Dibutyl phthalate

Endpoint summary

Additional information

Macroorganisms

The effect of DBP on the earthworm,Eisenia fetida, was tested in a short-term contact test (Neuhauser et al., 1985). DBP was within 10 least toxic compound among 44 tested. This result indicates that DBP is not very harmful to soil organisms. Ohtani at al., 2000 investigated whether the toxicity of DBP alters the process of gonadal sex differentiation in genetically maleR. rugosa tadpoles. Presented study was performed using tadpoles in water compartment and therefore this study is considered as unreliable for risk assessment and to derive a PNEC soil.

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. 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).

Plants

Hulzebos et al., 1993 studied the toxicity of 76 priority pollutants to lettuce (Lactuca sativa) in soil and in nutrient solution. In the first case a static and in the latter a semistatic exposure was established. The EC 50 of DBP after 7 days was 387 µg/g soil dw with 95% confidence limits: 262 -570 µg/g soil dw (nominal test concentration).

Ma et al., 2013 evaluated the individual toxicity of di-n-butyl phthalate (DnBP) and bis (2-ethylhexyl) phthalate (DEHP) to sown rape (Brassica chinensisL.) seeds within 72 h (as germination stage) and seedlings after germination for 14 days by monitoring responses and trends of different biological parameters.

No significant effects of six concentrations of DBP ranging from 0 (not treated/NT) to 500 mg/kg on germination rate in soil were observed. However, root length, shoot length, and biomass (fresh weight) were inhibited by DBP. Among all the estimated growth parameters, root elongation may be considered the most sensitive physical parameter with the lowest IC50 under exposure to DnBP, with a value of 456.4 mg/kg of soil.

According to EU RAR for DBP, 2004 in a limited greenhouse experiment in which seeds of corn Zea mays were planted in a sandy soil containing 0 to 20,000 mg DBP/kg, germination was not affected at any concentration. After 3 weeks of exposure, plant height and shoot fresh weight were reduced significantly at 2,000 mg/kg (17% and 25%, respectively); a concentration of 200 mg/kg was without effect (NOEC). After planting a second group of seeds in the soils, plant growth was only reduced at 20,000 mg/kg,

while concentrations <2,000 mg/kg were without effect. These results indicate that plant available DBP levels have decreased through complex formation with soil components and/or by degradation (Shea et al., 1982).

Microroganism

Shanaker et al., 1985 studied biodegradation of three phthalic acid esters including DBP in a garden soil. The soil microflora were able to degrade actively complet DBP up to concentration of 0.472 mg DBP/kg soil under aerobic condition whitin 15 days. There were observed no degradation of DBP in the autoclaved control. NOEC 15d (or 30d) was 0.472 mg of DBP /kg soil. Anaerobiosis created by flooding greatly retarded the degradation of the DBP.

The value was not used for PNEC estimation because the study is not a typical ecotoxicology study and only one concentration of DBP was tested.