From hazard quotients to a biomarker based weight of evidence: enhancing the science in ecological risk assessment

Johnson, Kelly Elaine (2011) From hazard quotients to a biomarker based weight of evidence: enhancing the science in ecological risk assessment. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This thesis was developed within the framework of a monitoring program for Saglek Bay, Labrador, Canada. Extensive polychlorinated biphenyl (PCB) contamination in soil and sediment associated with a former Polevault Line military station was identified at Saglek in the 1990s (ESG, 1997). PCB impacted soil remediation was carried out between 1997 and 1999 and thus, the terrestrial source of exposure has been removed. Ecological studies showed that PCBs remained in the coastal marine food web (Kuzyk et al., 2005a) and the terrestrial food chain (ESG, 2005; 2007). Recent evidence indicates that the concentrations in the marine environment are decreasing (Brown et al., 2009). Research for this thesis was conducted to evaluate the effects of PCBs on biomarker responses in wildlife at Saglek, and to evaluate the effectiveness of field verification of effects predicted at the screening risk assessment stage by comparing the results of a traditional food chain model approach to a biological effects based weight of evidence approach. Hazard quotients indicated that there was a potential for adverse risks to shorthorn sculpin at Saglek Beach (hazard quotient=1.6) in 1998/99 but adverse risks were unlikely (hazard quotient=0.9) in 2006/07. The biological effects based weight of evidence assessment supported the hazard quotient methodology indicating an intermediate risk to shorthorn sculpin in 1998/99 and a low risk in 2006/07. For black guillemots, the hazard quotients indicated that adverse risks were likely for both 1998/99 (hazard quotient=2.1) and 2006/07 (hazard quotient=1.2). The biological effects based weight of evidence assessment supported the hazard quotient indicating an intermediate to high risk to black guillemots for these time periods. The hazard quotients calculated for deer mice using the dietary approach (2.3) and the tissue residue approach (2.1) indicated that adverse effects to deer mice at Saglek Beach are likely. Results of bone mineral density analysis supported this conclusion but thyroid histomorphometry and histopathology did not. Despite the predicted health effects to black guillemots and deer mice at Saglek, the populations appear to be thriving. Measurement of population and/or community indices would be helpful in confirming the predicted adverse effects. A three tier iterative approach using hazard quotients, biomarkers, and population/and or community studies is recommended for large complex sites such as Saglek, where remediation strategies are expensive and potentially destructive to the environment. This thesis emphasises field verification of adverse health effects predicted through the screening (i.e., hazard quotient) assessment stage and supports an iterative tiered approach to ecological risk assessment.

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