Trixylyl phosphate

Endpoint summary

Description of key information

Discussion on terrestrial toxicity.

Additional information

Toxicity to soil macroorganisms except arthropods

There was no mortality of adult earthworms exposed to nominal concentrations of Trixylyl phosphate at 62.5, 125, 250, 500, and 1000 mg/kg dry soil for 28 days. Based on body weight and survival data of adult earthworms, the no observed effect concentration (NOEC) was determined to be 1000 mg/kg dry soil, the highest concentration tested. There were no reductions of 10% or greater for the numbers of juveniles produced in the treatment groups in comparison to the control group, therefore the EC10 and EC50 for reproduction were each greater than 1000 mg/kg dry soil, the highest concentration tested. The NOEC was 1000 mg/kg dry soil and the LOEC was greater than 1000 mg/kg dry soil, based on body weight and juvenile production.

 

Toxicity to terrestrial arthropods

 

In accordance with column 2 of REACH Annex IX, the effects on terrestrial arthropods study does not need to be conducted as direct and indirect exposure of the soil compartment is unlikely. The substance is not intended to be released directly to the environment.   Toxicity testing on other soil organisms indicates that the phosphates as a group do not show direct toxicity to terrestrial organisms.  As such, further assessment of this endpoint is not required, on the basis of existing data.

 

Toxicity to terrestrial plants

 

Acute

This study is read across to Phenol, isopropylated, phosphate (3:1); CAS No 68937-41-7; EC No 273-066-3. Justification is provided above.

The effects of Durad 310M, incorporated into soil at concentrations of 100, 10, 1 and 0 mg/kg, upon the germination (emergence) and growth of seedlings of wheat (Triticum aestivum), radish (Raphanus sativus)and mung bean (Phaseolus aureus) were determined over periods of 19, 18 and 19 days respectively, representing 14 days after at least 50% emergence of control seedlings.

 

The LC50 for emergence and EC50 for growth rate were both greater than the highest concentration tested, 100 mg/kg, in all species.

 

No phytotoxic effects were observed for any of the species tested.

 

Chronic

 

In accordance with column 2 of REACH Annex X, Long-term toxicity testing shall be proposed by the registrant if the results of the chemical safety assessment according to Annex I indicates the need to investigate further the effects of the substance and/or degradation products on terrestrial organisms. The choice of the appropriate test(s) depends on the outcome of the chemical safety assessment.

Based on the lack of toxicity within the short term plant study on an analogous material, and the fact that risk recommendations are implemented to avoid exposure to the environment, it is proposed that a long term toxicity test in plants is not required. 

 

Toxicity to soil microorganisms

 

This study is read across to Phenol, isopropylated, phosphate (3:1); CAS No 68937-41-7; EC No 273-066-3.

The long-term effects on nitrogen transformation activity of soil microorganisms were minimal at concentrations 10, 32, 100, and 318 mg/kg dry soil. There was an observed effect of the substance on nitrogen transformation activity of soil microorganisms at concentration level 1010 mg/kg dry soil. After 28 days of exposure, the mean nitrate concentration in soil treated at 10, 32, 100, 318, and 1010 mg/kg dry soil exhibited a -1%, 1%, 0%, 2%, and 23% reduction in nitrate formation, respectively, compared to the controls. The EC10 was calculated to be 582.7 mg/L using linear interpolation between concentrations 318 and 1010 mg/L. The EC25 and EC50 were estimated to be >1010 mg/L, the highest concentration tested.

The substance is not intended to be released directly to the environment. Review of the data set available for the phosphates as a group, indicates that these are unlikely to pose hazardous effects to micro-organisms. No effects are seen in other micro-organisms studies conducted across the phosphates. These are specifically Sludge Respiration Inhibition and biodegradation studies and no effects are seen in the micro-organisms utilised in these studies.

 

In addition, Playne and Smith (1983) investigated the toxicity of suspensions on the analogue Tris(methylphenyl) phosphate (CAS No 1330-78-5) to anaerobic bacteria. Little or no effect was seen on the anaerobic bacteria in this experiment.

 

Toxicity to birds

 

There is sufficient mammalian toxicology available on the substance to preclude the requirements to test for toxicity to birds. As such, this endpoint is waived on the grounds of animal welfare and sufficient information on toxicological properties being available to adequately assess the substance.