Renal trace elements in barren-ground caribou subpopulations: Temporal trends and differing effects of sex, age and season.

Caribou (Rangifer tarandus) are a culturally significant food resource for communities in northern Canada and Greenland. Many barren-ground caribou subpopulations are currently in decline, some dramatically; understanding the influence of stressors, such as toxic trace metals, is important. These contaminants enter Arctic terrestrial environments via atmospheric transport from industrialized areas and from local sources, accumulating there in the environment. Understanding how trace element concentrations interact and are influenced by caribou sex, age and season of collection is essential to evaluating trends in these elements over time and differences among subpopulations. We used path analysis to model the direct and indirect relationships between these variables in the Porcupine subpopulation and in barren-ground caribou from the Canadian Arctic and Greenland. Renal cadmium (Cd), copper (Cu) and mercury (Hg) varied significantly among subpopulations. Hg was positively correlated with Cd, Cu and selenium (Se) in female Porcupine caribou whereas Cd and Cu were negatively correlated in male Porcupine caribou. Age, season and sex influenced all three element concentrations and should be considered when comparing elements among caribou subpopulations or years. Renal Cd decreased slightly from the Canadian Western Arctic to Greenland and increased slightly over time, possibly reflecting patterns of atmospheric deposition. Renal Hg did not change significantly over time, and differences among subpopulations did not follow specific geographical patterns. Renal Cu declined over time, the changes being markedly different among subpopulations, sexes and seasons. This temporal decline is likely due to changes in diet, which could be driven by various environmental factors. Declining Cu concentrations in caribou is of concern as low levels could negatively affect reproductive success and therefore caribou at a population level. Continuing to monitor element concentrations in caribou is essential to better comprehend potential threats facing the species, and to promote food security in communities harvesting this important resource.

Measurements of cesium in Arctic beluga and caribou before and after the Fukushima accident of 2011.

Concern from northern communities following the Fukushima Daiichi nuclear accident of March 2011 has prompted a reassessment of the safety of their traditional foods with respect to radioactivity levels. To this end, a study was conducted to measure the levels of radionuclides in Arctic caribou (Rangifer tarandus) and beluga (Delphinapterus leucas). The main radionuclide of concern is cesium-137, which is easily transferred through the lichen-caribou food chain. Previous studies have been conducted on the cesium-137 levels in Canadian caribou herds from 1958 to 2000, allowing researchers to determine the amount of cesium-137 in caribou specifically attributable to atmospheric weapons testing and the Chernobyl nuclear accident in 1986. In this study, samples of lichens, mushrooms, caribou, beluga and beluga prey collected before and after the Fukushima accident were analyzed for radioactivity levels. Samples were processed and measured using gamma ray spectroscopy to identify the radionuclides present and determine the radioactivity concentration. Both calibration standards and Monte Carlo simulations were used to determine the efficiency of the detectors for the samples, taking into account differences in individual sample sizes as well as matrices. In particular, a careful analysis of the atomic composition of lichens and mushrooms was performed to ensure the efficiencies for these sample types were correct. A comparison of the concentrations from before and after the accident indicated that there was no increase in radioactivity as a result of the atmospheric plume from the Fukushima accident. Some cesium-137, likely attributable to fallout from atmospheric weapons testing of the 1950s and 1960s (since there was no cesium-134 measured in the samples), was measured in the post Fukushima caribou and beluga whale samples; however, this amount was determined to be insignificant for any radiological concern (9.1 ± 1.8 and 0.63 ± 0.23 Bq kg-1 ww respectively). The activity concentrations of cesium-137 was about 200 times smaller than that of natural radioactive potassium in the beluga samples. Both the caribou and beluga results showed that these foods continue to be a healthy food choice for northern Canadians with respect to radioactivity, and this result has been communicated to the nearby northern communities and stakeholders.

Cadmium and other elements in tissues from four ungulate species from the Mackenzie Mountain region of the Northwest Territories, Canada.

