A multiple lines of evidence approach for the ecological risk assessment of an accidental bitumen release from a steam assisted gravity drainage (SAGD) well in the Athabasca oil sands region.

To assess the ecological impacts of two independent accidental bitumen releases from two steam assisted gravity drainage (SAGD) wells in the Athabasca oil sands region, a multiple lines of evidence (LOE) approach was developed. Following the release in 2010, action was taken to minimize environmental impact, including the selective removal of the most highly impacted vegetation and the use of oil socks to minimize possible runoff. An ecological risk assessment (ERA) was then conducted based on reported concentrations of bitumen related contaminants in soil, vegetation, and water. Results of biological assessments conducted at the site were also included in the risk characterization. Overall, the conclusion of the ERA was that the likelihood of long-term adverse health effects to ecological receptors in the area was negligible. To provide evidence for this conclusion, a small mammal sampling plan targeting Southern red-back voles (Myodes gapperi) was carried out at two sites and two relevant reference areas. Voles were readily collected at all locations and no statistically significant differences in morphometric measurements (i.e., body mass, length, foot length, and adjusted liver weight) were found between animals collected from impact zones of varying levels of coverage. Additionally, no trends corresponding with bitumen coverage were observed with respect to metal body burden in voles for metals that were previously identified in the source bitumen. Hepatic ethoxyresorufin-O-deethylase (EROD) activity was statistically significantly elevated in voles collected from the high impact zones of sites compared to those collected from the reference areas, a finding that is indicative of continued exposure to contaminants. However, this increase in EROD was not correlated with any observable adverse population-wide biological outcomes. Therefore the biological sampling program supported the conclusion of the initial ERA and supported the hypothesis of no significant long-term population-wide ecological impact of the accidental bitumen releases.

Pulmonary hypertension and long-term mortality in aortic and mitral regurgitation.

BACKGROUND: Outcomes data in patients with aortic regurgitation or mitral regurgitation have been limited to small series with generally <10 years of follow-up. The quantitative impact of pulmonary artery hypertension has not been well described. The purpose of this study was to describe the 15-year mortality of aortic regurgitation and mitral regurgitation. METHODS: Our institution's electronic echocardiography database was queried to identify those patients examined in 1992 and reported to have at least mild aortic regurgitation or mitral regurgitation. Patients were classified by semi-quantitative degree of regurgitation. Pulmonary artery systolic pressure was categorized as normal, borderline, mild, or moderate or greater hypertension (pulmonary artery systolic pressure >40 mm Hg). Age-stratified Cox proportional hazards models compared survival among groups and adjusted for sex, depressed left ventricular ejection fraction, and pulmonary artery systolic pressure. Mortality data were obtained from the 2008 Social Security Death Index. RESULTS: Of 4984 echocardiograms performed in 4050 patients, 1156 patients (28%; aged 72±14 years) had at least mild aortic regurgitation and 1971 patients (49%; aged 69±16 years) had at least mild mitral regurgitation. Overall 15-year mortality in patients with aortic regurgitation was 74% and similar for all grades of aortic regurgitation. Overall 15-year mortality in patients with mitral regurgitation was 71% and got progressively worse with increasing severity grade of mitral regurgitation (63% for mild to 81% for at least moderate-to-severe). For both aortic and mitral regurgitation, moderate or greater pulmonary artery systolic hypertension was associated with increased mortality (in patients with aortic regurgitation, hazard ratio [HR], 1.94; 95% confidence interval [CI], 1.58-2.41, and in mitral regurgitation patients, HR, 1.48; 95% CI, 1.26-1.75). CONCLUSION: Long-term (15-year) survival of patients with aortic regurgitation is poor and is independent of regurgitation severity. In contrast, long-term survival of patients with mitral regurgitation correlates with regurgitation severity. For both groups, moderate or greater pulmonary artery systolic hypertension identified those at highest risk.