Relative bioavailability tests for application to environmental risk assessment of lead in birds Sleigh, Diana
Accurate assessment of relative bioavailability of lead is important because underestimation may lead to ecological damage and overestimation may lead to unnecessary and expensive cleanup causing site disturbance and also ecological damage. In vitro methods of determining relative bioavailability of lead are preferable over in vivo methods as they are less expensive and do not use live animals causing ethical issues. Of the various in vitro methods available for determining the relative bioavailability of lead, the Waterfowl – Physiologically Based Extraction Test (W-PBET) shows the most promise for use in birds. The W-PBET was designed specifically to meet physiological parameters of waterfowl, and has been positively correlated with in vivo feeding studies to gain validity. Additionally, the W-PBET was designed for use in temperate soils increasing its relevance for use at many North American mining sites. Correlation of environmental determinants with bioaccessibility of lead shows promise as an emerging method of initial site estimation of the relative bioavailability of lead. Environmental determinants that can affect the bioaccessibility of lead range from soil particle size, to soil composition (e.g., sand, silt, clay), to concentrations of iron, manganese and aluminum. Additionally, different speciations of lead vary in levels of bioaccessibility. Site assessment using X-ray techniques can be used as a tool to provide initial estimates of the specific bioaccessibility at a site. Recommendations resulting from this report include use and/or adaptation of the W-PBET to meet specific site and target species needs, and development of regression analysis for specific site condition variables for use as a framework for initial site analysis and estimation of risk. The solutions discussed within this report are recently developed and will become more streamlined and accurate as research in this field progresses.
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