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EC number: 202-486-1
CAS number: 96-18-4
An anaerobic toxicity assay was carried out with TCP using methanogens
in a static test over a period of 48 hours at a temperature of 35 °C
according to the principles laid down by Owen et al (1979). The
criterion for toxicity was the inhibition of gas production. A TCP
concentration of 0.63 mg/L inhibited the gas production by 50 % after 48
hours and was identified as the IC50
A modified respiratory inhibition test on TCP was carried out with
activated sludge obtained from a wastewater treatment plant. The study
is generally comparable to the OECD TGD 209 standards. The test was not
carried out according to standard procedures, but was designed to mimic
the standard toxicity assays by using cell concentrations typical of
standard assays such as the ETAD assay. The time period of observation
was extended beyond the 3 hours of the standard respiration inhibition
test to account for effects on cell growth in addition to respiration.
The experimental settings and test conditions are documented in
sufficient detail. The results are considered to be reliable with
Sealed 125-mL serum bottles supplied with 50 mL of additional pure
oxygen were used in the test. The toxic effect on aerobic heterotrophs
was determined by measuring the oxygen demand at approximately 0.5 -days
intervals. It was found that after 24 hours the respiration of aerobic
bacteria was inhibited by 50 % at a concentration of 290 mg/L, which was
taken as the IC50 value.
A static test on toxicity of TCP to Nitrosomonas was carried out at 25
°C using activated sludge from a plant treating meat-packing, rendering
and hide-curing wastewater. The criterion for toxicity to Nitrosomonas
was the inhibition of ammonia consumption. After 24 hours it was found
that ammonia consumption was inhibited by 50 % at a TCP concentration of
30 mg/L , which was taken as the IC50
Testing was performed using a Microtox® model 2055 toxicity analyzer and
standard procedures recommended by Microbics Corporation. The test was
performed using instrumentation and supplies from the Microbics
Corporation. No GLP conditions or officially recognized guidelines
The test is based in the bioluminescence of reconstituted freeze-dried
Microtox® bacteria (Photobacterium
phosphoreum) as a measure of biological activity. Light emission by
bacteria is decreased by the addition of toxicants. Five minutes test
results were used.
A TCP concentration of 19 mg/L in the test medium produced a reduction
of 50% biolumiescence and is accordingly regarded as IC50
TCP exhibits acute effects on aquatic micro-organisms.
Blum & Speece (1991) report results from four different assays
employing micro-organism communities and specific strains. However
methanogens were most susceptible with regard to the endpoint inhibition
of gas production (48-h IC50 0.63
mg/L), the aerobic heterotrophic community with the endpoint inhibition
of oxygen uptake represent the relevant community for assessment. The
study protocol is comparable to OECD TGD 209 and the study is considered
valid and conclusive and yielded a 24-h IC50
of 290 mg/L.
The assay employing nitrifying bacteria (Nitrosomonas sp.)
with the endpoint inhibition of ammonia consumption revealed an 24-h IC50
of 30 mg/L. This is in agreement with ECHA (2008, information
requirements and chemical safety assessment, chapter R.10., p 30) who
recommends an assessment factor (AF) of 10 to be applied to result of a
sludge respiration test, reflecting the lower sensitivity of this
endpoint as compared to nitrification.
Finally a Microtox® model
2055 assay (ISO 11348) employing a specific bacterial population (Vibrio
fischeri) with the endpoint inhibition of bioluminescence showed an
5-min IC50 value of 19 mg/L.
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