Implications of Bioremediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soils for Human Health and Cancer Risk
[3]
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, United States; Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, United States
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, United States; Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
Background: Bioremediation uses microorganisms to degrade polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. Its success is largely evaluated through targeted analysis of PAH concentrations in soil and cancer risk (exposure) estimates. However, bioremediation often fails to significantly degrade the most carcinogenic PAHs and can initiate formation of more polar metabolites, some of which may be more toxic. Objectives: We aimed to investigate whether the cancer risk associated with PAH-contaminated soils was reduced post-bioremediation and to identify the most effective bioremediation strategies for degrading the carcinogenic and high molecular weight (≥MW302) PAHs. Methods: Pre- and post-bioremediation concentrations of eight B2 group carcinogenic PAHs in soils were collated from the literature and used to calculate excess lifetime cancer risks (ELCR) for adult populations exposed via non-dietary ingestion, per current U.S. Environmental Protection Agency (USEPA) recommendations. Due to the nature of the collated data (reported as mean concentrations ± standard deviations pre- and post-bioremediation), we used simulation methods to reconstruct the datasets and enable statistical comparison of ELCR values pre- and post-bioremediation. Additionally, we measured MW302 PAHs in a contaminated soil prior to and following treatment in an aerobic bioreactor and examined their contributions to cancer risk. Results: 120 of 158 treated soils (76%) exhibited a statistically significant reduction in cancer risk following bioremediation; however, 67% (106/158) of soils had post-bioremediation ELCR values over 10 fold higher than the USEPA health-based ‘acceptable’ risk level. Composting treatments were most effective at biodegrading PAHs in soils and reducing the ELCR. MW302 PAHs were not significantly degraded during bioremediation and dibenzo(a,l)pyrene, alone, contributed an additional 35% to the cancer risk associated with the eight B2 group PAHs in the same bioremediated soil. Conclusions: Bioremediation strategies often fail to reduce carcinogenic PAH concentrations in contaminated soils below USEPA acceptable cancer risk levels. Additionally, MW302 PAHs and ‘unknown’ metabolites (compounds not routinely measured) are not included in current cancer risk assessments and could significantly contribute to soil carcinogenicity.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1406682
- Report Number(s):
- PNNL-SA-122323; 453060036
- Journal Information:
- Environmental Science and Technology, Vol. 51, Issue 17; ISSN 0013-936X
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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