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EC number: 204-066-3
CAS number: 115-11-7
Members of the butenes category are flammable gases at room temperature and therefore the requirement for data on oral and dermal repeat dose toxicity is waived in accordance with REACH Annex XI. Members of the butenes category have low sub-chronic toxicity. Inhalation exposure is the most relevant route. No significant exposure-related toxicological effects or target organ toxicity have been observed in inhalation studies of up to 2 years in rats or mice. Nasal lesions were observed in 2 year rodent studies at the highest concentration and the NOAEC of 2000 ppm (4589 mg/m3) in rats is based on the lack of effect at this concentration.
of the butenes category are flammable gases at room temperature and
therefore significant exposure via the dermal or oral routes is
accordance with Section 2 of REACH Annex XI, studies on oral and dermal
repeat dose toxicity do not need to be conducted as they are technically
not feasible. An
oral study is, however, available for 2-methylpropene (Hazleton 1986).
Although oral administration is an unusual and non-relevant route for a
gaseous substance, the analytical results indicated that the gas
remained dissolved in the corn oil vehicle and the target concentration
(148.6mg/kg) was achieved. No toxicologically significant changes were
observed in rats that received dose levels up to 148.6 mg/kg/day (the
maximum achievable concentration by this route) when 2-methylpropene was
administered orally to rats over 28 days. A NOAEL of 148.6 mg/kg/day was
established (Hazleton 1986).
dosing studies via inhalation exposure are available for but-1-ene,
2-butene and 2-methylpropene. All studies have shown minimal systemic or
target organ toxicity. Exposure of rats to but-1-ene at concentrations
of 500, 2000, 8000 ppm (1147, 4589, 18,359 mg/m3) did not induce
systemic toxicity in males or females exposed for a minimum of 28 days
or in pregnant female rats exposed for 14 days pre-mating, through
mating and gestation to day 19. No treatment-related effects on body
weight, clinical chemistry, organ weights or histopathology were found.
Neurotoxicity screening also showed no effects on motor activity or
functional observation battery. A NOAEC of 8000 ppm (18,359 mg/m3) (the
highest dose level) was established (Huntingdon, 2003).
of rats to 2-butene at target concentrations of 2500 or 5000 ppm (5737
or 11,474 mg/m3) did not induce significant systemic toxicity in males
and females exposed for 28 days, or in pregnant female rats exposed for
14 days pre-mating, through mating and gestation to day 19 (TNO 1992b). Mean
absolute organ weights and relative weights were comparable in all
abnormal, treatment-related macroscopic changes (all groups) or
pathological changes (only determined in control and 5000 ppm groups)
were observed. The only treatment-related changes were some small
decreases in body weights and body weight gains in both sexes at both
dose levels and decreased food consumption at 5000 ppm during the first
week (premating). Although the authors (TNO 1992b) interpreted
the NOAEC as 2500 ppm based on these findings, a reanalysis by RIVM
(2007) concluded that as these effects were not dose-related and not
consistently present during the study the NOAEC for 2-butene should be
5000 ppm (11,474 mg/m3) (RIVM 2007 and ammended SIDS report 2007).
also caused no toxicologically significant changes when rats were
exposed to 250, 1000 or 8000ppm (573, 2294 or 18,359 mg/m3)
for 13 weeks. The only clinical change was an elevation in ketone bodies
detected in urine at 1000 ppm and 8000 ppm (males), the toxicological
significance of this is unknown. The NOAEC was 8000 ppm (18,359 mg/m3)
the highest concentration level tested (Hazleton 1982). Similar results
were obtained in 14 week inhalation studies conducted by the NTP (NTP,
1998). F344/N rats and B6C3F1 mice were exposed to 2-methylpropene at
concentrations of 0, 500, 1,000, 2,000, 4,000, or 8,000 ppm, (1147,
2294, 4589, 9179, 18,359 mg/m3) for 14 weeks. There were no significant
exposure-related toxicologic effects in either species at any dose
level. Increased kidney weights in mice; and increased liver and kidney
weights and minimal hypertrophy of goblet cells lining the
nasopharyngeal ducts in rats, were considered to be non-toxic adaptive
responses. The NOAEL for both studies was 8000 ppm (18,359 mg/m3)
the highest concentration level tested.
studies on 2-methylpropene were also conducted by the NTP. F344/N rats
and B6C3F1 mice were exposed to 2-methylpropene at concentrations of 0,
500, 2,000 or 8,000 ppm, (1147, 4589, 18,359 mg/m3)
for 105 weeks (NTP, 1998). The
non-neoplastic findings from these studies were confined to effects on
nasal tissues. In mice, hyaline degeneration of the olfactory and
respiratory epithelium was increased in both sexes. The severities of
hyaline degeneration increased with increasing exposure concentration.
However, this was considered by the NTP to be a nonspecific adaptive
response that had no adverse effect on affected animals. The NOAEC for
toxicity in mice was therefore 8000ppm (18,359 mg/m3). Similar findings
were observed in rats although the lesions were more severe. An
additional finding in rats was that hypertrophy of goblet cells lining
the nasopharyngeal duct was marginally increased with 100% incidence in
males at 8000 ppm. The NOAEC for toxicity in the rat study was therefore
2000 ppm (4589 mg/m3), lower than that in mice (OECD SIDS Report for
There are no repeat dose toxicity data in
Members of the butenes category are
flammable gases at room temperature and therefore dermal and oral
exposure are unlikely. An oral study conducted at the maximum achievable
concentration (148.6 mg/kg/day) showed no adverse effects. As oral
exposure is not relevant for humans, this study is not considered
relevant for classification purposes. Inhalational exposure is the only
relevant route and members of the butenes category have low sub-chronic
inhalational toxicity and therefore do not warrant classification under
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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