Cumene

Endpoint summary

Additional information

Abiotic degradation

Photodegradation in air: Cumene is reported to have reaction rates of 6.14 -7.8 10 -12 cm3 molec-1 s-1 and a DT50 of 1 -2.4 days by Lloyd et al. (1976).

Photodegradation in water: Cumene is reported to have a DT50 of 0.4-5.1 h by Mill et al. (1980).

No experimental data on photo-degradation and hydrolysis of cumene are presented in the EU-RAR (2001) and no more recent experimental data for these endpoints could be identified.

Hydrolysis of cumene is not expected to occur due to the lack of hydrolyzable functional groups.The test substance is regarded as readily biodegradable. Therefore, the performance of an experimental study on hydrolysis is unjustified. Cumene is expected to biodegrade in soil and may volatilize from the soil surface. Therefore, phototransformation in soil is expected to be of no or minor relevance for the fate of cumene in the terrestrial environment and the performance of an experimental study on photodegradation in soil is unjustified.

Biotic degradation

 Two tests on biodegradation of cumene under aerobic and anaerobic conditions in water are available.

Under aerobic conditions a rapid degradation of cumene was detected following the guideline for BOD (biological oxygen demand) measurement over a period of 20 days. A degradation rate of > 60 % was determined within 10 days.

The degradation potential under methanogenic conditions was examined with an anaerobic digesting sludge. Degradation was assessed in terms of net total gas (CH₄plus CO₂) produced, expressed as a percentageof the theoretical production (ThGP). Cumene proved not to be degraded. After an incubation period of 60 days at 35 °C 2 ± 2.8 % degradation was determined.

Cumene can be classified as readily biodegradable under aerobic conditions.

No explicit information about biodegradation of cumene in soil is available. Supporting information reveal that some types of soil bacteria are capable to degrade cumene. Therefore, determination of biodegradability in soil is not regarded necessary

The biodegradation of cumene was analysed in a water-sediment study. The first-order mineralization rate constant at the test concentration of 2.5 mg/L was calculated to be 0.02 d-1 (DT50 35 d).

Bioaccumulation

The bioconcentration factor BCF of cumene was calculated using BCFBAF (v 3.00). The calculation yielded a BCF of 94.69 L/kg wet wt taking into account the measured log Kow of 3.5. Based on the result, a low potential for bioconcentration is to be expected, which is confirmed by an experimental BCF of 35.5 found in a poorly documented bioconcentration study with fish (C. auratus). Moreover, a metabolism study in rat (see Toxicokinetics chapter) has shown that “no bioaccumulation potential was found based on study results”

In summary, there is no concern regarding the bioaccumulation of cumene in aquatic organisms.

Transport and distribution

Data on the sorption of cumene are given in the EU-RAR (2001) in section 3.1.2.1. A value of 884 L/kg is used for PEC-calculations which is also recommended for the current assessment.

Data on Henry's law constant of cumene is presented in the EU-RAR (2001) in section 1.3 (physico-chemical properties). It is reported that cumene has a Henry's law constant of 1010.80 Pa m³/mol. This value is also recommended for the current assessment.

Based on the recommended distribution constants air (99.7%) is the most important compartment for cumene.

The results for the other compartments were water (0.16%), soil (0.02%), and sediment (0.08%).