Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

The calculated half life of tripropylene glycol is 0.19 days with a OH radical concentration of 1.5E6 OH/cm3 (Aopwin, 2000).

In accordance with column 2 of REACH Annex VIII, the hydrolysis test does not need to be conducted as the substance is readily biodegradable. Furthermore, ethers and glycols are generally known to be resistant to hydrolysis (Harris, J.C., 1990). Therefore, the substance is not expected to undergo hydrolysis under environmentally relevant conditions. No photodegradation in water is expected, because of lack of UV absorption (OECD SIDS, 1994)

Four reliable screening tests (GLP compliant guideline studies) and a non-GLP result from the MITI database are available which show different results on the biodegradability of the substance. In the OECD Guideline 301 F test (Ready Biodegradability: Manometric Respirometry Test) with sludge from a municipal sewage treatment plant, 81.9% biodegradation was found after 28 days determined as O2 consumption and 60.1% determined as CO2 removal (The Dow Chemical Company, 2003). This test is a better simulation of realistic conditions than the other screening tests and will therefore be further used as key study in the assessment. It can be concluded that the substance is ready biodegradable.

Under the conditions of other screening tests (OECD301B, OECD301C and OECD301D with municipal inoculum) the test substance was not ready biodegradable (Shell Research, 1993, MITI, 1995, The Dow Chemical Company, 1991). However, in an OECD301D test with industrial inoculum, 69% of the theoretical oxygen demand was consumed after 28 days in reaction mixtures containing the industrial inoculum. These data suggest that some adaptation of the microorganisms may be required for biodegradation. Significant biodegradation was found in an OECD306 test with natural seawater after 64 days (West, 2007). Therefore tripropylene glycol is not expected to persist in water or marine environments. Simulation studies with sediment and/or soil are not available.

The rate constant used in the assessment are (EUSES calculations):

 

Degradation for hydrolysis

6.93E-07 d-1

Degradation for photolysis

6.93E-07 d-1

Degradation in air

0.19 d-1 (QSAR calculation)

Degradation in the STP

24 d-1

Biodegradation in water

0.0462 d-1

Biodegradation in sediment

2.31E-03 d-1

Biodegradation in soil

0.0231 d-1

 

Based on the result of the octanol/water partition coefficient (log Kow = -0.379) tripropylene glycol is expected to have a low potential for bioaccumulation and adsorption/desorption.

The calculated Henry's law constant at environmental relevant temperature is 0.129 Pa.m3/mol using EUSES calculation (The European Union System for the Evaluation of Substances, 2008)

Volatility is not expected to be a significant fate process due to its low vapor pressure and high water solubility.

Using fugacity modelling (Mackay level IIII) tripropylene glycol will preferentially partition into water (9%), soil (34%) and sediment (57%) if released into the environment (OECD SIDS, 1994).