Tissue samples from four ungulate species from the south Mackenzie Mountain region of the Northwest Territories (NT), Canada, were analysed for stable and radioactive elements and (15)N and (13)C stable isotopes. Elevated Cd concentrations in moose (Alces americanus) kidney have been observed in the region and are a health care concern for consumers of traditional foods. This study examined the factors associated with, and potential renal effects from, the accumulation of cadmium, and interactions with other elements in four sympatric ungulate species. Mean renal Cd concentration was highest in moose (48.3mg/kg ww), followed by mountain caribou (Rangifer tarandus caribou) (13.9mg/kg ww) and mountain goat (Oreamnos americanus) (5.78mg/kg ww). No local sources of Cd were evident and the elevated levels in moose are considered to be natural in origin. Conversely, total Hg concentration was significantly higher in mountain caribou kidney (0.21mg/kg ww) than in moose (0.011mg/kg ww). (134)Cs (t½=2.1 y) in mountain goat and Dall's sheep (Ovis dalli) muscle is evidence of deposition from the Fukushima reactor accident in 2011. (137)Cs (t½=30.2 y) in all four ungulates is primarily a remnant of the nuclear weapons tests of the 1960s. The levels of both nuclides are low and the risk to the animals and people consuming them is negligible. Stable isotope δ(15)N and δ(13)C signatures in muscle showed a separation between the mountain caribou, with a lichen-dominated diet, and moose, which browse shrubs and forbs. Isotope signatures for mountain goat and Dall's sheep showed generalist feeding patterns. Differences in elemental and radionuclide levels between species were attributed to relative levels of metal accumulation in the different food items in the diets of the respective species. Kidneys from each species showed minor histological changes in the proximal tubule and glomerulus, although glomerular changes were rare and all changes were rare in mountain goat kidney. Kidney function was not expected to be affected in any species. Provisional Monthly Intake recommendations from the WHO indicate that Cd in moose organs will continue to be a public health care concern. However, traditional foods continue to be an important nutritional component of northern diets, particularly in consideration of the shift towards store-bought food.

Spatial and temporal trends of contaminants in Canadian Arctic freshwater and terrestrial ecosystems: a review.

The state of knowledge of contaminants in Canadian Arctic biota of the freshwater and terrestrial ecosystems has advanced enormously since the publication of the first major reviews by Lockhart et al. and Thomas et al. in The Science of the Total Environment in 1992. The most significant gains are new knowledge of spatial trends of organochlorines and heavy metal contaminants in terrestrial animals, such as caribou and mink, and in waterfowl, where no information was previously available. Spatial trends in freshwater fish have been broadened, especially in the Yukon, where contaminant measurements of, for example, organochlorines were previously non-existent. A review of contaminants data for fish from the Northwest Territories, Yukon and northern Quebec showed mercury as the one contaminant which consistently exceeds guideline limits for subsistence consumption or commercial sale. Lake trout and northern pike in the Canadian Shield lakes of the Northwest Territories and northern Quebec generally had the most elevated levels. Levels of other heavy metals were generally not elevated in fish. Toxaphene was the major organochlorine contaminant in all fish analyzed. The concentrations of organochlorine contaminants in fish appear to be a function not only of trophic level but of other aspects of the lake ecosystem. Among Arctic terrestrial mammals, PCBs and cadmium were the most prominent contaminants in the species analyzed. Relatively high levels (10-60 micrograms g-1) of cadmium were observed in kidney and liver of caribou from the Yukon, the Northwest Territories and northern Quebec, with concentrations in western herds being higher than in those from the east. For the organochlorine contaminants, a west to east increase in zigma PCBs, HCB and zigma HCH was found in caribou, probably as a result of the predominant west to east/north-east atmospheric circulation pattern which delivers these contaminants from industrialized regions of central and eastern North America to the Arctic via long-range atmospheric transport. Radiocesium contamination of lichens and caribou has continued to decrease. Significant contamination by PCBs and lead of soils and vascular plants was observed in the immediate vicinity and within a 20-km radius of DEW line sites in the Canadian Arctic. There was also evidence for transfer of PCBs from plants to lemmings. There was no evidence, however, that large mammals such as caribou living in the general area of the DEW line sites had elevated levels of PCBs. There is very limited temporal trend information for most contaminants in biota of Arctic terrestrial and freshwater environments.

Contaminant residue levels in arctic wolves (Canis lupus) from the Yukon Territory, Canada.

