The Arctic at Risk:
A Circumpolar Atlas of Environmental Concerns
The Arctic at Risk:
Following a map series depicting the physical and biological environment, the sequence of maps is grouped by contaminant and roughly follows the Arctic food chain. Starting in the marine environment, the maps move from ocean water, to sea ice, marine fish, seabirds, and marine mammals. In the terrestrial environment, the maps start with freshwater fish, then move to terrestrial mammals and humans. Because of inconsistent data availability, the species presented vary from one contaminant series to another.
In order to facilitate use of the information on the maps, links are provided to other related maps. This allows the you to view the map of, say, PCBs in ringed seals and compare it with PCBs in polar bears (since bears eat ringed seals) or with DDT in ringed seals (to see how the distribution of the two organochlorines differ). You may also want view maps of transport pathways in the atmosphere, ocean and ice several maps representing transport processes to better understand the data.
This compilation presents, to our knowledge, the best available data: most are from papers published in peer reviewed journals. Also, by restricting the data compiled to publications since 1980, analyses are more likely to use recent and comparable techniques. However, because some data are taken from institutional data reports, we also asked three outside scientists to review the text, map, and data tables that are presented here. Note that, in general, Russian sources do not provide information on quality assurance: data accuracy, precision, detection limits, or interlaboratory comparisons. As a result, concerns have been raised about the quality of some of these data; see accompanying text for discussion of concerns associated with particular data sets. Ensuring the quality and comparability of data between laboratories and methods is difficult; we hope that the new sampling guidelines developed by the AMAP will rectify this problem in the future.
In addition to data quality, there are many caveats regarding interpretation of these data, including issues of: seasonal and temporal variation; age, size, and sex of organisms; and migration and feeding patterns. Below we discuss each of these concerns to highlight the fact that the data presented in this atlas must be interpreted with care. We intend that they should be used mainly as: 1) an index to the primary data sources in your particular area of interest, 2) to indicate data gaps where future monitoring is required, and 3) to recommend areas for further research to better understand contaminant fates and effects.
Seasonal and Temporal Variations
In order to make clear change in the concentrations of contaminants from one season to the next, or over the course of a decade, it would be best to show a series of maps with data sampled at different times. Because none of the maps has enough data to illustrate such detailed changes, instead we have included all the data for one topic on one map. Trends through time in pollutant levels are confused when data spanning more than a decade are presented on one map. For example, levels of DDT have been decreasing in some Canadian marine mammals following decreased emissions into the environment. As a result, apparent regional variations may actually be due to the fact that some samples were taken while emissions were high, while other samples were taken later when the environmental burden had decreased.
Age, Size, and Sex
Interpreting pollutant loadings in animals requires information such as age, size, and sex -- data that often were not included in the publication. Many contaminants build up in organisms during their lifespan, so older age classes tend to have higher concentrations. Although this effect can be corrected for if the age or weight of the organism is known, and if the relationship between age and bioaccumulation has been determined, the authors did not always provide that information, and so we were not able to normalize the data. In addition, the relationship between contaminant level and age, size, and sex is often complicated.
We have indicated, when possible, where the data reflect an average of only juvenile data (for example, see mercury in seals). Also, in the case of DDT in belugas, we had sufficient information to separate females and males, and therefore have provided maps of both. Differences occur between female and male belugas when they are about six years old (Stern et al., 1994). At this point, females reach sexual maturity, and concentrations drop due to transfer of persistent organochlorines to offspring during nursing and, to a much lesser extent, to placental transport from the female lipid tissue to the fetus (Stern et al., 1994). Note that lactational transfer also results in increased contaminant levels in offspring, which often peak in three-month old belugas (Stern et al., 1994).
Because the data generally were not normalized for age, size, or sex, if the samples were biased toward either young or old individuals at a particular location, the mean value presented on the map and table will not represent the true population mean. As a result apparent geographic variations seen on the map may actually represent just sampling differences. This is a major complication in understanding geographic differences and should be corrected by having future studies provide detailed information on sampling that would allow for normalization of samples. Considering this issue from a dietary perspective: if samples were obtained primarily from old animals and people tend to eat the tissue from younger animals, then the value presented will represent a disproportionately high value. On the other hand, if the samples were obtained primarily from young animals, while people tend to eat the older animals, then the value presented may provide an underestimate of the level of concern.
Migration
Because many species migrate to the Arctic, often over long distances, contaminants accumulated in their tissues may derive from a variety of sources, both to the south as well as in the Arctic. Animals may feed and grow in one place, but be eaten or sampled in another. To interpret contaminant levels of migrating species, information is required on rates of ingestion and types--and contaminant levels--of prey taken throughout the year (Welch et al., 1992).
Back to the EDF homepage
Back to the Arctic Atlas main page