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The substance is manufactured as a 50% aqueous solution ans used usually in a much more diluted aqueous solution. Therefore the 50% aqueous solution as test substance is used to assess the environmental hazard of the substance for registration.

All aquatic toxicity tests were carried out with analytical monitoring using ion chromatography. Although the aqueous solution was used as test substance, the results refers to the measured concentrations of 2-phophonobutane-1,2,4-tricarboxylic acid and the effect concentrations obtained in these tests can therefore be used for the hazard assessment of the substance.

Fish

A LC50(96h) of >1042 mg/L was concluded from and a NOEC of =1042 mg/L

was found in a prolonged toxicity study in fish (OECD Guideline 204; species: zebra danio) over 14 days (Caspers; Müller, 1994).

Thus, the LC50(96h) is higher than the concentration of the limit test at 100 mg/L.

In respect of classification and labelling no further testing is required and Bayhibit AM regarded as not acute toxic to fish.

Daphnia

A prolonged toxicity study in Daphnia magna (covering to OECD guidelines 202 and 211) was performed over 21 days and the effect on mobility was determined:

EC 50 (immobilisation, 21d): >1071 mg/L.

Based on this result, an EC (24h) and a EC50 (48h) value was concluded of >1071 mg/L each (Caspers; Müller, 1994).

Thus, these EC50 values are higher than the concentration of the limit test at 100 mg/L.

In respect of classification and labelling no further testing is required and Bayhibit AM is regarded as not acute toxic to aquatic invertebrates (daphnia).

Other study results refer to effects on reproduction:

EC 50 (reproduction, 21d): >329 to < 1071 mg/L

NOEC (reproduction, 21d): 104 mg/L

LOEC (reproduction, 21d): 329 mg/L

Algae

The results found in the growth inhibition test of Bayhibit AM in algae are

EC50 (biomass) >140 mg/L and EC50 (growth rate) >1081 mg/L (Caspers; Müller, 1994).

As this values are higher than 100 mg/L, no ecotoxicological hazard is indicated for algae (respective aquatic environment) even it is the most sensitive species (compared to daphnia and fish).

Microoganisms

To assess the toxicity of Bayhibit AM to microorganisms, a study was conducted in accordance with Council Regulation (EC) No 440/2008, Method C.11 "Activated sludge respiration inhibition" (2008) - equivalent to OECD Guideline 209 (1984). The activated sludge was exposed to a 50.4 % water solution of Bayhibit AM at different concentrations. The respiration rate of each mixture was determined after aeration periods of 3 hours.

Bayhibit AM showed 4.3 % respiration inhibition of activated sludge at a test item concentration of 1000 mg/L.

The effect value related to nominal concentration of the water solution, since no analytical monitoring was performed (Neuhahn, 2008). Therefore the effect concentration is converted based upon the water content of the test item, resulting in an EC10 and EC50 of 504 mg/L.

Bayhibit AM is regarded of low toxicity towards microorganisms.

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