208-156-3 |
- |
LOA REACH registration dossier. High Hazard (no value derived). |
Buta-1,3 -diene | 106 -99 -0 |
203-450-8 |
2.21 |
Value from LOA REACH registration dossier. |
Based on this analysis, management of inhalation and dermal hazards associated with the presence of dicyclopentadiene should also provide adequate protection against hazards arising from other marker substances present. However, this conclusion does not consider the relative volatilities of the substances present, and overlooks the fact that benzene is a human carcinogen requiring an appropriate level of control.
Hence, in order to demonstrate safe use in worker exposure scenarios computed by application of the ECETOC TRA, estimates of inhalation exposure and risk characterisation will use benzene as the marker substance (based on its relatively high volatility and carcinogenicity), while estimates of dermal exposure and risk characterisation will use DCPD as the marker substance (based on its lower volatility and very low dermal DNEL).
Intrinsic hazards of marker substances and associated DN(M)ELs:
The following hazard information and DNELs are available for marker substances present in this Category.
Benzene
Benzene causes adverse effects on the haematopoietic system of animals and in humans after repeated dose exposure via oral or inhalation routes. Long term experimental carcinogenicity bioassays have shown that it is a carcinogen producing a variety of tumours in animals (including lymphomas and leukaemia). Human epidemiological studies provide clear and consistent evidence of a causal association between benzene exposure and acute myelogenous (non-lymphocytic) leukaemia (AML or ANLL). An effect on bone marrow leading to subsequent changes in human blood cell populations is believed to underpin this response.
In accordance with REACH guidance, a science-based Binding Occupational Exposure Limit value (BOELV) can be used in place of a formal DN(M)EL providing no new scientific information exists which challenges the validity of the BOELV. While some information regarding a NOAEC for effects of benzene on human bone marrow (Schnatter et al, 2010; NOAEC = 11.18 mg/m3)[b]post-date the BOELV, a DNEL based on these bone marrow findings would be higher than the BOELV. The BOELV (EU, 1999) will therefore be used as the basis of the DN(M)EL for long-term systemic effects associated with benzene, including carcinogenicity.
Worker – long-term systemic inhalation DNEL
The BOELV will be used with no further modification
DN(M)ELl-t inhalation =3.25 mg/m3
Worker - long-term systemic dermal DNEL
The dermal DNEL for benzene is based on the internal dose achieved by a worker undertaking light work and exposed to the BOELV for 8 hr, assuming 50% uptake by the lung and 1% by skin for benzene uptake from petroleum streams.The value of 1% is based on experiments with compromised skin and with repeated exposure (Blank and McAuliffe, 1985; Maibach and Anjo, 1981) as well as the general observation that vehicle effects may alter the dermal penetration of aromatic compounds through the skin (Tsuruta et al, 1996).
As the BOELV is based on worker life-time cancer risk estimates no assessment factor is needed.
Dermal NOAEL = BOELV xwRV8-hour[b] x [ABSinhal-human/ABSdermal-human] = 3.25 x 0.144 x [50 / 1]
DN(M)ELl-t dermal = 23.4mg/kg bw/d
Dicyclopentadiene
The potential of dicyclopentadiene to cause long-term systemic effects can judged based on the results of repeated dose toxicity and reproductive (fertility, developmental) testing.
For DCPD, the following NOAEL/NOAECs are available:
Oral:
sub-chronic effects: male rat NOAEL = 4 mg/kg bw/d
reproductive effects: rat NOAEL = 50 mg/kg bw/d
developmental toxicity: rat NOAEL = 60 mg/kg bw/d
Inhalation:
sub-chronic effects: mouse NOAEC = 27.6 mg/m3
sub-chronic effects: rat NOAEC = 276 mg/m3
Worker – long-term systemic inhalation DNEL
Dose descriptor
A mouse inhalation NOAEC of 27.6 mg/m3 will be used to derive the DNELl-t inhalation.
Modification of dose descriptor
Correct the NOAEC to adjust for differences in duration in the animal study (6 h) and the worker (8 h) and light work following the TGD Figure R.8-2:
27.6 mg/m3x [6 h / 8 h] x [6.7 m3/ 10 m3] = 13.9 mg/m3
It is assumed that DCPD is similarly and efficiently (100%) absorbed after inhalation by mice and humans.
Assessment factors
An assessment factor of 6is used based on worker intraspecies differences (3)and correction for duration of exposure (sub-chronic to chronic = 2).
DNELl-t inhal= 13.9 mg/m3/ 6 = 2.3 mg/m3
Worker - long-term systemic dermal DNEL
Dose descriptor
A mouse inhalation NOAEC of 27.6 mg/m3will be used to derive the DNELl-t dermal.
