Arctic air pollution: An overview of current knowledge

Toxicological consequences of toxaphene ingestion by cynomolgus (Macaca fascicularis) monkeys. Part 1: pre-mating phase

A total of 40 menstruating cynomolgus monkeys (Macaca fascicularis) with an average age of 7.25 +/- 1.06 years (standard deviation), five male cynomolgus monkeys with an average age of 12.6 +/- 0.66 years, and five male cynomolgus males with an average age of 6.2 +/- 0.23 years were obtained from the Health Canada breeding laboratory. The females were initially randomized to the four test groups in accordance with their previous reproductive success and body weight. They were then randomly allocated between two similar environmentally-controlled rooms (20 females/room). The males were randomly assigned to one of the test rooms (six or four males/room). The female test groups self-ingested capsules containing doses of 0, 0.1, 0.4 or 0.8 mg (Groups A, B, C, D) of technical grade toxaphene/kg body weight/day (i.e. five females/dose group/room). The older males (Group E) were proven breeders and were used exclusively for mating and their capsules contained no toxaphene. The younger males (Group F) ingested capsules containing 0.8 mg of technical grade toxaphene/kg body weight/day. After 20 weeks of daily dosing, it was assumed, based on the results of a pilot study [Andrews P., Headrick K., Pilon J.-C., Bryce F., Iverson F. (1996) Capillary GC-ECD and ECNI GCMS characterization of toxaphene residues in primate tissues during a feed study. Chemosphere 32, 1043-1053], that the treated monkeys had attained a qualitative pharmacokinetic steady state regarding the concentration of toxaphene in their adipose tissue and blood. On a daily basis, each monkey's feed and water consumption as well as its health were monitored. In addition, the females were swabbed daily to determine menstrual status. On a weekly basis, each monkey's body weight was determined and its dose of toxaphene adjusted. Detailed clinical examinations were conducted at intervals of 4 weeks or less. Periodically, starting prior to the initiation of dosing, blood samples were taken for serum biochemistry, haematology and toxaphene analysis. In addition, specimens from the nuchal fat pad were also obtained for toxaphene analysis. Statistical analysis did not reveal any effect of treatment on body weight gain, feed consumption, water consumption or haematological parameters during the 75-week pre-mating phase. The only serum biochemistry parameter which was consistently affected by treatment was cholesterol, the level of which decreased in a linear fashion as a consequence of dose, and this effect increased with time on test (P = 0.037). No other biological effects of toxaphene ingestion were found during the premating phase of this toxicological-reproduction study.

Scavenging of thorium isotopes in the Arctic regions: implications for the fate of particle-reactive pollutants

The sources of inorganic pollutants to the Arctic areas are reviewed using previously published results. The removal of particle-reactive pollutants is discussed using thorium scavenging as an analog. The scavenging of 234Th from the upper water column (approximately 100 m) and sediment inventory of 230Th from the deep Arctic waters is compared to different ocean basins in the subarctic areas. Such a comparison shows that 234Th is in equilibrium with its parent, 238U, in certain regions of the Canada Basin of the Arctic Ocean, while it is deficient in other regions of the arctic as well as in sub-polar ocean basins. This implies that the particle-reactive pollutants in the deep Arctic of the Canada Basin are less likely to be removed from the deep waters and will eventually be transported out of this area. We have utilized the 230Th inventory in sediments from the Arctic area to determine the removal rates of particle-reactive nuclides. The 230Th inventory in the deep Arctic Ocean of the Canada Basin is much lower than the Norwegian Sea and the Fram Strait of the Arctic as well as all other sub-polar world oceans. These observations suggest that any pollutants into the deep Arctic areas of the Canada Basin are less likely to be removed locally and may be transported out of this area. In those areas, the colloidal material could potentially play a major role in the removal of particle-reactive contaminants.

Contaminants in the Canadian Arctic: 5 years of progress in understanding sources, occurrence and pathways

