[1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide

Endpoint summary

Additional information

Water and sediment compartments

The hydrolysis of [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[1,1-dimethylethyl] peroxide was evaluated in a study performed in accordance with OECD testing guideline 111 and EPA OPPTS 835.2110 under GLP requirements.

The results from the hydrolysis test indicate that 64.6, 71.4 and 77.3% of the reaction were observed after 5 days at pH 4, 7 and 9 solutions respectively, at 50 °C. The test has demonstrated that the substance is hydrolytically stable at pH 2.6 after 24 hours. The degradation rates were calculated using first order kinetics as follows:

 

At 50°C:

 

pH 4 : half-life = 7.9 d

pH 7: half-life = 10.3 d

pH 9: half-life = 13.4 d

 

Extrapolated values at 25°C, using the Arrhenius equation:

 

pH 4 : half-life = 56.4 d

pH 7: half-life = 74.7 d

pH 9: half-life = 96.5 d

 

 

The ready biodegradability was evaluated in a study performed in accordance with OECD testing guideline 301 D and GLP requirements. The test substance is not biodegraded in the closed bottle test, and therefore should not be classified as readily biodegradable. This lack of biodegradation is not due to toxicity of the test compound because the endogenous respiration is not inhibited by bis (tert-butyl peroxy isopropyl) benzene.

Sediment and water compartment exposition is likely. Besides, based upon the adsorption potential of the substance of interest, a study was conducted to determine the biodegradation of [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[1,1-dimethylethyl] peroxide in water/sediment simulation test, according to US EPA guideline. The substance was not found in the water layers at all time points. In the sediment layer, an average of 94.7% of the applied dose was detected at day 0. The substance has decreased to an average of 9.7% of the applied dose at day 90. The half-life in sediment/water compartment under anaerobic conditions was determined as 29 days. Tert-butanol, the main expected breakdown product, was detected in water and sediment layers at all time point (except day 0) but below a quantifiable level until day 90: it represented an average of 61.5% of the test substance applied dose.

 

An OECD 309 was performed given the following rate of dissipation of combine (1,3)/(1,4)bis-peroxide from water over 61 days of incubation at 12 +/-2°C was determined to be 17.7 days by single-first order (SFO) kinetics. The rate of dissipation of (1,3)bis-peroxide from water over 61 days of incubation at 12 +/-2°C was determined to be 16.7 days (SFO). The rate of dissipation of (1,4)bis-perocide from water over 61 days of incubation at 12 +/-2°C was determined to be 19.3 days (SFO). Nevertheless due to lack of mass balance, it is not possible to make any definitive conclusions on whether volatilization or mineralization occurs when the test substance leaves the test system.

Therefore, a feasability study for an OECD 308 was performed.  The results of this study demonstrate the feasibility of conducting a full OECD  Guideline 308 study to investigate degradation of 1,3-bis(tert-butylperoxy isopropyl)benzene and 1,4-bis(tert-butylperoxy isopropyl)benzene in the aerobic and anaerobic aquatic sediments.

