Linseed oil, oxidized

Endpoint summary

Description of key information

The substance is considered to be readily biodegradable, but it has potential to adsorb to soil (Log Koc >4.96). Therefore long-term toxicity studies on soil organisms were performed as indicated in Annex IX, Column 2 and short term tests were waived.

The study organisms represent different ecological functions and trophic levels in the terrestrial ecosystem: 6 plant species (production), earthworms (detritus feeding and improvement of the soil structure) and a soil flora representing the nitrification capacity. A study on the toxicity to birds was waived. All studies were performed according to standard OECD test guidelines and under GLP. They were valid studies with reliabity 1.

The results are summarised in the table (concentrations in mg/kg soil dw) :

	(Lowest) EC10 <95%CL>	(Lowest) NOEC and LOEC	(lowest) EC50 <95%CL>
Plants, 18 d OECD 208	Rape, Shoot fresh weight 335 mg/kg <184-432> Oat, Shoot fresh weight 398 mg/kg <205-512>	Rape, Shoot fresh weight NOEC 444 mg/kg LOEC 667 mg/kg Oat, Shoot fresh weight NOEC 148 mg/kg LOEC 444 mg/kg Oat, Shoot fresh weight	Rape, Shoot fresh weight 778 mg/kg <681-927> Oat, Shoot fresh weight EC50 not determined
Earthworm, 56 d OECD 222		NOEC ≥ 1000 mg/kg Survival, Biomass, Reproduction
N-transformation, 28 d, OECD 216	217 mg/kg	NOEC 94.7 mg/kg LOEC 237 mg/kg	666 mg/kg

The lowest EC10 is the one for the N-transformation: 217 mg/kg. This is a statistically derived value that is protective for the other species as well.

It should be remarked that the test substance is highly insoluble in water. It was dosed to soil through a stock solution in acetone. At the EC10 of 217 mg/kg, with a soil moisture of 45% of the WHC, the water content in the soil is 15.9% or 159 g/kg soil dw. Thus at the EC10 level, the soil holds 217 mg test substance and 159 g water or 1365 mg test substance for 1 liter water. As the test material will not solve in water to any significant extent, the bioavailability is expected to be low. In particular for the two tests showing some effects (plants and nitrifying bacteria), there in no ingestion as for the earthworm and exposure is expected to occur mainly through the water phase. With the limited water solubility, one would not expect a dose/effect dependency at these high levels. The test material is known for its property to form a coating/film on surface substrates. When this occurs on the roots of the plants or on the micro-organism cells, the exchange of minerals, nutrients, oxygen and CO2 will be hampered. This is a likely explanation that the observed effects are due to a physical effect rather than to a toxicological effect.