Bis(α,α-dimethylbenzyl) peroxide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

2.34 µg/L

Assessment factor:

50

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

no hazard identified

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:

2.24 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

no exposure of sediment expected

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.447 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

The following effect concentrations and considerations are used for the assessment:

Aquatic toxicity

Short-term toxicity

Dicumyl peroxide showed no acute toxicity in any of the test organisms when tested up to the maximum water soluble concentration.

Long-term toxicity to fish

According to Annex IX of Regulation (EC) No 1907/2006 chronic fish toxicity tests should be proposed if the chemical safety assessment indicates the need to investigate further the effects on fish. However, the existing information is sufficient for risk assessment. Therefore, testing of chronic fish toxicity is not considered to be necessary.

Long-term toxicity to aquatic invertebrates

The 21-day-chronic toxicity of dicumyl peroxide to Daphnia magna was studied under static renewal conditions. The parental 21-day EC₅₀ based on mortality was 0.195 mg/L, the 21-day EC₅₀ for reproduction was 0.231 mg/L. The 21-day NOEC based on average cumulative number of offspring was 0.117 mg/L, the 21-day LOEC was 0.247 mg/L. Sublethal effects were observed at 0.247 mg/L (body colour brightening and growth inhibition, besides lethargy, immobility, and activity drop). No symptoms were observed in the other concentration levels. Dead larvae were observed in all the test levels, with 0.247 mg/L slightly higher than the control. Fallen eggs were also observed in all test levels, the 0.117 mg/L level showing a statistically significant difference. Production of offspring in the treated groups indicated that dicumyl peroxide had an effect on reproduction at concentrations greater than 0.117 mg/L. The most sensitive endpoint was reproduction.

Toxicity to algae

In a 72 hour toxicity study, cultures of Pseudokirchnerella subcapitata (reported as Selenastrum capricornutum), strain ATCC 22662, were exposed to dicumyl peroxide. Both the 72 h E_bC₅₀ and the 72 h NOE_bC values based on cell density were > 20 mg/L and 3.20 mg/L, respectively (nominal). Both the 24-48 h E_rC₅₀ and the 24-72 h E_rC₅₀ were > 20 mg/L, whereas the 24–48 h NOEC and the 24–72 h NOEC values based on growth rate were 8 mg/L, respectively (nominal). Both the EC₅₀ and the NOEC indicated no effect up to maximum water soluble concentrations.

Toxicity to microorganisms

In an activated sludge respiration inhibition test, secondary activated sludge of a sewage treatment plant receiving predominantly domestic sewage was exposed to dicumyl peroxide adsorbed on silica gel at a concentration of 1000 mg/L (nominal) under static conditions for 30 min, in accordance with OECD guideline 209 (activated sludge, respiration inhibition test). The NOEC based on respiration inhibition was > 1000 mg/L.

Toxicity to sediment dwelling organisms

The equilibrium partitioning method has been used for assessing the risk to sediment organisms. In view of the log P_ow of 5.6 a potentially increased hazard to sediment organisms is indicated, requiring application of an additional assessment factor to the EPM-based RCR (see guidance on information requirements and chemical safety assessment, part E: risk characterisation). However, the chemical safety assessment using the EPM gives no indication for an unacceptable risk towards sediment organisms. Therefore, in accordance with Annex X, column 2, point 9.5.1 of Regulation (EC) No 1907/2006, testing of sediment organisms is not considered to be required.

Terrestrial toxicity

The equilibrium partitioning method has been used for assessing the risk to soil organisms. In view of the log P_ow of 5.6 a potentially increased hazard to soil organisms is indicated, requiring application of an additional assessment factor to the EPM-based RCR (see guidance on information requirements and chemical safety assessment, part E: risk characterisation). However, the chemical safety assessment using the EPM gives no indication for an unacceptable risk towards soil organisms. Therefore, in accordance with Annex X, column 2, point 9.5.1 of Regulation (EC) No 1907/2006, testing of soil organisms is not considered to be required.

According to REACH Annex X, 9.6.1, column 2, there is no need for testing toxicity to birds. Dicumyl peroxide is unlikely to accumulate in the food chain based on the highest experimental BCF value.

Conclusion on classification

Due to the fact that dicumyl peroxide showed no acute toxicity towards algae, Daphnia and fish at maximum water solubility there is no need to change the current legal classification. The substance is legally classified as aquatic chronic 2 (H411) according to the CLP Regulation (1272/2008), and as R51/53 according to the DSD (67/548/EEC).