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EC number: 200-661-7
CAS number: 67-63-0
The 16 hour Toxicity Threshold concentration of 1050 mg/L for Pseudomonas putida (Bringmann & Kühn, 1980) is selected as the value to use for PNECstp calculations.Toxicity Threshold = 1050 mg/L; 16 hours, Pseudomonas putida (Bringmann & Kühn, 1980)Toxicity Threshold = 1050 mg/L; 16 hours, Pseudomonas putida (Bringmann & Kühn, 1977)Toxicity Threshold = 4930 mg/L; 72 hours, Entosiphon sulcatum (Bringmann, 1978)Toxicity Threshold = 3425 mg/L; 20 hours Uronema parduzci (Bringmann, 1980)Toxicity Threshold = 104 mg/L; 48 hours Chilomonas paramaecium (Bringmann et. al., 1980)
The toxicity of 2-propanol to Pseudomonas putida was assessed in
a published non-guideline study that predates GLP requirements for
excotoxicity studies (Bringmann & Kühn 1980). The
study used a static freshwater system. Cell culture
was maintained on nutrient agar slants and examined for purity
periodically. The inoculum was prepared by growing the
microorganism on nutrient agar plates for 24 hours. The
cells were washed off from the medium and resuspended in a nutrient
medium. By determining the extinction of the
monochromatic radiation at 436 nm for a 10 mm layer of the bacterial
suspension, the final turbidity value of the bacterial suspension was
adjusted, by means of sterile saline, such that it corresponded to the
extinction value of a Formazin standard suspension TE/F/436 nm = 10.
Four parallel dilution series in 300 mL Erlenmeyer flasks were prepared
of test solution. Each dilution contains 1 part v/v of
test solution in 20 to 214parts v/v mixture. The
first flask in the series contained 160 mL of test solution at the start. Starting
from this flask, the subsequent dilution steps were prepared at a
constant dilution ratio by consistently mixing 80 mL of preliminary test
dilution and 80 mL double distilled water. Consequently,
each flask contained 80 mL of culture liquid at the start. Each
flask of the three dilution series were inoculated to 100 mL by adding 5
mL each of stock solution I, 5 mL of stock solution II and 10 mL each of
the prepared bacterial suspension from the preliminary culture. Both
inoculated and non-inoculated flasks were incubated at 25ºC for 16 hours. After
16 hours, the extinction of the monochromatic radiation at 436 nm for a
10 mm layer of the bacterial suspension was determined.
The results were analyzed on a semi-logarithmic chart according to the
following scheme. The calculated values (A), (A-3%),
and (B) were located on the Y-axis (linear): the average (A) of all the
absorbance of the non-inhibited and non-stimulated cultures (as long as
those values were below a standard deviation of less than 3 %); and the
average (B) of all the absorbance of the cultures showing the lowest
toxic effect. The highest non-toxic concentration (a)
and the lowest toxic concentration (b) were located on the X-axis.
The placing of (A-3 %) on the line between the coordinates (a, A) and
(b, B) allowed the value (C) to be determined on the abscissa of the
initial concentration at which growth inhibition was determined or
Toxicity Threshold. The Bringmann & Kühn (1980)
results indicate that Pseudomonas putida had a 16 hour Toxicity
Threshold concentration of 1050 mg/L.
None of the five published studies presented documenting the toxicity of
2-propanol to microorganisms were conducted with a mixed inoculum that
would asses the functioning of the entire microbial community in a
sewage treatment plant, rather the tests were based on single species
systems. According to the ECHA Guidance on information
requirements and chemical safety assessment, Chapter R.7b: Endpoint
specific guidance section R.18.104.22.168 Laboratory data on toxicity on
sewage treatment plant microorganisms, results of the cell
multiplication inhibition test with P. putida (Bringmann and Kühn
1980) can be used for calculation of the PNECstp.
The supporting data report higher Toxicity Thresholds for Entosiphon
sulcatum (flagellated protozoa) (Bringmann, 1978) and Uronema
parduzci (ciliated protozoa) (Bringmann, 1980) and a lower Toxicity
Threshold for Chilomonas paramaecium (flagellated protozoa)
(Bringmann et. al., 1980). According to the ECHA
Guidance on information requirements and chemical safety assessment,
Chapter R.7b: Endpoint specific guidance section R.22.214.171.124 Laboratory
data on toxicity to STP microorganisms and its sources, no correlation
exists between activated sludge and ciliated protozoa test results. The
lower Toxicity Threshold is for flagellated protozoa and a contact time
of 48 hours. In
general in accordance with the hydraulic retention time in a sewage
treatment plant, short-term toxicity measurements in the order of hours
are preferred. As these three protozoan results
are equal to or greater than 20 hours contact time, these results should
not be used to determine the PNECstp.
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