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Review of Health Effects of Naphthenic Acids: Data Gaps and Implications for Understanding Human Health Risk Open Access

Descriptions

Author or creator
Kindzierski, W.
Jin, J.
Gamal El-Din, M.
Additional contributors
Subject/Keyword
Oil Sands
Alberta
Tailings
Tar Sands
Naphthenic Acid
OSRIN
Oilsands
TR-20
Tarsands
Human Health Risk Assessment
Type of item
Report
Language
English
Place
Canada, Alberta, Fort McMurray
Time
Description
Oil sands mining involves removal of water from the Athabasca River basin in northeastern Alberta. Water produced during the extraction of bitumen from oil sands is referred to as oil sands process water (OSPW). Information on the likelihood of human exposure to OSPW derived naphthenic acids and toxicological (dose-response) data are needed to have a complete understanding of the human health risk of these compounds. A review of literature was undertaken as a first step in framing potential human health risk associated with exposure to OSPW-derived naphthenic acids in surface water. Specifically, this review focused on chemical characteristics of, and potential toxicological effects related to, OSPW derived naphthenic acids. General Chemical Characteristics of Naphthenic Acid Mixtures in OSPW There are several important findings of the review with regard to chemical characteristics of naphthenic acid mixtures in oil sand process waters: • OSPW represents a complex mixture of naphthenic acids along with other organic chemicals that can also contribute to potential toxicity of the mixture. • There is a difference in the distribution of organic compounds and their contribution to potential toxicity of OSPW that is fresh (i.e., OSPW recently produced from the oil sands extraction process) versus OSPW that is allowed to age (i.e., OSPW that has been aged for a number of years in inactive storage ponds or pit lakes). Aged OSPW contains higher molecular weight, multi ring naphthenic acids that have been shown to be more resistant to microbial degradation and less potent in toxicity to biological organisms. • An understanding of the forms and composition of OSPW derived naphthenic acids and other organic compounds present in fresh and aged OSPW, and the effect of aging and aging environment on this composition, and variation in OSPW composition across oil sands processes is incomplete. Human Exposure Evidence OSPW-derived naphthenic acids are not used by the human population and the potential for human exposure in the oil sands region will arise from their presence in surface water or from potential future release of reclaimed OSPW to surface water. Based on the information reviewed, it was found that: • Direct contact activities with surface water (e.g., ingestion and skin contact) represent a plausible way in which human exposure may occur to OSPW derived naphthenic acids. • Low water to air transfer properties and dilute concentrations of aged and reclaimed OSPW derived naphthenic acids provide no meaningful scientific evidence to support the inhalation pathway as being important for potential human exposure. • Low octanol water partition values and apparent rapid depuration of aged OSPW-derived naphthenic acids offer no meaningful scientific evidence to support the fish ingestion pathway as being important for potential human exposure to these compounds. Toxicological Evidence Toxicity information of interest for understanding human health risk from chemicals in the environment includes: acute toxicity, subchronic/chronic adverse responses (e.g., weight loss, immunosuppression, etc.), neurotoxicity, developmental and reproductive toxicity, and genetic toxicity (mutagenicity and carcinogenicity). A general finding of this review is: • Toxicological evidence observed for commercial naphthenic acids derived from crude oils and/or commercial naphthenic acid salts will not be representative of naphthenic acids in aged and reclaimed OSPW. Higher molecular weight, multi ring naphthenic acids, which are more resistant to microbial degradation and less potent in toxicity to biological organisms, are the forms reported to be present in aged and reclaimed OSPW. • OSPW derived naphthenic acids come from bitumen which is considered to be extensively biodegraded petroleum, whereas commercial naphthenic acids are typically prepared from petroleum sources that have not undergone extensive biodegradation. Therefore, potential human toxicity and corresponding human exposure limits for OSPW derived naphthenic acids should not be inferred from studies of commercial naphthenic acids. Acute Toxicity Naphthenic acids found within crude oils exhibit similar oral toxicity to table salt. Acute toxicity testing in rats revealed behavioral and histopathological effects from a single administration of OSPW derived naphthenic acids, but at a dosage 50 times a worst case environmental exposure for small mammalian wildlife. This dosage is a not realistic exposure condition that would apply to humans in the oil sands region. Subchronic/Chronic Noncarcinogenic Toxicity A finding of this review is: • Based upon limited information reviewed, uncertainty remains in the understanding of toxicokinetic (fate in the body) and toxicodynamic (mode of action and dose response) information needed to infer noncarcinogenic human exposure related responses to naphthenic acids and other acid-extractable organics present in aged and reclaimed OSPW. A recommendation of this review is: • There is a need to further examine potential subchronic/chronic toxicity of naphthenic acids and other acid-extractable organics present in aged and reclaimed OSPW. Developmental and Reproductive Toxicity A finding of this review is: • Based upon limited information reviewed, uncertainty remains about knowledge of developmental and reproductive toxicity of naphthenic acids and other acid-extractable organics present in aged and reclaimed OSPW. A recommendation of this review is: • There is a need to further examine developmental and reproductive toxicity endpoints of naphthenic acids and other acid-extractable organics present in aged and reclaimed OSPW using in vitro/in vivo bioassay testing focusing on cellular response pathways. Genetic Toxicity A finding of this review is: • Based upon limited information reviewed, uncertainty remains about knowledge of genetic toxicity of naphthenic acids and other acid-extractable organics present in aged and reclaimed OSPW. A recommendation of this review is: • There is a need to further examine genetic toxicity endpoints (including carcinogenic endpoints) of naphthenic acids and other acid-extractable organics present in aged and reclaimed OSPW using in vitro genetic (micronucleus) testing and/or other suitable tests focusing on cellular response pathways.
Date created
2012/04/11
DOI
doi:10.7939/R3C53F466
License information
Creative Commons Attribution 3.0 Unported
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