Modification of dose descriptor
Correct the NOAEC to adjust for differences in duration of exposure; then convert the corrected mouse inhalation NOAEC (mg/m3) into a human dermal NOAEL (mg/kg bwt/d) after adjusting for differences in uptake between the two routes of exposure (TGD, Appendix R.8-2, Example B.4).
It is assumed that uptake of DCPD after inhalation is 100% and, in the absence of data, dermal absorption is assumed to be the default of 100%.
correctedDermal NOAEL = NOAECinhalationx sRVmouse[1]x [ABSinhal-mouse/ABSdermal-human]
correctedDermal NOAEL = 27.6 x 0.514 x [100/100] = 14.19 mg/kg bwt/d
Assessment factors
An assessment factor of 42 is used based on interspecies differences for the mouse (7), worker intraspecies differences (3) and correction for duration of exposure (sub-chronic to chronic = 2).
DNELl-t dermal= 14.19 mg/kg bwt/d / 42 = 0.34 mg/kg bw/d
Isoprene
Isoprenehas been shown to be carcinogenic to mice and rats. When inhaled in concentrations of 70 ppm and above, it was found to induce tumours in a range of tissues in male mice while tissue responses in females were more limited. No statistically significant increases in tumours were reported in either sex at a dose level of 10 ppm. Inhalation by rats of concentrations above 220 ppm caused a significantly increased incidence of mammary gland, testicular and kidney tumours in males, and mammary gland tumours in females. At the lowest dose tested, 220 ppm, a statistically significant increase in only mammary gland fibroadenoma was observed in females.
Worker – long-term systemic inhalation DNEL
In accordance with REACH guidance (Appendix R.8-13), the established MAK (2009) value of 3 ppm (equivalent to 8.4 mg/m3) - 8 hr TWA will form the basis of the inhalation DNEL for workers. It was concluded by the MAK Commission that a maximum admissible concentration can be established for humans and that the carcinogenic and genotoxic effects of isoprene is low. There would be no appreciable increase of carcinogenic risk in humans if this value is not exceeded.
DN(M) ELl-t inhalation =8.4 mg/m3
Worker - long-term systemic dermal DNEL
The long-term dermal DN(M) EL is calculated from the inhalation DN(M) EL using route-to-route extrapolation, having determined the net inhalation uptake or dose. Filser et al (1996) determined the rates of isoprene metabolism (µmol/hr/kg bw) in humans, rats, and mice at steady-state over a range of atmospheric concentrations to validate a PT model for isoprene. Metabolism of isoprene is linear up to 50 ppm. At the isoprene exposure concentration of interest 8.4 mg/m3(3 ppm), the rate of metabolism (µmol/hr/kg bw) can be determined and subtracted from the rate of metabolism at 0 mg/m3(0 ppm). At an exposure concentration of 3 ppm, the rate of isoprene metabolism is 0.13 µmol/hr/kg bw and in an 8-hr workday, net inhalation uptake (or dose) is: 0.13 µmol/hr/kg bw x 8 hr i. e. 1.04 µmol/kg (equivalent to 71 µg/kg). This value is adjusted for the low absorption factor of 0.003% giving a DN(M) EL of 23.7 mg/kg bw/d.
Ethylbenzene
The cooperation of the Styrenics Steering Committee in providing DNELs for ethylbenzene is acknowledged. Documentation supporting these values is in the Styrenics REACH consortium dossier for ethylbenzene.
Worker – long-term systemic inhalation DNEL
There is no IOELV for ethylbenzene, therefore the DNEL is based on sub-chronic effects (ototoxicity) in the rat following inhalation exposure: extrapolated NOAEC = 500 mg/m3(114 ppm). Correct the NOAEC to adjust for activity driven and absorption percentage differences following ECHA TGD (2008b) guidance:
DNELl-t inhalation= 500 mg/m3x [6.7 / 10] x [ABSinhal-rat/ ABSinhal-human] = 500 mg/m3x 0.67 x [45 / 65] = 232 mg/m3
An assessment factor of 3 is used for intraspecies differences within worker population:
DN(M)ELl-t inhalation= 232 mg/m3/ 3 = 77 mg/m3
Worker – long-term systemic dermal DNEL
The DNEL is based on sub-chronic effects (ototoxicity) in the rat following inhalation exposure: extrapolated NOAEC = 500 mg/m3(114 ppm). The NOAEC is corrected into a human dermal NOAEL (mg/kg bw/d) by adjusting for differences in uptake between the two routes of exposure (TGD, Appendix R.8-2, Example B.4). It is assumed that uptake of ethylbenzene after inhalation in rats is 45%.
correctedDermal NOAEL = NOAECl-t inhalationx sRVrat-8hr[2]x 0.45 = 500 x 0.38 mg/kg bw/d = 86 mg/kg bw/d
A value of 4% used for dermal absorption in humans (Susten et al, 1990):
correctedDermal NOAEL = 86 mg/kg bw/d x [100 /4] = 2150 mg/kg bw/d
An assessment factor of 12 is used based on interspecies differences for the rat (4) and intraspecies differences within worker populations (3).
