1,2,4-trichlorobenzene

Endpoint summary

Description of key information

For transported isolated intermediates according to REACh, Article 18, this endpoint is not a data requirement. However, data is available for this endpoint and is thus reported under the guidance of "all available data".

 

Bioaccumulation aquatic/ sediment

With a logKow >4.0, 1,2,4-TCB has a bioaccumulation potential. This was confirmed by several tests on different fish species and other aquatic species. The bioconcentration factor BCF for fish/water (whole body) is according to the realistic worstcase concept approximately 2000. Biological concentration factors of 50 - 2300 (Smith et al., 1981), calculated on fresh weight, and of up to 23790 (Geyer et al., 1985), calculated on fat content, have been found. In an experimental study similar to OECD guideline 305C, the BCF value in Cyprinus carpio after exposure to 1,2,4-TCB over a period of 56d was determined at two dose levels (0.04 and 0.004 mg/L) revealing values between 805 (whole body) and 17303 (total liquid content) (Markert, 1984).

The available data indicate that 1,2,4-trichlorobenzene can be considered as potentially accumulative (BCF values over 2000 were reported).

 

Bioaccumulation terrestrial

The accumulation in earthworms was studied by Beyer (1996) in a standard soil (69.7% sand, 20% clay, 10% peat and 0.3% CaCO3) where clitellate, i.e. sexually mature, Lumbricus terrestris were exposed to 10 ppm 1,2,4-TCB during 8 and 26 weeks. The BCF was 0.09 in the 8-week experiment and 0.06 in the 26-week experiment (Beyer, 1996). Because of 1,2,4 -TCB's high adsorption capacity and the high-soil organic matter content in the study, BCF would be expected to be lower than under most field conditions. Taking these results into consideration, results from other organochlorines including hexachlorobenzene indicate according to Beyer (1996) that BCF of 1,2,4-TCB for earthworms may be around 1 in soil with normal ranges of organic matter. Beyer (1996) shows that BCF earthworm for chlorobenzenes increases with the degree of chlorination and that the BCF of hexachlorobenzene for Lumbricus terrestris was 0.27. He compares this result in a study with an OECD standard soil with 10% organic matter with a study where a BCF for Lumbricus terrestris was 2 to 3 in a soil with 2.6% organic matter (Lord et al., 1980).
In comparison by employing the equilibrium method, the bioconcentration factor for earthworm, according to the TGD (equations 62 and 63) and taking the soil-water partition coefficient into account, is estimated to be: BCF earthworm = K earthworm-porewater . ((RHOsoil.10-3)/Ksoil-water) = 0.25.0.16.Kow.(1.700/42.2) =18; i.e an order of magnitude higher than the BCF based on experimental data, which however is regarded more reliable, because of the existence of comparable results in several studies with other chlorinated benzenes.