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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

It can be concluded that short-term toxicity testing of terrestrial organisms is not required based on the unlikely exposure of soil organisms to the DMDMH product or its degradation product (DMH). Based on the unlikely direct exposure to soil organisms, rapid biodegradability in the environment and the additional evidence of no toxicity observed in soil microbes based on long-term toxicity testing of the breakdown product.

Key value for chemical safety assessment

Additional information

In Annex IX of Regulation (EC) No 1907/2006, it is laid down that short-term toxicity to terrestrial organisms shall be proposed by the registrant if the chemical safety assessment indicates the need to investigate the effects of the substance and/or relevant degradation products on terrestrial organisms. Column 2 of Annex IX states that studies do not need to be conducted if direct and indirect exposure of the soil compartment is unlikely.

 

The product is not supposed to be directly applied to soil and indirect exposure of terrestrial organisms is unlikely since the test substance and its degradation product (DMH) are readily biodegraded in the aquatic environment and STP processes. Therefore no short-term tests on terrestrial organisms are required in accordance with Annex IX of Regulation (EC) No 1907/2006.

 

For information, there are no reliable short-term toxicity data for plants relating to DMDMH. However, reliable long-term toxicity data for terrestrial organisms are available for DMH, the hydrolysis product of DMDMH. DMDMH readily undergoes hydrolysis to DMH and therefore data are provided for both substances when available. In the case of long-term testing, the data on DMH are considered more relevant for environmental fate and ecotoxicology.

Clarke (2007) conducted a reliable (Klimisch 1) GLP compliant study following OECD 216 methods. Soil microbes were exposed to one concentration of DMH (1000 mg/kg) in a limit test for 28 days. The 28-day EC50, based on inhibition of microbial nitrogen transformation activity, was >1000 mg/kg and the NOEC was 1000 mg/kg.

 

It can be concluded that short-term toxicity testing of terrestrial organisms is not required based on the unlikely exposure of soil organisms to the DMDMH product or its degradation product (DMH). Based on the unlikely direct exposure to soil organisms, rapid biodegradability in the environment and the additional evidence of no toxicity observed in soil microbes based on long-term toxicity testing of the breakdown product.