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EC number: 204-411-8
CAS number: 120-61-6
A number of studies are consistent in demonstrating the low toxicity of DMT following repeated oral exposure. Marked effects (including mortality) were only seen at very high dietary dose levels at which food consumption was adversely affected due to poor dietary palatability. No dermal data are available, however low toxicity can be reliably predicted for DMT. The results of inhalation studies are conflicting, however the findings of a more modern and reliable dust inhalation study showed only mild local effects at the highest exposure concentration.
Repeated dose oral toxicity
In a range-finding study, five rats were given oral daily doses of 2000
mg/kg of dimethyl terephthalate for 10 treatments, another rat received
the same daily dose for 11 treatments (Du Pont, 1947). Only a slight
discomfort after receiving the treatment was observed. Below normal
weight gain was observed over the two week treatment group. No gross or
microscopic pathology was noted in the internal organs. Under the
conditions of this study, the NOAEL can be considered to be 2000 mg/kg.
In a 28 -day study (Fassett & Roudabush, 1958), reduced food consumption
and weight loss in a group of 10 male rats administered DMT in the diet
at 5% (50000 ppm; 3750 mg/kg bw/d) resulted in the death of all animals.
Haematological and pathological investigations did not reveal any
effects of treatment and the authors suggest that findings may be due to
poor dietary palatability.
In a further study (Du Pont, 1955), dimethyl terephthalate was
administered orally to six rats at a level of 5000 mg/kg bw/d, 5 days
per week for a total of ten treatments. There were no mortalities during
the exposure period, but all rats showed transient discomfort and
progressive weight loss. Weight loss continued after the exposure
period, and five out of six rats died by the 11th post-exposure day.
Pathology suggested the cause of death was starvation secondary to
palatability effects (Du Pont, 1955). In the same study, four dogs were
administered dimethyl terephthalate in capsule form at a dose of 100
mg/kg bw/d, 5 days/week for 8 weeks. In week 9 the dose was increased to
200 mg/kg bw/d and administration continued 5 days/week for 14 weeks.
Effects of administration in the dogs were some circulatory disturbance
and slight lowering of blood sugar level (Du Pont, 1955).
In a more recent and more comprehensive published proprietary study
(Krasavage & Terhaar, 1972; Krasavage et al, 1973), dimethyl
terephthalate was incorporated into the diet of male Long-Evans rats at
concentrations of 0.25, 0.5 and 1.0%. The only noticeable toxic effect,
following 96 days exposure, was a significant reduction in average body
weight gain at the highest concentration. Therefore the 96 day NOAEL is
0.5% (5000 ppm; equivalent to approximately 500 mg/kg bw/d using default
Repeated dose dermal toxicity
A waiver is proposed for the endpoint on scientific grounds and for
reasons of animal welfare. Performing a repeated dermal study is not
necessary as repeated dose studies via oral and inhalation routes are
already available. Previous acute dermal toxicity studies have not
indicated any greater sensitivity by this route of exposure;
toxicokinetics studies also demonstrate limited dermal absorption (11
Repeated dose toxicity: inhalation
In a non-standard published study (translated from the original Russian)
Sanina & Kochetkova (1963) exposed a group of rats to dimethyl
terephthalate vapour (generated by heating) for 2 hours per day, 6 days
per week for 2 months. The exposure concentration was 1 -6 mg/L.
Repeated exposure produced a pronounced a pronounced irritating effect
on the conjunctiva and respiratory tract, accompanied by moderate
haemodynamic disorders. The authors then conducted another study where
the rats were exposed for 5 months to concentrations of 0.001 -0.004
mg/L or 0.04 -0.07 mg/L: the two exposure concentrations were not run
concurrently. The 5 -month exposure generated the same effects as were
seen in the 2 month exposure study, but the effects were more clearly
expressed. At the higher concentration, function of the nervous and
vascular system and kidney function were disrupted. 30% of the rats died
from circulatory disorders. Exposure to the lower concentration resulted
in a chronic inflammation of the organs, a suppressed nervous system,
slight anaemia, reticulocytosis and hypotension. A NOAEL could not be
identified for either exposure period.
In a more recent study (Krasavage et al, 1973), male Long-Evans
hooded rats were exposed repeatedly to dimethyl terephthalate dust at
concentrations of 16.5 and 86.4 mg/m³ for 4 hours/day, 5 days/week for a
total of 58 exposure. Signs of irritation (blinking, preening and
rubbing) were seen during the exposure to the high concentration. No
other effects were observed. The respirable fraction of the total number
of aerodynamically sized particles (<5.0 µm) was 36%. Based on this
aerodynamic particle size value, the rats in the inhalation study
received calculated average doses of 4.0 and 0.7 mg/kg bw. The NOAEL can
be considered to be 86.4 mg/m³. Given the absence of overt toxicity in
this study, the findings of the previous study (Sanina & Kochetkova,
1963) are somewhat surprising and cannot be exaplained.
DMT was shown (in more reliable studies) to be of low toxicity. The
primary effects of repeated oral exposure appear to be secondary to
reduced food consumption due to poor dietary palatability and/or are
only seen at high dose levels. One published study reports marked
effects following inhalation exposure to DMT vapour, however a more
modern and reliable study involving exposure to DMT dust does not report
any effects of exposure with the exception of behavioural observations
consistent with mild (and possibly physical) irritation. No
classification is therefore proposed according to the CLP Regulation.
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