Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Adsorption/Desorption

In accordance with column 2 of REACH Annex IX Nr 9.3.3, the study does not need to be conducted as the substance has a low potential for adsorption (log Kow < 3, see Sect. 4.7) and is readily biodegradable (see Sect. 5.2.1).

 

Based on a calculated log Koc of 1.65 (Koc = 44.7) for the charged molecule, isobutyric acid is expected to have a high mobility in soil (OXEA, 2010).

 

The results of Hemphill (1962) are not suited to assess the adsorption of isobutyric acid to soils (sorbents are pure clays).

 

Henry’s Law constant

The Henry's law constants (HLC) of isobutyric acid at 25°C were determined by an experimental method (Khan, 1992; equilibrium partial pressure measurements over aqueous solutions) and by calculation methods (ETC, 2009; program HENRYWIN v 3.2, US EPA EPISUITE 4.00).

 

Experimental value: HLC (25°C) = 8.85E-7 atm m³/mol

 

Calculated Value:

Bond contribution method: HLC (25°C) = 9.65E-007 atm*m3/mol

Group contribution method: HLC (25°C) = 9.09E-007 atm*m3/mol

 

Isobutyric acid volatilizes only to a low degree from water.

 

Distribution modeling

Estimates obtained from Level III fugacity distribution modeling using US EPA EPI Suite v4.00, model component Level III fugacity model, indicate that emissions of isobutyric acid will distribute predominantly in soil (55%) and water (37.5%), and to a considerably lesser extent in air (7.4%). The fraction in sediment is minimal (0.07%). The estimated persistence time is 282 hr (ECT, 2009).

 

Other distribution data

Volatilization from Water

An experimental Henry's Law Constant (HLC) of 0.0897 Pa*m³/mol at 25 °C was reported from the EPIWIN database. Taking this value, isobutyric acid volatilization half-lives of 26 and 286 days were estimated for a model river and a model lake, respectively.

 

Isobutyric acid in the environment will be distributed predominantly in soil and to a lesser degree in water. Transfer to air will be minute.

 

Additional testing according to ANNEX X

Further testing on the environmental fate and behavior of the substance and/or degradation products will be proposed if the chemical safety assessment according to Annex X indicates the need to investigate further the fate and behavior of the substance.