Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability of DMDMH in the environment:

 

In accordance with Annex IX of the Regulation (EC) No 1907/2006 REACH concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), information regarding phototransformation in air, as well as in water and soil, is not mandatory. However, for informational purposes, information on the phototransformation in water of the hydrolysis product, DMH, is provided.

 

In Annex VIII column 2 of the REACH Regulation, it is suggested, that a study on the "Hydrolysis as function of pH" does not need to be conducted if the “substance is readily biodegradable". It can be concluded that a study on the hydrolysis as a function of pH is not required based the rapid biodegradability in the environment and the additional evidence of hydrolysis based on hydrolysis as a function of pH testing of the DMDMH and the breakdown product. However, for information, evidence of hydrolysis is included based on hydrolysis as a function of pH testing of DMDMH and its breakdown product.

 

Although according to Annex IX of the Regulation (EC) No 1907/2006 REACH concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), phototransformation in water is not a mandatory information requirement, Results from a reliable study (Schmidt 1992) are provided for information.

 

Biodegradation of DMDMH:

 

There are reliable biodegradation in studies for DMDMH. There is also a reliable degradation study available for the hydrolysis product, DMH.  Due to the rapid hydrolysis of DMDMH to DMH studies conducted with the hydrolysis product, DMH, are considered relevant for environmental fate and ecotoxicology and are considered in this dossier.

 

A reliable study (Mead 2001) determined that DMDMH was degraded 78% with the 10-day window and the test substance can be considered readily biodegradable. Additional studies with the degradation product showed that the hydrolysis product DMH is also readily biodegradable in water. Consequently, the test substance and its hydrolysis product are considered readily biodegradable in water.

 

In Annex IX column 2 of the Regulation (EC) No 1907/2006 REACH, it says that a study on the Biodegradation in Water and Sediment and a study on Biodegradation in soil does not need to be conducted if the substance is readily biodegradable. Therefore, a study on the Biodegradation in Water and Sediment and a study on Biodegradation in soil is not required as DMDMH and the hydrolysis product, DMH, are readily biodegradable.

 

Bioaccumulation of DMDMH:

 

There are no reliable bioaccumulation studies for aquatic or terrestrial organisms for DMDMH. However, there is a reliable aquatic bioaccumulation study and an estimated aquatic BCF available for the hydrolysis product, DMH.   Due to the rapid hydrolysis of DMDMH to DMH the active substance would not be available for bioconcentration to occur therefore, exposure to the degradation product, DMH, is considered. The BCFfish of <1.79 for DMH is not considered to be potentially bioaccumulative. 

 

DMH is readily biodegradable, and has high water solubility. The PEC/PNEC ratio for the terrestrial compartment has been calculated to be < 1 indicating that there is no cause for concern in terrestrial compartment. It is therefore considered that DMH would not bioconcentrate in terrestrial organisms based on these assessments and a test on terrestrial bioconcentration of DMH is scientifically unjustified.

 

Transport and distribution of DMDMH: 

As shown in Endpoint 5.2.1, reliable studies have shown that DMDMH and the hydrolysis product, DMH, are readily biodegradable in water.  Because the substance and its degradation product are readily biodegradable in water, as per the Reach Annex IX Column 2 exemption, the testing requirement for endpoint 5.4.1 is waived.  For information, studies on adsorption have been conducted for DMDMH or the hydrolysis product of DMDMH, DMH, which indicate that Koc value for DMDMH was <17.8 and ranged from 23.4 to 147 for DMH, with an average of 80.2. Therefore, DMDMH and the hydrolysis product are classified as having low potential (high mobility) for adsorption in soil or sewage sludge.