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EC number: 905-562-9
CAS number: -
In animal studies xylene isomers (including mixed xylene) exhibit low acute toxicity by oral and dermal routes with the reported LD50 values all exceeding 2000 mg/kg bw. Mixed xylene is considered harmful by inhalation.In humans critical effects of xylenes are irritation and CNS effects, with the overall NOAEC inhalation for the latter effect being 300 mg/m3.
single-administration study, groups of five F344/N rats of each sex
received 500, 1,000, 2,000, 4,000, or 6,000 mg/kg. Administration of
mixed xylenes caused deaths at 6,000 mg/kg in each sex and at 4,000
mg/kg in males. Clinical signs observed within 24 hours of dosing at
4,000 mg/kg included prostration, muscular incoordination, and loss of
hind limb movement; these effects continued through the second week of
observation. The LD50 was 3523 mg/kg/bw for males and greater than 4000
mg/kg/bw for females.
Groups of male and female rats were exposed
(head only) to measured concentrations p-xylene vapour for 4 hours
followed by a 14 day observation period. The LC50 was 6247
ppm (27124 mg/m3, 27.1 mg/L) Clinical observations including
body tremors suggestive of CNS involvement were seen at all
concentrations during and after exposure, on the day of exposure.
dermal LD50 of m-xylene in the male New Zealand White rabbit
was 14.1 mL/kg bodyweight, equivalent to 12126 mg/kg.
The multi-constituent substances covered by
this registration comprises of individual xylene isomers (m-xylene,
o-xylene, p-xylene) and ethylbenzene (>10% - <20%). The following
information is available to characterise their acute health hazards.
Acute toxicity: oral
Acute oral data is available for mixed
xylene, xylene isomers and ethylbenzene.
The acute oral LD50 of mixed xylene
(containing 17% ethylbenzene) in rats is 3523 mg/kg. This information is
derived from what is considered to be the key study (NTP, 1986) as this
is the most recent study with the lowest reported LD50 value.
Xylene is of low toxicity via the oral
route. The LD50 values for xylene isomers (including mixed xylene) range
from 3523 to 8400 mg/kg (NTP, 1986; Hine & Zuidema, 1970; Wolf et al.,
1956; Smyth et al., 1962).
The acute oral toxicity of ethylbenzene is
low with LD values above 2000 mg/kg. An oral LD50 of 3500 mg/kg was
determined for rats (male/female) (RAR 2008).
No relevant information sourced for mixed
xylene, xylene or ethylbenzene.
Acute toxicity: inhalation
An LC50 value of 27,571 mg/ m3 was obtained
for male rats exposed to mixed xylene (composition undefined) for 4
hours (Hine, 1970).
Considering xylene isomers, an LC50 of
27,124 mg/m3 has been derived for p-xylene from what is considered to be
the key study (HLE, 1986). This study provides the lowest reported LC50
value for a guideline exposure period of 4 hours. This is a GLP
compliant study and the most recently conducted. The LC50 value of
27,124 mg/m3 is a combined value for males and females; the LC50 for
males was 25,713 mg/m3 and for females, 28,570 mg/m3.
Ethylbenzene is harmful by inhalation, with
the LC50 in rats reported as 17,600 mg/m3after the guideline exposure
period of 4 hours (RAR, 2008).
Mild eye and upper tract respiratory tract
irritation has been reported (see 5.3 below).
Neurological and physiological symptoms have
been reported in workers exposed to xylene, but this is mainly resulting
from exposure to solvent mixtures and therefore difficult to attribute
directly to xylene. The lowest NOAEC reported for CNS effects which is
considered reliable is for p-xylene at 70 ppm (Anshelm Olson, 1985).This
value is consistent both with the SCOEL review and reviews (e. g. UK
HSC, 2001) supporting the existing IOELV for the xylene isomers.
There are no specific human data for ethyl
benzene (RAR, 2008).
Acute toxicity: dermal
The data for mixed xylene (composition
undefined) supports the conclusion that the LD50 would be >2000 mg/kg
bw, with an LD50 of >4600 mg/kg bw reported (Hine & Zuidema, 1970).
A dermal LD50 in rabbits of 12,126 mg/kg is
derived for m-xylene from what is considered to be the key study (Smyth,
1962) as the lowest reported LD50 value.
The acute dermal toxicity of ethylbenzene
has been reported as being tested with rabbits and revealed a dermal
LD50 of 15500 mg/kg (RAR, 2008).
No human information is available.