The DNEL for long-term dermal exposure is derived as follows:
DN(M)ELl-t dermal= 2150 mg/kg bw/d / 12 = 180 mg/kg bw/d
Styrene
The cooperation of the Styrenics REACH consortia in providing DN(M)ELs for styrene is acknowledged. Documentation supporting these values is in the Styrenics REACH consortium dossier for styrene.
The EU transitional RAR(2008c) identified the following end-points as of concern for human health: acute toxicity (CNS depression), skin, eye and respiratory tract irritation, effects on colour vision discrimination following repeated exposure, effects on hearing (ototoxicity) following repeated exposure, developmental toxicity.
Worker – long-term systemic inhalation DNEL
The DN(M)EL is based on ototoxicity in humans (Triebig et al, 2009). A NOAEC for humans of 20 ppm (85 mg/m3) can be derived as starting point from this study. As the DNEL is derived from studies on exposed workers an assessment factor is not necessary.
DN(M)ELl-t inhalation= 85 mg/m3
Worker – long-term systemic dermal DNEL
The DN(M)EL is based on long term inhalation NOAEC of 20 ppm (86 mg/m3) for ototoxicity in workers. The dose descriptor is corrected into a human dermal NOAEL. Using a respiratory volume for workers under light physical activity of 10 m3/person/day and a body weight of 70 kg (ECHA, 2008b) the external exposure would be 86 x 10/70 = 12.3 mg/kg bw/d.
This is then converted to a dermal dose by adjusting for differences in exposure. Absorption of styrene from the respiratory tract is considered to be 66% based on a study in 7 volunteers at 50 ppm under light physical activity (50 Watt) (Engström et al, 1978). In humans only 2% of a dermal dose of liquid styrene is likely to be absorbed (EU, 2008c).
Dermal NOAEL = 12.3 x [ABSinhal-human/ ABSdermal-human] = 12.3 x [66/2] = 406 mg/kg/d.
Since the worker-DNEL long-term for dermal exposure was directly derived from that for inhalation exposure no further assessment factors are necessary.
DN(M)ELl-t dermal= 406 mg/kg bw/d
Toluene
Toluene exposure can produce central nervous system pathology in animals after high oral doses. Repeated inhalation exposure can produce ototoxicity in the rat and high concentrations are associated with local toxicity (nasal erosion). In humans neurophysiological effects and disturbances of auditory function and colour vision have been reported, particularly when exposures are not well controlled and/or associated with noisy environments.
Documentation supporting the IOELV (SCOEL, 2001) concluded that an exposure limit of 50 ppm (192 mg/m3) would protect against chronic effects hence, in accordance with REACH guidance and since no new scientific information has been obtained under REACH which contradicts use of the IOELV for this purpose, the established IOELV of 50 ppm (192 mg/m3)[c]– 8 hr TWA (EU, 2006) will be used as the starting point for calculating the chronic dermal DNEL for workers.
Worker – long-term systemic inhalation DNEL
The IOELV will be used with no further modification
DN(M)ELl-t inhalation = IOELV = 192 mg/m3
Worker – long-term systemic dermal DNEL
The dermal DNEL for toluene is based on the internal dose achieved by a worker undertaking light work and exposed to the IOELV for 8 hr, assuming 50% uptake by the lung and 3.6% uptake by skin (ten Berge, 2009).
As the IOELV is based on worker life-time exposure no assessment factor is needed.
Dermal NOAEL = IOELV x wRV8-hourx [50/3.6] = [192 x 0.144 x 13.89]
DNELl-t dermal = 384 mg/kg bw/d
n-Hexane
Background information supporting the SCOEL decision on n-hexane is not available, however ACGIH (2001) and ATSDR (1999) identify peripheral polyneuropathy as the lead effect for n-hexane in humans. Since n-hexane is not a core LOA substance, it has been assumed that no significant new information has come available to challenge the SCOEL position, and that the IOELV (included in the 2ndlist of indicative occupational exposure limit values - EU, 2006) remains valid.
Worker – long-term systemic inhalation DNEL
The long-term systemic DNEL for n-hexane will therefore be based upon the IOELV with no further modification:
DN(M)ELl-t inhalation = IOELV = 72 mg/m3
Worker – long-term systemic dermal DNEL
The dermal NOAEC is extrapolated from the IOELV. The IOELV (mg/m3) is converted into a human dermal NOAEL (mg/kg bw/d) after adjusting for differences in uptake between the two routes of exposure (TGD, Appendix R.8-2, Example B.4).
