Bis(4-chlorophenyl) sulphone

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.006 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.008 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.001 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

100 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.12 mg/kg sediment dw

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.012 mg/kg sediment dw

Assessment factor:

1 000

Extrapolation method:

assessment factor

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.355 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

1 mg/kg food

Assessment factor:

30

Conclusion on classification

As shown in all studies conducted according to international guidelines DCDPS is not acutely toxic to algae, daphnids and fish.

Assessment of Long-term Toxicity of DCDPS

The finding on classification in the registration dossier (from the Section 6 endpoint summary, as cited above) correctly states that “the NOECs for chronic toxicity to daphnia and algae are <1 mg/L”, but does not incorporate these results into the environmental classification. The 21-d NOEC of 0.32 mg/L and EC₅₀ of 0.61 mg/L in daphnids, and the 72-h NOEC of 0.28 mg/L coupled with the observed growth inhibition in algae (at measured test concentrations of 0.49 mg/L and 0.80 mg/L) are indicators of the long-term toxicity of DCDPS at concentrations below the water solubility. The long-term daphnid reproduction study and the algal growth inhibition are key studies assigned Klimisch-1 and Klimisch-2 reliability scores, respectively, and are therefore acceptable as the basis for hazard assessment.  The limitation on the estimation of the EC₅₀in the algal growth inhibition study (the basis for the assigned reliability value of Klimisch-2, as described above) does not adversely affect the reliability of the 72-h NOEC value for purposes of hazard classification.

The reported long-term NOEC of 0.05 mg/L derived from the 35-day fish study (NITE, 2002) was defined as a supporting study and thus is not an adequate basis for environmental classification. The endpoint study summary in Section 6.1.2 of the registration dossier states that the “test concentrations chosen did not permit the determination of threshold level for the lethal and other observable effects because of the absence of a LOEC. Thus the NOEC for chronic exposure is assigned to this EC₀value (0.05 mg/L), which constitutes a large safety margin to the assumed chronic effect levels.” Although the NOEC defined in the long-term fish toxicity supporting study is inadequate for use in hazard classification, it does indicate the absence of long-term toxicity in fish, and supports the quantification of long-term toxicity in the basis of the NOEC values from the key studies on the other two trophic levels.

Table 4.1.0(b) of EC Regulation 1272/2008 states that the classification criteria should be used when “there are adequate chronic toxicity data available”. The key studies on long-term reproduction toxicity in daphnids and the algal growth inhibition test are adequate to define chronic toxicity in accordance with Table 4.1.0(b) of EC Regulation No. 1272/2008 for non-rapidly biodegradable substances such as DCDPS (which was shown to be non-rapidly biodegradable in Section 5.2 of the registration dossier). Since the chronic NOEC values are below the limit of water solubility, and fall within the range of > 0.1 mg/L and ≤ 1 mg/L, the environmental hazard classification should be Chronic Category 2. 

Conclusion

Based on the observed NOEC values from both the long-term daphnid reproduction study (0.32 mg/L) and algal growth inhibition study (0.28 mg/L) on DCDPS, and the non-rapid biodegradability of the substance, the environmental hazard classification should be Chronic Category 2 in accordance with Table 4.1.0(b) of EC Regulation 1272/2008. The classification should be accompanied by hazard statement H411 (“Toxic to aquatic life with long lasting effects”).