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EC number: 216-653-1
CAS number: 1634-04-4
MTBE exhibits low acute toxicity via oral, dermal and inhalation in humans and test animals. In rats, the average oral LD50 is about 4000 mg/kg bw. The dermal LD50 is over 2000 mg/kg bw in rats and over 10000 mg/kg bw in rabbits.
For inhalation, an LC50 of approximately 85 mg/l has been determined. In animals, the most typical effect at high exposures is decreased ability for muscle coordination and hypoactivity.
acute oral toxicity studies with rats are available for assessment, all
leading to the same conclusion. Out of these studies, the study
performed according to OECD Guideline 401 was chosen as a key study
(RBM, 1996a). In this study, 5 male and female rats were exposed by
gavage with 2000 mg/kg bw MTBE. No deaths occurred. The LD50 value in
rats was determined to be > 2000 mg/kg bw. Animals showed hunching and
piloerection starting from 2-4 hours after gavage, which disappeared
within 2-6 days.
inhalation toxicity studies with rats have been located. Although none
of the studies was performed according to the current guidelines, they
both were found to be reliable and the study with the lowest determined
LC50 value was chosen as a key study (Industrial Bio-test Laboratories,
Inc, 1969b). Five female and five male per group albino rats were
exposed to MTBE vapour at 44, 65, 86, 99, 167 and 395 mg/l for 4 hours.
The clinical signs included ataxia, tremors, lacrimation, clonia,
unconsciousness and hyperactivity. Surviving animals appeared normal the
morning after exposure. In the 86 mg/l group, six animals died and in
the higher dose groups, all animals died. Necropsy of the animals which
died revealed slight to moderate hyperemia in the lungs. The animals
that survived the 14-day observation period had minimal to mild lung
hyperemia. An LC50 value of 85 mg/l/4h was calculated based on the
results of this study.
acute dermal toxicity studies, one with rats and two with rabbits, were
available for assessment, all leading to the same conclusion. Out of
these studies, the rat limit test (RBM, 1996b) was chosen as a key
study. Animals were exposed via the dermal route to 2000 mg/kg bw under
occlusion. No animals died and neither general clinical signs nor
behavioural alterations were observed in any treated rat during the
observation period. At the treatment site slight erythema was noted in 4
animals during the first 8 hours after the 24 hours exposure period.
Based on the results of the test, the LD50 value in rats was determined
to be > 2000 mg/kg bw.
male volunteers reported mild symptoms, mainly feelings in the head and
feeling less cheerful (FIOH, 1997). The frequency of symptoms was
related to the exposure level (0, 25, 75 ppm) and reached statistical
significance at 75 ppm after 3 hours of exposure to MTBE. These effects
were rated as slight. There was no indication found of an objective sign
of CNS function impairment in terms of psychomotor performance,
sustained attention, or standing steadiness. This study suggests a LOAEC
of 75 ppm. It should be noted that although sensory symptoms may show
greater sensitivity than objective indices, it is possible that symptoms
are mediated by mechanisms other than CNS depression, especially as MTBE
has an unpleasant odour.
human volunteer study investigated whether CNS effects occurred after
exposure up to 50 ppm MTBE for two hours while the persons were
exercising at 50W on a bicycle ergometer (Nihlen, 1998). Effects were
measured by a questionnaire. No indications for the occurrence of CNS
effects were reported. The study results suggested a NOAEC of 50 ppm.
SCOEL considered these two human volunteer studies, which show only mild
symptoms at 75 ppm after 3 hours exposure, as key in case of acute
toxicity of MTBE and derived a 15-min short-term occupational exposure
limit (STEL) of 100 ppm using the results of these studies.
rats, the LD50 figure of the acute oral toxicity key study was >2000
mg/kg bw. The LD50 values of the two supporting studies were 3800 and
3866 mg/kg bw/day, respectively. The dermal LD50 is over 2000 mg/kg bw
in rats and over 10000 mg/kg bw in rabbits. For inhalation, an LC50 of
approximately 85 mg/l has been determined.
accordance with EU Classification, Labelling and Packaging of Substances
and Mixtures (CLP) Regulation (EC) No. 1272/2008, classification is not
required for acute toxicity based on the available data.
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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