Information cited by ACGIH indicates that uptake of n-hexane after inhalation is in a range 5-28%, with pulmonary retention of 25% reported for volunteers involved in work. ACGIH briefly reports a human case report which described “severe intoxication” following percutaneous absorption. However, the UK HSE (1990) concluded that “there is limited absorption of liquid through the skin” although no quantitative information is provided. No substance-specific data are available, hence a conservative default of 10% uptake will be used.
Dermal NOAEL = IOELV xwRV8-hour[b] x [ABSinhal-human/ABSdermal-human] = 72 x 0.144 x [25 / 10] = 25.9 mg/kg bw/d
As the IOELV is based on human data no assessment factor is needed.
DN(M)ELl-t dermal = 25.9 mg/kg bw/d
Xylene isomers
Worker – long-term systemic inhalation DNEL
For xylenes, the following rodent inhalation NOAECs are presented in the IUCLID dossier:
Sub-chronic effects – ototoxicity (deficits in brainstem auditory evoked response)
m-xylene and o-xylene = 1800 ppm (7817 mg/m3)
mixed xylene (2 samples) = 500 ppm (2171 mg/m3) or 1000 (4342 mg/m3)
p-xylene = 450 ppm (1954 mg/m3)
The lowest overall NOAEC for repeated dose effects after inhalation is 450 ppm (1954 mg/m3; ototoxicity, p-xylene). It is noted that (relative to other xylene isomers) this is a conservative no-effect concentration.
The equivalent worker NOAEC (Example A.2, ECHA Guidance, Chapter R.8) is therefore:
Worker NOAEC = inhalatory NOAEC x [sRVhuman / wRV]
= 1954 mg/m3 x [6.7 m3 / 10 m3]
= 1309.2 mg/m3
Assessment factors:
Long-term DNEL Assessment Factors (Worker, inhalation) |
||
AF for dose response relationship |
1 |
NOAEC used as starting point |
AF for differences in duration of exposure |
2 |
Default (correction for sub-chronic to chronic exposure) |
AF for interspecies differences (allometric scaling) |
1 |
Default (none required inhalation route) |
AF for other interspecies differences |
1 |
An analysis of assessment factors conducted by ECETOC (2003, 2010) showed that a standard approach of applying a default AF for any remaining differences is not appropriate since, in the majority of cases, this is adequately covered by the inherent interdependence of the inter- and intra-species assessment factors and taken into account by allometric scaling (see, for instance, ECETOC analysis of information from Calabrese and Gilbert (1993) Reg. Tox. Pharmacol. 17: 44-51). Furthermore, data available for xylene isomers, together with information available for chemically-related structures do not raise concern for possible differences in effect within or between species. Overall, no factor for remaining differences will therefore be applied. |
AF for intraspecies differences |
3 |
There are no data to quantify variability in susceptibility to the effects of exposure to xylene isomers in the human population. However the population exposed in the workplace is highly homogeneous and the health of the work force is typically good (healthy worker effect) while metabolic differences due to genetic polymorphisms do not automatically require an increased assessment factor since compensating mechanisms (including alternative pathways of elimination) are often present (ECETOC, 2003, 2010). Following a review of the distribution of variability in toxicokinetic and toxicodynamic parameters for populations of different ages, genders and disease states, ECETOC concluded that human data (Renwick and Lazarus (1998) Reg. Tox. Pharmacol. 27:3-20 ; Hattis et al. (1999) Risk Anal. 19: 421-431) support the use of an assessment factor of 3 (i.e. the 90th percentile of human toxicokinetic and toxicodynamic variability) to account for intra-species variability present within workers. |
AF for quality of the whole data base |
1 |
No issues with quality of the whole database identified |
AF for remaining uncertainties |
1 |
None identified (conservative NOAEC used as starting point) |
Overall AF |
6 |
The DNEL for long-term inhalation exposure is therefore:
DNEL l-t inhalation = Worker NOAEC / AF = 1309.2 mg/m3 / 6 = 218.2 mg/m3
As the magnitude of the DNEL l-t inhalation is essentially identical to the IOELV, the IOELV of 221 mg/m3 (50 ppm, 8h TWA) should provide adequate protection and is proposed as the worker DNELl-t inhalation.
Worker – long-term systemic dermal DNEL
Dose descriptor
The IOELV of 50 ppm (221 mg/m3, 8h TWA) will be used for derivation of the worker DNELl-t dermal.
Modification of dose descriptor
The IOELV (mg/m3) is corrected into a human dermal NOAEL (mg/kg bwt/d) by adjusting for differences in uptake between the two routes of exposure (TGD, Appendix R.8-2, Example B.4).
It is assumed that uptake of xylenes after inhalation is 100% with a value of 15% for dermal absorption (ten Berge, 2009):
correctedDermal NOAEL = IOELV x wRVhuman-8hr x [ABSinhal-human/ABSdermal-human]
correctedDermal NOAEL = 221 x 0.144 x (100/15) = 212 mg/kg bwt/d
Note:
worker respiratory volume (wRV) is 50% greater than the resting standard respiratory volume of 0.2 L/min/kg bw (wRV8-hour = (0.2 L/min/kg bw x 1.5 x 60 x 8) / 1000 = 0.144 m3/kg bw)
No assessment factor is necessary.
