Guaiacol

Endpoint summary

Additional information

1    Degradation

1.1 Abiotic degradation

1.1.1  Hydrolysis

Guaiacol is not expected to undergo hydrolysis due to lack of hydrolysable functions. This is confirmed by Lyman et al. (1990).

1.1.2  Phototransformation/photolysis

1.1.2.1  Phototransformation in air

Atkinson (1988) estimated a rate constant for indirect photolysis for guaiacol of 0.0000000000317 cm3/(molecule.sec) and a half-life with hydroxyl radical of 0.5 days.

1.1.2.2  Phototransformation in water

Two publications reported phototransformation of guaiacol in water estimated by QSAR, but the conditions of the experimental part that lead to equations were insufficiently detailed to be considered as reliable.

1.1.2.3  Phototransformation in soil

Direct photolysis on sunlit soil surfaces may not be environmentally important process for guaiacol due to lack of absorption sunlight (HSDB, 2007).

1.2 Biodegradation

1.2.1  Biodegradation in water

Six biodegradation screening studies in water (either ready and inherent, in aerobic and anaerobic conditions) are available on guaiacol.

Concerning the ready biodegradability in water, one study (MITI, 1989) has been selected as key study since performed according to OECD test guideline (301C) by the Japanese Competent Authorities. In this study, the biodegradation of guaiacol was followed during 28 days, at an initial concentration of 100 mg/L using a mixed, non adapted inoculum (30 mg/L). After 28 days, the measured percentage of biodegradation was 90 % (based on Biological Oxygen Demand) and 97% (based on Total Organic Carbon removal). Guaiacol is therefore considered as readily biodegradable.

Palla & Gard (1987) studied the inherent biodegradability of effluent containing guaiacol following the OECD guideline 302B. Based on the DOC removal, they found 95.5% of effluent biodegradability after 4 days, and 96.4% after 28 days.

Guaiacol has been demonstrated to be biodegradable in anaerobic conditions also (Sierra-Alvarez, 1990; Boyd, 1983).

1.2.2  Biodegradation in soil

Alexander & Lustigman (1966) studied biodegradation of substituted benzenes by soil microflora. Based on loss of UV absorbancy, they found that guaiacol was degraded by soil microorganisms in 4 days.

1.3 Environmental distribution

1.4 Adsorption/desorption

Boyd (1982) has been selected as key study and reported a measured Koc of 40 in a clay loam soil. Poole and Poole (1999) calculated a Koc of 36.3, which is consistent with the experimental one. Based on these results, guaiacol is not expected to have a high adsorptive behaviour.

1.5 Volatilisation

Volatilisation either from soil or water is not expected to be an important process for guaiacol because of relatively low vapour pressure (14Pa at 25°C), relatively high water solubility (18.5 g/l) and an experimental Henry's law constant of 0.11 Pa.m3/mole at 25°C.

1.6 Distribution modelling

Necessary data to run MacKay were available (Molar mass = 124.14 g/mol Water solubility = 18500 g/m3 Vapour pressure = 14 Pa Log Kow = 1.47 Melting point = 28°C). According to MacKay level I version 3.00, Guaiacol has the following distribution:

- Water: 96.35%

- Air: 1.83%

- Soil: 1.78%

2    Bioaccumulation

No study of bioaccumulation is available. Two values of BCF of 2.07 and 7.76 have been calculated on the basis of equations involving Log Kow (Lyman et al., 1990, BCFwin, 2008). Based on these values, guaiacol is considered not to bioaccumulate.