Earthworm Comet Assay for Assessing the Risk of Weathered Petroleum Hydrocarbon Contaminated Soils: Need to Look Further than Target Contaminants

  • Kavitha RamadassEmail author
  • Thavamani Palanisami
  • Euan Smith
  • Srinithi Mayilswami
  • Mallavarapu Megharaj
  • Ravi Naidu


Earthworm toxicity assays contribute to ecological risk assessment and consequently standard toxicological endpoints, such as mortality and reproduction, are regularly estimated. These endpoints are not enough to better understand the mechanism of toxic pollutants. We employed an additional endpoint in the earthworm Eisenia andrei to estimate the pollutant-induced stress. In this study, comet assay was used as an additional endpoint to evaluate the genotoxicity of weathered hydrocarbon contaminated soils containing 520 to 1450 mg hydrocarbons kg−1 soil. Results showed that significantly higher DNA damage levels (two to sixfold higher) in earthworms exposed to hydrocarbon impacted soils. Interestingly, hydrocarbons levels in the tested soils were well below site-specific screening guideline values. In order to explore the reasons for observed toxicity, the contaminated soils were leached with rainwater and subjected to earthworm tests, including the comet assay, which showed no DNA damage. Soluble hydrocarbon fractions were not found originally in the soils and hence no hydrocarbons leached out during soil leaching. The soil leachate’s Electrical Conductivity (EC) decreased from an average of 1665 ± 147 to 204 ± 20 µS cm−1. Decreased EC is due to the loss of sodium, magnesium, calcium, and sulphate. The leachate experiment demonstrated that elevated salinity might cause the toxicity and not the weathered hydrocarbons. Soil leaching removed the toxicity, which is substantiated by the comet assay and soil leachate analysis data. The implication is that earthworm comet assay can be included in future eco (geno) toxicology studies to assess accurately the risk of contaminated soils.


Comet Assay Petroleum Hydrocarbon Total Petroleum Hydrocarbon Soil Leachate Total Petroleum Hydrocarbon Concentration 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This research was supported by the Project funded by Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE).


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Kavitha Ramadass
    • 1
    Email author
  • Thavamani Palanisami
    • 2
    • 3
  • Euan Smith
    • 1
  • Srinithi Mayilswami
    • 1
  • Mallavarapu Megharaj
    • 2
    • 3
  • Ravi Naidu
    • 2
    • 3
  1. 1.Centre for Environmental Risk Assessment and Remediation (Changed as Future Industries Institute)University of South AustraliaAdelaideAustralia
  2. 2.Global Centre for Environmental Research (GCER)University of NewcastleNewcastleAustralia
  3. 3.CRC for Contamination Assessment and Remediation of the EnvironmentUniversity of NewcastleNewcastleAustralia

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