Naphthalene
The cooperation of the REACH for Coal Chemicals (R4CC) consortium in permitting access to DNEL information present on the ECHA Dissemination pages for naphthalene is acknowledged.
Worker – long-term systemic inhalation DNEL
The long-term systemic DNEL for naphthalene is based upon (EU and USA) OEL values of generally 50 mg/m3, with an assessment factor of 2:
DN(M) ELl-t inhalation= 50 mg/m3/ 2 = 25 mg/m3
Worker – long-term systemic dermal DNEL
The long-term dermal DNEL is based upon the systemic dose achieved following 8 hr exposure at the DNEL of 25 mg/m3.
DN(M) ELl-t dermal= 3.57mg/kg bw/d
2-methyl-2-butene
Since 2 -methylbut-2-ene (2M2B) is concluded to be an invivo mutagen (Cat 2, H341 under GHS/CLP) with no relevant dose-response information and no cancer data, neither a DMEL nor a DNEL can be derived.
A qualitative assessment is therefore considered. Since 2M2B is assigned the H-phrase H341 (suspected of causing genetic defects), it is allocated to the high hazard category on the basis that exposure to such substances should be strictly contained because they may cause serious health effects for which a dose threshold is not usually identifiable (TGDSection E.3.4).
With the strict control measures for a non-threshold mutagen, applying the RMMs/OCs as stipulated for the high hazard category, exposure control is considered to be sufficient and will cover any other relevant effects for which DNELs can be derived, for all routes of exposure.
In accordance with REACH guidance, it is concluded that this qualitative risk characterisation is sufficient and there is no need to conduct a quantitative risk characterisation.
1,3-Butadiene
1,3-Butadiene is a multi-species carcinogen. In the mouse, it is a potent multi-organ carcinogen. Tumours develop after short durations of exposure, at low exposure concentrations and the carcinogenic response includes rare types of tumours. In the rat, fewer tumour types, mostly benign, develop at exposure concentrations of 100 to1000-times higher than in the mouse. In humans, 1,3-butadiene is a recognised carcinogen. A positive association was demonstrated between workplace exposure to butadiene for men employed in the styrene-butadiene rubber industry and lymphohaematopoietic cancer (leukaemia). Various models have established a dose response-relationship for cumulative exposure to 1,3-butadiene, especially concentrations above 100 ppm. The estimates for occupational and population human risk are based on these models.
Worker – long-term systemic inhalation DNEL
The association between 1,3-butadiene exposure and leukaemia has been extensively modeled using Cox and Poisson regression models and the excess risk of leukaemia determined. The preferred model for workers is the Cox continuous model (Cheng et al, 2007) as employed by Sielken et al (2008), using the exposure metric that excluded exposure that occurred more than 40 years ago or excluded the 5% of workers with the highest cumulative 1,3-butadiene exposures and included as covariate, the cumulative number of exposures to 1,3-butadiene concentrations > 100 ppm (the number of High Intensity Tasks [HITs]). This model incorporates dose descriptors and assessment factors and therefore further corrected dose descriptors and overall assessment factors are not required. The estimate of the excess risk of death from leukaemia as a result of exposure to a DMEL of 2.21 mg/m3(1 ppm) is 0.33 x 10-4(with an upper bound of 0.66 x 10-4based on a one-sided 95% upper confidence limit for the regression parameter).
This estimate is less than 0.4 x 10-4, which has been proposed as a future limit for acceptable occupational risk (AGS, 2008). Regression coefficients from other Cox regression models reported by Cheng et al (2007) and TCEQ (2008), and estimates from Poisson regression models, indicate that other risk estimates are generally close to 0.4 x 10-4, even if based on regression models that do not adjust for 1,3-butadiene HITs. All of the estimates are considerably lower than the current limit for acceptable occupational risk of 4 x 10-4that has recently been proposed (AGS, 2008).
DN(M) ELl-t inhalation= 2.21 mg/m3
Worker – long-term systemic dermal DNEL
As 1,3-butadiene is a gas a dermal DNEL is not quantifiable.
Anthracene
The toxicological properties of anthracene have been reviewed (EU, 2009), with a conclusion that it is of low toxicity following repeated exposure (NOAEC of 1000 mg/kg/day in mouse oral toxicity study) and is not of concern for mutagenicity or carcinogenicity. Although data are lacking with respect to reproductive and developmental toxicity no detectable toxic effects on the reproductive system of mice were seen during a 90-day feeding study it was concluded that anthracene may possess weak, if any, developmental toxicity. However, extensive studies in animals and humans demonstrate that anthracene possess phototoxic potential following exposure in combination with UV light.