Recent studies of contaminants under the Canadian Northern Contaminants Program (NCP) have substantially enhanced our understanding of the pathways by which contaminants enter Canada's Arctic and move through terrestrial and marine ecosystems there. Building on a previous review (Barrie et al., Arctic contaminants: sources, occurrence and pathways. Sci Total Environ 1992:1-74), we highlight new knowledge developed under the NCP on the sources, occurrence and pathways of contaminants (organochlorines, Hg, Pb and Cd, PAHs, artificial radionuclides). Starting from the global scale, we examine emission histories and sources for selected contaminants focussing especially on the organochlorines. Physical and chemical properties, transport processes in the environment (e.g. winds, currents, partitioning), and models are then used to identify, understand and illustrate the connection between the contaminant sources in industrial and agricultural regions to the south and the eventual arrival of contaminants in remote regions of the Arctic. Within the Arctic, we examine how contaminants impinge on marine and terrestrial pathways and how they are subsequently either removed to sinks or remain where they can enter the biosphere. As a way to focus this synthesis on key concerns of northern residents, a number of special topics are examined including: a mass balance for HCH and toxaphene (CHBs) in the Arctic Ocean; a comparison of PCB sources within Canada's Arctic (Dew Line Sites) with PCBs imported through long-range transport; an evaluation of concerns posed by three priority metals--Hg, Pb and Cd; an evaluation of the risks from artificial radionuclides in the ocean; a review of what is known about new-generation pesticides that are replacing the organochlorines; and a comparison of natural vs. anthropogenic sources of PAH in the Arctic. The research and syntheses provide compelling evidence for close connectivity between the global emission of contaminants from industrial and agricultural activities and the Arctic. For semi-volatile compounds that partition strongly into cold water (e.g. HCH) we have seen an inevitable loading of Arctic aquatic reservoirs. Drastic HCH emission reductions have been rapidly followed by reduced atmospheric burdens with the result that the major reservoir and transport agent has become the ocean. In the Arctic, it will take decades for the upper ocean to clear itself of HCH. For compounds that partition strongly onto particles, and for which the soil reservoir is most important (e.g. PCBs), we have seen a delay in their arrival in the Arctic and some fractionation toward more volatile compounds (e.g. lower-chlorinated PCBs). Despite banning the production of PCB in the 1970s, and despite decreases of PCBs in environmental compartments in temperate regions, the Arctic presently shows little evidence of reduced PCB loadings. We anticipate a delay in PCB reductions in the Arctic and environmental lifetimes measured in decades. Although artificial radionuclides have caused great concern due to their direct disposal on Russian Shelves, they are found to pose little threat to Canadian waters and, indeed, much of the radionuclide inventory can be explained as remnant global fallout, which was sharply curtailed in the 1960s, and waste emissions released under license by the European reprocessing plants. Although Cd poses a human dietary concern both for terrestrial and marine mammals, we find little evidence that Cd in marine systems has been impacted by human activities. There is evidence of contaminant Pb in the Arctic, but loadings appear presently to be decreasing due to source controls (e.g. removal of Pb from gasoline) in Europe and North America. Of the metals, Hg provokes the greatest concern; loadings appear to be increasing in the Arctic due to global human activities, but such loadings are not evenly distributed nor are the pathways by which they enter and move within the Arctic well understood.

Controlling persistent organic pollutants-what next?

Within the context of current international initiatives on the control of persistent organic pollutants (POPs), an overview is given of the scientific knowledge relating to POP sources, emissions, transport, fate and effects. At the regional scale, improvements in mass balance models for well-characterised POPs are resulting in an ability to estimate their environmental concentrations with sufficient accuracy to be of help for some regulatory purposes. The relevance of the parameters used to define POPs within these international initiatives is considered with an emphasis on mechanisms for adding new substances to the initial lists. A tiered approach is proposed for screening the large number of untested chemical substances according to their long-range transport potential, persistence and bioaccumulative potential prior to more detailed risk assessments. The importance of testing candidate POPs for chronic toxicity (i.e. for immunotoxicity, endocrine disruption and carcinogenicity) is emphasised as is a need for the further development of relevant SAR (structure activity relationship) models and in vitro and in vivo tests for these effects. Where there is a high level of uncertainty at the risk assessment stage, decision-makers may have to rely on expert judgement and weight-of-evidence, taking into account the precautionary principle and the views of relevant stake-holders. Close co-operation between the various international initiatives on POPs will be required to ensure that assessment criteria and procedures are as compatible as possible.

Biological specimen banking in Arctic research: an Alaska perspective

The cryogenic archival of biological specimens for retrospective analysis is of significant value for present and future research on population genetics, pathology, systematics, toxicology and environmental monitoring. This realization is emphasized by the increasing support of this activity by various government agencies, institutions and international groups. The international Arctic community is no exception. Canada has been conducting such activities in association with environmental monitoring programs for many years. Similar efforts appear to be underway in other polar nations. From the perspective of the United States Arctic, the Alaska Marine Mammal Tissue Archival Project (AMMTAP) was the earliest organized effort to develop an environmental specimen bank specifically designed for longterm archival of biological specimens under cryogenic conditions. The AMMTAP emphasizes use of standardized rigorous sampling and archival protocols, procedures that minimize contamination of samples during collection and maintaining a detailed record of sample history. The development of this specimen bank, recent activities of this project and other cryogenic specimen banks being developed in Alaska are described.