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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:
0.5 mg/L
Assessment factor:
50
Extrapolation method:
assessment factor
PNEC freshwater (intermittent releases):
2 mg/L

Marine water

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

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
0.81 mg/L
Assessment factor:
10
Extrapolation method:
assessment factor

Sediment (freshwater)

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

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
0.26 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:
0.23 mg/kg soil dw
Extrapolation method:
equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Constituent 2 of the registration substance hydrolyses in water (<12 h at pH 7 and 25˚C, QSAR) giving 3-aminopropylsilanetriol (1 mole) and methanol (3 moles). As described in Section 4.8, condensation reactions of the silanetriol are possible.

REACH guidance (ECHA 2016b, 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”. REACH guidance (R.16c, 2016) also suggests 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 assessments that follow, including those for the sediment and soil compartments due to water and moisture being present, is based on the properties of the silanol hydrolysis product, (3-aminopropyl)silanetriol in accordance with REACH guidance.

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).

 

The PNEC for the silanol hydrolysis product, 3-aminopropylsilanetriol, is based on ecotoxicity data derived from reliable studies with analogous alkoxysilanes. In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The non-silanol hydrolysis products are not toxic (see below) and hence are considered not to have contributed significantly to toxicity. As such the observations from these studies are attributable to 3-aminopropylsilanetriol in the test system.

 

Additional information is given in a supporting report, PFA 2016y, attached in Section 13 of the IUCLID dossier.

  • Read-across from (3-aminopropyl)triethoxysilane (CAS 919 -30 -2) to Silanol HP2 (3-aminopropylsilanetriol)

The surrogate substance (3-aminopropyl)triethoxysilane hydrolyses in water (8.5 h at pH 7 and 25˚C, measured) giving (3-aminopropyl)silanetriol and ethanol. (3-Aminopropyl)silanetriol, the silanol hydrolysis product, is one of the Assessment Entities on which the chemical safety assessment is based. Therefore read-across from ecotoxicity studies conducted with (3-aminopropyl)triethoxysilane under conditions in which the test organisms would have been predominantly exposed to hydrolysis products, to Silanol HP2 (3-aminopropyl)silanetriol), is considered to be valid.

 

  • Considerations on the non-silanol hydrolysis products:

Methanol and ethanol are well characterised in the public domain literature and are not hazardous at the concentrations relevant to the studies; the short-term EC50 and LC50 values for these substances are in excess of 1000 mg/l (OECD2004a - SIDS for methanol, CAS 67-56-1, OECD 2004b - SIDS for ethanol, CAS 64-17-5).Therefore, at the loading rates experienced in these tests it is unlikely that the presence of either would significantly affect the results of the tests.

 

Conclusion on classification