Based on the lack of systemic toxicity no substance-specific DNELs will therefore be developed for this marker substance. It is considered that the low concentration of anthracene present in this stream would not impact on the overall toxicity assessment and that risk management measures and occupational controls intended to minimise human exposure to the other toxicologically-active marker substances also present would limit exposure to anthracene.
References
ACGIH (2001). n-Hexane: TLV Documentation, 7th Edition, p1-16.
AGS (2008). Committee on Hazardous Substances. Guide for the quantification of cancer risk figures after exposure to carcinogenic hazardous substances for establishing limit values at the workplace. 1. Edition. Dortmund: Bundesanstalt für Arbeitsschutz und Arbeitsmedizin. Available from:http://www.baua.de/nn_21712/en/Publications/Expert-Papers/Gd34,xv=vt.pdf
ATSDR (1999).Toxicological Profile for n-Hexane. http://www.atsdr.cdc.gov/toxprofiles/tp113.html
ATSDR (2005).Toxicological profile for naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene.http://www.atsdr.cdc.gov/toxprofiles/tp67.pdf
Blank IH, McAuliffe DJ (1985). Penetration of benzene through human skin. J. Invest. Dermatol. 85, 522–526.
Cheng H, Sathiakumar N, Graff J, Matthews R, Delzell E (2007). 1,3-Butadiene and leukemia among synthetic rubber industry workers: exposure-response relationships. Chem Biol Interact, 166,15-24.
Engstrom K, Harkonen H, Pekari K and Rantanen J. (1978). Evaluation of occupational styrene exposure by ambient air and urine analysis. Scand. J. Work Environ. Health, 4 (Suppl. 2):121-123.
EU (1999). Council Directive 1999/38/EC of 29 April 1999 amending for the second time Directive 90/394/EEC on the protection of workers from the risks related to exposure to carcinogens at work and extending it to mutagens. Official Journal of the European Communities, L138, 66-69, 1 June 1999.
EU (2000). Council Directive 2000/39/EC of 8 June 2000 establishing a first list of indicative occupational exposure limit values (IOELV) in implementation of Council Directive 98/24/EC on the protection of the health and safety of workers from the risks related to chemical agents at work.Official Journal of the European Communities, L142, 47-50.
EU (2003b). Risk assessment report for naphthalene. http://ecb.jrc.ec.europa.eu/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/REPORT/naphthalenereport020.pdf EU (2006). Directive 2006/15/EC of 7 February 2006 establishing a second list of indicative occupational exposure limit values in implementation of Council Directive 98/24/EC and amending Directives 91/322/EEC and 2000/39/EC. Official Journal of the European Union, l 38, 36-39.EU (2006). Directive 2006/15/EC of 7 February 2006 establishing a second list of indicative occupational exposure limit values in implementation of Council Directive 98/24/EC and amending Directives 91/322/EEC and 2000/39/EC. Official Journal of the European Union, l 38, 36-39.
EUROPEAN UNION RISK ASSESSMENT REPORT, Styrene. CAS No: 100-42-5 EINECS No 202-851-5; Draft for publication, June 2008. United Kingdom. EU RAR Styrene, UK
EU (2009). Anthracene (CAS No 120-1207; EINECS No 204-371-1): Summary risk assessment report, October 2009. Available from: http://ecb.jrc.ec.europa.eu/risk-assessment/Filser JG, Csanady GA, Denk B, Hartmann M, Kauffmann A, Kessler W, Kreuzer PE, Putz C, Shen JH, Stei P.(1996). Toxicokinetics of isoprene in rodents and humans. Toxicology 113:278-287.
MAK (2009). MAK Commission 46 Lieferung.
Maibach HI, Anjo DM (1981). Percutaneous penetration of benzene and benzene contained in solvents used in the rubber industry. Arch. Environ. Health 36, 256–260.
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.
SCOEL (2001). Recommendation from the Scientific Committee on Occupational Exposure Limits for toluene108-88 -3. http://ec.europa.eu/social/BlobServlet?docId=3816&langId=en
SCOEL (2010) Consolidated Indicative Occupational Exposure Limits Values (IOELVs). Available from http://ec.europa.eu/social/main.jsp?catId=153&langId=en&intPageId=684
Sielken RL, Valdez-Flores C, Delzell E (2008). Quantitative Risk Assessment of Exposures to Butadiene in European Union Occupational Settings Based on the University of Alabama at Birmingham Epidemiological Study: All Leukemia, Acute Myelogenous Leukemia, Chronic Lymphocytic Leukemia, and Chronic Myelogenous Leukemia. Unpublished report to Lower Olefins Sector Group, Brussels, Belgium.
