Ethanone, 2,2-dichloro-1-(2,3-dihydro-3-methyl-4H-1,4-benzoxazin-4-yl)-

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.022 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.014 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.002 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

10 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.559 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.056 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.099 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Calculation of PNECs with assessment factors

PNEC values have been determined for environmental compartments using the assessment factor approach in accordance with the ECHA guidance R.10 on the characterisation of dose [concentration]-response for the environment.

PNEC aqua (freshwater) = 0.022 mg/L

PNEC aqua (marine water) = 0.0022 mg/L

PNEC aqua (intermittent release) = 0.014 mg/L

PNECstp = 10 mg/L

PNEC sediment (freshwater) = 0.559 mg/kg dry weight

PNEC sediment (marine water) = 0.0559 mg/kg dry weight

PNEC soil = 0.099 mg/kg dry weight

Benoxacor has been also evaluated in accordance with the principles of the Plant Protection Directive 91/414/EEC. The risk assessments, and proposed endpoints used therein, have been evaluated by EU member States as part of pre-marketing authorisations of herbicidal products used with the safener benoxacor. Although the safener benoxacor has not been considered an active substance in accordance with 91/414/EEC, it has been evaluated with the same rigour with respect to exposure and risk to humans and the environment.

Calculation of PNECsoil with Equilibrium Partitioning Method(EPM)

The calculation of PNECsoil from PNECwater using the equilibrium partitioning method (EPM) is discussed and described in the following guidance documents:

· Guidance on information requirements and chemical safety assessment, Chapter R.10: Characterisation of dose [concentration]-response for environment (May 2008)

· Guidance on information requirements and chemical safety assessment, Chapter R.16: Environmental Exposure Estimation (V2, May 2010)

The calculation details are given in Equations R.10-5, R.16-4, R.16-5, R.16-6, R.16-7, R.16-16 and in Table R.16-9. The involved input, default and output values are given in the following table.

Variable/parameter (unit)	Symbol	Unit	Value	Source
Molecular weight	MOLW	[g/mol]	260.1	Input
Vapour pressure	VP	[Pa]	0.0018	Input
Solubility in water	SOL	[mg/L]	38	Input
Henry’s law constant	HENRY	[Pa/m^3/mol]	0.0123	Output
Gas constant	R	[Pa/m^3/mol/K]	8.314	Default
Temperature at the air-water interface	TEMP	[K]	285	Default
Air-water partitioning coefficient	Kair-water	[-]	5.1996E-06	Output
Partition coefficient organic carbon -water	Koc	[L/kg]	218	Input
Fraction organic carbon in the soil	Foc	[-]	0.02	Default
Soil water partition coefficient	Kpsoil	[L/kg]	4.36	Output
Fraction air in soil	Fair	[-]	0.2	Default
Fraction water in soil	Fwater	[-]	0.2	Default
Fraction solid in soil	Fsolid	[-]	0.6	Default
Bulk density of solids	RHOsolid	[kg/m3]	2500	Default
Soil-water equilibrium partition distribution coefficient	Ksoil-water	[m^3/m^3]	6.740	Output
Bulk density of wet soil	RHOsoil	[kg/m3]	1700	Default
Bulk density of dry soil	RHOsoil dry	[kg/m3]	1500	Default

 

Remark: The value given in guidance R.10 on page 40 for RHOsoil (bulk density of wet soil) is considered wrong (value given: 1150 kg m-3, correct value: 1700 kg m-3; this assumption is supported by Equation R.16-16).

The final calculation of PNECsoil is made according to the following equation:

PNECsoil = (Ksoil-water/RHOsoil) * PNECwater * 1000

               with [PNECsoil]: mg/kg, [PNECwater]: mg/L, [RHOsoil]: kg/m3

Based on PNECwater of 0.022 mg/L and the default values for the bulk density of soil (1700 kg/m3 for wet soil and 1500 kg/m3 for dry soil) the following values PNECsoil, based on EPM, were derived:

·        PNECsoil: 0.087 mg/kg (EPM, based on wet soil)

·        PNECsoil: 0.099 mg/kg (EPM, based on dry soil)

 

 

Conclusion on classification

CLP classification of the substance

For environmental classification, the results of available, reliable acute and chronic aquatic toxicity studies are considered. Aquatic toxicity studies are available for various species from three trophic levels.

Acute aquatic toxicity

All effect concentrations (LC50 or EC50 values) observed in these studies are greater than 1 mg/L, which is the cut-off value for classification for acute aquatic toxicity. One exception is the 72-hour EbC50 = 0.63 mg/L observed in a static algal toxicity test conducted with green algae (Scenedesmus subspicatus) according to OECD TG 201 (Rufli, 1989). This effect concentration is based on a decrease in the biomass of treated cultures. In Note 2 of Table 4.1.0 describing the classification criteria for hazards to the aquatic environment according to Regulation (EC) No. 1272/2008, amended by Commission Regulation (EU) No. 286/2011, it is stated that for classification the effect concentrations from algal toxicity studies should be based on the growth rate, where such data are available. A reliable algal toxicity study providing a growth-rate based ErC50 = 13.5 mg/L is available for benoxacor (Hertl, 1997). Therefore, the EbC50 value of less than 1 mg/L (Rufli, 1989) should not be taken into account for classification. It can be concluded that benoxacor should not be classified for acute aquatic toxicity according to CLP Regulation (EC) No. 1272/2008, amended by Commission Regulation (EU) No. 286/2011.

Chronic aquatic toxicity

Adequate and reliable chronic aquatic toxicity data are available for benoxacor from three long-term studies on species from three trophic levels. The NOEC values observed in long-term studies with fish, daphnids and algae were all in the range from >0.1 mg/L to ≤ 1mg/L. For the classification of long-term aquatic hazard, the results from a prolonged short-term toxicity study with rainbow trout are also considered. This study resulted in a NOEC <0.1 mg/L over the test period of 21 days. In combination with the finding that the substance was not readily biodegradable a precautionary classification into "Category Chronic 1" is derived from all available data according to CLP Regulation (EC) No. 1272/2008, amended by Commission Regulation (EC) No. 286/2011.

The proposed M-factor is 1, which is based on the robust information on the long-term aquatic toxicity of the substance.