Kidney, liver and bone samples were taken from 19 wolves (Canis lupus) collected from two locations in the Yukon Territory. Liver samples pooled by age and sex were analyzed for 22 organochlorine pesticides and 101 PCB congeners. Individual kidney and liver samples were analyzed for arsenic, cadmium, copper, lead, total mercury, selenium and zinc. Thirteen individual bone samples were analyzed for lead. While most organochlorines were not present at detectable levels in wolf liver, some chlorobenzenes, dieldrin and sigma PCB were present at low levels. PCB congeners 149, 153, 170/190, 180 and 187/182 made up 86% of the total PCBs measured in wolf liver. The hexa- and heptachlorobiphenyls dominated the pattern in wolf liver, while congeners containing less than five chlorine atoms were not detected. The pattern of chlorobenzene and PCB homologues found in wolf liver are more similar to those found in marten (Martes americana) and other carnivores than caribou (Rangifer tarandus), perhaps reflecting similarities in food habits and metabolic capacities. With the exception of cadmium, average element concentrations in all wolf tissues are similar to those found in other arctic carnivores. Cadmium concentrations in wolf liver and kidney were somewhat higher in Yukon wolves than other arctic wolves. This may reflect high cadmium concentrations found in livers and kidneys of moose and some caribou herds in the Yukon. Renal arsenic and bone lead decreased significantly with age in wolves, while renal mercury increased with age. Because the ranges seen are relatively small, and all values are within the range normally seen in wildlife, it is difficult to determine the biological significance of these relationships. Contaminant levels in Yukon wolves are generally low and are similar to those found in other arctic terrestrial carnivores. They do not approach levels that are known to potentially cause adverse effects in animals. Contaminant concentrations found in this study should be considered baseline levels.

Cadmium in caribou and muskoxen from the Canadian Yukon and Northwest Territories.

Cadmium, zinc, copper and metallothionein concentrations were measured in liver and kidney tissue of caribou and muskoxen collected from various sites in the Canadian Yukon and Northwest Territories. Cadmium concentrations in caribou tissues were substantially higher than in muskoxen for all age classes and were comparable to concentrations reported for caribou from northern Québec and Norway. No geographical site differences in cadmium concentration were observed. Cadmium concentrations were positively correlated with age for both caribou and muskoxen. The highest cadmium concentration observed (166 micrograms/g dry wt.) was in renal tissue of a 15-year-old caribou. Metal concentrations tended to be higher in spring than in fall for animals of comparable age. Renal cadmium concentrations were highly correlated with metallothionein concentrations, especially for cadmium concentrations exceeding 20 micrograms/g (dry wt.). It is estimated that the regular weekly consumption of kidney tissue from Arctic caribou of any age, and from muskoxen older than 1 year, will probably cause the WHO provisional weekly tolerable intake of cadmium to be exceeded.

Ceramometal crowns and bridges. Focus on failures.

There are numerous factors that can have an adverse or beneficial effect upon the esthetic appearance of a ceramometal restoration. Some of these factors are beyond the influence of the dentist unless he or she is aware of them. As knowledgable practicing dentists, they have the ability to prescribe for their patients in such a manner as to achieve greater success and, in turn, greater patient acceptance and recognition. These are the rewards of a successful crown and bridge practice, and the ceramometal restoration is the basic state of the art prosthesis in present use. Knowing how to take a shade under the proper lighting conditions is generally well taught as part of the dental school curriculum, but the knowledge that shade guides are manufactured with built in idiosyncrasies of color variations from guide to guide is an enlightening experience. O'Brien of the Department of Dental Materials at the University of Michigan School of Dentistry clearly demonstrated the variabilities of color intensities between porcelain manufacturers. Laboratory technicians have been frustrated by the inconsistency of shades of porcelains from one lot number to another. It is now more fully understood that fluorescence is an important factor in patient satisfaction, as patients observe and have their restorations seen under differing lighting conditions. The type of alloy used in the ceramometal combination can have an effect upon the esthetic result. The wider use of silver-palladium alloys requires that the porcelain employed be of a nongreening nature, or else the final glazed prosthesis will give off a greenish cast. The ability of the opaque to block out the metal substructure while blending with the gingival and incisal shades eliminates the graying out, which can be esthetically objectionable to the patient. However, one of the most important considerations in aesthetic ceramometal restorations is the correct anatomy, placement, and harmonious blending with the oral and facial features and coloring of the patient. It would be comforting if we could all agree on a definition of esthetics. There is perhaps no more important aspect of marketing the ceramometal restoration to the patient than arrive, in advance, on a common ground and understanding of what the esthetic goals of the case are in realistic terms.(ABSTRACT TRUNCATED AT 400 WORDS)