Susten, AS et al (1990). In vivo percutaneous absorption studies of volatile organic solvents in hairless mice II; Toluene, ethylbenzene and aniline. J. Appl. Toxicol. 10: 217-225.
ten Berge W (2009). A simple dermal absorption model: Derivation and application. Chemosphere, 75, 1440-1445.
TCEQ (2008). Texas Commission on Environmental Quality. Development Support Document. 1,3-Butadiene. Chief Engineer’s Office. Available from:http://tceq.com/assets/public/implementation/tox/dsd/final/butadiene,_1-3-_106-99-0_final.pdf
Triebig G, Bruckner T and Seeber A (2009). Occupational styrene exposure and hearing loss: a cohort study with repeated measurements. Int Arch Occup Environ Health, 82 (4), 463-481.
Tsuruta H (1996). Skin absorption of solvent mixtures-effect of vehicle on skin absorption of toluene. Ind. Health 34, 369–378.
UK HSE (1990). N-Hexane occupational exposure hazard. HSE Review 1990, D34-D35, Published 1993.
[1] 6 hour value calculated from TGD Table R.8-17 values (as per guidance Appx R.8-2, example B.4) – sRV for mouse (mean male/female) is 1.43 L/min/kg bw = 0.514 m3/kg bw for 6 hours
[a]1,3-butadiene is a gas and a dermal DNELs is not quantifiable
[b] Data reported as 3.5 ppm, and converted to mg/m3using tool available from http://www.cdc.gov/niosh/docs/2004-101/calc.ht
[c] Worker respiratory volume (wRV) is 50% greater than the resting standard respiratory volume of 0.2 L/min/kg bw (wRV8-hour= (0.2 L/min/kg bw x 1.5 x 60 x 8) / 1000 = 0.144 m3/kg bw
[d] mg/m3values quoted in this document are as reported in the publication or calculated using a conversion at 25°C as used by ACGIH (http://www.cdc.gov/niosh/docs/2004-101/calc.htm).It is recognized that SCOEL used a different calculation
General Population - Hazard via inhalation route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DMEL (Derived Minimum Effect Level)
- Value:
- 3.25 µg/m³
- Most sensitive endpoint:
- carcinogenicity
- Route of original study:
- By inhalation
DNEL related information
- DNEL derivation method:
- other: The value that is proposed is based on a modification of the approach used by WHO (2000) which combined estimates of excess risk for leukaemia calculated by Crump (1994) for four models into a geometric mean estimate.
- Overall assessment factor (AF):
- 1
- Modified dose descriptor starting point:
- other: The Crump (1994) estimate of excess risk for AMML was substituted by estmates from TCEQ (2007), giving a median risk estimate of 0.9 x 10-5 per 1 ppb (3 x 10-6 per 1 µg/m3)
- Value:
- 3.25 µg/m³
- Explanation for the modification of the dose descriptor starting point:
None used
- AF for dose response relationship:
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
- AF for differences in duration of exposure:
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
- AF for other interspecies differences:
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
- AF for intraspecies differences:
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
- AF for the quality of the whole database:
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
- AF for remaining uncertainties:
- 1
- Justification:
- Excess risk estimates were based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984). No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure.
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
General Population - Hazard via dermal route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
General Population - Hazard via oral route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DMEL (Derived Minimum Effect Level)
- Value:
- 0.464 µg/kg bw/day
- Most sensitive endpoint:
- carcinogenicity
- Route of original study:
- By inhalation
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 1
- Modified dose descriptor starting point:
- other: The inhalatory DMEL (ug/m3) was converted into a human oral DMEL (ug/kg bwt/d) by adjusting for differences in uptake between the two routes of exposure (REACH Guidance, Appendix R.8-2, Example B.4).
- Value:
- 0.464 µg/kg bw/day
- Explanation for the modification of the dose descriptor starting point:
The inhalatory DMEL (ug/m3) was converted into a human oral DMEL (ug/kg bwt/d) by adjusting for differences in uptake between the two routes of exposure (REACH Guidance, Appendix R.8-2, Example B.4).
- AF for dose response relationship:
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
- AF for differences in duration of exposure:
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
- AF for other interspecies differences:
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
- AF for intraspecies differences:
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
- AF for the quality of the whole database:
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
- AF for remaining uncertainties:
- 1
- Justification:
- Excess risk estimates based on a human multiplicative risk, linear in cumulative exposure model (Crump and Allen, 1984), were used as the starting point. No additional assessment factors have been applied given the conservative nature of model, which is based on human lifetime exposure
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
General Population - Hazard for the eyes
Local effects
- Hazard assessment conclusion:
- no hazard identified
Additional information - General Population
According to REACH Annex XVII, benzene shall not be placed on the market as a constituent of other substances, or in mixtures, in concentrations>0.1% by weight with the exception of motor fuels which are the subject of a separate directive (98/70/EC). Since these streams all contain at least 0.1% benzene, their supply to the general population is prohibited and no formal risk characterisation is therefore required. General population DN(M)ELs for benzene have been developed, however, to support risk assessment of man exposed via the environment with the background discussed below.
