Toxicity effects of di-(2-ethylhexyl) phthalate to Eisenia fetida at enzyme, cellular and genetic levels

Di-(2-ethylhexyl) phthalate (DEHP) is a dominant phthalic acid ester (PAE) that has aroused public concern due to its resistance to degradation and its toxicity as an endocrine-disrupting compound. Effects of different concentrations of DEHP on Eisenia fetida in spiked natural soil have been studied in the body of the earthworm by means of soil cultivation tests 7, 14, 21 and 28 days after exposure. The results indicated that, in general, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, metallothionein (MT) content, the expression of heat shock protein 70 (HSP 70) and all the tested geno-toxicity parameters are promoted as time elapses and with increasing concentration of DEHP. However, peroxidase (POD) activity, neutral red retention time (NRRT) and mitochondrial membrane potential difference values were found to decrease even at a low concentration of DEHP of 1 mg kg-1 soil (p<0.05). Clear toxic effects of DEHP on E. fetida have been generally recognized by means of the disturbance of antioxidant enzyme activity/content and critical proteins, cell membrane and organelle disorder and DNA damage estimated by length of tail, tail DNA ratio, and tail moment parameters. A concentration of DEHP of 3 mg kg-1 may be recommended as a precaution against the potential risk of PAEs in soils and for indicating suitable threshold values for other soil animals and soil micro-organisms.