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Azimuth, Canada

MacMillan J.W.,Mount Allison University | Behinaein S.,McMaster University | Chettle D.R.,McMaster University | Inskip M.,McMaster University | And 6 more authors.
Environmental Sciences: Processes and Impacts | Year: 2015

The Canadian population is currently subject to low, chronic lead exposure and an understanding of its effects is of great significance to the population's health. Such low exposure is difficult to measure directly; approximation by physiologically based modeling may provide a preferable approach to population analysis. The O'Flaherty model of lead kinetics is based on an age-dependent approach to human growth and development and devotes special attention to bone turnover rates. Because lead is a bone-seeking element, the model was deemed ideal for such an analysis. Sample from 263 individuals of various ages from the Greater Toronto Area were selected to evaluate the applicability of the current version of the O'Flaherty model to populations with low lead exposure. For each individual, the input value of lead exposure was calibrated to match the output value of cortical bone lead to the individual's measured tibia lead concentration; the outputs for trabecular bone, blood, and plasma lead concentrations obtained from these calibrations were then compared with the subjects' measured calcaneus, blood, and serum lead concentrations, respectively. This indicated a need for revision of the model parameters; those for lead binding in blood and lead clearance from blood to bone were adjusted and new outputs were obtained in the same fashion as before. Model predictions of trabecular lead concentration did not agree with measurements in the calcaneus. The outputs for blood and plasma lead concentrations were highly scattered and, on an individual level, inconsistent with corresponding measurements; however, the general trends of the outputs matched those of the measurements reasonably well, which indicates that the revised blood lead binding and lead clearance parameters may be useful in future studies. Overall, the analysis showed that with the revisions to the model discussed here, the model should be a useful tool in the analysis of human lead kinetics and body burden in populations characterized by low, chronic exposure to lead from the general environment. © 2015 The Royal Society of Chemistry. Source

Allard P.,Azimuth Consulting Group | Fairbrother A.,Exponent, Inc. | Hope B.K.,11 SW Sixth Avenue | Hull R.N.,Intrinsik Environmental Sciences Inc. | And 5 more authors.
Integrated Environmental Assessment and Management | Year: 2010

Toxicity reference values (TRVs) are essential in models used in the prediction of the potential for adverse impacts of environmental contaminants to avian and mammalian wildlife; however, issues in their derivation and application continue to result in inconsistent hazard and risk assessments that present a challenge to site managers and regulatory agencies. Currently, the available science does not support several common practices in TRV derivation and application. Key issues include inappropriate use of hazard quotients and the inability to define the probability of adverse outcomes. Other common problems include the continued use of no-observed- and lowest-observed-adverse- effect levels (NOAELs and LOAELs), the use of allometric scaling for interspecific extrapolation of chronic TRVs, inappropriate extrapolation across classes when data are limited, and extrapolation of chronic TRVs from acute data without scientific basis. Recommendations for future TRV derivation focus on using all available qualified toxicity data to include measures of variation associated with those data. This can be achieved by deriving effective dose (EDx)-based TRVs where x refers to an acceptable (as defined in a problem formulation) reduction in endpoint performance relative to the negative control instead of relying on NOAELs and LOAELs. Recommendations for moving past the use of hazard quotients and dealing with the uncertainty in the TRVs are also provided. © 2009 SETAC. Source

Behinaein S.,McMaster University | Chettle D.R.,McMaster University | Marro L.,Health Canada | Malowany M.,Health Canada | And 6 more authors.
Environmental Sciences: Processes and Impacts | Year: 2014