Thus the fate of bis peroxide, a mixture of 1,3-bis(tert-butylperoxy isopropyl)benzene and 1,4-bis(tert-butylperoxy isopropyl)benzene, has been studied in two natural aquatic sediment systems under laboratory conditions following the OECD 308 guideline using radiolabelled substances. A mixture of 1,3 and 1,4 radiolabelled bis peroxides was applied to silica gel and added to the sediment layer of samples of two aquatic sediment types.  This method of application was used to avoid losses by volatilization and to obtain a good mass balance.  As a result, levels detected in the water phase were low compared to the sediment phase.  The total recovery of radioactivity, or mass balance, for both aquatic sediments were between 83.9% and 97.2% applied radioactivity (AR) throughout the incubation period. Bis peroxide dissipated rapidly from the water of aquatic sediment systems with none detected from 30 days after treatment onwards.  This gave an estimated DT₅₀ values of 3.4 days (Calwich Abbey Lake) and 1.0 days (Lumsdale Middle Pond).  After 100 days incubation bis peroxide accounted for 2.0 to 4.7% of applied radioactivity in the overall system, corresponding to an estimated DT₅₀ values of 10.5 days (Calwich Abbey Lake) and 12.6 days (Lumsdale Middle Pond) at 12°C. Bis peroxide was degraded to up to 5 major components and 14 minor components in the Calwich Abbey lake system.  The main component formed eluted at 3.1 minutes (component 4), accounting for a maximum of 38.7% AR in the total system at 59 days after treatment and then declined.  In the Lumsdale Middle pond 3 major and 11 minor components were formed.  The main component formed eluted at 3.2 minutes (component 3), accounting for a maximum of 40.9% AR in the total system at 30 days after treatment and then declined.  One component was identified as 2,2-(1,4-phenylene)di(propan-2-ol).  The 1,3 isomer was also shown to co-elute with this reference.

The available OECD308 data support the OECD309 data (observed in water not air) and also demonstrated rapid primary (bio)degradation. The OECD 308 showed sufficient recovery in both preliminary and definitive testing indicating a valid result according to the test guideline. Therefore, it is concluded that primary degradation of the test material will occur in the environment. Further assessment of PBT properties should therefore be based on the properties of the transformation products (2,2-(1,4-phenylene)di(propan-2-ol) and 2,2-(1,3-phenylene)di(propan-2-ol)) as indicated in Reach Guidance on PBT assessment: R11.23.2.1 Page 24 2017. If this data is not available, it should be generated. The PBT assessment cannot therefore be stopped until conclusive data on these products is available.

 

 

Soil compartments

Chemicals can reach the soil via several routes:

 

1.                 Application of sewage sludge in agriculture.

Organic peroxides, when released into the sewage of a plant production or of a downstream’s user plant, are treated with other substances in dedicated sewage treatment plants. The activated sludge stemmed from these sewage treatment plants are then extracted and treated as chemical waste

From the production plant, the release of organic peroxide into the sewage is very limited, not to say completely negligible. The waste water from production plant is usually treated: at least a physical/chemical treatment, which will neutralize potential residual organic peroxide, and that can be followed by a biological treatment. So it is expected that organic peroxides won’t be present in sludge.

Regarding the rest of the lifecycle, organic peroxides are mainly used as cross-linking agent/polymerization initiator for the production of resins/rubbers/polymers. Based upon the fact that organic peroxides are totally consumed during the process (>99%) and that those processes are water-free (so no production of sewage sludge), it is assumed that the soil is not exposed to organic peroxides via use of sludge.

As a consequence, we can assume that soil is not exposed to organic peroxides via the application of sewage sludge in agriculture.

 

2.                 Direct application of chemicals.

Based on the uses inventoried for organic peroxides we can consider that there is no direct application of these substances on the soil compartment. Hereunder, the relevant Environmental Release Categories (ERC), as described in guidance R12 (version 2.0, dated 7/11/2010)

 

3.                 Deposition from the atmosphere.

Deposition from the atmospheric compartment involves volatilization, vaporization or direct release of a considered substance into the atmosphere. Due to their dangerous intrinsic physico-chemical properties, organic peroxides are carefully handle in closed systems and their transport and production are ruled by several regulations. Based on organic peroxides uses too, we may assume that deposition on soil from the atmosphere is unexpected.

 

Bioaccumulation in aquatic organisms

A bioaccumulation in fish study according to the OECD 305 using the aqueous exposure was performed under flow-through conditions. The results are based on the time-weighted average as requested in the Echa decision. Based on this, the steady-state BCFss is equal to 1083 L/Kg and the steady-state BCFss normalised to a fish lipid content of 5% is equal to 1635 L/Kg.The lipid normalised and growth corrected kinetic BCFkLg value is equal to 1820 L/kg.