Benzene
Epidemiology studies provide clear and consistent evidence of a causal association between benzene exposure and acute myelogenous (non-lymphocytic) leukaemia (AML or ANLL). IARC (Baan et al., 2009) has recently concluded that, although there is “sufficient” evidence for an increased risk of AML/ANLL in humans, there is only “limited” or “inadequate” evidence of carcinogenicity in humans for other types of leukaemia. An effect of benzene on bone marrow leading to subsequent changes in human blood cell populations is believed to underpin this response. The long-term systemic DN(M)EL for benzene will therefore be based upon the following information:
Human chronic toxicity (Schnatter et al., 2010): NOAEC = 11.18 mg/m3
Human carcinogenicity (Crump, 1994; WHO, 2000; TCEQ, 2007) = 3.25 µg/m3
References:
Crump KS (1994). Risk of benzene-induced leukemia: a sensitivity analysis of the Pliofilm cohort with additional follow-up and new exposure estimates. J Toxicol Environ Health 42, 219-242.
WHO (2000) Air Quality Guidelines for Europe, Second Edition. WHO regional publications, European series; No. 91.
TCEQ (2007). Texas Commission on Environmental Quality. Development Support Document. Benzene. Chief Engineer’s Office. Available: http: //tceq. com/assets/public/implementation/tox/dsd/final/benzene_71-43-2_final_10-15-07.pdf
The value that is proposed is based on the approach used by WHO (2000) which combined estimates of excess risk for leukaemia calculated by Crump (1994) for four models into a geometric mean estimate. The same four models were used for the derivation of this DMEL but estimates of excess risk for acute myelogenous or acute monocytic leukaemia (AMML) calculated by Crump (1994) were used instead of those for leukaemia. For three of the four models, excess risk estimates calculated by Crump (1994) were used. A more recent estimate of excess risk was available for one model (TCEQ, 2007) and this was used instead of the estimate calculated by Crump (1994). The value of 3.25 µg/m3(1 ppb) is protective against haematotoxicity, genotoxicity and carcinogenicity and results in a geometric mean excess lifetime risk of AMLL of 0.9 x 10-5.
While information regarding the NOAEC for effects on human bone marrow post-date WHO (2000), a DNEL based on these bone marrow (threshold) findings would be higher (and hence offer less protection) than one based on AMML. It is also the case that it is not possible to ascribe precise concentrations of benzene to the occurrence of human myelodysplastic syndrome, precluding use of this information for development of a DN(M)EL.
As a consequence, a DMEL for benzene of 1.0 ppb (3.25 µg/m3) is proposed. This value is lower than the air quality limits of 10 µg/m3and 5 µg/m3that were established for benzene in subsequent European Directives 2000/69/EC and 2008/50/EC, respectively.
General population - long-term systemic inhalation DNEL
Dose descriptor
The inhalation DMEL will be used with no further modification.
DN(M)ELl-t inhalation= 3.25 µg/m3
General population - long-term systemic dermal DNEL
Dose descriptor
The inhalation DMEL of 3.25 µg/m3will be used.
Modification of dose descriptor
Convert the inhalation DMEL into a human dermal NOAEL (mg/kg bw/d) after adjusting for differences in uptake between the two routes of exposure (TGD, Appendix R.8-2, Example B.4).
It is assumed that uptake of benzene after inhalation is approximately 50% while dermal absorption is only 0.1% (Modjtahedi and Maibach, 2008).
sRV24 -hour (20 m3) and body weight (70 kg) are based on REACH defaults.
Dermal LOAEL = [AQS x sRV24-hour x [ABSinhal-human/ABSdermal-human]] / body weight
= 3.25 x 20 x 500 / 70 = 464 µg/kg bw/d
Assessment factors
As the AQS is based on general population life-time exposure no assessment factor is needed.
DN(M)ELl-t dermal = 464 µg/kg bw/d
General population - long-term systemic oral DNEL
Dose descriptor
The inhalation DMEL of 3.25 µg/m3will be used.
Modification of dose descriptor
Correct the inhalation DMEL to an oral NOAEL (mg/kg/day) by converting the dose absorbed after inhalation into a systemic dose, assuming 50% uptake by the lung and 100% uptake from the GI tract, a sRV24 -hour of 20 m3and body weight of 70 kg (REACH TGD, Appendix R.8 -2):
Oral NOAEL = [AQS x sRV24 -hour x [50/100]] / body weight
= 3.25 x 20 x 0.5 / 70 = 0.464 µg/kg bw/d
Assessment factors
As the inhalation DMEL is based on general population life-time exposure no assessment factor is needed.
DN(M)ELl-t oral = 0.464 µg/kg bw/d
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Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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