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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Key value is set to default value of 180 in line with remark 2 to Table 7.11-2 TGD IR/CSA R.7c

Key value for chemical safety assessment

Half-life in soil:
180 d
at the temperature of:
20 °C

Additional information

Breedveld et al. examined the aerobic and anaerobic degradation of Benzotriazole in the terrestrial compartment. Therefore, series of batch reactors were inocculated with microorganisms from the area of the abandoned airport Gardermoen, Norway and airport Fornebu, Norway. Benzotriazole (1 mg/L) as substrate as well as other substances for achieving necessary oxygen consumption (benzoate or glycol) were added. As control (aerobic conditions) CuSO4 was used.

After five month period no degradation of the test substance was observed under anaerobic conditions. In parallel series under aerobic conditions degradation of Benzotriazole in liquid phase was observed. Since similar loss has been observed in the control evaporation is assumed to be the major process responsible.

Gruden et al. reported findings from 18-month study with activated sludge from the STP in Boulder, Colorado exposed to different concentrations of Methylbenzotriazoles showing no breakdown products in all microcosms and bench-scale digesters used for the study. Due to the high similarity of used Methylbenzotriazoles and Benzotriazole results have been considered relevant for the degradation of both substances.

In addition, available information on inhibition of nitrification in topsoil samples indicate the strong inhibitory potential of Benzotriazole and Tolyltriazole. In observations with 45 heterocyclic N compounds in three different soils significant inhibition of nitrification (35, 55, and 81 %) at 12 µg Benzotriazole /g soil was found (McCarty et al.).

In summary, based on the existing information it can be concluded that Benzotriazole and Tolyltriazole as well as their conjugated sodium salts are stable with regard to biodegradation in soils under environmental conditions. Available information are considered to be adequate for regulatory purposes. Biodegradation in soil is expected to show a lower rate of degradation in general. As Benzotriazole and Tolyltriazole are not readily biodegradable in the aquatic environement the same result is expected for test in soil at least indicating a non-rapidly degradation of the substances. Hence, the substances are classified for long-term hazards in the environment. For the PBT assessment the default half-life for non-readily biodegradable substances is used (DT50 > 180 days) while for the chemical safety assessment the substances are considered as non-biodegradable in soil under environmental conditions.

Breedveld GD et al. (2002) Triazoles in the terrestrial environment – Final report, NGI report no. 20001103-1,http://www.statsbygg.no/FilSystem/files/prosjekter/fouprosj/miljo/50192_BTfinalreport.pdf

Gruden CL et al. (2001) Fate and Toxicity of Aircraft Deicing Fluid Additives Through Anaerobic Digestion, Water Environ. Res., 73, 1, 72-79.

McCarty GW, Bremmer JM (1989) Inhibition of nitrification in soil by heterocyclic nitrogen compounds, Biol Fertil Soils, 8:204-211.