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EC number: 201-207-0 | CAS number: 79-43-6
- 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
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
When the physicochemical properties of Dichloroacetic acid were assessed for toxicokinetic properties, the substance was expected and studied to be easily absorbed from the gastro-intestinal tract. On the other hand, respiratory deposition and absorption was assessed to be very low. Dermal absorption was considered to be possible based on physicochemical properties, and confirmed by calculation of the dermal flux (1.21 mg/(cm2.h)).
Distribution in the body is expected to take place rapidly, mainly based upon the low molecular weight, high water solubility and the clinical observations and target organs (liver, brains, testes) seen in the toxicity studies. Experimental studies also demonstrated rapid distribution in various tissues.
Indication of rapid metabolism were already deduced from toxicological studies (e.g. increased liver weights rats, peroxisome proliferation). Experimental studies in animals and humans showed an oxidative dechlorination to form glyoxylate, which may then be routed through several different pathways leading to oxalate, glycine, serine, glycolate and even carbon dioxide. Among humans there are known polymorphisms which may account for differences in the ability to metabolize DCA.
Based on the low molecular weight and high water solubility, rapid urinary excretion of parent substance and metabolites are expected. In experimental studies in animals and humans, only a small fraction of DCA (-1-2%) was found in the feces , whereas in humans, the amount is a slightly higher Both in humans and animals, variable quantities of glyoxylate, glycolate, monochloracetic acid, and thiodiacetic acid are found in the urine. A fraction of the glyoxylate produced from DCA is oxidized to carbon dioxide and is exhaled.
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
- Absorption rate - oral (%):
- 100
- Absorption rate - dermal (%):
- 30
- Absorption rate - inhalation (%):
- 10
Additional information
The assessment below is based on the ECHA Guidance on information requirements and chemical safety assessment (Chapter R.7c: Endpoint specific guidance, November 2012 Version 1.1), for which physicochemical and toxicological data may be used for a qualitative toxicokinetics assessment. In addition, experimental values were found in secondary and primary literature references.
Absorption of DCA was assessed as follows based on physicochemical/toxicological data. The substance is a liquid compound with a molecular weight of128.94g/mol and experimental water solubility of1e+006 mg/L. The logPow has a value of 0.52 (QSAR) or 0.92 (experimental) The vapour pressure is 0.19 hPA (20°C).Hydrolysis data showed that the substance is stable in water at at pH 4, 7 and 9.
- Oral/GI
absorption:
The
substance is expected to be easily absorbed from the gastro-intestinal
tract based on the physicochemical properties (low molecular weight and
high water solubility) and toxicological data (toxicity in acute oral
and subchronic toxicity studies indicate a good systemic availability of
the substance underlining an oral absorption).
Studies
in humans and animals also indicate that DCA is readily absorbed by the
gastrointestinal tract. Following
oral administration of radiolabeled DCA to rats and mice, only about
1-2% of the label was found in the faeces, indicating almost complete
gastrointestinal absorption. In
fasted human subjects, peak plasma DCA concentration occurs within 15 to
30 minutes of oral dosing.
Based upon this rationale, an absorption rate of 100% is considered.
- Respiratory
absorption:
Based
on the low vapour pressure of DCA, inhalation
and deposition in the respiratory tract is very unlikely. If any
substance is deposited in the higher respiratory tract (e.g. by fluid
particles) they will be easily removed from the aqueous fluid (mucus)
lining the respiratory tract due to the high water solubility. Therefore
systemic availability by inhalation is not expected to be a realistic
exposure.
Based
upon this rationale, an absorption rate of 10% is considered.
- Dermal
absorption:
The
fact that DCA is a liquid substance with low molecular weight and high
water solubility leads to favorable conditions to be absorbed by the
skin. The
corrosive properties might stimulate further penetration, however repair
may also lead to decreased uptake.
When Dermwin was applied, the dermal penetration rate seems to be rather
low. A
dermal penetration rate of 0.00121cm/h was found. However because of the
high water solubility, the value of the maximum ‘dermal flux’ is slightly
higher: 1.21 mg/(h.cm2) Taking all this into account, it can be expected
that the dermal absorption is realistic.
Based
upon this rationale, an absorption rate of 30% is considered.
For the assessment of distribution, metabolism and excretion,physicochemical and toxicological properties are also taken into account according to ECHA guidanceChapter R.7c.
- Distribution:
Based
upon the molecular weight below 200 g/mol and high
water solubility, distribution
in the body is expected to take place rapidly. This is further confirmed
by the presence of clear target organs (e.g. liver , brain and testes
findings) and clinical observations (including state of narcosis or
seminarcosis) in the toxicity studies.
The
distribution of DCA was also investigated in experimental animals (EPA,
2003). After 48 hours upon oral gavage DCA administration. 21 to 36% of
the tracer [14C] was recovered from tissues; the majority of tracer was
found in the liver, muscle, skin, blood and intestines. After 24 hours,
all of the other tissues combined (kidney, adipose, stomach, testis,
lung, spleen, heart, brain, and bladder) contained 10 to 15% of the
label, while at 48 hours these tissues contained ~1-2% of the original
dose given.
- Metabolism
and accumulation potential:
Metabolism
cannot be deduced from the data available, except for the increase in
liver weights and hepatomegaly in male and female rats in the repeated
dose toxicity studies, which may be indicative of enzyme induction. In
addition, mechanistic toxicity studies were peformed, indicating
peroxisome proliferation and induction of carnitine acetyl-transferase,
palmityl-CoA oxidase and the PPA-protein in the liver of rats and mice.
The
metabolism of DCA was also investigated in experimental animals and
humans. The primary metabolic pathway for DCA involves oxidative
dechlorination to form glyoxylate, which may be routed through several
different pathways. Transamination by peroxisomal alanine-glyoxylate
transaminase forms glycine, which can be incorporated into proteins,
used in the synthesis of serine, or degraded releasing carbon dioxide.
Glyoxylate can also be converted to glycolate by glyoxylate reductase. Data
on DCA metabolism in humans support the hypothesis that DCA metabolism
is similar in both humans and rodents. The
occurrence of oxalic acid in the urine of DCA-treated patients indicates
that DCA is oxidatively dechlorinated to glyoxylate, which is then
converted to oxalate. Among humans there are known polymorphisms which
may account for differences in the ability to metabolize DCA and other
halogenated compounds.
- Excretion:
Based
on the low molecular weight and high water solubility, urinary excretion
of parent substance and metabolites are assumed realistic. Excretion via
the other routes are not expected based on the low logPow value.Accumulation
is not expected.
The elimination of DCA was also investigated in experimental animals and
humans. Only a small fraction of DCA (1-2%) was found in the feces in
animal studies. In humans,
the amount is a slightly higher fraction of the ingested dose than has
been reported for animals. Oxalate is the primary urinary metabolite of
DCA. Both in humans and animals, variable quantities of glyoxylate,
glycolate, monochloracetic acid, and thiodiacetic acid are found in the
urine. A fraction of the glyoxylate produced from DCA is oxidized to
carbon dioxide and is exhaled.
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