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EC number: 203-997-2
CAS number: 112-69-6
For DMA category member C12-14 DMA and supporting substances reliable chronic studies assessing sediment toxicity on representatives of two different sediment organism groups (Nematoda, Oligochaeta) are available. The NOEC (28 d; reproduction & body weight) obtained for C20/22 ATQ in the sediment test with Lumbriculus variegatus of 62.5 mg/kg sed. dw may be regarded as a worst case estimate for sediment toxicity of DMA category members.
Overview of the available Key Freshwater sediment test
For the DMA category member C12-14 DMAa reliable (RL 2) key
study on Caenorhabditis elegansassessing chronic sediment toxicity
is available. The study was performed similar toISO 10872 (pre-guideline
test). Over an exposure period of 72 hours growth (length of worms) and
fertility (number of gravid worms, number of eggs per worm) were
assessed. ANOEC (72 h; growth & fertility) of 1620 mg/kg sed. dw.
and a LOEC (72 h; growth & fertility) of 2030 mg/kg sed. dw. were
determined. Because at the LOEC about 80% size reduction and zero %
gravid worms were observed, fertility seems not to be significantly more
sensitive than growth. Rather, the severely impaired growth at the LOEC
most probably reflects an overall poor constitution of the worms such
that failure of pregnancy is rather a secondary effect.
Two further supporting studiesare available
assessing chronic sediment toxicity on Caenorhabditis elegans:
The first supporting study was performed with the supporting
substance tallow alkyl amines (C16-18-(even numbered,
C18-unsaturated)-alkylamines) which is very similar to DMA category
member C16-18-(even numbered, C18 unsaturated) DMA (for details on
similarity see Category Document, chapter 1). The study was performed
similar toISO 10872 (pre-guideline test; RL 2). Over an exposure period
of 72 hours growth (length of worms) and fertility (number of gravid
worms, number of eggs per worm) were assessed. An unboundedNOEC (72h,
growth rate & reproduction) of 2030 mg/kg sed. dw was determined.
The second supporting study – areliable Caenorhabditis elegans
reproduction test performed according to ISO/DIS 10872 (2008) and
compliant to GLP (reliability category 1) -was performed with the
supporting C20/22 ATQ.C22 ATQ may be regarded as worst case for DMA
category members due to its longer alkyl chain. A further difference is
that it has - in addition to the two methyl substituents at the amino
group inherent to all DMA category members - an additional methyl
substituent at the amino group, rendering it a quaternary amine being
permanently positively charged. Indeed, compared to the afore mentioned
results obtained with C12-14 DMA andtallow alkyl aminesa considerably
lower NOEC (Mortality, Fertility, Reproduction, Growth) and LOEC of 250
and 500 mg/kg sed. dw., respectively, was determined for C20/22 ATQ.
However, in line with the results obtained with C12-14 DMA at the LOEC
no specific reproductive toxicity had been found, rather growth and
reproduction were affected at the same time. Thus, compared with DMA and
primary alkyl amines (tallow alkyl amine), C20/22 ATQ can be regarded to
be of higher sediment toxicity, possibly due to its stronger adsorptive
behaviour caused by the longer alkyl chain (hydrophobic interaction) and
the permanent positive charge (ionic interaction).
In this regard,the second key studyfor sediment toxicity of
DMA category members performed with supporting substance C20/22 ATQ may
be taken as conservative worst case estimate of DMA sediment toxicity.
Lumbriculus variegatus as representative of a second sediment organism
group was used as test organism in a reliable reproduction test
performed in a water-sediment system according to OECD 225 and compliant
to GLP (RL 1). Test duration was 28 days after insertion of the test
organisms. The study was performed by spiking the test item into the
sediment with five concentrations of 62.5 - 125 - 250 - 500 and 750
mg/kg sediment dry weight. Six replicates per control as well as solvent
control and four replicates per test item concentration were set up for
the biological investigation. Analytical verification of test item
concentrations at 0 d, 14 d and 28 d demonstrated that the nominal range
of the test item concentrations was met. TheNOEC (28 d) determined
for all endpoints assessed was 62.5 mg/kg sed. dw. In line with the
results from the studies on C. elegans outlined above no specific
reproductive toxicity was found: At the LOEC of 125 mg/kg sed. dw. a
mean reduction in body mass of 34% and concurrently an inhibition of
reproduction by 24% was observed. An EC50 (28 d) for reproduction and
biomass of 169 and 221 mg/kg, respectively, was estimated.
In conclusion, the results of the C. elegans studies performed
with C12-14 DMA, tallow alkyl amine (primary fatty alkyl amine, PFA) and
C20/22 ATQ strongly suggest a higher sediment toxicity of C20/22 ATQ
compared to DMA and PFA, probably caused by its stronger adsorptive
properties.Thus the NOEC obtained for C20/22 ATQ in the sediment test
with Lumbriculus variegatus of 62.5 mg/kg sed. dw may be regarded as a
worst case estimate for sediment toxicity of DMA category members. This
value will be used for derivation of a PNEC for sediment organisms.
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