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Ecotoxicological information

Ecotoxicological Summary

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Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
0.062 mg/L
Assessment factor:
50
Extrapolation method:
assessment factor
PNEC freshwater (intermittent releases):
0.62 mg/L

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
0.006 mg/L
Assessment factor:
500
Extrapolation method:
assessment factor

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
25 mg/L
Assessment factor:
1
Extrapolation method:
assessment factor

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
0.22 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
0.022 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
0.009 mg/kg soil dw
Extrapolation method:
equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

The hydrolysis half-life of the registration substance, N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3), is 0.025 hours at pH 7 and 25°C. The substance will hydrolyse in contact with water and atmospheric moisture to form N-(3-(trihydroxysilyl)propyl)ethylenediamine and methanol. REACH guidance (ECHA 2016, R.16) states that “for substances where hydrolytic DT50 is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself”. TGD and ECHA guidance, (ECHA 2016) also suggest that when the hydrolysis half-life is less than 12 hours, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Therefore, the environmental hazard assessment, is based on the properties of the silanol hydrolysis product, in accordance with REACH guidance. As described in Section 4.8 (water solubility), the silanol hydrolysis products may be susceptible to condensation reactions.

The silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine, has a high water solubility (calculated solubility is 1E+06 mg/l at 20°C using a QSAR method)

and low log Kow (-4.0 (corrected for ionisation)).

As described in IUCLID Section 4.8 (water solubility), the silanol hydrolysis products may be susceptible to condensation reactions.

Amines are basic, therefore once dissolved they will increase the pH of the test media. In addition, the un-ionised form of the amine is more toxic than the ionised form. This pattern of toxicity is consistent with ammonia, where the un-ionised form, NH3, is more toxic than the ionised form, NH4+. The difference in toxicity is attributed to bioavailability, where the un-ionised form can cross cell membranes more readily than the ionised form. Many of the aquatic toxicity studies for amine-containing organosilicon substances were conducted at pH ~8 and in some cases the pH was not adjusted after the test substances were added to the test media. Therefore, for media and natural waters having a pH closer to 7 it is likely that ecotoxicity might be expected to be less severe than indicated by these test results (i.e. the value of E(L)C50 may possibly be higher under pH-neutral conditions).

Considerations on the non-silanol hydrolysis methanol

The properties of methanol have been discussed extensively in the public literature and it is not hazardous at the concentrations at which it would have been present in the toxicity tests reviewed in this assessment; the short-term EC50 and LC50 values for methanol are in excess of 1000 mg/l (OECD 2004a - SIDS for methanol). Therefore, the environmental hazard assessments that follow (including those for sediment and soil compartments) are based on the assumption that the observed effects are the result of exposure to the silanol hydrolysis product, N-[3-(dihydroxymethylsilyl)propyl]ethylenediamine of the registered substance.

Conclusion on classification

The substance has reliable short-term E(L)C50 values of 597 mg/l in fish, 81 mg/l in invertebrates and 8.8 mg/l in algae . It has a reliable NOEC value of 3.1 mg/l in algae and reliable long-term NOEC value of ≥1 mg/l in Daphnia. The long-term data set comprise 'adequate' chronic data available in the context of classification and labelling.

The substance hydrolyses rapidly in water and is not readily biodegradable.

These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):

Acute toxicity: Not classified.

Chronic toxicity: Not classified.