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EC number: 203-398-6
CAS number: 106-44-5
Regarding all available test on toxicity to microorganisms, the most relevant test resulting in the lowest PNEC value is used for assessment.The sensitivity of activated sludge to p-cresol was determined by a respiration inhibition test according to OECD Guideline 209. The 2h IC50 for respiration inhibion of microorganisms is 440 mg/L.The effect of p-cresol on Nitrosomonas activity was measured as a nitrification inhibition method comparable to ISO/DIS 9509. The 24 h-IC50 was 27 mg/L.For respiration, the 49 h-IC50 was 260 mg/L. Nitrification inhibition by p-cresol was also measured by a similar method yielding an EC75 of 16.5 mg/L during a 2 -4 h incubation period. The EC50(48 h) with respect to growth of Tetrahymena pyriformis accounts for 157 mg/L testing p-cresol.In order to protect the efficiency of sewage treatment plants, inhibition of nitrification is identified to be the most sensitive test system.
Several tests are available to evaluate the toxicity of p-cresol to
The influence of p-cresol on the nitrification process in domestic
wastewater is described in an experiment. A purified activated sludge
was incubated for 2 to 4 hours to the wastewater (BSB5 = 250 mg/l, 50 to
80 mg NH4-N/l) fortified with different concentrations of p-cresol. The
effect on the inhibition of the nitrification was determined by
photometric analysis of nitrite and nitrate. An EC75-value of 16.5 mg/l
is given for the inhibition of the reaction step of ammonia to nitrite.
Nitrification inhibition by p-cresol was also measured by a similar
method yielding an IC50 of 27 mg/L during a 2 h incubation period.
The protozoa Tetrahymena pyriformis was exposed to p-cresol for 48 hours
using the cell multiplication inhibition test method. An EC50 of 157
mg/l was obtained.
The sensitivity of activated sludge to p-cresol was determined by a
respiration inhibition test according to OECD Guideline 209. The 3h IC50
for respiration inhibion of microorganisms is 440 mg/L.
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