Abstract
BackgroundUnderstanding mercury (Hg) distribution in blood and the importance of hair as an excretory pathway is critical for evaluating risk from long term dietary Hg exposure. The major objective of this study was to characterize changes in total Hg concentrations in specific blood compartments and hair over time due to long term piscivory.MethodsEight sled dogs (Canis lupus familiaris) were fed either a fish and kibble diet (n = 4), or a fish-free control diet (n = 4) for 12 weeks. Concentrations of Hg were monitored throughout the exposure period, and for 10 weeks post exposure, until Hg concentrations in all blood compartments of one of the exposed dogs dropped below detection limit. Additionally, foreleg hair was sampled during acclimation and weeks 0 and 12.ResultsHg was detected primarily in whole blood and packed cells, although it was sporadically detected at low concentrations in plasma and serum in two of the fish fed dogs. Dogs ingested an estimated average of 13.4 ± 0.58 μg Hg per kg body weight per day. Hg was detectable in whole blood and packed cells within a week of exposure. Detected concentrations continued to rise until plateauing at approximately 3-6 weeks of exposure at a mean of 9.2 ± 1.97 ng/g (ppb) in whole blood. Hg concentration decreased post exposure following 1st order elimination. The mean half-life (t1/2) in whole blood for Hg was 7 weeks. Mean Hg in hair for the fish-fed dogs at week 12 was 540 ± 111 ppb and was significantly greater (about 7-fold) than the Hg hair concentration for the control dogs. The hair to blood ratio for Hg in fish-fed dogs was 59.0 ± 7.6:1.ConclusionsThis study found the sled dog model to be an effective method for investigating and characterizing blood Hg distribution (whole blood, serum, plasma, packed cells) and toxicokinetics associated with a piscivorous diet, especially for Hg-exposed fur bearing mammals (such as polar bears). Although hair excretion and hair to blood Hg ratios were not similar to human concentrations and ratios, the sled dog toxicokinetics of Hg in blood, was more similar to that of humans than traditional laboratory animals (such as the rat).
Highlights
Understanding mercury (Hg) distribution in blood and the importance of hair as an excretory pathway is critical for evaluating risk from long term dietary Total mercury (Hg) exposure
Published fish consumption advice for Alaskans developed by the Alaska Scientific Advisory Committee for Fish Consumption recommend an acceptable daily intake level (ADIL) of Hg, based on consumer body weight (BW), of 0.4 μg/kg BW/day [7]
This paper describes the toxicokinetics of Hg in blood, including partitioning in whole blood (WB), serum, plasma and packed cells from serum and plasma preparations (PCserum and PCplasma)
Summary
Understanding mercury (Hg) distribution in blood and the importance of hair as an excretory pathway is critical for evaluating risk from long term dietary Hg exposure. Published fish consumption advice for Alaskans developed by the Alaska Scientific Advisory Committee for Fish Consumption recommend an acceptable daily intake level (ADIL) of Hg, based on consumer body weight (BW), of 0.4 μg/kg BW/day [7]. This is intermediate to the Health Canada fish consumption recommendations of 0.2 μg/kg BW/day for children and women of childbearing age, and 0.5 μg/kg BW/day for everyone else [8]. The limit for Alaskan salmon species is listed as unlimited
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