Comparative toxicity of two diluted bitumens to developing yellow perch (Perca flavescens).

Increasing demand for diluted bitumen (dilbit) has led to the development of the oil sands industry and the expansion of transcontinental pipelines. Dilbit is an unresolved complex mixture with variable diluent and bitumen composition. Thus, it is important to understand the effects of the two most transported dilbits in Canada, Access Western Blend (AWB) and Cold Lake Blend (CLB) on a North America native and freshwater fish species, the yellow perch (Perca flavescens). Fertilized embryos were exposed to both dilbits for 16 days, from <24 h post-fertilization until hatch. The treatment regime was a static daily renewal of water accommodated fractions (WAF) and chemically-enhanced water accommodated fractions (CEWAF) at concentrations ranging from 0.01 to 21.3 µg/L of total polycyclic aromatic compounds (TPACs). Hatched embryos were assessed for malformations and changes in the expression of genes associated with phase I and II detoxification and oxidative stress. The prevalence of developmental malformations increased significantly at the highest concentrations of all treatments, with WAF treatments yielding a higher prevalence than CEWAF. The EC50s for AWB and CLB WAF and CEWAF solutions ranged from 9.8 to 24 µg/L TPACs, with the CEWAF of AWB being the least toxic. Relative mRNA levels of cyp1a showed induction by up to 18-fold in WAF and 50-fold in CEWAF treatments at similar concentrations of measured dilbit in solution. Complementary DNA methylation analysis was assessed and fish embryos exposed to AWB CEWAF and CLB WAF showed decreased DNA methylation profiles with increasing exposure to dilbit, suggesting that global gene expression is increasing in these treatments. With recent approvals of pipelines in North America, these data will support site-specific risk assessments and monitoring of Canadian ecosystems should a pipeline spill occur.

Long-term survival of McKee-Farrar total hip prostheses.

Because of the recent resurgence of interest in metal-on-metal bearing components for total hip arthroplasties, the long-term results of 153 consecutive McKee-Farrar total hip arthroplasties done in 129 patients by one surgeon between 1969 and 1973 were evaluated. A retrospective chart review provided patient demographics (age, gender, weight, primary diagnosis), revision dates, indications, and implant survival data. The average age of the patients at implantation surgery was 61 years (range, 28-85 years) and these patients were observed as many as 28 years. Primary diagnoses included osteoarthritis (49% of implants), rheumatoid arthritis (38%), and other conditions (13%). During the 28 years of followup, five implants were revised for infection and 14 implants were revised for aseptic loosening. Survivorship analysis of the McKee-Farrar prostheses had a 20-year probability of implant survivorship of 84%, and a 28-year implant survivorship of 74%. Excellent long-term results of the McKee-Farrar prosthesis were seen. Given the inherent problems associated with implant wear debris, especially polyethylene wear particles, second generation metal-on-metal bearing implants may offer a viable alternative to current designs. Their excellent long-term survival may infer particular suitability for use in younger patients.