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EC number: 205-746-2
CAS number: 149-74-6
Table 1: Oxygen consumption rates,
percentage inhibition values and pH values in the definitive test after
3 hours contact time
Nominal conc. (mg/l)
Initial oxygen reading (mg O2/l)
Final oxygen reading (mg O2/l/)
Oxygen consumption (mg O2/l/min)
based on mg of trichloro(phenyl)silane/L
after adjustment to that of the dechlorinated tap water.
Initial test results: EC50 360 mg/l; NOEC
180 mg/l (based on mg of trichloro(phenyl)silane/L). The pH of test
solutions dropped to 6.5 at 320 mg/l, 2.3 at 560 mg/l and 1.5 at 1000
Toxicity to microorganisms:
Activated sludge respiration inhibition 3 hour EC50 value of >1000 mg/L
(nominal) and NOEC value of ≥1000 mg/L (nominal) read-across from the
structurally-related substance trichloro(phenyl)silane.
There are no microorganism
toxicity data available for dichloro(methyl)(phenyl)silane, therefore
good quality data for the structurally-related substance
trichloro(phenyl)silane (CAS 98-13-5), have been read across. Both
substances hydrolyse to structurally-related hydrolysis products,
methylphenylsilanediol and phenylsilanetriol respectively; the other
hydrolysis product being hydrochloric acid.
Hydrochloric acid is not
expected to have adverse effects on microorganisms in a sewage
treatment plant, where the pH is maintained within a favourable range.
and trichloro(phenyl)silane are within a wider analogue
group than the aryl analogue group. Substances within this wider
analogue group, in general, exhibit no evidence of significant
toxicity to microorganisms. This wider analogue group for the toxicity
to microorganisms endpoint consists of a number of different
functional groups but specific read-across is between substances with
Table 7.4.2 presents
microorganism toxicity data for substances relevant to the registered
It is considered valid to
read-across the results for trichloro(phenyl)silane (CAS 98-13-5) to
fill the data gap for the registered substance since the source and
target substances generate structurally analogous silanol hydrolysis
products. Additional information is given
in a supporting report (PFA 2013j) attached
in Section 13.
Table 7.5.2. Microorganism
toxicity data for relevant substances
Result: NOEC (or EC10/ EC20) (mg/l)
>1000 mg/l (Phenylsilanetriol >740mg/l) with pH adjustment
≥1000 mg/l (Phenylsilanetriol 740mg/l) with pH adjustment
A 3 hr EC50 of >1000
mg/L and NOEC of ≥1000 mg/L were determined for trichloro(phenyl)silane.
Trichloro(phenyl)silane hydrolyses very rapidly to phenylsilanetriol and
was used in the test as parent substance on the understanding that it
would hydrolyse rapidly to produce the phenylsilanetriol. Initial and
definitive tests were carried out, under the same conditions but pH
regulation was employed in the definitive test as significant reduction
in pH of test vessels occurred in the initial test due to hydrolysis of
trichloro(phenyl)silane producing hydrogen chloride, and thus toxic
effects may be related to hydrogen chloride rather than
phenylsilanetriol. Effects of hydrogen chloride on microorganisms are
limited to those that result from changes to pH in unbuffered media,
therefore it is appropriate to use the results from the definitive test
with pH adjustment.
(2013j). Peter Fisk Associates, STP Microorganism toxicity Main Analogue
Group report, PFA.300.003.006
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