Evaluation of DNA damage and antioxidant system induced by di-n-butyl phthalates exposure in earthworms (Eisenia fetida)

• We used SOD, CAT, MDA content and DNA damage as biomarkers to analyze the relationship between DNA damage and oxidative stress and to evaluate the genotoxic effect of DBP on earthworms (Eisenia fetida).
• DBP induced serious oxidative damage on earthworms and induced the formation of reactive oxygen species (ROS) in earthworms.
• The excessive generation of ROS caused damage to vital macromolecules including lipids and DNA.

Di-n-butyl phthalates (DBP) are recognized as ubiquitous contaminants in soil and adversely impact the health of organisms. The effect of DBP on the activity of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT), malondialdehyde (MDA) content and DNA damage were used as biomarkers to analyze the relationship between DNA damage and oxidative stress and to evaluate the genotoxic effect of DBP on earthworms (Eisenia fetida). DBP was added to artificial soil in the amounts of 0, 5, 10, 50 and 100 mg per kg of soil. Earthworm tissues exposed to each treatment were collected on the 7th, 14th, 21st, and 28th day of the treatment. The results showed that SOD and CAT levels were significantly inhibited in the 100 mg kg−1 treatment group on day 28. MDA content in treatment groups was higher than in the control group throughout the exposure time, suggesting that DBP may lead to oxidative stress in cells. A dose–response relationship existed between DNA damage and total soil DBP levels. The comet assay showed that increasing concentrations of DBP resulted in a gradual increase in the OTM, Comet Tail Length and Tail DNA %. The degree of DNA damage was increased with increasing concentration of DBP. These results suggested that DBP induced serious oxidative damage on earthworms and induced the formation of reactive oxygen species (ROS) in earthworms. The excessive generation of ROS caused damage to vital macromolecules including lipids and DNA. DBP in the soils were responsible for the exerting genotoxic effects on earthworms.