Sublethal health effects in laboratory rodents from environmentally relevant exposures to oil sands contaminants

Abstract

Increasing activity of oil sands extraction and processing in northern Alberta is marked by ongoing controversy about the nature and extent of associated environmental impacts. Bitumen contains a mixture of toxic chemicals, including metals and residual polycyclic aromatic hydrocarbons (PAHs), whose release into the environment poses a distinct risk to the surrounding environment, plus wildlife and human health. In the present study, the authors evaluated several subclinical biomarkers of exposure and effect to mixtures of metals (Pb, Cd, and Hg) and/or PAHs (3 alkylated forms) at environmentally relevant concentrations (100-fold and 10-fold higher than the maximum dissolved concentrations found in snow, to simulate a worst-case scenario), using laboratory mice as a model for future studies of small mammals in the wild. Both metals and alkyl-PAHs exposure were associated with 1) increased relative liver, kidney, and spleen size; 2) alterations in the homeostasis of the antioxidant vitamins A and E in liver; and 3) compromised glutathione redox status in testes, with results also indicating synergistic interactions from co-exposure. The combination of morphometric and oxidative stress biomarkers provide reliable and sensitive measures of the response to contaminant exposure in a mammalian model, suggesting associated physiological costs. Based on the present experimental study, the authors propose that wild small mammals will prove to be valuable sentinel species reflecting sublethal health effects from oil sands-related contaminants. The present study's results also present a basis for the interpretation of future field data.

Deposition Mapping of Polycyclic Aromatic Compounds in the Oil Sands Region of Alberta, Canada and Linkages to Ecosystem Impacts

“…The dominant species in both cases were NAP, C1/C2-NAP, C1/C2-FL, and C1-PHE. Furthermore, the larger deposition impact of alk-PAHs compared to PAHs and DBTs identified in this study is also consistent with the higher alk-PAH concentrations in wetlands and in wildlife including wood frogs, muskrats, minks, river otters, moose, and wolves. − Alk-PAHs exposure has led to changes in the organ size indicative of developmental issues and reduction in antioxidant defenses potentially leading to increased oxidative stress in laboratory mice . Tree swallow nestlings exposed to PAHs and other air contaminants has resulted in increased EROD (ethoxyresorufin O-dealkylase) levels, which signifies increased detoxification activity .…”

“…30−32 Alk-PAHs exposure has led to changes in the organ size indicative of developmental issues and reduction in antioxidant defenses potentially leading to increased oxidative stress in laboratory mice. 33 Tree swallow nestlings exposed to PAHs and other air contaminants has resulted in increased EROD (ethoxyresorufin O-dealkylase) levels, which signifies increased detoxification activity. 34 Most of the research into wildlife effects focused on the exposure to oil sands processed water (OSPW), which includes tailings ponds, other detention ponds, wetlands, and reclaimed ponds.…”

European Starlings (Sturnus vulgaris) As Sentinels of Urban Air Pollution: A Comprehensive Approach from Noninvasive to Post Mortem Investigation

“…Our findings are different from others in which contaminant exposure has exhausted antioxidant resources in wildlife species. 39,42 Although the laboratory technique to determine rGSH:GSSG is challenging and the accuracy of results has been questioned, 53 we argue that precision in analyzing samples within one study, produces meaningful comparative results.…”

“…Total glutathione (tGSH) and oxidized glutathione (oxGSH) were measured in 2014 using the methods and reagents described for liver samples in Rodri ́guez-Estival et al; 39 thiobarbituric acid-reactive substances (TBARS) were measured using the same methods in both 2014 and 2015. Minor adjustments were made in 2015 to improve efficiency of the analysis of tGSH and oxGSH (see SI, p S4).…”

“…Reduced glutathione (rGSH) and glutathione disulfide (GSSG) were calculated using the following formulas: rGSH = tGSH-oxGSH and GSSG = oxGSH/2. 39 We report TBARS, a measure of malonaldehyde reflecting membrane lipid peroxidation, 41 as well as total glutathione (tGSH) and the ratio of the reduced to oxidized forms of glutathione (rGSH:GSSG), since these latter two provide an indication of up-regulation of the antioxidant defense system. 42 This combined, multipronged approach provides more complete insight into the actual oxidative stress from contaminant exposure, since any biomarker in isolation is inconclusive in such a redundant system.…”