Phenol, 4-nonyl-, branched

Endpoint summary

Additional information

From results on a test for ready biodegradability nonylphenol appeared to be inherently biodegradable (Gledhill 1999; OECD 301B). A second experiment (Staples 1999; OECD 301F) confirmed the biodegradability of nonylphenol: in this study nonylphenol met the criteria for ready biodegradability except for the 10-day window. These data indicate that nonylphenol is inherently biodegradable.

Simulation tests for the biodegradation of Nonylphenol are available for the environmental compartments freshwater, freshwater sediment, seawater, marine sediment, and soil.

The results from simulation experiments demonstrate that nonylphenol is unlikely to persist under most oxic conditions in surface waters and sediments. In anoxic conditions, particularly in sediments, nonylphenol is less biodegradable. Adsorption to sediments is also a significant route of removal of nonylphenol from the water column, as demonstrated in abiotic sterile controls of sediment experiments by the loss of the test substance from the liquid phase in closed systems where volatilization losses were possible.

The available data indicate that nonylphenol also undergoes biodegradation in soil systems. The mineralization of nonylphenol is not dependent of the initial concentration except for very high concentrations (e.g. 1000 mg/kg, Trocmé et al, 1988) with inhibits biodegradation of nonylphenol because of toxicity to micro-organisms.

Furthermore, nonylphenol degradation in soils is dependent on soil temperature and soil moisture conditions (Topp et al, 2000) as well as on oxygen conditions. In a study conducted by Topp et al, 2000, nonylphenol degradation was limited due to lack of oxygen related to high BOD as a result of increased concentrations of sewage sludge.

Conclusion:

In view of the stringent conditions employed in screening tests on ready biodegradability, nonylphenol cannot be considered persistent. Biodegradation is an important removal process of nonylphenol in surface water and treatment plants.

In river bed sediments, marine sediments, and surface waters nonylphenol is biodegradable under most oxic conditions but is likely biodegrade more slowly under lower temperature and anoxic conditions. 

Nonylphenol is biodegradable in soils and would be rapidly dissipated in well-aerated soils following application of sewage sludge.

According to Annex XIII of Regulation (EC) No 1907/2006 and to the Guidance on information requirements and chemical safety assessment Chapter R.11 (PBT Assessment, ECHA (2008)), a substance does fulfil the criteria “persistent (P)”, if:

-      the half-life in marine water is higher than 60 days, or

-      the half-life in fresh- or estuarine water is higher than 40 days, or

-      the half-life in marine sediment is higher than 180 days, or

-      the half-life in fresh- or estuarine water sediment is higher than 120 days, or

-      the half-life in soil is higher than 120 days.

From assessment of the results obtained for nonylphenol against the Persistence criteria defined above, it can be concluded that nonylphenol is not Persistent (P) or very Persistent (vP) under the majority of oxic environmental conditions.