A 109Cd K X-ray fluorescence (KXRF) measurement system consisting of four detectors in clover-leaf geometry is a non-invasive, low-radiation-dose method of measuring bone lead concentration. Its high precision in estimating the bone lead content makes it a promising tool for the determination of the low levels of lead currently found in the general population. After developing the clover-leaf geometry system, the system was used for the first time in a major survey in 2008 to measure the lead levels of 497 smelter employees (an occupationally exposed group with high lead levels). Since the delivered effective dose of the bone lead system in clover-leaf geometry is small (on the order of nSv), the technique can be used to measure the bone lead of sensitive populations such as the elderly and children. This detector system was used from 2009 to 2011, in a pilot study that measured the bone lead concentration of 263 environmentally exposed individuals (termed the EG group) residing in Toronto, Ontario, Canada. In this paper, the factors that influence uncertainties in lead content in tibia (cortical bone) and calcaneus (trabecular bone) are discussed based on gender, age, and body mass index (BMI) by using analysis of variance (ANOVA) and multiple linear regression models. Results from the two study groups (the EG group versus the occupationally exposed smelter employees) are compared where appropriate (i.e. for males older than 20). Results from univariate analyses showed that females have higher tibia uncertainty compared to males. We observed significant differences for both calcaneus and tibia uncertainty measures (p < 0.0005) among different age groups, where the uncertainties were highest in the lowest age group (<11 years). Lastly, and perhaps most significantly, we found that the product of source activity and measurement time influenced the precision of measurements greatly, and that this factor alone could account for the higher uncertainties observed for the male cohort of the EG group versus the smelter employees. © 2014 The Royal Society of Chemistry. Source

Depew D.C.,Queens University | Depew D.C.,National Water Research Institute | Burgess N.M.,Environment Canada | Anderson M.R.,Canadian Department of Fisheries and Oceans | And 13 more authors.
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2013

Fish mercury (Hg) concentrations have been measured over the last 30-40 years in all regions of Canada as part of various monitoring and research programs. Despite this large amount of data, only regional assessments of fish Hg trends and patterns have previously been attempted. The objective of this study was to assemble available freshwater fish Hg concentration data from all provinces and territories and identify national patterns. The Canadian Fish Mercury Database includes over 330 000 records representing 104 species of freshwater fish collected from over 5000 locations across Canada between 1967 and 2010. Analysis of the 28 most frequently occurring species (>1000 records) showed that the majority of variation in Hg concentrations (when normalized to a standard size) was accounted for by geographic location. Median Hg concentrations increased with trophic level (r = 0.40, p < 0.05), with the highest Hg concentrations found in piscivorous species such as walleye (Sander vitreus), northern pike (Esox lucius), and lake trout (Salvelinus namaycush). The Canadian Fish Mercury Database provides the most comprehensive summary of fish Hg measurements in Canada, and the results indicate that several regionally observed trends in fish Hg concentrations (e.g., Hg biomagnification and geographic variation) are observed at a national scale. Implications for the effective assessment of changes in fish Hg concentrations in relation to changes in Hg emission regulations are discussed. Source

Power B.A.,Azimuth Consulting Group | Tinholt M.J.,SNC - Lavalin | Hill R.A.,Azimuth Consulting Group | Fikart A.,Azimuth Consulting Group | And 4 more authors.
Integrated Environmental Assessment and Management | Year: 2010

The Crown Land Restoration Branch (CLRB) of the British Columbia Ministry of Agriculture and Lands is responsible for managing thousands of historic and abandoned mine sites on provincial lands (referred to as Crown Contaminated Sites). For most of these sites, there is limited information available regarding the extent of potential contamination or potential human health and ecological risks. Given the large number of sites, the CLRB sought a system for prioritizing investigation and management efforts among them. We developed a Risk-Ranking Methodology (RRM) to meet this objective, which was implemented in 2007/2008 with an emphasis on historic mine sites because of the significant number of sites and related potential risk. The RRM uses a risk-based Preliminary Site Investigation to gather key information about the sites. The information for each site is analyzed and summarized according to several attributes aimed at characterizing potential health and ecological risks. The summary information includes, but is not limited to, generic comparisons of exposure with effects levels (screening quotients) for human and ecological exposure pathways. The summary information (more than 25 attributes) is then used in a workshop setting to evaluate relative rankings among sites, and also to identify subsequent management actions for each site. Application of the RRM in 2007/2008 was considered successful, because there was confidence in the process, the content and the outputs. A key challenge was keeping the number of attributes to a manageable level. Ranking was based on discussion and consensus, which was a feasible approach given the relatively small number of sites that need to be ranked each year, and facilitated transparency in the ranking process.We do not rule out the future possibility of developing a quantitative function to capture trade-offs among attributes. © 2009 SETAC. Source

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