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Mercury risk to avian piscivores across western United States and Canada.

ABSTRACT: The widespread distribution of mercury (Hg) threatens wildlife health, particularly piscivorous birds. Western North America is a diverse region that provides critical habitat to many piscivorous bird species, and also has a well-documented history of mercury contamination from legacy mining and atmospheric deposition. The diversity of landscapes in the west limits the distribution of avian piscivore species, complicating broad comparisons across the region. Mercury risk to avian piscivores was evaluated across the western United States and Canada using a suite of avian piscivore species representing a variety of foraging strategies that together occur broadly across the region. Prey fish Hg concentrations were size-adjusted to the preferred size class of the diet for each avian piscivore (Bald Eagle=36cm, Osprey=30cm, Common and Yellow-billed Loon=15cm, Western and Clark's Grebe=6cm, and Belted Kingfisher=5cm) across each species breeding range. Using a combination of field and lab-based studies on Hg effect in a variety of species, wet weight blood estimates were grouped into five relative risk categories including: background (<0.5?g/g), low (0.5-1?g/g), moderate (1-2?g/g), high (2-3?g/g), and extra high (>3?g/g). These risk categories were used to estimate potential mercury risk to avian piscivores across the west at a 1degree-by-1degree grid cell resolution. Avian piscivores foraging on larger-sized fish generally were at a higher relative risk to Hg. Habitats with a relatively high risk included wetland complexes (e.g., prairie pothole in Saskatchewan), river deltas (e.g., San Francisco Bay, Puget Sound, Columbia River), and arid lands (Great Basin and central Arizona). These results indicate that more intensive avian piscivore sampling is needed across Western North America to generate a more robust assessment of exposure risk.

SUBMITTER: Jackson A

PROVIDER: S-EPMC5461577 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Mercury risk to avian piscivores across western United States and Canada.

Jackson Allyson A Evers David C DC Eagles-Smith Collin A CA Ackerman Joshua T JT Willacker James J JJ Elliott John E JE Lepak Jesse M JM Vander Pol Stacy S SS Bryan Colleen E CE

The Science of the total environment 20160317

The widespread distribution of mercury (Hg) threatens wildlife health, particularly piscivorous birds. Western North America is a diverse region that provides critical habitat to many piscivorous bird species, and also has a well-documented history of mercury contamination from legacy mining and atmospheric deposition. The diversity of landscapes in the west limits the distribution of avian piscivore species, complicating broad comparisons across the region. Mercury risk to avian piscivores was ...[more]

PMID: 26996522

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Project description:Methylmercury contamination of the environment is an important issue globally, and birds are useful bioindicators for mercury monitoring programs. The available data on mercury contamination of birds in western North America were synthesized. Original data from multiple databases were obtained and a literature review was conducted to obtain additional mercury concentrations. In total, 29219 original bird mercury concentrations from 225 species were compiled, and an additional 1712 mean mercury concentrations, representing 19998 individuals and 176 species, from 200 publications were obtained. To make mercury data comparable across bird tissues, published equations of tissue mercury correlations were used to convert all mercury concentrations into blood-equivalent mercury concentrations. Blood-equivalent mercury concentrations differed among species, foraging guilds, habitat types, locations, and ecoregions. Piscivores and carnivores exhibited the greatest mercury concentrations, whereas herbivores and granivores exhibited the lowest mercury concentrations. Bird mercury concentrations were greatest in ocean and salt marsh habitats and lowest in terrestrial habitats. Bird mercury concentrations were above toxicity benchmarks in many areas throughout western North America, and multiple hotspots were identified. Additionally, published toxicity benchmarks established in multiple tissues were summarized and translated into a common blood-equivalent mercury concentration. Overall, 66% of birds sampled in western North American exceeded a blood-equivalent mercury concentration of 0.2 μg/g wet weight (ww; above background levels), which is the lowest-observed effect level, 28% exceeded 1.0 μg/g ww (moderate risk), 8% exceeded 3.0 μg/g ww (high risk), and 4% exceeded 4.0 μg/g ww (severe risk). Mercury monitoring programs should sample bird tissues, such as adult blood and eggs, that are most-easily translated into tissues with well-developed toxicity benchmarks and that are directly relevant to bird reproduction. Results indicate that mercury contamination of birds is prevalent in many areas throughout western North America, and large-scale ecological attributes are important factors influencing bird mercury concentrations.

Project description:Interest in the role of fibrates intensified after the publication of the negative results from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial, which assessed therapy with fenofibrate plus statins. The evidence for clinical benefit in outcomes with the use of fibrates is heavily weighted on the use of the older fibrates such as gemfibrozil and clofibrate.To examine trends in the current use of fibrates and to examine the relationship between differences in the availability and use of brand-name vs generic formulations of fenofibrate and the economic implications in the United States compared with Canada.Population-level, observational cohort study using IMS Health data from the United States and Canada of patients prescribed fibrates between January 2002 and December 2009.Fibrate prescriptions dispensed and expenditures.In the United States, fibrate prescriptions dispensed increased from 336 prescriptions/100,000 population in January 2002 to 730 prescriptions/100,000 population in December 2009, an increase of 117.1% (95% confidence interval [CI], 116.0%-117.9%), whereas in Canada, fibrate prescriptions increased from 402 prescriptions/100,000 population in January 2002 to 474 prescriptions/100,000 population in December 2009, an increase of 18.1% (95% CI, 17.9%-18.3%) (P <.001). In the United States, fenofibrate prescriptions dispensed increased from 150 prescriptions/100,000 population in January 2002 to 440 prescriptions/100,000 population in December 2009, an increase of 159.3% (95% CI, 157.7%-161.0%), comprising 47.9% of total fibrate prescriptions in 2002 and 65.2% in 2009. In Canada, fenofibrate prescriptions increased from 321 prescriptions/100,000 population in January 2002 to 429 prescriptions/100,000 population in December 2009. The annual ratio of generic to brand-name fenofibrate use in the United States ranged from 0:1 to 0.09:1 between 2002 and 2008, while the ratio in Canada steadily increased from 0.51:1 to 1.89:1 between 2005 and 2008. In the United States, crude fenofibrate expenditures increased from $11,535/100,000 population/month in 2002 to $44,975/100,000 population/month in 2009, while the rates in Canada declined from $17,695/100,000 population/month in 2002 to $16,112/100,000 population/month in 2009. Fibrate expenditures per 100,000 population were 3-fold higher in 2009 in the United States compared with Canada.During the past decade, prescriptions for fibrates (particularly fenofibrate) increased in the United States, while prescriptions for fibrates in Canada remained stable.

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Mercury risk to avian piscivores across western United States and Canada.

Publications

Mercury risk to avian piscivores across western United States and Canada.

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