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Data on the toxicity of 6-methyl-2-oxoperhydropyrimidin-4-yl urea to terrestrial organisms are not available.
In accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. the assessment of the toxicity of the substance to soil macroorganisms is based on information on the structurally related substance N,N''-(isobutylidene)diurea (CAS No 6104-30-9). 6-methyl-2-oxoperhydropyrimidin-4-yl urea (CAS No 1129-42-6) and N,N''-(isobutylidene)diurea (CAS No 6104-30-9) show extensive structural similarities. These similarities comprise the molecular structure of both substances as well as their molecular masses (N,N''-(isobutylidene)diurea: 174 g/mol, 6-methyl-2-oxoperhydropyrimidin-4-yl urea: 172 g/mol). The potential of both analogue substances to bioaccumulate is low according to their log Kow values (N,N''-(isobutylidene)diurea: -0.9; 6-methyl-2-oxoperhydropyrimidin-4-yl urea: -1.34). Both substances are slightly soluble with a water solubility of 0.3 up to 3 g/L for N,N''-(isobutylidene)diurea and 5.1 g/L for 6-methyl-2-oxoperhydropyrimidin-4-yl urea respectively. Both substances are characterized by a low adsorption potential (log Koc N,N''-(isobutylidene)diurea: 1.4, log Koc 6-methyl-2-oxoperhydropyrimidin-4-yl urea: 0.098) and by a low vapour pressure (VP N,N''-(isobutylidene)diurea: 4.7 E-12 Pa, VP 6-methyl-2-oxoperhydropyrimidin-4-yl urea: < 0.35 Pa). Thus a similar toxicity of the analogue substances can be expected.

For the structural analogue N,N''-(isobutylidene)diurea (CAS No 6104-30-9) on study investigating the toxicity of the substance to earthworms is available. The test was conducted according to guideline 207. Earthworms of the species Eisenia fetida were exposed to the substance for 14 days. At test termination a LC50 of 648 mg/kg soil was determined (NOEC: 250 mg/kg).

Based on the chemical safety assessment and in accordance with Regulation (EC) No. 1907/2006, Annex IX, column 2, 9.4 further studies on the effect of 6-methyl-2-oxoperhydropyrimidin-4-yl urea on terrestrial organisms were not conducted. The substance is not expected to induce acute or chronic effects in terrestrial organisms due to the physic-chemical properties and expected environmental fate. The bioavailability the substance for soil organisms is expected to be very low. The substance is readily biodegradable thus transfer of the substance to soil or persistence in soil is not likely. The substance is furthermore characterised by a low log Koc indicating a low potential to adsorb to soil particles and suspended matter and to accumulate in soils. Accumulation of the substance in organisms is also unlikely as indicated by the low log Kow. Thus based on data for soil macroorganisms obtained by read-across and on the expected environmental fate of the substance acute and chronic effects to soil organisms are not expected.