Dibutyl phthalate

Toxicity to terrestrial arthropods

Description of key information

For DBP, adult reproduction was a more sensitive endpoint than was survival, with an EC10 and EC50 of 14 and 68 mg/kg, respectively.
 Juvenile molting frequency seems to be a sensitive parameter, because number of cuticles produced by young springtails was reduced at 1 mg/kg.
  Toxicitywas reduced when soil spiked with DBP was stored at 20°C for a period of up to 28 d before adding the animals. Reduction in
toxicity of DBP may be due a combination of degradation, evaporation, and adsorption of DBP to soil material. 

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil dwelling arthropods:

10 mg/kg soil dw

Long-term EC10, LC10 or NOEC for soil dwelling arthropods:

0.5 mg/kg soil dw

Additional information

Jensen et al. (2001) studied the effects of DEHP and DBP on the collembolan Folsomia fimetaria. Survival and reproduction on adult individuals (aged 23-26 days) were investigated by the use of small microcosms. The organisms were exposed for 21 days to DBP in moist soil (< 1.5% organic carbon) at the nominal concentrations of 0, 100, 250, 500, 750 and 1000 mg/kg dwt.

The DBP was added in acetone to dry soil. The acetone was evaporated and the soil remoistened with water before start of the experiment. Effects of the two phthalates on newly hatched collembolans were also tested in a multidish system. The endpoints were juvenile mortality, growth, and development (number of cuticles), the nominal test concentrations were 0, 1, 5, 10, and 25 mg DBP/ kg soil (dwt), and the test duration was six weeks.

To study the time course of observed DBP toxicity and to link DBP toxicity with its chemical fate in soil, soil spiked with DBP was stored at 20°C for 3, 7, 14, or 28 d before adding animals. After adding animals, tests were conducted as for the 21-d reproduction test described above. Four replicates of the test concentrations of DBP at 0, 50, 100, 200, 300, and 500 mg/kg were made.

DBP caused increased adult mortality at 250 mg/kg and juvenile mortality at 25 mg/kg. For DBP, adult reproduction was a more sensitive endpoint than was survival, with an EC10 and EC50 of 14 and 68 mg/kg, respectively.

Juvenile molting frequency seems to be a sensitive parameter, because number of cuticles produced by young springtails was reduced at 1 mg/kg ( EC10 = 0.5 mg/kg dry wt and EC50 was more than 10 mg/kg dry wt).

Toxicity was reduced when soil spiked with DBP was stored at 20°C for a period of up to 28 d before adding the animals. Reduction in toxicity of DBP may be due a combination of degradation, evaporation, and adsorption of DBP to soil material. This was confirmed by chemical analyses, which showed a rapid initial disappearance followed by a much slower disappearance. The results lead to the overall conclusion that significant adverse effects of phthalates on collembolans are not likely to occur as a result of normal sewage sludge application.