Justification for selection of
acute toxicity – oral endpoint
For mixed xylene an acute oral LD50 in rats of 3,523 mg/kg is
derived from NTP (1986). This is the most recent investigation available
and provides the lowest oral LD50 value for xylene isomers (including
mixed xylene). The oral LD50 of ethyl benzene in rats is 3500 mg/kg
Justification for selection of acute toxicity – inhalation endpoint
For p-xylene an acute inhalation LC50 in rats of 27,124 mg/m3 is
available (HLE, 1986). This is the most recent investigation available
and provides the lowest inhalation LC50 value for a 4-hr exposure
period. For mixed xylene, an LC50 of 27,571 mg/m3 has been reported
(Hine and Zuidema, 1970). A 4 hr LC50 of 17,600 mg/m3 has been reported
for ethyl benzene in rats (RAR, 2008).
Note: Although xylene isomers (including mixed xylenes) are classified
H332 - Harmful if inhaled according to the CLP regulation, the rationale
for this is not clear since the available LC50 values are clearly
greater than 20,000 mg/m3. Ethylbenzene is also classified H332
according to the CLP regulation.
Justification for selection of acute toxicity – dermal endpoint
A dermal LD50 in rabbits of 12,126 mg/kg bw is derived for m-xylene
from Smyth et al. (1962) while an LD50 of >4200 mg/kg bw is reported for
mixed xylene (Hine and Zuidema, 1970). The dermal LD50 of ethyl benzene
in rabbits is 15,500 mg/kg bw (RAR, 2008).
Note: Although xylene isomers (including mixed xylene) are classified
H312 - Harmful in contact with skin according to the CLP regulation, the
rationale for this is not clear since the LD50 is clearly above 2,000
Substance selection for risk
The approach developed by the LOA Exposure
Working Group on the selection of constituents for use in human health
exposure assessments was implemented for this Reaction Mass substance.
The primary constituents used are ethylbenzene and xylenes. A full
description of this approach is available in Section 13 (”Selection of
constituents for HH exposure” in section 13.2).
xylene (individual and pure mixed isomers) is classified as Acute
Tox Cat 4 H332 Harmful if inhaled under CLP,the
rationale for this is not clear since the LC50 is clearly above 20,000
mg/m3 and classification would appear not to be justified.
classification is warranted for acute toxicity via oral route under CLP.
xylene (individual and pure mixed isomers) is currently classified as Acute
Tox Cat 4 H312 Harmful in contact with skin,the
rationale for this is not clear since the LD50 is clearly above 2,000
mg/kg bw and classification would appear not to be justified.
is a known hazard of hydrocarbons and classification is based on
physical characteristics. The kinematic viscosity of xylenes is
considered to be below the cut off values for CLP
20.5 mm2, and therefore classification as Aspiration
Tox Cat 1 H304 May be fatal if swallowed and enters airways is warranted under
LD50 for rats: 3500 mg/kg bw. In accordance with EU CLP (Regulation (EC)
No. 1272/2008), classification is not required for acute oral toxicity
based on the available data.
LD50 for rabbits: 15.4 g/kg bw. No classification in accordance with EU
CLP (Regulation (EC) No. 1272/2008) and UN GHS.
LC50 for rats: 17.6 mg/l/4h (approx. 4000 ppmV). Acute Toxicity Cat. 4,
H332, harmful if inhaled in accordance with EU CLP (Regulation (EC) No.
toxicity after oral exposure; There is indication from animal
experiments that pulmonary injury resulting in chemical pneumonitis
might be the principal cause of the deaths observed after oral
administration of ethylbenzene to rats because necropsy after oral
administration revealed hyperaemia and haemorrhage of the lungs.
Therefore, aspiration of even a small amount of ethylbenzene may cause
severe lung injury. And due to its low viscosity and surface tension
ethylbenzene would spread over a large area of pulmonary tissue, causing
oedema and haemorrhage.
the following classification is proposed:
Cat 1(b) based on animal and physico-chemical data; H304; may be fatal
if swallowed and enters the airways in accordance to EU CLP (Regulation
(EC) No. 1272/2008).
After reviewing this information, the
Committee for Risk Assessment concluded that ethylbenzene may be fatal
if swallowed and enters the airways (RAC, 2012 a).
RAC (2012) Opinion proposing
harmonised classification and labelling at EU level of ethylbenzene.
ECHA/RAC/CLH-O-0000001542-81-03/F. Committee for Risk Assessment,
adopted 5 June 2012.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.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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