p-cresol

Endpoint summary

Additional information

Stability

The tropospheric half-life of p-cresol is approximately 8 h due to degradation by OH radicals with an average concentration of 500000 radicals/mL . An even shorter half-life of 3.8 h is calculated for p-cresol from smoke chamber experiments at different tempertures.

With regard to its chemical structure p-cresol is not expected to hydrolyse under environmental conditions.

Biodegradation:

In tests according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)), 80 to 95 % of p-cresol were degraded within 40 d. Biodegradation of p-cresol was also tested in seawater where it was biodegradable as well.

The inherent degradability of p-cresol was studied in two different tests. Using an adapted activated sludge, p-cresol degraded to 96 % within 5 days and 100% after within 10 days.

Cresols isomers are also anaerobically biodegradable. As measured from methane release and carbon dioxide formation, and m- and p-cresol are mineralized under methanogenic conditions by anaerobic sludges from wastewater treatment plants.

Although the substances are readily biodegradable and no biodegradation simulation test has to be performed for sediments, there are studies available on biodegradation in sediments.

p-Cresol is biodegraded in aquifer sediment under anaerobic conditions and by anoxic river sediment within 3-4 weeks. p-Cresol was completely biodegraded within 4 weeks in a freshwater sediment. Furthermore p-cresol was rapidly biodegraded (ca. 90 % after 70 h) in water, water-sediment-suspensions, and by intact sediment-water cores (eco-cores) of marine, estuarine, and freshwater origin. No lag-phase was observed. Pre-exposure did not accelerate degradation.

For the soil compartiment, the degradation behaviour of m- and p-cresol was in two different soils examined. The first soil (acidic) was a sandy loam with an organic carbon content of 0.94%. The second soil (basic) was a sandy silt loam with an organic carbon content of 3.25%. The loadings of the soils (45 to 130 mg/kg) and the degradation were monitored by an HPLC method. Maintained in the dark at 20°C, the test compounds degraded with a half life times and degradation rate constants. p-Cresol degraded with half-live times of <1d for the sandy loam and 0.5 d for the sandy silt loam.

Bioaccumulation:

There are no reliable experimental data on bioaccumulation for p-cresol available. Therefore, data of the isomer m-cresol and o-cresol are taken into account to describe the potential for bioaccumulation of p-cresol. Because of the similar log Kow values 1.95 for o-cresol, 1.96 for m-cresol- and 1.94 for p-cresol, a similar accumulation behaviour is expected.

As the experimentally determined BCF for m-cresol and o-cresol (BCF = 20 and 10.7) indicates a low bioaccumulation potential, the potential for bioaccumulation of p-cresol is also considered to be low.

Adsorption / desorption:

The Koc of p-cresol was determined with batch equilibrium method, similar to OECD Guideline 106. The low Koc values of 49 L/kg for p-cresol suggest a low potential for sorption in soil.

The Henry’s law constant (HLC) of p-cresol is reported to be 0.1 Pa m³/mol at 25 °C.

Distribution modelling:

The distribution of p-cresol in a "unit world" was calculated according to the Mackay fugacity model level I (Currenta, 2009) based on the physico-chemical properties. The main target compartment for p-cresol is water with 96.2 %, followed by air with 2.5 %, soil and sediment each with 0.7%.